achieving quality in clinical decision making: cognitive strategies and detection of bias

1184 Croskerry QUALITY IN CLINICAL DECISION MAKING

Achieving Quality in Clinical Decision Making:Cognitive Strategies and Detection of Bias

Pat Croskerry, MD, PhD

AbstractClinical decision making is a cornerstone of high-qualitycare in emergency medicine. The density of decisionmaking is unusually high in this unique milieu, and acombination of strategies has necessarily evolved tomanage the load. In addition to the traditional hypo-thetico-deductive method, emergency physicians useseveral other approaches, principal among which areheuristics. These cognitive short-cutting strategies are es-pecially adaptive under the time and resource limitationsthat prevail in many emergency departments (EDs), butoccasionally they fail. When they do, we refer to themas cognitive errors. They are costly but highly prevent-able. It is important that emergency physicians be

aware of the nature and extent of these heuristics andbiases, or cognitive dispositions to respond (CDRs).Thirty are catalogued in this article, together with de-scriptions of their properties as well as the impact theyhave on clinical decision making in the ED. Strategiesare delineated in each case, to minimize their occurrence.Detection and recognition of these cognitive phenomenaare a first step in achieving cognitive de-biasing to im-prove clinical decision making in the ED. Key words:emergency medicine; quality; decision making; cognitivestrategies; heuristics; biases; cognitive disposition to re-spond. ACADEMIC EMERGENCY MEDICINE 2002; 9:11841204.

DECISION MAKINGThe ultimate cornerstone of high-quality care inemergency medicine is the accuracy, efficacy, andexpediency of clinical decision making. It is a clearbarometer of good care. There is ample reason tobelieve that decision making in emergency medi-cine has unique characteristics that distinguish itfrom decision making in other medical settings.1 Itis important, therefore, that we understand its spe-cial properties, and the range of strategies thatemergency physicians use to make decisions.

Emergency physicians are required to make anunusually high number of decisions in the courseof their work. In few other workplace settings, andin no other area of medicine, is decision density ashigh. Decision requirements depend upon uncer-tainty, and uncertainty levels are extremely high inthe emergency department (ED). For the most part,patients are not known and their illnesses are seenthrough only small windows of focus and time. Anumber of other factors, unique to the ED milieu,constrain the decision-making process.2 During the

From the Division of Emergency Medicine, Dalhousie Univer-sity Medical School, Halifax, Nova Scotia Canada (PC).Received June 18, 2002; accepted June 26, 2002.Supported by the Department of Emergency Medicine and theDivision of Medicine at Dalhousie University, Halifax, NovaScotia, and AHQR grant #P20 HS11592 to the Center for Safetyin Emergency Care.Address for correspondence and reprints: Pat Croskerry, MD,PhD, Division of Emergency Medicine, Dalhousie UniversityMedical School, 5849 University Avenue, Halifax, Nova Scotia,Canada B3H 4H7.

course of a shift, both clinical and nonclinical de-cisions are required and many considerations con-tribute to the decision burden, including resourceavailability, cost, and patient preferences (Table 1).

Continuously, emergency physicians are requiredto make decisions about allocating their own timeand effort deciding who needs to be seen next,whether to initiate treatment immediately or wait,and how to deal with increasing numbers of pa-tients. Typically, attending physicians may be re-quired to maintain clinical responsibility for up toten patients at a time, perhaps more if admittedpatients are waiting in the ED. The process is sim-ilar to plate-spinning on sticks, where a significantnumber have to be maintained in motion withoutallowing one to slow and fall, and as one plate istaken off, it is replaced with another. It sometimesresults in excessive cognitive loading.

Once the interaction with the patient is initiated,the first decision is often whether or not immediateaction is required.3 Further thinking and behaviorof the clinician are largely driven by a search for aworking diagnosis, often tightly coupled to treat-ment, and the goal of safe disposition or transfer.Once the chief complaint has been established, nu-merous important decisions are made in the courseof taking the history of presenting illness (HPI), andpast medical history (PMH). What questions areasked, and how they are asked,4,5 may have a sig-nificant impact on the decisions that follow. Whatto examine in the physical examination and deci-sions around the significance of findings are

ACAD EMERG MED November 2002, Vol. 9, No. 11 www.aemj.org 1185

TABLE 1. Clinical and Nonclinical Decisions

ClinicalPatient preferencesHistory of presenting illness, past medical history, physical

examTest orderingInterpretation of data: laboratory, imaging studies,

electrocardiograms, otherTreatmentReferralDiagnosisDispositionTeaching

NonclinicalAllocation of resourcesPriority settingAdministrativeCost

Figure 1. Overview of clinical decision making in the emer-gency department. HPI = history of present illness; PMH = pastmedical history.

TABLE 2. Strategies in Decision Making

Pattern recognitionRule out worst-case scenario (ROWS)Exhaustive methodHypothetico-deductive methodHeuristicsCognitive disposition to respond (CDR)

equally critical. Next, decisions need to be madeabout what tests and imaging studies are required.Every test result needs to be assessed: Is the valueabnormal or not? Might the abnormal value be alaboratory error? If it is abnormal, is it acceptable,or does it require an intervention? Is this abnor-mality expected in this patient? For imaging stud-ies: Is the radiograph of the right patient? Has thecorrect radiograph been ordered? Is it the rightside, and has the side been identified correctly? Isthe film centered? Is the exposure reasonable? Is itabnormal or not? Are there other significant find-ings? Is this a variant or an abnormality? Similarconsiderations apply for the electrocardiogram(ECG): Is this the right patient? Have the leads beenapplied correctly? Is this a variant of normal? Is thisan old or a new finding? Do I need to see oldECGs? What is the interpretation? Is immediate ac-tion required? What should that action be? The vol-ume of decisions around the indications for, andchoice of, procedures and treatment is similarlydense. Numerous further decisions will be madefor other aspects of the clinical encounter, as wellas for nonclinical activity.

