CLINICAL BOTTOM LINE & AVAILABLE LITERATURE

 

...ABOUT MINIMUM CLINICALLY SIGNIFICANT DIFFERENCES IN PAIN SCORES IN THE EMERGENCY DEPARTMENT

CLINICAL BOTTOM LINE

A total of 11 studies evaluated the Minimum Clinically Significant Differences in pain scores in the Emergency Department.

Of these studies, one had level of evidence 3b and the rest had level of evidence 4.

In these studies several populations were evaluated:

- pain of any cause / mixed study populations (6 studies: 967 patients)

- traumatic injuries (2 studies: 121 patients)

abdominal pain (1 study: 101 patients)

- vaso-occlusive crisis in sickle cell disease (1 study: 74 patients)

physician-assigned pain scores in simulated case scenarios (1 study)

Eight studies evaluated VAS as a pain scoring tool, two studies both VAS and NRS and one study evaluated NRS only.

Taken together, it can be concluded* that...

1. the Minimum Clinically Significant Difference in VAS pain scores (on a 100 mm scale) varies between 9 mm and 19 mm and 5 studies reported a value between 12 and 14 mm.

Level of recommendation C

When looking at all MCSDs that were found and the different painful conditions:

- 9 mm (95%-CI 6 to 13) in any pain

- 11.9 mm (95%-CI 9.7 to 14.9) in any pain

- 12 mm (95%-CI 9 to 15) in any pain

- 13 mm both in traumatic injuries (95%-CI 10 to 17) and in any pain (95%-CI 10 to 16)

- 13.5 mm (95%-CI 11.25 to 15.74) in vaso-occlusive crisis

- 14 mm (95%-CI 10 to 15) in any pain

- 16 mm (95%-CI 13 to 18) in abdominal pain

- 18 mm (95%-CI 16 to 20) in simulated scenarios (physician assigned scores)

- 19 mm (+/- 15) in traumatic injuries

2. the Minimum Clinically Significant Difference in NRS pain scores varies between 1.25 and 1.39.

Level of recommendation C

When looking at the MCSDs found and the different painful conditions:

- 1.25 (95%-CI 1.05 to 1.45) in any pain

- 1.3 (95%-CI 1.0 to 1.5) in any pain

- 1.39 (95%-CI 1.27 to 1.51) in any pain

3. it is not clear whether the baseline pain score influences the Minimum Clinically Significant Difference in (VAS) pain scores

Level of recommendation C 

This was evaluated in two studies. One study found that there was a significant difference when looking at changes in pain scores from several different baseline pain scores:

<34 mm: MCSD 11 mm when less pain and 16 mm when more pain

34 - 67 mm: MCSD 17 when less pain and 18 when more pain

67 - 100 mm: MCSD 30 when less pain and 14 when more pain

However, another study did not find significant differences from different baseline scores:

mild pain: 11 mm (95%-CI 4 to 18)

moderate pain: 14 mm (95%-CI 10 to 18)

severe pain: 10 mm (95%-CI 6 to 14)

 

* Disclaimer:

Included studies were different in several items, such as timing and methods of measurement of several endpoints; study population; baseline situation and pain medication. Due to these large differences in study methodology, results cannot be pooled and the level of recommendation should be regarded as an estimation of the true effect. The levels of recommendation were derived according to the OCEBM levels of evidence

The included studies were found using PubMed (Medline) and Embase with the following search terms and synonyms: pain AND (scale OR score OR measure) AND emergency. The search was updated in September 2020. 

Validation of pain scores and finding the Minimal Clinically Important Difference for patients is a difficult thing to do. Patient-reported pain intensity has been related to many factors, such as culture, age, gender, level of education, anxiety or beliefs. It is subjective and might even serve hidden goals such as trying to achieve faster treatment or asking for (opioid) pain medication. So, pain scores are potentially prone to multiple confounding factors.

And a final note on these validation studies: in general, validation of a diagnostic measure requires an independent reference standard that ideally is to be applied in a blinded fashion to all patients. This seems impossible in comparing pain scores to the answers of 5-point Likert scales (which was the preferred method of validating pain scores in most studies), as patients usually remember their previous pain scores.

Available literature on MCID in pain scores:

 

1996

Todd KH, Funk JP. The minimum clinically important difference in physician-assigned visual analog pain scores. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine 1996;3:142-6.

