Laboratory Test Utilization: The Laboratory Test Utilization: The Good, the Bad and the OverusedGood, the Bad and the OverusedLaboratory Test Utilization: The Laboratory Test Utilization: The Good, the Bad and the OverusedGood, the Bad and the Overused

Tim Hamill, MDTim Hamill, MD

Director, UCSF Clinical LaboratoriesDirector, UCSF Clinical Laboratories

Tim Hamill, MDTim Hamill, MD

Director, UCSF Clinical LaboratoriesDirector, UCSF Clinical Laboratories

The Good, The Bad & The UglyThe Good, The Bad & The UglyThe Good, The Bad & The UglyThe Good, The Bad & The Ugly• A ‘Good’ test:A ‘Good’ test:

• Provides information that is useful in patient Provides information that is useful in patient management decisionsmanagement decisions

• Screening: High sensitivity & NPVScreening: High sensitivity & NPV

• Diagnosis: High specificity & PPVDiagnosis: High specificity & PPV

• A ‘Bad’ test:A ‘Bad’ test:• Uses resources but fails to provide information Uses resources but fails to provide information

useful in patient management decisionsuseful in patient management decisions

• The ‘Ugly’ test: The ‘Ugly’ test: • Uses resources and provides information that is Uses resources and provides information that is

misleading or irrelevantmisleading or irrelevant

• A ‘Good’ test:A ‘Good’ test:• Provides information that is useful in patient Provides information that is useful in patient

management decisionsmanagement decisions• Screening: High sensitivity & NPVScreening: High sensitivity & NPV

• Diagnosis: High specificity & PPVDiagnosis: High specificity & PPV

• A ‘Bad’ test:A ‘Bad’ test:• Uses resources but fails to provide information Uses resources but fails to provide information

useful in patient management decisionsuseful in patient management decisions

• The ‘Ugly’ test: The ‘Ugly’ test: • Uses resources and provides information that is Uses resources and provides information that is

misleading or irrelevantmisleading or irrelevant

UCSF Test UtilizationUCSF Test UtilizationUCSF Test UtilizationUCSF Test Utilization

• In 2009 UCSF performed an average of In 2009 UCSF performed an average of 486,000 tests per month 486,000 tests per month • Annual test volume 5.8MAnnual test volume 5.8M

• Inpatient tests : Outpatient tests = 1:1Inpatient tests : Outpatient tests = 1:1• Inpatients: 15 tests/dayInpatients: 15 tests/day• Outpatients: 4 tests per visitOutpatients: 4 tests per visit

• Stat : Routine = 1:3 overall (1:1 inpatient)Stat : Routine = 1:3 overall (1:1 inpatient)

• In 2009 UCSF performed an average of In 2009 UCSF performed an average of 486,000 tests per month 486,000 tests per month • Annual test volume 5.8MAnnual test volume 5.8M

• Inpatient tests : Outpatient tests = 1:1Inpatient tests : Outpatient tests = 1:1• Inpatients: 15 tests/dayInpatients: 15 tests/day• Outpatients: 4 tests per visitOutpatients: 4 tests per visit

• Stat : Routine = 1:3 overall (1:1 inpatient)Stat : Routine = 1:3 overall (1:1 inpatient)

UHC Comparison DataUHC Comparison DataUHC Comparison DataUHC Comparison Data

UCSF Ranks #1 in Tests Used per Patient UCSF Ranks #1 in Tests Used per Patient DischargedDischarged

Causes of Test Overutilization*Causes of Test Overutilization*Causes of Test Overutilization*Causes of Test Overutilization*• Ordering test panels rather than ala carte’Ordering test panels rather than ala carte’

• Ordering tests as groupsOrdering tests as groups

• Repetitive test orders (esp. normal results)Repetitive test orders (esp. normal results)• Incomplete understanding re: impact of low pre-test probabilityIncomplete understanding re: impact of low pre-test probability• Poor understanding of the consequences of overutilizationPoor understanding of the consequences of overutilization• Patient pressurePatient pressure• Defensive testingDefensive testing• Perverse financial incentives (more tests = more revenue)Perverse financial incentives (more tests = more revenue)

* * Astion ML. 2006. Interventions that improve laboratory utilization: from gentle guidance to strong restrictions. Astion ML. 2006. Interventions that improve laboratory utilization: from gentle guidance to strong restrictions.