Many of these decisions will be straightforward.For example, examining a panel of values for acomplete blood count often requires no more thanlooking for abnormal values, and these may beflagged automatically. A second stage of decisionmaking may then be required, however, to deter-mine the cause of combinations of abnormalities.Similarly, an abnormal arterial blood gas may re-quire up to ten separate decisions to determine thecause(s) of the abnormality. If the physician sees anaverage of three patients an hour, the total numberof these individual decisions on each patient re-quiring a significant workup may go into the hun-dreds, and the total for a shift will be in the

thousands. The sheer number of decisions can cre-ate stress and tension for the decision maker, whichmay compromise decision making. Other intrinsicoperating features of the ED environment, such asresource limitations, interruptions, distractions, andthe transitions of care that result from shift changes,may further increase the likelihood that clinical de-cision quality might not be maintained.2,6

How, then, is this decision density handled? It isclear that emergency physicians do not methodi-cally go through a quantitative clinical utility ap-proach to decision making; i.e., for the most part,they are not formal Bayesians. Instead, they appearto have developed several decision-making strate-gies that are part of an informal Bayesian ap-proach,7 which reduces decision complexity andbuilds economy and redundancy into the process(Table 2). They correspond more to the recogni-tionprimed decision model advocated by Kleinet al.19 than to any formal, analytical decision-mak-ing process. These informal methods mediate whatReason has termed flesh-and-blood decisionmaking, which occurs at the point where the cog-nitive reality departs from the formalized ideal,8

and is schematized in Figure 1. It seems that emer-

1186 Croskerry QUALITY IN CLINICAL DECISION MAKING

TABLE 3. Failed Heuristics, Biases, and Cognitive Dispositions to Respond

Aggregate biasAnchoringAscertainment biasAvailability and non-

availabilityBase-rate neglectCommission bias

Confirmation biasDiagnosis momentumFundamental attribu-

tion errorGamblers fallacyGender biasHindsight bias

Multiple alternativesbias

Omission biasOrder effectsOutcome biasOverconfidence biasPlaying the odds

Posterior probabilityerror

Premature closurePsych-out errorRepresentativeness

restraintSearch satisfying

Suttons slipTriage-cueingUnpacking principleVertical line failureVisceral biasYinyang outZebra retreat

gency physicians either make a flesh-and-blood de-cision fairly soon after the presentation of a patientat the ED, or they commit to a formal workup in-volving an array of tests, imaging techniques, andconsultations. Good flesh-and-blood decision mak-ing saves time and resources, and characterizesphysicians with good acumen. Many of the strate-gies they use have proved their efficacy with thetest of time, but occasionally they fail. Therefore, itis important that emergency physicians understandhow to detect the weaknesses and biases in each ofthese strategies.

PATTERN RECOGNITIONCombinations of salient features of a presentationoften result in pattern recognition of a specific dis-ease or condition. It reflects an immediacy of per-ception, and may result in anchoring bias (Tables 3and 4). At the outset, these features are often visualand drive the process of perception in a largely bot-tom-up fashion (Fig. 2). Later, additional incomingdata supplement the process. The beliefs and ex-pectations of the clinician also exert an influencethrough a top-down process,9 which is more of agoal-directed behavior. The combination and con-tinuous interplay of these two processes enable thepercept to be recognized and the problem solved.The obvious application of this strategy is in der-matological cases, but pattern recognition drivesdecision making in many other contexts in the ED.For example, a patient lying on a stretcher with ex-cruciating flank pain and vomiting initiates the bot-tom-up perception that generates the diagnosis ofureteral colic. The presence of blood in the urineprovides further supporting data. From the clini-cians standpoint, past experience with this presen-tation and knowing that the patient has a historyof urinary calculi provide top-down knowledgethat guides and adds certainty to the diagnosis. Aswith many strategies, they work most of the timebut occasionally fail. Several difficulties arise withpattern recognition: First, initial top-down process-ing biases such as the clinicians prior beliefs andexpectations may lead to the selection of inappro-priate data sets that misdirect subsequent reasoningand problem solving. Second, bottom-up data can

be misleading; visual data, in particular, are vul-nerable to misinterpretation.1012 A number of otherpossibilities can account for the initial presentationof this patient with severe flank pain. Also, the find-ing of hematuria is not specific to ureteral colic andmay be a manifestation of other conditions, e.g., anabdominal dissecting aneurysm. Finally, not all in-coming data are used objectively. For example,when confirmation bias is evident, data can be selec-tively marshaled to support a favored hypothesis.The biases described below appear to affect bothtop-down and bottom-up processing.

RULE OUT WORST-CASE SCENARIO (ROWS)

The ROWS strategy is almost pathognomonic of de-cision making in the ED. Above all else, emergencyphysicians must not miss critical diagnoses. This isa form of pattern matching combining with theavailability heuristic (Table 4). For most presenta-tions the physician will have available, or carrymental templates of, the top five or so diagnosesthat should be excluded. Thus, for chest pain thephysician might match the presentation against thescenarios for unstable angina, acute myocardial in-farct, aortic dissection, tension pneumothorax, andpericarditis. This is not an exclusive list of diag-nostic possibilities for chest pain, but these are di-agnoses that must be excluded before judicious dis-position. For the most part, ROWS is a strategy ofsafety and errs on the side of caution. It also qual-ifies as a form of value-induced bias in that any bi-asing tendency toward worst-case scenarios in-creases the likelihood of detection of diagnoses thatmust not be missed. Similar overreading behav-ior has been described for radiologists.13 One of thegoals of developing clinical decision rules is to re-duce value-induced biases in clinical behavior,thereby improving utilization of resources. ROWSis also an example of a generic cognitive forcing strat-egy (CFS) that increases the probability that all crit-ical diagnoses have received consideration in theED.1 One of the important features of the avail-ability heuristic, however, is its dependence on per-sonal experience, and idiosyncratic applications ofROWS may lead to overutilization of resources.

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TABLE 4. Catalogue of Failed Heuristics, Biases, and Cognitive Dispositions to Respond (CDRs) with Descriptors, Consequences, and Strategiesto Avoid Them

FailedHeuristic/CDR/Bias

Synonyms/Allonyms Descriptors Consequences Avoiding Strategy Refs.