Study design

Prospective, descriptive study

Setting

One morning didactic lecture series at a university Emergency Medicine program in the USA

Population

Physicians attending the lectures, mainly residents

Objectives

To determine the minimum clinically significant (or important) difference in physician-assigned 10cm VAS pain scores

Methods

11 scenarios were randomly assigned to the physicians, in which patients with acute pain were described with various medical or traumatic causes.

The physicians were asked to read the scenario and then to indicate estimation of pain intensity. They were also asked to contrast this to the previous scenario (regarding pain severity, using 5-point Likert scales)

Results

23 physicians were included, performing 11 scenarios and therefore 10 comparisons, yielding a total of 230 comparisons for analysis.

 

The median VAS was 68mm (representing mainly moderate and severe pain).

There were 120 ‘little less’ or ‘little more’ contrasts. The 64 ‘little less’ had a mean VAS difference of -19mm. The 56 ‘little more’ had a mean difference of 16mm.

When calculating both, this yielded a mean VAS difference of 18 mm (95%CI 16-20), corresponding to a change of 23%.

Authors’ conclusions

The MCSD in physician assigned VAS pain scores was 18mm

Pros

Physicians were blinded for the study purpose

Limitations

The pain scores were physicians’ reports and not pain scores as reported by patients.

Level of evidence 4

 

1996

Todd KH, Funk KG, Funk JP, Bonacci R. Clinical significance of reported changes in pain severity. Ann Emerg Med 1996;27:485-9.

 

Study design
Prospective descriptive study
Setting

Emergency Department of a level 1 trauma center in the USA

Population

Adult patients of 18 years and older presenting with pain due to traumatic injury excluding altered mental status or clinical instability.

Objectives
To define the minimum change in visual analog pain scores that is clinically meaningful to ED patients with acute pain
Methods
The study was conducted on 8 non-consecutive days when research assistants were available between the hours of 10AM and 6PM. 100mm VAS was recorded and repeated at 20 minutes interval and contrasting questions using 5-point Likert scales for 2 hours
Outcome

Minimum clinically significant change in VAS

Results

48 patients with 248 pain contrasts were analysed in the study.

The mean baseline pain score was 56 mm.

Of the 248 comparisons, 139 were ‘about the same’. For these comparisons, the mean VAS difference was 0.4 mm.

 

‘A little less’ as an answer corresponded to a mean VAS difference of -16 mm (95%CI -22 to -10) and the answer ‘a little more’ with 10 mm (95%CI 6 to 14).

These two contrasts were also analysed together and this resulted in a mean of 13 mm (95%CI 10 to 17) VAS difference. 

Of all paired measurements, 18% were discordant. 

Authors' conclusions
The minimum clinically significant difference in pain score differences using VAS in patients with traumatic injuries was 13 mm
Limitations
There was no sample size calculation and patients were recruited non-consecutively. Therefore the results were prone to selection bias. Reference standard 5-point Likert scale not applied independently and in a blinded fashion.
Level of evidence 4
 

1998

Kelly AM. Does the clinically significant difference in visual analog scale pain scores vary with gender, age, or cause of pain? Acad Emerg Med 1998;5:1086-90.

 

Study design

Prospective descriptive study

Setting

Emergency Department in a teaching hospital in Australia

Population

All patients who presented during a 1-week period between 8AM and midnight with acute pain.

Exclusion criteria: age <16 years; inability to understand the questions in English; inability to give Informed Consent; inability to mark a VAS pain score; altered level of consciousness, including intoxication.

Objectives

1. To determine the minimum clinically significant difference in VAS pain scores for acute pain in the ED

2. To determine whether this difference varies with gender, age and cause of pain.

Methods

Patients marked their pain on a 100 mm VAS pain scale on admission and at disposition and at 20 minutes intervals they were asked to rate it descriptively utilizing a 5-point Likert scale. Pain was reassessed with VAS at these intervals also.

Interviews performed by independent research team.

Results

Of 156 patients who were potentially eligible for inclusion; 4 were withdrawn due to inadequate documentation.

93 patients had 3 comparisons; 14 had 2 comparisons and 45 had 1 comparison.

The mean age was 44 years old; male 85 years and female 67 years.

Mean initial VAS was 51 mm.

Origin of pain was trauma in 65 patients, with mean VAS 47 mm

Non-trauma in 88 patients with mean VAS 54 mm.