Laboratory Errors and Patient Safety. 2(4):8-9Laboratory Errors and Patient Safety. 2(4):8-9

• Ordering test panels rather than ala carte’Ordering test panels rather than ala carte’• Ordering tests as groupsOrdering tests as groups

• Repetitive test orders (esp. normal results)Repetitive test orders (esp. normal results)• Incomplete understanding re: impact of low pre-test probabilityIncomplete understanding re: impact of low pre-test probability• Poor understanding of the consequences of overutilizationPoor understanding of the consequences of overutilization• Patient pressurePatient pressure• Defensive testingDefensive testing• Perverse financial incentives (more tests = more revenue)Perverse financial incentives (more tests = more revenue)

* * Astion ML. 2006. Interventions that improve laboratory utilization: from gentle guidance to strong restrictions. Astion ML. 2006. Interventions that improve laboratory utilization: from gentle guidance to strong restrictions.

Laboratory Errors and Patient Safety. 2(4):8-9Laboratory Errors and Patient Safety. 2(4):8-9

The Origin of Test PanelsThe Origin of Test PanelsThe Origin of Test PanelsThe Origin of Test Panels

• Technicon SMAC (1974):Technicon SMAC (1974):

• Sequential Multiple Analyzer with Sequential Multiple Analyzer with ComputerComputer

• Technicon SMAC (1974):Technicon SMAC (1974):

• Sequential Multiple Analyzer with Sequential Multiple Analyzer with ComputerComputer

Modern ‘Discreet’ AnalyzersModern ‘Discreet’ AnalyzersModern ‘Discreet’ AnalyzersModern ‘Discreet’ Analyzers

Ordering Test PanelsOrdering Test PanelsOrdering Test PanelsOrdering Test Panels• A study of orders for repeat electrolyte panels indicated that 10% were A study of orders for repeat electrolyte panels indicated that 10% were

medically unnecessary and in 65% of cases a single test could have medically unnecessary and in 65% of cases a single test could have substituted for the entire panelsubstituted for the entire panel. . (Baigelman et al, Intensive Care Med, 11(6) 1985)(Baigelman et al, Intensive Care Med, 11(6) 1985)

• A study of orders for repeat electrolyte panels indicated that 10% were A study of orders for repeat electrolyte panels indicated that 10% were medically unnecessary and in 65% of cases a single test could have medically unnecessary and in 65% of cases a single test could have substituted for the entire panelsubstituted for the entire panel. . (Baigelman et al, Intensive Care Med, 11(6) 1985)(Baigelman et al, Intensive Care Med, 11(6) 1985)

Impact of Electrolyte ReductionImpact of Electrolyte ReductionImpact of Electrolyte ReductionImpact of Electrolyte Reduction

Ordering Tests in GroupsOrdering Tests in GroupsOrdering Tests in GroupsOrdering Tests in Groups• Redundant tests:Redundant tests:

• BUN & CreatinineBUN & Creatinine• Troponin & CK-MBTroponin & CK-MB• ALT & ASTALT & AST

• Tests that just seem to trip off the tongue:Tests that just seem to trip off the tongue:• Calcium, magnesium, phosphorusCalcium, magnesium, phosphorus• PT & PTTPT & PTT• T3, T4 & TSHT3, T4 & TSH

• Redundant tests:Redundant tests:• BUN & CreatinineBUN & Creatinine• Troponin & CK-MBTroponin & CK-MB• ALT & ASTALT & AST

• Tests that just seem to trip off the tongue:Tests that just seem to trip off the tongue:• Calcium, magnesium, phosphorusCalcium, magnesium, phosphorus• PT & PTTPT & PTT• T3, T4 & TSHT3, T4 & TSH

Separating BUN & CreatinineSeparating BUN & CreatinineSeparating BUN & CreatinineSeparating BUN & Creatinine

Repetitive TestingRepetitive TestingRepetitive TestingRepetitive Testing

• A study of the impact on serum potassium A study of the impact on serum potassium orders using a simple algorithm based on orders using a simple algorithm based on prior tests being normal or abnormal could prior tests being normal or abnormal could reduce potassium testing by 34% reduce potassium testing by 34% (Schubart et al, (Schubart et al,

MEDINFO 2001)MEDINFO 2001)