Aggregatebias

Ecological fallacy The aggregate fallacy is when associations between variables repre-senting group averages are mistakenly taken to reflect what is truefor a particular individual, usually when individual measures are notavailable. Physicians may use the aggregate bias to rationalize treat-ing an individual patient differently from what has been agreedupon through clinical practice guidelines for a group of patients (i.e.,there is a tendency for some physicians to treat their own patients asatypical). However, the aggregate fallacy argument does not applybecause clinical practice guidelines have been established on indi-vidual data. Further, the clinicians behavior may be augmented bya patients demanding behavior. Thus, a particular patient judged tohave a viral upper respiratory tract infection may be treated with anantibiotic for perverse (irrational) reasons, or a patient with an anklesprain who doesnt satisfy the Ottawa Ankle Rules may be x-rayed.The aggregate bias may be compounded by those with a commis-sion bias, who have a tendency to want to be seen as doingsomething for the patient.

Physician noncompliance and idiosyncraticapproaches may result in patients receiv-ing tests, procedures, and treatment out-side of accepted clinical practice guide-lines. Patients may be inadvertentlyreinforced for demanding some kind ofactive intervention (antibiotic, x-ray, refer-ral, etc.).

Physicians should recognize that the aggregatefallacy does not apply to clinical decision rulesthat have been validly developed. Unlessthere are compelling and rational reasons fordoing otherwise, physicians should, therefore,follow clinical decision rules and clinical path-ways. They should avoid the tendency to be-lieve their patients are atypical or excep-tions, and resist the temptation towarddoing something. They should avoid havingtheir clinical decision making influenced bydemanding behavior of patients and relatives.

28

Anchoring Tram-lining, firstimpression,jumping to con-clusions

Anchoring is the tendency to fixate on specific features of a presenta-tion too early in the diagnostic process, and to base the likelihood ofa particular event on information available at the outset (i.e., the firstimpression gained on first exposure, the initial approximate judg-ment). This may often be an effective strategy. However, this initialimpression exerts an overly powerful effect in some people and theyfail to adjust it sufficiently in the light of later information. Anchoringcan be particularly devastating when combined with confirmationbias (see below).

Anchoring may lead to a premature closureof thinking. Patients may be labeled withan incorrect diagnosis very early on in theirpresentation. Diagnoses, once attached,are difficult to remove (see diagnosis mo-mentum, below) and may seal the pa-tients fate.

Awareness of the anchoring tendency is impor-tant. Early guesses should be avoided. Wherepossible, delay forming an impression untilmore complete information is in.

1, 10, 17,2931

Ascer-tainmentbias

Response bias,seeing whatyou expect tofind

Ascertainment bias occurs when the physicians thinking is pre-shapedby expectations or by what the physician specifically hopes to find.Thus, a physician is more likely to find evidence of congestive heartfailure in a patient who relates that he or she has recently been non-compliant with his or her diuretic medication, or more likely to be dis-missive of a patients complaint if he or she has already been la-beled as a frequent flyer or drug-seeking. Gratuitous orjudgmental comments at hand-off rounds and other times can domuch to seal a patients fate. Ascertainment bias characteristicallyinfluences goal-directed, top-down processing. Stereotyping andgender biases are examples of ascertainment bias.

Ascertainment bias leads to pseudo-informa-tion, which subsequently may prove mis-leading. Any prejudgment of patients isdangerous and may result in underassess-ing or overassessing their conditions.

It is important for physicians to detach them-selves from any type of pre-formed notion, ex-pectation, or belief that will impact on subse-quent interpretation of data. They should bealert for discriminatory comments about pa-tients that may lead to unjustified expecta-tions. Making negative or judgmental com-ments about patients before they have beenassessed, especially at shift changeover,should be discouraged.

32

Availabilityand non-avail-ability

Recency effect,common thingsare common(availability),the sound ofhoofbeatsmeans horses,out of sight outof mind (non-availability), ze-bra

Availability is the tendency for things to be judged more frequent ifthey come readily to mind. Things that are common will be readilyrecalled. The heuristic is driven by the assumption that the evidencethat is most available is the most relevant. Thus, if an emergencyphysician saw a patient with headache that proved to be a sub-arachnoid hemorrhage (SAH), there will be a greater tendency tobring SAH to mind when the next headache come along. Availabilityis one of the main classes of heuristic and underlies recency effect(see below). Availability may influence a physicians estimates ofbase rate of an illness. Non-availability (out of sight out of mind), oc-curs when insufficient attention is paid to that which is not immedi-ately present (zebras). Novices tend to be driven by availability, asthey are more likely to bring common prototypes to mind, whereasexperienced clinicians are more able to raise the possibility of theatypical variant or zebra.

Availability and non-availability lead to dis-proportionate estimates of the frequencyof a particular diagnosis or condition. Theyboth distort estimates of base rate (seebase rate neglect, below), which influ-ences pre-test probability. This may lead tofaulty Bayesian reasoning and under- oroverestimates of particular diagnoses.

Objective information should be gathered andused systematically to estimate the true baserate of a diagnosis, and clear clinical evi-dence is needed to support a particular diag-nosis for the patient being seen. Physiciansshould be aware of the tendency to pay toomuch attention to the most readily availableinformation, or be unduly influenced by high-profile, vivid, or recent cases. They should rou-tinely question the soundness of their estimatesor judgmentsdo they rely excessively on eas-ily available evidence?

1, 8, 17, 26,33

continued

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TABLE 4. Catalogue of Failed Heuristics, Biases, and Cognitive Dispositions to Respond (CDRs) with Descriptors, Consequences, and Strategiesto Avoid Them (cont.)