 

Regarding the 5-point Likert scales and VAS comparisons:

- 'pain about the same': mean VAS difference -0.4 mm (95%CI -1.5 to 0.7)

- 'a little better': mean VAS difference -8 mm (95%CI -12 to -4)

- 'a little worse': mean VAS difference 12 mm (95%CI 6 to 18)

- 'a lot better': mean VAS difference -25 mm (95%CI -34 to -16)

- 'much worse': mean VAS difference 21 mm (95%CI 13 to 29)

The two descriptors 'a little better' and 'a little worse' analyzed together revealed a mean VAS difference of 9 mm (95%CI 6 to 13).

Regarding gender there were no significant differences in minimum clinical differences in pain scores (11 mm for males and 7 mm for females).

The same applied for causes as this was 10 mm in trauma and 11 mm in non-trauma.

Authors’ conclusions

The minimum clinically significant difference in VAS pain scores is 9 mm without differences regarding age or gender or cause of pain.

Limitations

There was no sample size performed; patients were recruited non-consecutively; as pain scores were a bit skewed to the left, there is more room for patients to descriptively improve pain in stead of report worse pain after 20 minutes.

Level of evidence 4

 

2001

Bird SB, Dickson EW. Clinically significant changes in pain along the visual analog scale. Ann Emerg Med 2001;38:639-43.

 

Study design

Prospective study

Setting

ED in the USA

Population

Patients older than 17 years with isolated extremity trauma.

Exclusion criteria: injuries older than 24 hours; intoxication

Objectives

To test the hypothesis that change in VAS that is associated with a minimum clinically significant change (MCSC) in pain, is related to the initial VAS pain score.

Methods

Patients rated their VAS pain score as a horizontal VAS at baseline and every 30 minutes, including descriptors with 5-point Likert scales in which ‘a little less’ and ‘a little more’ was regarded the minimum clinically significant value.

VAS was categorized for analysis in three cohorts.

Results

77 patients were included and 4 were excluded because of incomplete study data.

There were 157 changes in VAS: 34% lowest cohort; 39% middle cohort and 27% highest cohort. Only 4 changes in VAS were opposite to the prescriptors used.

The greatest change in VAS occurred when patients with an initial score of 34mm or less had much more pain 46mm (+/-19) or when patients with an initial VAS of 67mm or higher had much less pain 48mm (+/-7).

Overall, a 'little less' and a 'little more' represented a mean VAS change of 19mm (+/-15).

The changes were higher in the highest cohort than in the lowest cohort (p<0.05).

VAS <34: MCSC was 11mm (+/-6) and 16mm (+/-8) for a 'little less' and a 'little more'

VAS 34-67: MCSC was 17mm (+/-8) and 18mm (+/-13), respectively

VAS 67-100: MCSC was 30mm (+/-22) and 14mm (+/-12), respectively

 

Authors’ conclusions

MCSCs in VAS are not uniform among the entire VAS and the concept of must be rethought in the context of the patient’s baseline level of pain

Limitations

Convenience sample of patients were recruited and it was not specifically described by whom (the word 'investigator' was used in the discussion) and what level of training this or these person(s) had.

There was no sample size calculation.

Analgesic administration was not recorded  and results were limited to isolated extremity trauma.

Level of evidence 4

Remarks

Patients with greater pain require a greater decrease in pain to reach clinically significant reduction or increase in pain, this is a valid argument to report proportional changes as end points in research studies, besides absolute decreases in pain scores.

 

2001

Gallagher EJ, Liebman M, Bijur PE. Prospective validation of clinically important changes in pain severity measured on a visual analog scale. Ann Emerg Med 2001;38:633-8.

 

Study design

Prospective observational study

 

Setting

Two urban Emergency Departments in the USA

Population

Patients who were 18 years and older and speaking English and Spanish and who presented with acute pain.

Exclusion criteria: altered mental status, decreased visual acuity; non-English and non-Spanish speaking; unchanged chronic pain.

Objectives

To test the hypothesis that the minimum clinically significant difference in VAS is approximately 13 mm in an independent validation cohort of ED patients with heterogeneous causes of pain

Methods

Patients were selected as a convenience sample and included by trained research assistants from 8AM to 8PM on selected days, including weekends during a 9-month period. In all patients (horizontal) VAS (0-100 mm) was recorded at baseline and every 30 minutes during 2 hours. At each repeat assessement contrasting questions were asked about  pain compared to the previous assessment. These questions were asked as 5-point Likert scales.

Results

166 patients were approached; 28 refused and 42 were unable to participate. This resulted in 96 patients who were included in the study. These 96 patients generated 332 paired pain measurements.

Causes of pain were traumatic in 39%; non-traumatic in 38% and unknown in 24%. Distribution of pain was abdomen in 44%; extremities in 23%; back in 11%; head in 8%; chest in 6% and other in 7%.