• Renal function: BUN, CreatinineRenal function: BUN, Creatinine• CBC & CBC w/differentialCBC & CBC w/differential

• A study of the impact on serum potassium A study of the impact on serum potassium orders using a simple algorithm based on orders using a simple algorithm based on prior tests being normal or abnormal could prior tests being normal or abnormal could reduce potassium testing by 34% reduce potassium testing by 34% (Schubart et al, (Schubart et al,

MEDINFO 2001)MEDINFO 2001)

• Renal function: BUN, CreatinineRenal function: BUN, Creatinine• CBC & CBC w/differentialCBC & CBC w/differential

Problems with Test Over-Problems with Test Over-utilizationutilization

Problems with Test Over-Problems with Test Over-utilizationutilization

• Patient issuesPatient issues• Pain & morbidity from repeated venipuncturesPain & morbidity from repeated venipunctures• Iatrogenic anemiaIatrogenic anemia

• Medical issuesMedical issues• Follow-up on clinically irrelevant abnormalsFollow-up on clinically irrelevant abnormals• Tracking just the ‘numbers’ instead of the entire clinical Tracking just the ‘numbers’ instead of the entire clinical

picturepicture• Instituting inappropriate therapiesInstituting inappropriate therapies

• Economic & Environmental issuesEconomic & Environmental issues• Lack of reimbursement for inpatient testingLack of reimbursement for inpatient testing• Biohazardous waste generationBiohazardous waste generation

• Patient issuesPatient issues• Pain & morbidity from repeated venipuncturesPain & morbidity from repeated venipunctures• Iatrogenic anemiaIatrogenic anemia

• Medical issuesMedical issues• Follow-up on clinically irrelevant abnormalsFollow-up on clinically irrelevant abnormals• Tracking just the ‘numbers’ instead of the entire clinical Tracking just the ‘numbers’ instead of the entire clinical

picturepicture• Instituting inappropriate therapiesInstituting inappropriate therapies

• Economic & Environmental issuesEconomic & Environmental issues• Lack of reimbursement for inpatient testingLack of reimbursement for inpatient testing• Biohazardous waste generationBiohazardous waste generation

Studies on iatrogenic anemiaStudies on iatrogenic anemiaStudies on iatrogenic anemiaStudies on iatrogenic anemia

• Smoller et al NEJM 314, 1986:Smoller et al NEJM 314, 1986:• General wards: 1.1 draws/d, Ave. 12.4 mL/d, Total General wards: 1.1 draws/d, Ave. 12.4 mL/d, Total

175 mL for hospitalization175 mL for hospitalization• ICU: 3.4 draws/d, Ave. 41.5 mL/d, Total 762.2mLICU: 3.4 draws/d, Ave. 41.5 mL/d, Total 762.2mL• ICU w/Art line: 4.0 draws/d, Total 944 mLICU w/Art line: 4.0 draws/d, Total 944 mL

• Low et al Chest 108(1) Jul, 1995:Low et al Chest 108(1) Jul, 1995:• Presence of Art. Line in ICU patients increased Presence of Art. Line in ICU patients increased

blood volume loss from phlebotomy by 44%blood volume loss from phlebotomy by 44%

• Smoller et al NEJM 314, 1986:Smoller et al NEJM 314, 1986:• General wards: 1.1 draws/d, Ave. 12.4 mL/d, Total General wards: 1.1 draws/d, Ave. 12.4 mL/d, Total

175 mL for hospitalization175 mL for hospitalization• ICU: 3.4 draws/d, Ave. 41.5 mL/d, Total 762.2mLICU: 3.4 draws/d, Ave. 41.5 mL/d, Total 762.2mL• ICU w/Art line: 4.0 draws/d, Total 944 mLICU w/Art line: 4.0 draws/d, Total 944 mL

• Low et al Chest 108(1) Jul, 1995:Low et al Chest 108(1) Jul, 1995:• Presence of Art. Line in ICU patients increased Presence of Art. Line in ICU patients increased

blood volume loss from phlebotomy by 44%blood volume loss from phlebotomy by 44%

Impacts of Iatrogenic anemiaImpacts of Iatrogenic anemiaImpacts of Iatrogenic anemiaImpacts of Iatrogenic anemia

• Critically ill patients may not have the bone Critically ill patients may not have the bone marrow reserve or erythropoietin drive to marrow reserve or erythropoietin drive to compensate for iatrogenic blood loss.compensate for iatrogenic blood loss.