Base-rateneglect

Representative-ness exclusivity

Emergency physicians tend not to be formal Bayesians and insteadmake judgments based on how well the patients presentationmatches their mental prototype for a particular diagnosis. This is anexample of the representativeness heuristic (see below). It involvesusing a heuristic that emphasizes how things typically present in thenatural setting of the emergency department (ED) (substantive ap-proach) rather than adopting specific decision rules and statistics,typified by subjective expected utility theory (formalistic ap-proach). In many instances, the substantive approach is successfulbut occasionally this heuristic may be used to the exclusion of otherimportant considerations such as the base rate or prevalence of thatdisease. Failing to adequately take into account the prevalence of aparticular disease is referred to as base rate neglect.Some diagnoses that are made in the ED are unambiguous but

many will be uncertain and have probabilities attached to them.Probabilities are only estimates and depend on the personal experi-ence of the clinician. Prior probability (pre-test) reflects the physi-cians belief about the likelihood of the diagnosis prior to any testing.The posterior probability (post-test) reflects the revised belief aboutthe likelihood of the diagnosis once the test result is known. The effi-cacy of the test is a function of its sensitivity and specificity. Bayesrule combines these variables: the pre-test probability with the testresult and the efficacy of the test, and the validity of the approachdepends upon objective data about disease prevalence. Thus, if aphysician gives all possible explanations for pleuritic chest pain equalpre-test probabilities then they are effectively being assigned equalprevalence rates; i.e., true base rates are being neglected. Testingfor pulmonary embolus (worst-case scenario) is more likely to bedone, and its post-test likelihood overestimated.Some will argue that the rule out worst-case scenario (ROWS) strat-

egy forces a distortion of Bayesian reasoning by giving undue em-phasis to remote possibilities. This erring on the side of caution will re-sult in overutilization but would be considered by many to be anacceptable downside.

Base-rate neglect may result in overesti-mates of unlikely diagnoses, leading towastefulness and overutilization of re-sources. The pursuit of esoteric diagnoses isoccasionally successful and the intermit-tent reinforcement sustains this behavior insome physicians.

Physicians should be wary of relying on represen-tativeness to the exclusion of other data. Theyshould have reliable estimates of disease prev-alence in their geographical area, and be fa-miliar with the principles underlying Bayesianreasoning and the judicious ordering of tests.In particular, they should be aware that inter-pretation of diagnostic tests depends on dis-ease prevalence.

18, 3438

Commis-sion bias

Actions speaklouder thanwords

Commission bias is the tendency toward action rather than inaction.An error arises when there is an inappropriate committal to a particu-lar course of action. It is more likely to occur in someone who is over-confident, and reflects an urge to do something. It satisfies the ob-ligation of beneficence in that harm can only be prevented byactively intervening. However, it is more likely to violate the obligationof non-malfeasance (refraining from an action that exposes the pa-tient to unnecessary risk or harm), as well as the opening caveat ofthe Hippocratic oath First do no harm. Thus, errors of commissionare less likely than errors of omission. Errors of omission typically out-number errors of commission. Commission bias may be augmentedby team pressures or by the patient. It may underlie ascertainmentbias, which tends to result in physicians doing something (prescrib-ing an antibiotic, ordering an x-ray), i.e., committing to an actionwhen the clinical practice guidelines promote inaction as the bestcourse.

Commission errors tend to change thecourse of events, because they involve anactive intervention, and may therefore beless reversible than an error of omission.The premature adoption of a diagnosis(see premature closure) is a tacit form ofcommission error.

Before committing to an intervention, physiciansshould review the evidence very closely. Is theact justified? What are the consequences ofthe action? Is there a danger associated withit? Are there other options? Is it irrevocable?How much of it can be reversed?

39

ACAD EMERG MED November 2002, Vol. 9, No. 11 www.aemj.org 1189C

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Funda-mentalattribu-tion error

Judgmental be-havior, negativestereotyping

Fundamental attribution error is the tendency to blame people whenthings go wrong rather than circumstances. Thus, someones behav-ior may be explained by attributing it to the dispositional qualities ofa person rather than to situational circumstances. We have a stronginclination to make such attributions in a social context and carrythem over into the ED. Thus, judgments are made about certaingroups of patients e.g., alcoholics, frequent flyers, drug-seekers, so-matizers, and those with personality disorders. We hold them responsi-ble for their behavior, imagining they have as much control over it aswe do, and attributing insufficient consideration to their social orother circumstances.Generally we tend to be less judgmental about ourselves than oth-

ers (actor-observer bias), and are more inclined to take the credit forsuccess than accept responsibility for failure (self-serving attributionalbias); this may lead to overconfidence. There also exists a self-punish-ing attribution bias, reflected in the often harsh reaction we have to-ward ourselves when we make an error; i.e., there appears to be astrong tendency in some physicians to attribute blame to themselvesrather than look for systemic or circumstantial explanations. The bi-ases described here are distinct from the illusion of control that un-derlies attribution bias, the tendency to attribute outcomes to unre-lated events, e.g., rain dances. However, attribution bias mightexplain why some clinicians occasionally persist in superstitious, idio-syncratic behaviors.

Fundamental attribution error reflects a lackof compassion and understanding for cer-tain classes of patient and may result in in-appropriate or compromised care. Somestudies have suggested attribution errormay worsen the condition of some psychi-atric patients.

Physicians should avoid being judgmental aboutthe behavior of others. It is impossible to beaware of all the circumstances that contributeto a persons behavior. They should try toimagine a relative or themselves in the sameposition. Care should be consistent across allgroups of patients, especially for minorities andthe marginalized. It is very important to re-member that for psychiatric patients, the be-havior is often the only manifestation of theunderlying disease.

1, 9

Gamblersfallacy

Monte Carlo fal-lacy, law of av-erages, se-quence effect

If a coin is tossed ten times and comes up heads each time, the gam-blers fallacy is the belief that the 11th toss will be tails; i.e., that thesequence will reverse. Although the 50:50 odds of heads or tails re-mains the same (the coin has no memory), there is a tendency tobelieve the sequence cannot continue. An example of the gam-blers fallacy in the ED is the situation where the emergency physi-cian sees a series of chest pains. If the first, second, and third pa-tients are all diagnosed with an acute coronary syndrome (ACS), aninertia begins to build whereby the physician begins to doubt thatthe sequence can continue. Thus, there may develop an increasingtendency to believe that the likelihood of a subsequent patient withchest pain having ACS has diminishedthat the sequence cannotcontinue. All these patients, of course, are independent of eachother and should be objectively assessed on their own merits, but itappears that sequences or runs can give rise to superstitious behav-ior and influence decision making. Except under epidemic condi-tions, the ED is one of the few areas in medicine where the diseaseof one patient may influence the management of another. The gam-blers fallacy is contrasted with posterior probability error (see below),where, for different reasons, the belief is that the sequence will notreverse but continue.

