12673256

INTEGRATIVE LITERATURE REVIEWS AND META-ANALYSES

Postoperative pain assessment tools in day surgery: literature review

Anne Marie Coll BA MSc PhD PGCEd RGN

Research Fellow, Research Unit, School of Care Sciences, University of Glamorgan, Pontypridd, Mid Glamorgan, UK

Jamal R.M. Ameen BSc MSc PhD PGCEd

Senior Lecturer, Research Unit, School of Care Sciences, University of Glamorgan, Pontypridd, Mid Glamorgan, UK

Donna Mead MSc PhD RGN RCNT RNT

Professor and Head of School, Research Unit, School of Care Sciences, University of Glamorgan, Pontypridd, Mid Glamorgan,

UK

Submitted for publication 12 January 2003

Accepted for publication 14 November 2003

Correspondence:

Anne Marie Coll,

Research Unit,

School of Care Sciences,

University of Glamorgan,

Pontypridd,

Mid Glamorgan CF37 1DL,

UK.

E-mail: [email protected]

COLL A.M. , AMEEN J.R.M. & MEAD D. (2004)COLL A.M., AMEEN J.R.M. & MEAD D. (2004) Journal of Advanced Nursing

46(2), 124–133

Postoperative pain assessment tools in day surgery: literature review

Background. Postoperative pain is an expected phenomenon. However, its passage

beyond acceptable limits is a common and costly experience. This is particularly the

case in day surgery, partly because of the increasing demand to reduce waiting lists

for elective surgery, and partly because of lack of knowledge about patients’

experiences of postoperative pain and relevant published research. The latter is

mainly concerned with different interpretations of the phenomenon of pain that

appear to have led to a variety of often inappropriate pain measurement tools.

Aim. This paper critically reviews some of the available objective and subjective

measures of pain and establishes the suitability of a Visual Analogue Scale (VAS) for

measuring the intensity of pain after day surgery.

Method. Nursing and health care papers published since 1983 were sought using

the keywords: postoperative pain, day surgery, ambulatory surgery, rating scales,

VAS, severity, assessment, tool, nursing, validity, sensitivity, reliability and their

various combinations. The databases used were Medline, CINAHL, Nursing

Collection, Embase, Healthstar, BMJ and several on-line Internet journals, specif-

ically Ambulatory Surgery. The search included only papers published in the English

language.

Findings. A range of interpretations of pain have led to the development of various

measurement tools that address different components of pain. This inconsistency

has led to ineffective pain management. Based on established criteria, the VAS was

found to be methodologically sound, conceptually simple, easy to administer and

unobtrusive to the respondent. On these grounds, the VAS seems to be most suitable

for measuring intensity of pain after day surgery.

Conclusions. Common guidelines on the definition and measurement of pain are

needed. In day surgery, the availability of a unified and reliable measure of pain that

can address its sensory component, such as the VAS, will provide more reliable

information about the pain experience and, hence, improve its overall management.

Keywords: postoperative pain, day surgery, rating scales, nursing, literature review

124 � 2004 Blackwell Publishing Ltd

Background

Severe pain and the effects attributed to pain-relieving

medication are the most common problems after day surgery,

both before discharge and afterwards (Chung et al. 1997,

Rawal et al. 1997, McMenemin 1999). It has been demon-

strated that patients continue to experience pain at this level

as late as the seventh postoperative day (Beauregard et al.

1998). Uncontrolled pain has also been cited as the main

reason for delayed discharge (Joshi 1994, Chung 1995),

contact with a general practitioner (Ghosh & Sallam 1994,

Kong et al. 1997) and unanticipated admission (Gold et al.

1989, Fortier et al. 1996). Plowman (2000) has estimated

that the average total daily cost incurred by the United

Kingdom National Health Service on the day of surgery is

approximately £174 per patient. However, some patients are

likely to require further treatment and be admitted for a

period of up to 4 days (Coll 2001). This raises the overall

average daily cost of a typical day surgery patient to £199.