• Transfusion to correct for this anemia has been Transfusion to correct for this anemia has been shown to negatively impact long term survivalshown to negatively impact long term survival

• Other risks of phlebotomy:Other risks of phlebotomy:• Nerve damage, arterial damage, venous sclerosis, Nerve damage, arterial damage, venous sclerosis,

infectioninfection

• Critically ill patients may not have the bone Critically ill patients may not have the bone marrow reserve or erythropoietin drive to marrow reserve or erythropoietin drive to compensate for iatrogenic blood loss.compensate for iatrogenic blood loss.

• Transfusion to correct for this anemia has been Transfusion to correct for this anemia has been shown to negatively impact long term survivalshown to negatively impact long term survival

• Other risks of phlebotomy:Other risks of phlebotomy:• Nerve damage, arterial damage, venous sclerosis, Nerve damage, arterial damage, venous sclerosis,

infectioninfection

Irrelevant ‘abnormals’Irrelevant ‘abnormals’Irrelevant ‘abnormals’Irrelevant ‘abnormals’• Virtually all quantitative laboratory test ‘normal ranges’ are based on the mean +/- 2 Virtually all quantitative laboratory test ‘normal ranges’ are based on the mean +/- 2

SD (95% confidence interval) for a subject populationSD (95% confidence interval) for a subject population

• 5% of normal patients will have values that lie outside this 5% of normal patients will have values that lie outside this range (magnified for ill patients)range (magnified for ill patients)

• Virtually all quantitative laboratory test ‘normal ranges’ are based on the mean +/- 2 Virtually all quantitative laboratory test ‘normal ranges’ are based on the mean +/- 2 SD (95% confidence interval) for a subject populationSD (95% confidence interval) for a subject population

• 5% of normal patients will have values that lie outside this 5% of normal patients will have values that lie outside this range (magnified for ill patients)range (magnified for ill patients)

2.5%2.5%

Irrelevant ‘abnormals’Irrelevant ‘abnormals’Irrelevant ‘abnormals’Irrelevant ‘abnormals’

• If a patient has 10 tests ordered, each with a If a patient has 10 tests ordered, each with a 5% chance that the test may have a result 5% chance that the test may have a result outside the normal range. Then there is a outside the normal range. Then there is a 50% chance that at least one test will have 50% chance that at least one test will have an ‘abnormal’ resultan ‘abnormal’ result

• This is especially true with ordering This is especially true with ordering chemistry ‘panels’chemistry ‘panels’

• If a patient has 10 tests ordered, each with a If a patient has 10 tests ordered, each with a 5% chance that the test may have a result 5% chance that the test may have a result outside the normal range. Then there is a outside the normal range. Then there is a 50% chance that at least one test will have 50% chance that at least one test will have an ‘abnormal’ resultan ‘abnormal’ result

• This is especially true with ordering This is especially true with ordering chemistry ‘panels’chemistry ‘panels’

Economics & EnvironmentEconomics & EnvironmentEconomics & EnvironmentEconomics & Environment

• The vast majority of inpatient care is covered by The vast majority of inpatient care is covered by DRG or per diem paymentsDRG or per diem payments• Laboratory tests are not individually reimbursed and Laboratory tests are not individually reimbursed and

merely represent cost against the what the hospital is merely represent cost against the what the hospital is paidpaid

• The 3 UCSF Clinical Laboratories generate The 3 UCSF Clinical Laboratories generate approx. 11,500 lbs of biowaste per monthapprox. 11,500 lbs of biowaste per month• Cost to incinerate this waste is approx. $88K per yearCost to incinerate this waste is approx. $88K per year

• The vast majority of inpatient care is covered by The vast majority of inpatient care is covered by DRG or per diem paymentsDRG or per diem payments• Laboratory tests are not individually reimbursed and Laboratory tests are not individually reimbursed and

merely represent cost against the what the hospital is merely represent cost against the what the hospital is paidpaid

• The 3 UCSF Clinical Laboratories generate The 3 UCSF Clinical Laboratories generate approx. 11,500 lbs of biowaste per monthapprox. 11,500 lbs of biowaste per month• Cost to incinerate this waste is approx. $88K per yearCost to incinerate this waste is approx. $88K per year

The Solution?The Solution?The Solution?The Solution?