The fallacy erroneously changes the pre-testprobability of a particular diagnosis for apatient. This may result in the diagnosis re-ceiving insufficient consideration and be-ing delayed or missed.

When unusually sequences or runs are experi-enced, physicians should remind themselves ofthe laws of probability and the independenceof diagnoses. Effectively, the physician mustrestart his or her approach with each new pa-tient.

31, 56

ACAD EMERG MED November 2002, Vol. 9, No. 11 www.aemj.org 1191G

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1,8,

44

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Multiple al-terna-tives bias

Status quo bias,wallpaper phe-nomenon

Imagine having to choose a new wallpaper when there are only twooptions. Many would find the choice relatively easy. If now the op-tions are expanded to five, it becomes increasingly difficult, the deci-sion making process becomes delayed, and there is a tendency torevert back to choosing between the original two (or even stayingwith the original). In a particular clinical situation of relatively lowcomplexity, a physician may feel comfortable about choosing be-tween two alternatives. If the options now expand, physicians ap-pear to experience difficulty with the additional choices, and tend tofall back on the status quo. Paradoxically, it appears that instead ofthe new alternatives inviting a wider range of choice and treatmentoptions, from which the physician might evaluate the benefits andrisks to choose the most superior, the uncertainty and conflict drivethe physician back to more conservative behavior. For example, as-sume a physician has established a practice of using thrombolytic Ain acute myocardial infarction. He subsequently receives informationabout a new thrombolytic, B, which appears to be a reasonable al-ternative to A. Then a third thrombolytic, C, becomes available,which also appears efficacious. The rational approach would be toevaluate the evidence for all three thrombolytics and choose thebest available. However, the multiple alternatives bias predicts that,at least at the outset, there would be a tendency to revert to A, be-cause the multiple choices generate conflict and uncertainty. This avariant of the status quo biaspreferring the known to the unknown.Exhortations are often made to stick with what you know, but themultiple alternatives bias goes a little further than that in creating anirrational inertia against optimizing choice among competing alter-natives. The bias has been described only in the context of medicalchoices for treatment, but may have applicability in diagnostic situa-tions. For example, if a physician had decided on a choice betweentwo working hypotheses, but additional information emerges thatraises additional and reasonable possibilities, the bias would predictthat the tendency to avoid conflict and added uncertainty inclinesthe physician back to choosing among the original hypotheses.

Situations that create multiple alternativescan lead to irrational decision making,and result in suboptimal treatments and,perhaps, missed diagnoses.

To optimize decision making and minimize bias,physicians should avoid simply trying to selectthe best option from an array of options. In-stead, they should clearly identify all compet-ing options and compare each one individu-ally with the status quo. This should ensure thatany change is an improvement over what ex-isted earlier.

58

Omissionbias

Temporizing, tinc-ture of time,watchful ex-pectancy,watchful wait-ing, let wellenough alone

Omission bias is the tendency toward inaction, or reluctance to treat.Inaction is preferred over action through fear of being held directlyresponsible for the outcome. Blame tends to be directed at the lastperson to have touched the patient. It has its origin in the idea thatwhen a bad outcome occurs, blame will be more likely if you didsomething rather than did not. It also fits the First do no harm partof the Hippocratic oath, and the principle of non-maleficence. It ispreferable that an event is seen to happen naturally rather thanhave the event directly attributed to the action of a physician. Thistendency toward inaction may explain why passive euthanasia ispreferred over active euthanasia, even though the end result is iden-tical. The bias may be sustained by the reinforcement that oftencomes from not doing anything (tincture of time, watchful waiting,temporizing), human physiology having a natural tendency to restorehomeostasis, and the body having a tendency to recover from mostacute insults.

While inaction may often be the most ap-propriate course, omission bias may leadto disastrous outcomes in the ED. Temporiz-ing in urgent conditions may result in thedevelopment of worsening emergencies.

The maxim When you think of it is the time todo it is often applicable. Some medical con-ditions evolve very quickly in the ED and it isprudent to anticipate as early as possiblewhen an intervention might be required. Onequality that characterizes the competentemergency physician is a willingness to actdecisively.

8, 22, 39,4547

ACAD EMERG MED November 2002, Vol. 9, No. 11 www.aemj.org 1193O

miss

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mn

on

-de

libe

rate

,c

og

niti

vefa

ilure

s:sli

ps,

lap

ses,

mist

ake

s,a

nd

dist

rac

tion

s.Th

ese

are

am

on

gth

em

ost

pre

vale

nt

of

an

ye

rro

rty

pe

.Th

ey

typ

ica

llyo

utn

um

-b

er

co

mm

issio

ne

rro

rs.

Ina

stu

dy

of

tra

um

am

an

ag

em

en

t,th

ey

ac

-c

ou

nte

dfo

ra

pp

roxi

ma

tely

ha

lfo

fa

lle

rro

rs.

Ord

er

ef-

fec

tsP

rima

cy,

rec

en

cy

The

rea

rem

an

yo

cc

asio

ns

inth

eED

wh

en

info

rma

tion

istr

an

sfe

rre

dfr

om

on

ep

ers

on

toth

eo

the

r.It

ha

pp

en

sa

tth

eo

uts

et

be

twe

en

the

pa

tien

ta

nd

the

tria

ge

nu

rse

,b

etw

ee

nth

ep

atie

nt

an

dp

hys

icia

n,

be

-tw

ee

nn

urs

es

an

dp

hys

icia

ns,

be

twe

en

ph

ysic

ian

sa

nd

ph

ysic

ian

s,a

nd

be

twe

en

nu

rse

sa

nd

nu

rse

s.A

nim

po

rta

nt

fea

ture

of

info

rma

tion

tra

nsf

er

isth

at

rec

all

isb

iase

da

sa

U-f

un

ctio

n.