 

The median pain score at baseline was 71 mm.

For patients whose pain was ‘about the same’ the mean change was 0 mm (95%CI -1 to 2) and for the comparison ‘a little less’ this was -15 mm (95%CI -18 to -11).

For patients whose pain was ‘a little more’ this was 10 mm (95%CI 5 to 15).

For patients whose pain was ‘much less’ this was -24 mm (95%CI -35 to -13).

The outcome ‘a lot more’ corresponded with a mean change of 19 mm (95%CI 6 to 31).

 

When trying to find the minimal clinically significant difference (for patients), the two least changes (both upward and downward) as detected by the Likert scale were combined:  

Results of ‘a little less’ and ‘a little more’ combined: mean difference of 13 mm (95%CI 10 to 16).

By the way: 15% of all paired measurements were discordant.

Authors’ conclusions

The minimum clinically significant difference in VAS in Emergency Department patients with pain from various causes was 13 mm

Pros

A formal sample size calculation was performed; patients were recruited by trained research assistants.

Limitations

Not all consecutive patients were recruited, but they tried to minimize selection bias by inlcuding patients during all possible shifts during a long study period. Reference standard 5-point Likert scale cannot be applied independently and in a blinded fashion.

Level of evidence 4

 

2001

Kelly AM. The minimum clinically significant difference in visual analogue scale pain score does not differ with severity of pain. Emergency medicine journal : EMJ 2001;18:205-7.

Study design

Prospective descriptive study

Setting

ED in Australia

Population

All patients presenting with pain.

Exclusion criteria: age under 16 years; inability to understand the questions in English; inability to give IC; inability to mark a VAS and altered level of consciousness, including intoxication

Objectives

To determine whether the minimum clinically significant difference in VAS pain score varied with severity of experienced pain

Methods

During a 1-week period recruitment between 8AM and midnight; patients were asked to rate pain using VAS, max of 3 comparisons, excluded when they became pain free in the ED. Patients also had to describe pain using the 5-point Likert scale more often used together with VAS scores each 20 minutes interval.

Results

156 patients were included, 22 withdrawn due to lack of data, at patient request or because of protocol violation. There were 88 evaluable comparisons.

 

The minimum clinical significant difference for each pain group was as follows;

- Mild pain 11mm (95%CI 4 to 18)

- Moderate pain 14 mm (95%CI 10 to 18)

- Severe pain 10mm (95%CI 6 to 14)

When combining ‘a little worse’ and ‘a little better’, the minimum clinically significant difference in VAS was 12mm (95%CI 9 to 15).

No statistical differences between groups of severity of pain.

Authors’ conclusions

Minimum clinically significant difference in VAS pain scores between pain severity groups did not differ.

Pros

Independent researchers approached and included and interviewed patients, not involved in clinical care; authors tried to calculate a sample size beforehand (156)

Limitations

Sample size was not achieved; non-consecutive recruitment

Level of evidence 4

 

2002

Gallagher EJ, Bijur PE, Latimer C, Silver W. Reliability and validity of a visual analog scale for acute abdominal pain in the ED. Am J Emerg Med 2002;20:287-90.

Study design
Prospective observational cohort study
 
Setting
Two large academic EDs in the USA
 
Population
A convenience sample of adult (18 years and older) patients presenting to the ED between 08AM to 08PM, six days a week, for a period of two months, with acute abdominal pain and speaking English or Spanish.
Exclusion criteria were altered mental status or decreased visual acuity.
 
Objectives
1. to evaluate the validity of VAS pain scores in patients with acute abdominal pain
2. to determine reliability of VAS scores in these patients
3. to identify the minimum clinically significant difference in these patients 
Methods
All patients were asked to rate their pain twice with one-minute apart and did this every 30 minutes during two hours. At the end of each 30 minute interval, patients were also asked whether their pain was ‘much less’, ‘little less’, ‘about the same’, little worse’ or ‘much worse’ (5-point Likert scale)
 
Results
As a result they included 101 patients with a total of 469 VAS measures.
Intraclass correlation between VAS 1 minute apart was 0.99 (95%CI 0.989 to 0.992). Bland-Altman analysis showed that 50% of differences between 1-minute VAS scores ranged from -3 mm to +2 mm and 90% from -8 mm to +9 mm. 95% were within 11 mm.
 