• Approaches that have been triedApproaches that have been tried• Place limits on housestaff ordersPlace limits on housestaff orders• Provide information on test costsProvide information on test costs• Requisition designRequisition design• EMR warnings and remindersEMR warnings and reminders• EducationEducation• IncentivesIncentives

• Approaches that have been triedApproaches that have been tried• Place limits on housestaff ordersPlace limits on housestaff orders• Provide information on test costsProvide information on test costs• Requisition designRequisition design• EMR warnings and remindersEMR warnings and reminders• EducationEducation• IncentivesIncentives

Factors that Impact Laboratory Factors that Impact Laboratory Test Results & InterpretationTest Results & Interpretation

Factors that Impact Laboratory Factors that Impact Laboratory Test Results & InterpretationTest Results & Interpretation

• Pre-analytic issuesPre-analytic issues• Diagnostic testing issuesDiagnostic testing issues

• Pre-test probabilityPre-test probability

• Appropriateness of test in your patientAppropriateness of test in your patient

• Impact of the test result on care decisionsImpact of the test result on care decisions

• Chasing ‘diagnostic certainty’Chasing ‘diagnostic certainty’

• Impact of other disorders, therapy on resultsImpact of other disorders, therapy on results

• Monitoring issuesMonitoring issues• Which test is going to be used?Which test is going to be used?

• How fast does the test change?How fast does the test change?

• What is the impact of monitoring on clinical care?What is the impact of monitoring on clinical care?

• Pre-analytic issuesPre-analytic issues• Diagnostic testing issuesDiagnostic testing issues

• Pre-test probabilityPre-test probability

• Appropriateness of test in your patientAppropriateness of test in your patient

• Impact of the test result on care decisionsImpact of the test result on care decisions

• Chasing ‘diagnostic certainty’Chasing ‘diagnostic certainty’

• Impact of other disorders, therapy on resultsImpact of other disorders, therapy on results

• Monitoring issuesMonitoring issues• Which test is going to be used?Which test is going to be used?

• How fast does the test change?How fast does the test change?

• What is the impact of monitoring on clinical care?What is the impact of monitoring on clinical care?

Factors Impacting Laboratory Factors Impacting Laboratory TestsTests

Factors Impacting Laboratory Factors Impacting Laboratory TestsTests

Pre-analytic Test IssuesPre-analytic Test IssuesPre-analytic Test IssuesPre-analytic Test Issues

• Time of sample collectionTime of sample collection

• Proper collection techniqueProper collection technique

• Proper labelingProper labeling

• Proper storage and transportProper storage and transport

• Time of sample collectionTime of sample collection

• Proper collection techniqueProper collection technique

• Proper labelingProper labeling

• Proper storage and transportProper storage and transport

Time of CollectionTime of CollectionTime of CollectionTime of Collection

• Relative to time of management decisionsRelative to time of management decisions

• Relative to therapyRelative to therapy• Platelet counts after transfusionPlatelet counts after transfusion• Drug levels: relative to doseDrug levels: relative to dose

• Peak: PO vs. IVPeak: PO vs. IV

• TroughTrough

• Relative to time of dayRelative to time of day• CortisolCortisol

• Relative to time of management decisionsRelative to time of management decisions

• Relative to therapyRelative to therapy• Platelet counts after transfusionPlatelet counts after transfusion• Drug levels: relative to doseDrug levels: relative to dose

• Peak: PO vs. IVPeak: PO vs. IV

• TroughTrough

• Relative to time of dayRelative to time of day• CortisolCortisol

Proper Collection TechniqueProper Collection TechniqueProper Collection TechniqueProper Collection Technique

• Prolonged use of tourniquetProlonged use of tourniquet

• IV’s and line drawsIV’s and line draws

• Order of collectionOrder of collection• Trace metal (Royal blue), Blood culturesTrace metal (Royal blue), Blood cultures• Blue; Gold/Red; Green; PurpleBlue; Gold/Red; Green; Purple