The subjective character of pain and the complexity of the

feelings that it evokes make its reliable measurement by

health professionals a key factor in its successful manage-

ment. Despite its importance, very little research has been

conducted to identify patients’ perspectives on their pain

experiences. However, studies report problems in using

insufficient or less potent analgesia for longer than expected

duration of pain and the need to take extra time off before

resuming normal activities (Thatcher 1996, Coll 2001).

Aim

The aim of this study was to review critically the most

frequently used objective and subjective measures of pain,

which are based on a logical categorization of its compo-

nents, as developed by Melzack and Casey (1968). The

suitability of these tools to measure pain intensity after day

surgery is assessed using criteria provided by Fitzpatrick et al.

(1998).

Search method

Nursing and health care journals published since 1983 were

reviewed, using the keywords postoperative pain, day

surgery, ambulatory surgery, rating scales, VAS, severity,

nursing, assessment tool, validity, sensitivity and reliability in

various combinations. The databases used were Medline,

CINAHL, Nursing Collection, Embase, Healthstar, BMJ and

several on-line Internet journals, specifically Ambulatory

Surgery. The search included only papers published in the

English language.

Findings

Definitions and measures of pain

Carr and Goudas (1999, p. 2051) describe pain as ‘the

normal, predicted physiological response to an adverse

chemical, thermal or mechanical stimulus associated with

surgery, trauma or an acute illness’ and, thus, characterize it

as a sensory response. While this definition relates to

objective changes, the International Association for the Study

of Pain (1994) includes some elements of subjectivity in its

definition, describing pain as an unpleasant sensory and

emotional experience associated with actual or potential

tissue damage. According to Katz and Melzack (1999), pain

is a personal and subjective experience that can only be felt by

the sufferer. This view is also supported by McCaffery’s

(1989, p. 7) definition in which ‘pain is whatever the

experiencing person says it is and exists whenever they say

it does’.

Indeed, the experience of pain can go beyond physiological

sensation to a situation which is central to the psychogenic

perspective, in which diagnostic tests fail to reveal any

pathology. Turk and Okifuji (1999) maintain that the

experience of pain affects emotional, social, familial, occu-

pational and physical functioning. In addition to pain being a

physiological phenomenon, it is also influenced by psycholo-

gical and cultural factors.

In summary, research has evolved to reflect changing ideas

about pain. These have shifted from the notion of a purely

sensory phenomenon to that of an experience composed of

both sensory and reactive (emotional) components (Hardy

et al. 1952, Beecher 1959) and, finally, to one in which

sensory/discriminative, motivational/affective and cognitive/

behavioural components play a part (Melzack & Casey

1968). During this process, researchers have emphasized

different interpretations and, hence, measurement tools have

been developed to investigate these different components, as

discussed below.

Sensory/discriminative

The sensory/discriminative component of pain has been

quantified primarily through psychophysical methods that

attempt to establish a threshold for pain and through rating

scale methods. The measured variable is generally the severity

or intensity of pain.

Psychophysical methods have been used extensively since

the Second World War (Atkins et al. 1996). Pain threshold

has been determined by asking respondents to identify a point

on a continuum of increasing stimuli of pain that separates

painful from non-painful experiences. However, these

Integrative literature reviews and meta-analyses Postoperative pain assessment tools in day surgery

� 2004 Blackwell Publishing Ltd, Journal of Advanced Nursing, 46(2), 124–133 125

methods have been criticized for producing inconsistent

outcomes (Kutscher & Kutscher 1957). The non-linearity

that exists in respect of different levels of pain could be the

reason behind the failure of these tools to assess pain reliably.

More recently, Atkins et al. (1996) devised a pain-measuring

instrument called a ‘palpometer’. The minimum pressure

required to establish tenderness as felt by a patient (the

tenderness threshold) is recorded using this instrument.

Pressure readings from 0 to 9 are directly linked to two

critical variables: the force and the nature of the probe

through which it is applied. However, more recent studies

have favoured the use of Quantitative Sensory Testing, a non-

invasive computer-assisted method for assessing activity in

peripheral small and large sensory fibres (Compton et al.