Besides correlation, the authors also evaluated validity.
They showed that with increasing pain descriptors according to the Likert scale questions, from much less to much more pain, VAS scores increased in a parallel fashion.
The 80 ratings of 'a little less' pain were associated with a mean change in VAS of -17 mm (95%CI -18 to 12) and the 51 ratings of 'a little more' pain were associated with a mean change in VAS of 13 mm (95%CI 6 to 16).
Combining the descriptors 'a little less' and 'a little more' pain in the analysis revealed a minimum clinically significant pain difference of 16 mm (95%CI 13 to 18).

Authors' conclusions

Utilizing VAS pain scores in ED patients with acute abdominal pain is valid with high correlation between scores indicating high reliability of repeated scores. The minimum clinically significant difference in pain scores in patients with acute abdominal pain in the ED is 16 mm.
Pros
Sophisticated statistic analyses were used in order to measure intraclass correlation and reliability between two measures and also served as a sensitivity analysis, decreasing influence of bias and confounders. 
 
Limitations
Abdominal pain tends to fluctuate (depending on the cause) and fluctuating pain might have influenced serially reported pain scores. Not all consecutive patients were recruited in the study. As mentioned in the other studies as well, the reference standard (5-point Likert scale) cannot be administered while patients were blinded for their reported pain scores. 
Level of evidence 3b
 

2003

 Bijur PE, Latimer CT, Gallagher EJ. Validation of a verbally administered numerical rating scale of acute pain for use in the emergency department. Acad Emerg Med 2003;10:390-2

Study design

Observational prospective cohort study

Setting

Emergency Department of an academic medical center in the USA

Population

A convenience sample of patients presenting with acute pain to the ED, speaking English or Spanish and 18 years and older.

Exclusion criteria: altered mental status, decreased visual acuity and motor abnormalities precluding scoring of VAS

Objectives

1. To validate the NRS in the ED by assessing comparability to the VAS

2. To identify minimum clinically significant difference in pain that could be detected by patients on the NRS

3. To compare the latter with the minimum clinically significant difference measured on VAS

Methods

A trained research associate recruited patients three days per week from 8AM to 8PM

Outcomes patients rated their pain with horizontal VAS (10 cm) and also verbally rated score with NRS in randomly variable order at baseline, 30, 60 minutes including the 5-point Likert scales at each reassessment.

Results

108 patients rated pain at baseline, 103 at 30 minutes and 86 at 60 minutes.

33% had pain at extremities, 29% abdomen, 13% back, 10% head, 7% chest, 8% other.

83% of initial NRS was >5.

There was a strong correlation between VAS and NRS: r=0.94 (95%CI 0.93 to 0.95). The minimum clinically significant difference for NRS was 1.3 (95%CI 1.0 to 1.5) and 1.4 (95%CI 1.0 to 1.5) for VAS.

For each 1-point increment in NRS, VAS increases with 1.01 cm.

At NRS 0, VAS was -0.34 (95%CI -0.67 to -0.01), meaning that NRS is slightly higher than corresponding VAS.

Authors’ conclusions

NRS is strongly correlated with VAS and can be used for acute pain measurement in the ED

Limitations

Recruitment was non-consecutively and no sample size calculation was performed.

Level of evidence 4 

 

2005

Kendrick DB, Strout TD. The minimum clinically significant difference in patient-assigned numeric scores for pain. Am J Emerg Med 2005;23:828-32.

Study design

Prospective descriptive trial

Setting

Emergency Department of an academic hospital in the USA

Population

All patients with acute pain (8 years and older) and able to give IC.

Exclusion criteria: unable to speak English and/or read English instructions or left before being seen by a physician

Objectives

1. To determine the minimum clinically significant difference in (11-point) NRS pain scores

2. To determine whether this difference varies with age, sex, ethnicity, language or pain etiology

Methods

Patients were recruited during 8-hours shifts on 50 non-consecutive days including all days of the week and all shifts. Pain was rated using NRS every 20 minutes during two hours, including contrast-questions with previous measurement using 5-point Likert scales

Results

356 patients signed the Informed Consent and 2 left the ED before being seen, leaving 354 patients for analysis.

Causes of pain were 65.3% non-traumatic and 34.7% traumatic.

The mean NRS at baseline was 6.60.

There were a total of 1515 comparisons of which 338 were ‘a little more’ (94) or ‘a little less’ (244) with a total mean NRS difference of 1.39 NRS points (95%CI 1.27-1.51), without differences between gender or cause of pain.

Authors’ conclusions

The mean minimum clinically significant difference in pain scores was 1.39 NRS points, consistent with previous studies and not dependent of sex or cause of pain.