• Proper fillingProper filling

• Proper mixingProper mixing

• Special needsSpecial needs

• Prolonged use of tourniquetProlonged use of tourniquet

• IV’s and line drawsIV’s and line draws

• Order of collectionOrder of collection• Trace metal (Royal blue), Blood culturesTrace metal (Royal blue), Blood cultures• Blue; Gold/Red; Green; PurpleBlue; Gold/Red; Green; Purple

• Proper fillingProper filling

• Proper mixingProper mixing

• Special needsSpecial needs

Proper LabelingProper LabelingProper LabelingProper Labeling

• The person who collects a sample should The person who collects a sample should label itlabel it

• Double check the label before submittingDouble check the label before submitting

• Special Blood Bank requirementsSpecial Blood Bank requirements• Check specimenCheck specimen

• Body fluidsBody fluids

• Lab policies on handling unlabeled and Lab policies on handling unlabeled and mislabeled samplesmislabeled samples

• The person who collects a sample should The person who collects a sample should label itlabel it

• Double check the label before submittingDouble check the label before submitting

• Special Blood Bank requirementsSpecial Blood Bank requirements• Check specimenCheck specimen

• Body fluidsBody fluids

• Lab policies on handling unlabeled and Lab policies on handling unlabeled and mislabeled samplesmislabeled samples

Proper Storage & TransportProper Storage & TransportProper Storage & TransportProper Storage & Transport

• Refrigeration vs. Room temperatureRefrigeration vs. Room temperature

• Protection from lightProtection from light

• Transport to the labTransport to the lab• Effects of cellular metabolismEffects of cellular metabolism

• Blood gas samplesBlood gas samples

• Serum chemistriesSerum chemistries

• Pneumatic tube considerationsPneumatic tube considerations

• Refrigeration vs. Room temperatureRefrigeration vs. Room temperature

• Protection from lightProtection from light

• Transport to the labTransport to the lab• Effects of cellular metabolismEffects of cellular metabolism

• Blood gas samplesBlood gas samples

• Serum chemistriesSerum chemistries

• Pneumatic tube considerationsPneumatic tube considerations

What is the effect of Pre-test What is the effect of Pre-test probability?probability?

What is the effect of Pre-test What is the effect of Pre-test probability?probability?

• The pretestThe pretest probability of disease is critically probability of disease is critically important to test orderingimportant to test ordering• If the disorder has a low pretest probability then even a If the disorder has a low pretest probability then even a

very sensitive and specific test may have little clinical very sensitive and specific test may have little clinical utilityutility

• If the pretest probability is very high tests may not If the pretest probability is very high tests may not provide much (if any) additional ‘certainty’ of the provide much (if any) additional ‘certainty’ of the diagnosisdiagnosis

• The pretestThe pretest probability of disease is critically probability of disease is critically important to test orderingimportant to test ordering• If the disorder has a low pretest probability then even a If the disorder has a low pretest probability then even a

very sensitive and specific test may have little clinical very sensitive and specific test may have little clinical utilityutility

• If the pretest probability is very high tests may not If the pretest probability is very high tests may not provide much (if any) additional ‘certainty’ of the provide much (if any) additional ‘certainty’ of the diagnosisdiagnosis

Low pretest probability exampleLow pretest probability exampleLow pretest probability exampleLow pretest probability example• You are thinking of ordering a test that is 95% sensitive and specificYou are thinking of ordering a test that is 95% sensitive and specific• The pretest probability that the disorder is present is, however, only 10% in The pretest probability that the disorder is present is, however, only 10% in

your patientyour patient• Positive predictive value: 68%Positive predictive value: 68%• Negative predictive value: 99% Negative predictive value: 99%

• only represents a 9% increase in certainty over the pretest probabilityonly represents a 9% increase in certainty over the pretest probability

• At a pre-test probability of 1% the PPV is only 16% and the NPV is 100%At a pre-test probability of 1% the PPV is only 16% and the NPV is 100%

• You are thinking of ordering a test that is 95% sensitive and specificYou are thinking of ordering a test that is 95% sensitive and specific• The pretest probability that the disorder is present is, however, only 10% in The pretest probability that the disorder is present is, however, only 10% in

your patientyour patient• Positive predictive value: 68%Positive predictive value: 68%• Negative predictive value: 99% Negative predictive value: 99%

• only represents a 9% increase in certainty over the pretest probabilityonly represents a 9% increase in certainty over the pretest probability