2000, Meier et al. 2001). As a fundamental component of

these measurements must be the patient’s reported level of

pain, their practicality is questionable. A study by Raak and

Wahren (2002) also used this method to measure pain in

fibromyalgia (n ¼ 55). The pain experienced during investi-

gation of thermal pain thresholds was measured using a

Visual Analogue Scale (VAS).

Most of these commonly adopted methods can be viewed

as rating scales, including:

• the Verbal Descriptor/Rater Scale (VD/RS) (Keele 1948),

• the Numerical Rating Scale (NRS) (Downie et al. 1978),

• the Visual Analogue Scale (VAS) (Clarke & Spear 1964).

Keele (1948) devised the VDS, based on three to five

numerically ranked words such as ‘none’, ‘slight’, ‘mild’,

‘moderate’ and ‘severe’, for assessing responses to analgesia

over a 24-hour period. Its reliability was established by

repeatedly administering it to patients with painful medical

conditions, such as angina, and then examining the trajectory

of pain on a time–intensity curve, in relation to factors such

as physical activity and treatment.

Twenty years later, Melzack and Casey (1968) introduced

the Present Pain Intensity (PPI) scale into the McGill Pain

Questionnaire (MPQ) as a modified VDS; this was a five-

point scale with an intensity range from ‘no pain’ through to

‘excruciating’.

More recently, a VDS has been used in combination with a

VAS to measure pain (Bernston & Svensson 2001, Dudgeon

et al. 2001, Kamel et al. 2001). Flaherty (1996) has described

this scale as simple to complete and usable for patients with

chronic and acute pain. However, the scale does restrict

patients to indicating the intensity of their pain by selecting

one word only, although this may not always reflect their

experience (McGuire 1988, Flaherty 1996). There is also the

potential for ambiguity in some of the words used. ‘Mild’ to

one person may mean ‘slight’ pain to another. Severity of

pain can also be confused with its frequency. For example,

pain may be severe but not experienced very often. Someone

may, therefore, describe this pain as mild.

Downie et al. (1978) described the NRS as either a

horizontal or vertical line with ‘0’, indicating no pain, located

at the bottom or one extremity and ‘10’, indicating severe

pain, at the top or the other. Although the NRS was

originally published as a line with a scale of 0–10, there are

currently multiple versions of it, which attempt to improve

ease of administration and scoring, rate of correct response,

sensitivity, and ability to detect treatment effects (Flaherty

1996).

The main advantages of the NRS are its simplicity of

administration, scoring and use, and the fact that it does not

involve a need for knowledge of the English language

(Flaherty 1996). Unlike the VDS, there is no potential for

ambiguity of words, as numbers are used. Its main disadvan-

tage is its unreliability for elderly or very young patients, who

may not be able to differentiate between the numbers

(Flaherty 1996).

Although the NRS does have more categories than the

VDS, they are both composed of discrete categories, of which

the respondent must choose one only. As a result, there is an

element of forced choice. The NRS continues to be a popular

choice amongst researchers, either on its own (Heron &

Lozinguez 1999, Visser et al. 2000, Chen et al. 2001, Jensen

et al. 2001) or in conjunction with a VDS (Mercadente et al.

2000, Kamel et al. 2001). For example, in Mercadente et al.

(2000), pain was assessed in cancer patients (n ¼ 10) using a

VAS, and other symptoms of nausea, vomiting, drowsiness,

confusion and dry mouth were assessed by a VDS.

The VAS was first developed over 70 years ago (Maxwell

1978) and is possibly the most widely used assessment tool in

the measurement of pain (Ohnhaus & Adler 1975, Gudex

et al. 1996, Briggs & Dean 1998). During its early years, the

VAS was popular for measuring subjective phenomena. Two

of the leading advocates of this method were Clarke and

Spear (1964) and Huskisson (1974). The latter used a VAS to

measure intensity of pain. Since then, many researchers who

have attempted to measure pain, have used the VAS

(Ohnhaus & Adler 1975, Price et al. 1983, Banos et al.