We

ten

dto

rem

em

be

rm

ore

of

info

rma

tion

tra

nsf

err

ed

at

the

be

gin

nin

go

fth

ee

xch

an

ge

(prim

ac

ye

ffe

ct)

an

dso

me

time

se

ven

mo

rea

bo

ut

wh

at

wa

str

an

s-fe

rre

dto

wa

rdth

ee

nd

of

the

exc

ha

ng

e(r

ec

en

cy

eff

ec

t).

Wh

at

we

ten

dn

ot

tore

me

mb

er

isth

ein

form

atio

nin

the

mid

dle

.(T

his

fea

ture

of

rec

all

wa

sh

um

oro

usly

de

mo

nst

rate

din

the

mo

vie

AFi

shC

alle

dW

an

da

.K

evi

nK

line

isre

pe

ate

dly

un

ab

leto

rem

em

be

rth

e

mid

dle

bit

o

fva

riou

sin

stru

ctio

ns

he

isg

ive

n.)

Prim

ac

ye

ffe

ct

ma

yb

ea

ug

-m

en

ted

by

an

ch

orin

g,

wh

ere

att

en

tion

all

oc

kin

go

nto

salie

nt

an

dvi

vid

fea

ture

sin

cre

ase

sth

eir

ch

an

ce

so

fb

ein

gre

me

mb

ere

d.

Prim

ac

ye

ffe

ct

for

pa

tien

tsc

an

resu

ltin

stro

ng

initi

ali

mp

ress

ion

s,c

rea

ting

an

ine

rtia

tha

tm

ay

req

uire

co

nsid

era

ble

wo

rkto

ove

rco

me

late

r.

Ord

er

eff

ec

tsm

ay

resu

ltin

sele

ctiv

ep

art

so

fin

form

atio

nb

ein

gre

me

mb

ere

d.P

rima

cy

eff

ec

tc

an

resu

ltin

stro

ng

lyp

ola

rize

dvi

ew

so

fp

atie

nts

at

the

ou

tse

tth

at

ca

nin

flu-

en

ce

sub

seq

ue

nt

de

cisi

on

ma

kin

g(s

ee

vis-

ce

ralb

ias)

.

Giv

en

rec

all

bia

ses,

we

sho

uld

ma

kee

ffo

rts

tore

co

rdp

ert

ine

nt

info

rma

tion

an

dre

lyle

sso

nm

em

ory

.W

esh

ou

ldu

nd

ers

tan

dth

at

pla

cin

gin

form

atio

n(e

spe

cia

llyif

itis

vivi

do

rc

ha

rge

d)

at

the

be

gin

nin

go

re

nd

of

exc

ha

ng

es

will

af-

fec

tits

rec

all.

This

ph

en

om

en

on

ma

yb

eu

sed

toa

dva

nta

ge

or

disa

dva

nta

ge

.

9

Ou

tco

me

bia

sC

ha

grin

fac

tor,

valu

eb

ias

The

ou

tco

me

bia

sre

flec

tsth

ete

nd

en

cy

toju

dg

eth

ed

ec

isio

nb

ein

gm

ad

eb

yits

like

lyo

utc

om

e.

We

ten

dto

pre

fer

de

cisi

on

sth

at

lea

dto

go

od

ou

tco

me

sth

an

tho

seth

at

lea

dto

ba

do

utc

om

es.

Va

lue

bia

sre

fers

toth

ete

nd

en

cy

of

pe

op

leto

exp

ress

ast

ron

ge

rlik

elih

oo

dfo

rw

ha

tth

ey

ho

pe

will

(or

will

no

t)h

ap

pe

nra

the

rth

an

wh

at

the

yb

e-

lieve

will

ha

pp

en

.W

ete

nd

tob

elie

veth

at

po

sitiv

ely

valu

ed

eve

nts

are

mo

relik

ely

toh

ap

pe

nth

an

ne

ga

tive

lyva

lue

de

ven

ts.

The

mo

reo

bje

ctiv

ee

vid

en

ce

ac

cu

mu

late

s,th

ew

ea

ker

the

valu

eb

ias

be

-c

om

es.

The

sein

tru

sion

so

fw

ha

tw

ew

an

t(a

ffe

ct)

rath

er

tha

nw

ha

tw

eb

elie

ve(c

og

niti

on

)c

an

co

mp

rom

ised

ec

isio

nm

aki

ng

.

Allo

win

gp

ers

on

alh

op

es

an

dd

esir

es

toe

nte

rc

linic

ald

ec

isio

nm

aki

ng

red

uc

es

ob

jec

tiv-

itya

nd

ma

ysig

nifi

ca

ntly

co

mp

rom

iseth

ep

roc

ess

.

Besid

es

be

ing

min

dfu

lof

this

ten

de

nc

y,p

hys

i-c

ian

ssh

ou

ldst

rive

too

bta

ino

bje

ctiv

ed

ata

.Th

em

ore

the

reis,

the

we

ake

rth

eb

ias.

1,38

,45

,48

50

Ove

rco

n-

fide

nc

eb

ias

Ove

rco

nfid

en

ce

ma

yb

ea

ne

ffo

rtto

ma

inta

ina

po

sitiv

ese

lf-im

ag

e,

an

dm

ay

pla

ya

role

inh

ind

sigh

tb

ias.

Itis

de

scrib

ed

as

self-

serv

ing

att

ribu

tion

bia

s.It

isa

da

ng

ero

us

pe

rso

na

lch

ara

cte

ristic

inm

ed

icin

e,

an

de

spe

cia

llyin

the

ED.