• At a pre-test probability of 1% the PPV is only 16% and the NPV is 100%At a pre-test probability of 1% the PPV is only 16% and the NPV is 100%

High pretest probabilityHigh pretest probabilityHigh pretest probabilityHigh pretest probability

• The same theoretic test (95% sensitive and The same theoretic test (95% sensitive and 95% specific) but in a patient with a 90% 95% specific) but in a patient with a 90% likelihood of having the disorder:likelihood of having the disorder:

• Positive predictive value: 99% (9% incr.)Positive predictive value: 99% (9% incr.)• Negative predictive value: 68%Negative predictive value: 68%

• The same theoretic test (95% sensitive and The same theoretic test (95% sensitive and 95% specific) but in a patient with a 90% 95% specific) but in a patient with a 90% likelihood of having the disorder:likelihood of having the disorder:

• Positive predictive value: 99% (9% incr.)Positive predictive value: 99% (9% incr.)• Negative predictive value: 68%Negative predictive value: 68%

When do tests add the most When do tests add the most information?information?

When do tests add the most When do tests add the most information?information?

• When the pretest probability is in the range When the pretest probability is in the range of 30-70%of 30-70%

• At a pretest probability of 50%, a test that is At a pretest probability of 50%, a test that is 95% sensitive and specific yields:95% sensitive and specific yields:• Positive predictive value: 95% Positive predictive value: 95% • Negative predictive value: 95%Negative predictive value: 95%

• When the pretest probability is in the range When the pretest probability is in the range of 30-70%of 30-70%

• At a pretest probability of 50%, a test that is At a pretest probability of 50%, a test that is 95% sensitive and specific yields:95% sensitive and specific yields:• Positive predictive value: 95% Positive predictive value: 95% • Negative predictive value: 95%Negative predictive value: 95%

Is the test appropriate for your Is the test appropriate for your patient?patient?

Is the test appropriate for your Is the test appropriate for your patient?patient?

• How does the patient’s diagnosis impact the test?How does the patient’s diagnosis impact the test?• VTE and Protein C/S levelsVTE and Protein C/S levels

• How does the patient’s treatment impact the test?How does the patient’s treatment impact the test?• Galactose or Maltose containing medications and Galactose or Maltose containing medications and

POCT Glucose testingPOCT Glucose testing

• D-dimer in a surgical patientD-dimer in a surgical patient

• How do other disorders impact the test?How do other disorders impact the test?• HgbA1c and shortened red cell lifespanHgbA1c and shortened red cell lifespan

• How does the patient’s diagnosis impact the test?How does the patient’s diagnosis impact the test?• VTE and Protein C/S levelsVTE and Protein C/S levels

• How does the patient’s treatment impact the test?How does the patient’s treatment impact the test?• Galactose or Maltose containing medications and Galactose or Maltose containing medications and

POCT Glucose testingPOCT Glucose testing

• D-dimer in a surgical patientD-dimer in a surgical patient

• How do other disorders impact the test?How do other disorders impact the test?• HgbA1c and shortened red cell lifespanHgbA1c and shortened red cell lifespan

Impact of the test on patient care Impact of the test on patient care decisions?decisions?

Impact of the test on patient care Impact of the test on patient care decisions?decisions?

• Ask yourself….’What will I do if the test is Ask yourself….’What will I do if the test is negative/normal vs. positive/abnormal’ if the negative/normal vs. positive/abnormal’ if the answer is essentially the same for both then the answer is essentially the same for both then the test has little utilitytest has little utility• E.g. Haptoglobin in anemiaE.g. Haptoglobin in anemia

• Will the result be available before the patient is Will the result be available before the patient is discharged?discharged?

• Chasing diagnostic ‘certainty’Chasing diagnostic ‘certainty’• How much information is needed before a treatment How much information is needed before a treatment

is initiated or withheld?is initiated or withheld?

• Ask yourself….’What will I do if the test is Ask yourself….’What will I do if the test is negative/normal vs. positive/abnormal’ if the negative/normal vs. positive/abnormal’ if the answer is essentially the same for both then the answer is essentially the same for both then the test has little utilitytest has little utility• E.g. Haptoglobin in anemiaE.g. Haptoglobin in anemia

• Will the result be available before the patient is Will the result be available before the patient is discharged?discharged?