1989, Collins et al. 1997, De Groot et al. 1997, DeLoach

et al. 1998, Mercadente et al. 2000, Koho et al. 2001).

This scale consists of a line, usually 100 mm in length or,

occasionally, 150 or 160 mm (as in Price et al. 1983). The

anchors at each end of the, VAS line indicate extremes of the

sensation being measured, with the left side representing ‘no

pain’ and the other end representing ‘unbearable pain’. The

respondent is asked to mark a point on the line that indicates

their current degree of sensation. Intensity of sensation is

scored by measuring the millimetres from the left-hand

A.M. Coll et al.

126 � 2004 Blackwell Publishing Ltd, Journal of Advanced Nursing, 46(2), 124–133

(lower) end of the scale to the mark made by the respondent,

thereby obtaining a number between 0 and 100 that

represents the severity of pain.

Traditionally, the VAS has been formed as a horizontal line

without markings. Alternatively, vertical scales have been

introduced. A study by Scott and Huskisson (1976) (n ¼ 100)

found no significant difference between the distribution of

scores measured on a vertical and a horizontal VAS. The

correlation between the two scales was also found to be very

high (r ¼ 0Æ99, P < 0Æ001), adding to validity.

Some authors (Kremer et al. 1981, McDowall & Newall

1987) have claimed that the VAS is confusing. However, it

has been reported that only 7% of respondents could not use

it after one explanation (Huskisson 1974). Although only a

small percentage of respondents had difficulty in completing

the VAS, it would seem appropriate for an explanation and

an example to be given to respondents before administration.

As Katz and Melzack (1999) argue, given clear instructions,

its ease and brevity of administration/scoring, minimal

intrusiveness and conceptual simplicity outweigh its limita-

tions. A further criticism relates to the way that the VAS is

designed to present and aggregate different levels of pain

within a standardized framework of ratio scores. Chapman

et al. (1985) contend that although scores are treated as

points on ratio scales, there is no evidence that respondents

actually use the numbers in this way. However, the fact that

patients may not be aware of the way that the VAS is

designed, might make the measures obtained more objective

representations of pain severity. Respondents are simply

invited to indicate what level of pain they are experiencing

between two anchor points and this is measured by the

researcher afterwards.

Finally, the VAS could prove difficult to use in the

postoperative period, because of the effects of the anaesthetic,

nausea and blurred vision (DeLoach et al. 1998). Respond-

ents with motor problems arising from conditions such as

rheumatoid arthritis might also experience difficulty in

completing the scale (Katz & Melzack 1999). However, this

limitation has been remedied by Choiniere and Amsel (1996),

who developed a visual analogue thermometer (VAT). The

latter is very similar to the VAS and consists of a plasticized

card with a red band which can be moved from left (no pain)

to right (unbearable pain).

Motivational/affective

The motivational/affective component of pain is usually

measured in relation to its subjective as well as its sensory

aspects, thus seeking to measure the total pain experience

rather than just intensity. Johnson’s (1972) Two-Component

Scale was, possibly, one of the earliest tools to include

measurement of sensory and subjective aspects of pain, each

measured on a separate scale. Physical sensation of experi-

mentally induced pain was rated on a scale ranging between 0

and 100. Distress caused by the sensation was then rated

using a VDS labelled ‘slightly distressing’, ‘moderately dis-

tressing’, ‘very distressing’ and ‘just bearable’. The research

concluded that a high intensity of pain was not always

accompanied by a high distress level. Ten years later, Wells

(1982) used the instrument to assess the effects of relaxation

on postoperative pain and distress. As the scale has a simple

format and does not take long to complete, it could be used

for almost any type of clinical pain. However, it is surprising

that this scale does not have a ‘none’ or ‘not distressing’

category. It is also remarkable that no discussion of its reli-

ability and validity has been presented (McGuire 1988).

A second tool, Tursky’s (1976) Pain Perception Profile

(PPP) was developed to measure intensity, sensory and

reactive components of pain. The intensity component

comprises 15 terms, such as ‘excruciating’ and ‘very intense’.