Ing

en

era

l,w

eu

sua

llyth

ink

we

kno

wm

ore

tha

nw

ed

o,

oft

en

with

ou

th

avi

ng

ga

the

red

suffi

cie

nt

info

rma

tion

,a

nd

ge

ne

rally

pla

ce

too

mu

ch

faith

ino

ur

ow

no

pin

ion

s.Th

ose

wh

oa

reo

verc

on

fide

nt

ten

dto

spe

nd

insu

ffic

ien

ttim

ea

cc

um

ula

ting

evi

-d

en

ce

an

dsy

nth

esiz

ing

itb

efo

rea

ctio

n.

The

ya

rem

ore

inc

line

dto

ac

to

nin

co

mp

lete

info

rma

tion

an

dh

un

ch

es.

Wh

en

ove

rco

nfid

en

tp

eo

ple

be

lieve

tha

tth

eir

invo

lve

me

nt

mig

ht

ha

vea

sign

ific

an

tim

-p

ac

to

no

utc

om

es

(wh

eth

er

ita

ctu

ally

do

es

or

no

t),

the

yte

nd

tob

e-

lieve

stro

ng

lyth

at

the

ou

tco

me

will

be

po

sitiv

e.

Thu

s,th

ey

disp

rop

or-

tion

ate

lyva

lue

the

irc

on

trib

utio

n.

Ove

rco

nfid

en

ce

ca

np

ote

ntia

teb

ad

lyw

itha

nc

ho

ring

an

da

vaila

bili

ty,

lea

din

gto

an

ove

rre

lian

ce

on

rea

dily

ava

ilab

le(r

ath

er

tha

nva

lua

ble

)in

form

atio

n.

Ove

rco

nfid

en

ce

ma

yre

sult

insig

nifi

ca

nt

er-

rors

of

bo

tho

miss

ion

an

dc

om

miss

ion

an

dre

sult

inu

nw

arr

an

ted

inte

rve

ntio

ns,

co

stly

de

lays

,o

rm

isse

dd

iag

no

ses.

Effo

rts

sho

uld

be

ma

de

toa

nsw

er

the

follo

win

g:

Ha

sin

telli

ge

nc

eg

ath

erin

gb

ee

nsy

ste

ma

tic?

Ho

wm

uc

his

rea

llykn

ow

n?

Ha

se

vid

en

ce

be

en

ga

the

red

ina

log

ica

lan

dth

oro

ug

hfa

shio

n,

an

dd

oe

sit

sup

po

rto

ur

est

ima

tes

an

dju

dg

me

nt?

Ha

sto

om

uc

hre

lian

ce

be

en

pla

ce

do

na

nc

ho

rs,

or

too

rea

dily

ava

ilab

lein

-fo

rma

tion

?

18,

51,

52

co

ntin

ue

d

1194C

roskerry

QU

AL

ITY

INC

LIN

ICA

LD

EC

ISION

MA

KIN

G




Playing theodds

Frequency gam-bling, law of av-erages, oddsjudgments

An odds judgment in the ED is the physicians opinion of the relativechances that a patient has a particular disease or not. It is clearlyinfluenced by the actual prevalence and incidence of the disease.Playing the odds refers to the process by which the physician, con-sciously or otherwise, decides that the patient does not have the dis-ease on the basis of an odds judgment; i.e., the decision has beenprimarily determined by inductive thinking (the physicians percep-tion of the odds), rather than by objective evidence that has ruledout the disease. Typically, this occurs before any workup of a patient,but may also occur in patients who have been worked up but forwhom the results remain equivocal. Again, influenced by his or heropinion regarding prevalence and incidence, the physician mayreach a decision that the patient does not have the disease. It isclear, too, that odds judgments will be influenced by availability,leading to fluctuating (subjective) opinions about prevalence and in-cidence.In the ED there are many conditions that present equivocally. The

signs and symptoms of an acute aortic dissection may be compara-ble in the early stages to those of constipation. However, benignconditions overwhelmingly outnumber the serious ones, and, moreoften than not, playing the odds will be a relatively effective strat-egy. Should the more rare condition be present, the failure to con-sider it could have a serious outcome. Use of the strategy probablyincreases under conditions of fatigue and/or circadian dysynchronic-ity.

Playing the odds clearly runs the risk of im-portant conditions being missed. It is anti-thetical to the ROWS strategy.

Although estimates of probability are an integralfeature of any decision-making process, EDphysicians should be aware that playing theodds should not be influential, especially in theinitial stages of decision making. At the time ofdisposition, if there is residual doubt and thediagnosis remains equivocal, it is importantthat physicians review the available evidenceand reflect on their thinking. This is particularlyimportant when they are fatigued.

12, 18

Posteriorprobabil-ity error

History repeats it-self

If a physician bases his or her estimate of the likelihood of disease onwhat has gone before, a posterior probability error may occur. Forexample, if a patient has had six visits to an ED with a headache inthe last year and on each occasion has been diagnosed as havingmigraine, to make the assumption that the patient has migraine onthe seventh visit is a posterior probability error. Assuming that the pre-vious diagnoses were all correct, the probability that this headache ismigraine is high, but there is also a possibility that the headache isdue to some other less benign cause such as a subarachnoid hemor-rhage. There is no reason why migraineurs should not get subarach-noid hemorrhages, and the symptoms and signs may be very similar.Every presentation of this patient to an ED requires a thorough assess-ment of the complaint of headache, and no assumptions should bemade that a particular diagnosis is present until the evidence justifiesit. There is also the possibility that previous visits have been misdiag-nosed, in which case the posterior probability error will result in thefurther propagation of a series of errors. For all patients, presentationat the ED mandates an appropriate history and physical exam andwhatever investigations are indicated. Patients with somatization dis-order are particularly vulnerable to posterior probability error. Makingposterior probability assumptions about likely diagnoses and perform-ing cursory examinations are fraught with error in the ED.

Posterior probability error may result in awrong diagnosis being perpetrated, or in anew diagnosis being missed.

Physicians should be alert to the dangers of bas-ing their clinical decisions on past decisions. Insituations involving repeat visits, they shouldmentally emphasize the need for objectivity inassessment of the patient, without consideringpast diagnoses. A helpful strategy is to ignoreold records, disregard any comments by otherphysicians or nurses about the patient, and fo-cus on the chief complaint and physical exambefore reviewing past medical history.