Pros

Trained independent research assistant approached and included patients

Limitations

Non-consecutive recruitment (but selection bias was minimized as all shifts were included); no sample size was performed

Level of evidence 4
 

 

2007

Lopez BL, Flenders P, Davis-Moon L, Corbin T, Ballas SK. Clinically significant differences in the visual analog pain scale in acute vasoocclusive sickle cell crisis. Hemoglobin 2007;31:427-32.

Study design

Prospective observational study

Setting

ED of a USA hospital

Population

Adults 18 years and older with Sicke Cell Disease (SCD) presenting with an uncomplicated Vaso-Occlusive Crisis (VOC).

Exclusion criteria: <18 years of age; atypical pain; prior study entry within 5 days earlier; evidence of acute co-existing illness.

Objectives

To determine the amount of change in pain severity, as measured by VAS, that constitutes the minimum clinically significant change in pain perception during the ED management in adult SCD patients with VOC

Methods

Each patient has a personalized pain treatment protocol and standard care included a VAS pain score at baseline and at 1 hour after each analgesic administration. Additionally, at this point patients were asked verbal descriptors (much less pain, little less, about the same, a little more, much more pain) to describe changes in pain intensity.

Outcomes

VAS difference associated with a determination of a change in pain of a little less or a little more pain (to determine minimum clinically significant difference).

Results

A total of 74 patients were included with initial mean pain scores of 79.47 mm and these scores decreased over time. There patients supplied a total of 172 VAS contrast scores.

 

In the group of 'little less' or 'little more' pain, the change in VAS was 13.5mm (95%-CI 11.25 to 15.74mm) and in the groups 'much worse' this was 4.8mm and 23.4mm in the 'much better' group.

When correcting for initial pain score, these differences remained the same.

Authors’ conclusions

Degree of pain relief can be reliably measured using VAS pain scores; a change of 13.5mm on 100mm VAS score represents minimum clinically significant differences in pain scores

 

Pros

A sample size calculation was performed

Limitations

Atypical pain was an exclusion criterion but was not specified; not clear who included patients, the study population was a convenience sample. 

Level of evidence 4
 

 

2010

Mohan H, Ryan J, Whelan B, Wakai A. The end of the line? The Visual Analogue Scale and Verbal Numerical Rating Scale as pain assessment tools in the emergency department. Emergency medicine journal : EMJ 2010;27:372-5.

 

Study design

single center prospective observational study

 

Setting

ED in Ireland

Population

Convenience sample of patients 18 years and older presenting with pain and speaking English.

Exclusion criteria: speaking English insufficiently; altered mental status or to acutely unwell to participate; patients who gave only one pain reading.

Objectives

- To test agreement between VAS and vNRS in the ED

- To determine whether agreement was altered by patient characteristics

Methods

Patients’ pain was recorded using 100mm VAS and with vNRS 0-10 and was reassessed every 30 minutes up to 2 hours. The order of pain scores was alternated between patients and was consistent within patients.

Outcomes

1. Agreement between VAS and vNRS

2. - Patient utility

    - Effect of demographics on pain scores

Results

A total of 123 patients were included, with 531 paired measurements of VAS and vNRS. Causes: trauma in 44.7% and location of pain: limb 50.4%; abdomen 24.4%; chest 8.9%; headache 5.7%; orofacial 4.9%; back 4.1% and testicular 1.6%.

 

Correlation between VAS and vNRS was significant (rs=0.93 with 95%CI 0.92-0.94). Variability was tested using Bland-Altman method: difference between means VAS – vNRS was -7.1mm (95%CI -7.9 to -6.2). Differences between VAS and vNRS were significant for educational level, gender and increasing age.

Majority (59.4%) of patients found that using a pain scale helped them describe pain severity; 17.9% found VAS easier and 35% found vNRS easier; 47.2% no difference.

The minimum clinically significant difference for VAS was 11.9mm (95%CI 9.7 to 14.9); for vNRS 1.25 (95%CI 1.05 to 1.45). MCSD not influenced by patient demographics.

Authors’ conclusions

There is an almost linear correlation between both pain scores, however, their use is not interchangeable as there is no perfect agreement. Age, gender and level of education affected this agreement, but did not affect the individual measurements or the MCSDs. Therefore self-reported pain does not differ based on age, gender, cause or level of education. vNRS is a good alternative for VAS in the ED.

Limitations

The study population was a convenience sample

Level of evidence 4

 
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