The sensory list includes 13 words, such as ‘piercing’ and

‘burning’, and reactive aspects are covered by 11 words, such

as ‘agonising’ and ‘miserable’. Respondents are required to

select one word/term from each list. However, it should be

noted that the tool has not been used in much clinical

research. Furthermore, it was developed and tested on college

undergraduates who did not have clinical pain and, thus, has

no established reliability or validity.

Cognitive/behavioural

Instruments which measure the cognitive/behavioural com-

ponent of pain include variables such as perceptions of pain

from a spatial and temporal perspective. These have included

time estimation of pain magnitude (Bilting et al. 1983) and the

pain chart (Margoles 1983). The former attempted to use

patients’ estimates of pain duration as a measure of pain

magnitude, based on its assumed spatial and temporal com-

ponents. Patients, including a control group, were asked to

estimate the duration of pain and the amount of pain experi-

enced. Those experiencing pain thought that a specific meas-

ured time period was significantly longer than their control

counterparts did (P < 0Æ001). A high correlation (r ¼ 0Æ88)

with a clinical assessment of pain severity was also found.

Margoles’s (1983) pain chart was designed for use by

patients to report subjective features of pain. The chart has

drawings of the body so that patients can graphically identify

pain location as well as describe its sensory aspects (e.g. red

indicates burning). In addition, the chart has a temporal

component, so that changes in pain experience can be

recorded. However, reliability and validity have not been

established and, therefore, it requires further evaluation.



The behavioural component of pain includes certain

characteristics identified by observing people in pain. The

Pain Rating Scale (PRS), devised by Hanken (1964), is an

example of a tool which measures observable behaviours in

patients experiencing acute pain. This is based on meas-

urement of six pain-related variables: pain, anxiety, verbal

statement of degree of pain, skeletal muscle response,

respiration and amount of perspiration. Although the

authors argue that reliability was satisfactory, correlation

values were not provided. However, construct validity was

evaluated, with correlation coefficients between 0Æ44 and

0Æ71 for the six variables. The scale was modified 3 years

later by Chambers and Price (1967) and 7 years later by

Bruegel (1971).

The behavioural component of pain assessment continues

to be a popular choice among contemporary researchers.

Tools include Crying, Requires oxygen to maintain satura-

tion greater than 95%, Increased vital signs, Expression,

Sleeplessness (CRIES) devised by Krechel and Bildner (1995)

and the ‘COMFORT’ scale designed by Van Dijk et al.

(2001). In the latter study (of 204 infants, aged 0–3 years,

admitted for major/thoracic surgery), the scale was used in

conjunction with the variability in the patient’s heart rate and

mean arterial blood pressure. An attempt was made to

predict the level of association between the three measures,

and this revealed that physiological indicators correlated

significantly with COMFORT ‘behaviour’ scores. It was

concluded that behavioural and physiological indicators tend

to be inter-related in highly painful situations and can

corroborate diagnoses of pain. Finally, Koho et al. (2001)

observed and videotaped patients with chronic back pain

(n ¼ 51) as they underwent a range of physical tasks, during

which a VAS was used as an additional assessment tool to

measure pain experience.

Several authors have argued that pain is not unidimen-

sional and, therefore, it is difficult to convert a subjective

sensation into a straight line (Gift 1989, Flaherty 1996, Katz

& Melzack 1999). This sensation comprises location (part of

the body), duration (length of time), pattern (continuous or

intermittent, only after food), type (dull, sharp or throbbing)

and intensity. The MPQ devised by Melzack and Torgerson

(1971) is an attempt to capture the multidimensional

perspective of pain. This allows measurement of several

features of the pain experience, including location, intensity

and pattern of pain over time. The scoring method acknow-

ledges the sensory, affective and evaluative components of

pain. The indices used are the Total Pain Rating Index (PRI-

T), four sub-indices (PRI-sensory, PRI-affective, PRI-evalua-

tive and PRI-miscellaneous), the number of words chosen to

describe the pain and the PPI.