• Chasing diagnostic ‘certainty’Chasing diagnostic ‘certainty’• How much information is needed before a treatment How much information is needed before a treatment

is initiated or withheld?is initiated or withheld?

Questions to ask about tests used Questions to ask about tests used to monitor a patientto monitor a patient

Questions to ask about tests used Questions to ask about tests used to monitor a patientto monitor a patient

• How fast do I expect the test to change? How fast do I expect the test to change? • What is the best monitoring test for the disorder in What is the best monitoring test for the disorder in

question?question?• Is more than one test needed?Is more than one test needed?• How much change would trigger a therapeutic How much change would trigger a therapeutic

intervention?intervention?• Once an intervention is made is monitoring still Once an intervention is made is monitoring still

needed? With the same test? At the same needed? With the same test? At the same frequency?frequency?

• How fast do I expect the test to change? How fast do I expect the test to change? • What is the best monitoring test for the disorder in What is the best monitoring test for the disorder in

question?question?• Is more than one test needed?Is more than one test needed?• How much change would trigger a therapeutic How much change would trigger a therapeutic

intervention?intervention?• Once an intervention is made is monitoring still Once an intervention is made is monitoring still

needed? With the same test? At the same needed? With the same test? At the same frequency?frequency?

How fast do tests change?How fast do tests change?How fast do tests change?How fast do tests change?• While many test results can change rapidly in an While many test results can change rapidly in an

individual there are other tests which may only individual there are other tests which may only change slowly or not at all over timechange slowly or not at all over time• Positive serologic studiesPositive serologic studies

• Enzyme levels: AST TEnzyme levels: AST T1/21/2 = 17 hr, ALT T = 17 hr, ALT T1/21/2 = 48 hr, Alk = 48 hr, Alk Phos TPhos T1/21/2 = 7 d,, GGT T = 7 d,, GGT T1/21/2 = 9 d (28 d in hepatic Dz) = 9 d (28 d in hepatic Dz)

• D-dimersD-dimers

• WBC differential (if no change in WBC)WBC differential (if no change in WBC)

• Understanding how rapidly a given analyte may Understanding how rapidly a given analyte may change is important to selecting how often it change is important to selecting how often it should be orderedshould be ordered

• While many test results can change rapidly in an While many test results can change rapidly in an individual there are other tests which may only individual there are other tests which may only change slowly or not at all over timechange slowly or not at all over time• Positive serologic studiesPositive serologic studies

• Enzyme levels: AST TEnzyme levels: AST T1/21/2 = 17 hr, ALT T = 17 hr, ALT T1/21/2 = 48 hr, Alk = 48 hr, Alk Phos TPhos T1/21/2 = 7 d,, GGT T = 7 d,, GGT T1/21/2 = 9 d (28 d in hepatic Dz) = 9 d (28 d in hepatic Dz)

• D-dimersD-dimers

• WBC differential (if no change in WBC)WBC differential (if no change in WBC)

• Understanding how rapidly a given analyte may Understanding how rapidly a given analyte may change is important to selecting how often it change is important to selecting how often it should be orderedshould be ordered

Laboratory ManualLaboratory ManualLaboratory ManualLaboratory Manual

• The UCSF Clinical Laboratories maintain an on-The UCSF Clinical Laboratories maintain an on-line laboratory manual that is constantly updatedline laboratory manual that is constantly updated• http://labmed.ucsf.edu/labman/http://labmed.ucsf.edu/labman/

• It has important information about:It has important information about:• Sample type and amount, incl. minimumsSample type and amount, incl. minimums

• Test availability and turnaround timeTest availability and turnaround time

• Patient preparation, collection instructions and sample Patient preparation, collection instructions and sample handlinghandling

• Test utilization tipsTest utilization tips

• The UCSF Clinical Laboratories maintain an on-The UCSF Clinical Laboratories maintain an on-line laboratory manual that is constantly updatedline laboratory manual that is constantly updated• http://labmed.ucsf.edu/labman/http://labmed.ucsf.edu/labman/

• It has important information about:It has important information about:• Sample type and amount, incl. minimumsSample type and amount, incl. minimums

• Test availability and turnaround timeTest availability and turnaround time

• Patient preparation, collection instructions and sample Patient preparation, collection instructions and sample handlinghandling

• Test utilization tipsTest utilization tips