31, 56

ACAD EMERG MED November 2002, Vol. 9, No. 11 www.aemj.org 1195Pr

em

atu

rec

losu

reC

ou

ntin

gc

hic

k-e

ns

be

fore

the

ya

reh

atc

he

d

Ph

ysic

ian

sty

pic

ally

ge

ne

rate

seve

rald

iag

no

ses

ea

rlyin

the

ire

nc

ou

nte

rw

itha

clin

ica

lpro

ble

m.

Pre

ma

ture

clo

sure

oc

cu

rsw

he

no

ne

of

the

sed

iag

no

ses

isa

cc

ep

ted

be

fore

ith

as

be

en

fully

verifi

ed

.Th

ete

nd

en

cy

toa

pp

lyc

losu

reto

the

pro

ble

m-s

olv

ing

pro

ce

ssc

an

resu

ltfr

om

vivi

dp

rese

ntin

gfe

atu

res

tha

tm

ay

be

co

nvi

nc

ing

for

ap

art

icu

lar

dia

gn

o-

sis,

or

by

an

ch

orin

go

nto

salie

nt

fea

ture

se

arly

inth

ep

rese

nta

tion

.A

tta

ch

ing

ad

iag

no

sisto

ap

atie

nt

pro

vid

es

ac

on

ven

ien

t,sh

ort

-ha

nd

de

scrip

tion

(se

ed

iag

no

sism

om

en

tum

).It

ma

ya

lsore

flec

tso

me

lazi

-n

ess

of

tho

ug

ht

an

da

de

sire

toa

ch

ieve

co

mp

letio

n,

esp

ec

ially

un

-d

er

co

nd

itio

ns

of

fatig

ue

or

circ

ad

ian

dys

ync

hro

nic

ity.

Pre

ma

ture

clo

sure

ten

ds

tost

op

furt

he

rth

ink-

ing

.A

sfa

ra

sis

po

ssib

lein

the

circ

um

sta

nc

es,

ph

ysi-

cia

ns

sho

uld

kee

pa

no

pe

nm

ind

ab

ou

tth

ed

i-a

gn

ost

icp

oss

ibili

ties

ina

clin

ica

lca

se.

The

ysh

ou

ldb

ec

are

fult

ha

ta

wo

rkin

gd

iag

no

sisd

oe

sn

ot

pre

ma

ture

lyb

ec

om

eth

ed

efa

cto

dia

gn

osis

.A

bso

lute

verifi

ca

tion

of

the

hyp

oth

e-

sism

ay

be

un

att

ain

ab

le,

bu

tth

ed

iag

no

sism

ust

be

sub

jec

ted

tote

sts

of

ad

eq

ua

cy,

co

-h

ere

nc

e,

pa

rsim

on

y,a

nd

falsi

fica

tion

.

10,

17,

53

Psyc

h-o

ut

err

or

Ap

syc

h-o

ut

err

or

isa

ny

err

or

invo

lvin

gp

syc

hia

tric

pa

tien

ts.

The

ya

ree

s-p

ec

ially

vuln

era

ble

toe

rro

rin

the

ED,

an

dm

an

yo

fth

ee

rro

rsd

e-

scrib

ed

he

rea

rep

erv

asiv

ein

the

ma

na

ge

me

nt

of

psy

ch

iatr

icp

a-

tien

ts.

An

ove

rrid

ing

pro

ble

mis

tha

tp

syc

hia

tric

pa

tien

tsd

on

ot

fitth

e

mo

de

lty

pe

of

pa

tien

tth

at

the

EDlik

es

tose

e.

Fun

da

me

nta

latt

ri-b

utio

ne

rro

rre

sults

inju

dg

me

nta

lbe

ha

vio

ra

nd

the

pa

rad

oxi

ca

lvie

wth

at

the

pa

tien

tis

som

eh

ow

resp

on

sible

for

his

or

he

rc

on

diti

on

.C

rud

e

ne

ga

tive

rein

forc

ing

a

ttitu

de

so

fc

are

giv

ers

ma

ye

ven

ex-

ac

erb

ate

the

pa

tien

ts

co

nd

itio

n.

Co

un

tert

ran

sfe

ren

ce

ca

nre

sult

inp

oo

rtr

ea

tme

nt

of

seve

ralc

on

diti

on

s(s

ee

visc

era

lbia

s),

esp

ec

ially

of

pe

rso

na

lity

diso

rde

rs.

Sea

rch

satis

ficin

gc

an

lea

dto

the

sea

rch

be

ing

ca

lled

off

on

ce

ap

syc

hia

tric

dia

gn

osis

ha

sb

ee

nm

ad

ea

nd

co

mo

r-b

idm

ed

ica

lilln

ess

es

ma

yg

ou

nd

ete

cte

d;

the

reis

ah

isto

ricfa

ilure

of

EDs

tom

ed

ica

llyst

ab

ilize

psy

ch

iatr

icp

atie

nts

be

fore

disp

osit

ion

.A

lso,

the

reis

ate

nd

en

cy

tose

eb

eh

avi

ora

lab

no

rma

litie

sa

sp

syc

hia

tric

ino

rigin

;h

en

ce

,a

nu

mb

er

of

sign

ific

an

till

ne

sse

sth

at

are

ass

oc

iate

dw

ithb

eh

avi

ora

lch

an

ge

sm

ay

be

misd

iag

no

sed

as

psy

ch

iatr

icill

ne

ss.

This

ma

yb

ea

refle

ctio

no

fp

urs

uin

gth

eo

bvi

ou

s(S

utt

on

ssli

p)

or

an

-c

ho

ring

on

tob

eh

avi

or

an

do

verlo

oki

ng

the

po

ssib

ility

of

un

de

rlyin

gm

ed

ica

lilln

ess

.Th

ere

ma

yb

efu

rth

er

pro

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achieving quality in clinical decision making: cognitive strategies and detection of bias

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