A principal advantage of this scale is the number of

studies supporting its reliability and validity (Graham et al.

1980, Prieto et al. 1980, Klepac et al. 1981, Byrne et al.

1982, McGuire 1984). Not only can this tool be successfully

used in obtaining data on qualitative and quantitative

aspects of pain, it can also address its multidimensionality

(Flaherty 1996). However, one of its main disadvantages is

that it is demanding on the patient and requires up to

30 minutes to complete (McGuire 1988, Flaherty 1996). As

with any attempt to measure a subjective experience using

words, it is also possible that patients might not understand

the adopted descriptions of pain (Flaherty 1996). Since its

design over 20 years ago, the MPQ continues to be used by

researchers (Manz et al. 2000, Watt-Watson et al. 2000,

Caraceni 2001). There is also a short form version

(SF MPQ), used by Zalon (1999) for postoperative pain

and Baker et al. (2001) for assessing pain experience during

labour.

Pain assessment tool selection

When selecting the most appropriate health assessment tool

for the measurement of pain severity after day surgery, it

must be realized that patients are, to all intents and pur-

poses, ‘healthy’. Furthermore, they have been selected for

routine, elective surgery, having fulfilled preoperative

selection criteria and, in some settings American Society of

Anesthesiologists criteria, and are judged to be fit enough to

have surgery and return home on the same day, given

adequate social support. Other considerations involve

variation in age range (18–74), socio-economic status and

educational level. On the basis of these considerations, a

pain assessment tool must be easy to understand, complete,

valid, reliable and able to take into account the health

status of the patient.

In this respect, the methodological framework provided by

Fitzpatrick et al. (1998) appears to be both the most

comprehensive and easily applied in practice. It provides

eight criteria, based on a review of 5621 abstracts and articles

that focus on methodological aspects of ‘patient-based

outcome measures’ (p. 1), which state that the instrument

should be:

• appropriate, i.e. it should match the specific purpose of the

study;

• reliable, in terms of reproducibility and internal consis-

tency;

• valid, in that it measures patients’ perceptions of pain;

• responsive to changes of importance to patients;

• precise (accurate and discriminating);

• interpretable, in that meaningful scores are produced;

• acceptable to those completing it;

A.M. Coll et al.


• feasible, i.e. the degree of burden and effort involved in

using it is acceptable.

In addition, it is important that the choice of health

assessment tool reconciles the research objectives and the

nature of the patient population. The selected assessment

tool must also incorporate respondents’ subjective percep-

tions of their pain rather than relying on an external

observer.

Discussion

In this section, the methodological framework proposed by

Fitzpatrick et al. (1998) is used to assess the suitability of the

tools discussed for measuring pain related to day surgery.

For the psychophysical methods used to assess Melzack

and Casey’s (1968) sensory/discriminative component of

pain, the VDS is arguably unsuitable in terms of its

interpretability. This is because of the ambiguity of the

verbal descriptions used, and the fact that respondents can

choose one word only from a collection of words which may

not adequately reflect their experience of pain. This restric-

tion may also limit the acceptability of the scale. The NRS

also has discrete response options and the respondent chooses

one integer only, thus its acceptability and preciseness can be

questioned. There is also potential for this scale to be

unreliable, as some respondents may not be able to differen-

tiate between the numbers; this factor may also limit its

interpretability.

Two tools that measure the affective component of pain,

Johnson’s (1972) two-component scale and Tursky’s (1976)

PPP, although developed for ability to measure clinical pain

and ease of use, may be unsuitable as no reliability or validity

has been established.

With regard to the cognitive component, the time

estimation of pain magnitude instrument devised by Bilting

et al. (1983), may be unsuitable for use in day surgery, given

that estimations are based on respondents’ retrospective

records of pain duration. Furthermore, there is no discussion

of its reliability or validity. For the behavioural component,

appropriateness as well as feasibility of the PRS is ques-

tionable, given that only one of the six pain-related variables

(the verbally stated degree of pain) is measured. This could

easily be established in a busy day surgery unit by asking the

patient directly. The CRIES and the COMFORT Scale are

likely to be inappropriate for use with a day surgery

population, given that they have both been devised for use

with infants.

Finally, the MPQ was presented as a multidimensional tool

accounting for three main components of pain. Although

validity and reliability have been established for this tool, its

use for a day surgery population cannot be supported as it

takes approximately 30 minutes to complete and, therefore,

does not meet the criteria of acceptability, appropriateness

and feasibility. Even when the short form version of this tool

is used, given the transient nature of the day surgery stay, it is

more appropriate to measure the intensity of pain rather than

its duration and pattern over time.

The VAS is recommended, based on its methodological

qualities of reliability, validity, sensitivity and appropriate-

ness for a day surgery population. It is also one of the most

widely used assessment tools for postoperative pain (Gudex

et al. 1996, Briggs & Dean 1998). The use of the VAS as a

pain measurement tool benefits the respondent, as it uses few

words and, therefore, vocabulary is less of an issue (Flaherty

1996). Provided that clear instructions are given to respon-

dents, it is reasonably simple to complete (Katz & Melzack

1999). Furthermore, for the assessor:

• it is easy and brief to administer and score (Katz &

Melzack 1999);

• it is a good method of expressing pain severity (Scott &

Huskisson 1976, Huskisson 1982);

• because it has the properties of a ratio scale it has a true

zero point and, thus, differences between VAS measure-

ments can be interpreted as meaningful percentages

(Flaherty 1996);

• it has a continuous frequency distribution, which allows

rigorous statistical tests to be conducted on average pain

levels.

We therefore argue that the VAS is more sensitive than

the NRS, as the latter can both underestimate and overes-

timate scores on a VAS, depending on where the precise

VAS score is on a scale between any two anchor points. For

example, underestimated NRS score occurs by rounding

down a VAS score of 34Æ9 mm to 3 on an NRS and

overestimation occurs by rounding up a score of 35Æ0 mm to

4. This means that a difference of 0Æ1 mm on a VAS would

constitute a whole integer difference (of 3–4) on the NRS.

These examples show that VAS is a more sensitive measure

than the NRS.

The reliability of the VAS is well documented in the

literature. Clarke and Spear (1964) found the VAS reliable

and sensitive to changes in self-assessed well-being. In a

later study, Revill et al. (1976) demonstrated test re-test

reliability when using the VAS with 10 women in labour

(r ¼ 0Æ95, P < 0Æ001). In another test re-test study,

Seymour (1982) reached the same result. In addition,

Dixon and Bird (1981) established its reproducibility using

a sample of eight respondents. In this study, each respond-

ent was presented with a series of 10 cm reference lines

that had been crossed at some point and they were invited



to duplicate the position of the cross. Good reproducibility

was established at the extreme ends of the scale and at the

centre. Furthermore, Bijur et al. (2001) established that the

VAS could be used reliably in the emergency setting for

acute pain experience. Intra-class correlation coefficients

with 95% confidence intervals were calculated (0Æ97, with

95% confidence intervals of 0Æ96–0Æ98) for measurements

of acute pain in adult respondents, made 1 minute apart

every 30 minutes over 2 hours. The study concluded that

90% of pain ratings could be reproduced within 9 mm,

indicating the scale’s high reliability when used in assessing

acute pain.

As noted above, McCaffery (1989) asserts that ‘pain is

whatever the patient says it is and exists whenever they say

it does’. Therefore, one of the reliability aspects of VAS

must be the degree to which it can represent patients’

feelings of pain. In a recent study by Freeman et al. (2001),

a high correlation (r ¼ 0Æ92) was established between VAS

results and respondents’ non-verbal facial expressions using

a Faces Rating Scale.

The validity of the VAS for measuring pain has been

established using a variety of techniques including establish-

ment of concurrent, construct and criterion-related validity

(Seymour 1982, Price et al. 1983, Gift 1989). In the second

of these studies, a VAS was validated as a ratio scale

measure in chronic and experimental pain, and concurrent

validity was established in the latter study. Downie et al.

(1978) compared the validity of a VAS, and its simplicity

and ease of use, with a similar NRS and VDS. It was found

that all scales correlated well and had similar loadings on a

factor analysis. Seven years later, Littman et al. (1985)

compared a VDS with a VAS as well as a verbal pain relief

scale in patients with acute and chronic pain (n ¼ 1497). It

was concluded that all three measures correlated well

(r ¼ 0Æ89–0Æ93). Banos et al. (1989) found correlations

between the latter two scales in patients (n ¼ 212) who

underwent abdominal (0Æ87), orthopaedic (0Æ71) and gynae-

cological surgery (0Æ69) (P < 0Æ001).

A study by Collins et al. (1997) (n ¼ 1080) compared a

VAS with a four-point VDS scale (with categories labelled

‘none’, ‘mild’, ‘moderate’ or ‘severe’) in an attempt to

establish which point on the VAS represented moderate pain

intensity. It was found that VAS scores could be mapped

onto the VDS, in that the majority of patients recording a

baseline VAS score in excess of 30 mm selected ‘moderate’

or ‘severe’ on the categorical scale. In their view, a VAS

score in excess of 50 mm would, be likely to equate to

severe pain.

As mentioned earlier, Clarke and Spear (1964) found the

VAS to be sensitive to changes in self-assessed well-being. It

has also been demonstrated that it is sensitive to all

procedures which alter the experience of pain, e.g. the use

of pharmacological interventions, and changes in intensity in

a variety of patients with acute or chronic pain (Belanger

et al. 1989, Price et al. 1989, Choiniere et al. 1996).

Furthermore, Cotanch (1988) maintains that the VAS is a

more sensitive measure of pain intensity than the VDS, given

its straight-line continuum as opposed to categorized

responses.

The VAS continues to be cited in much of the contem-

porary literature on pain as the main assessment tool (Good

1999, Kelly 2000, Sjostrom et al. 2000, Blank et al. 2001,

Chung et al. 2001, Freeman et al. 2001, Quigley et al.

2002, Marquie et al. 2003). In this last study, 200 patients

and their physicians used a VAS for rating patients’ pain

both on arrival and at discharge from the emergency

department. It was established that physicians gave signi-

ficantly lower ratings than the patients in both cases

(P < 0Æ001), emphasizing the subjectivity of the pain

experience and the importance of accepting the patient’s

report of it. It has also been used in conjunction with a

VRS (Jensen et al. 2002), the MPQ (Sekiyama & Hanaoka

2001) and combined with a VRS, the MPQ and the PPI

(Gagliese & Katz 2003). In the latter study, which focused

on the first 2 days following radical prostatectomy in

200 men, an analysis of age-related patterns, based on

three scales, is presented. However, the VAS was found not

to be sensitive in detecting age differences. It was recom-

mended that verbal descriptions are better than non-verbal

measures of intensity at capturing age differences in

postoperative pain.

What is already known about this topic

• Pain is multidimensional.

• Many tools have been established to measure different

components of pain.

• These tools have been used to measure the severity of

pain, irrespective of their suitability.

What this paper adds

• Severe pain experiences after day surgery occur despite

advancements in anaesthesia and analgesia.

• A review of appropriate pain assessment tools for use

after day surgery.

• A recommendation that the Visual Analogue Scale

should be used in assessment of pain intensity after day

surgery.

A.M. Coll et al.


Conclusion

The diversity of pain assessment tools has created a problem

of choice that can be a daunting task. In the first instance, it is

important to choose a tool that meets most, if not all, of the

methodological considerations detailed by Fitzpatrick et al.

(1998).

There is an urgency to establish common guidelines on the

definition and measurement of pain. In day surgery, the

availability of a unified and reliable measure of pain, such as

a VAS that can address its sensory components, will provide

more trustworthy information about the intensity of pain

and, hence, improve its overall management.

Acknowledgement

We would like to thank Professor Laurie Moseley for his

support and insightful comments during the conduct of this

study.

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