Table 2 Key studies that support response scale selection for PRO instruments based on responsiveness

Grotle et al. 2004 [26]

11-point NRS VAS

SRM

In acute pain, for improved patients NRS SRM = 2.0 and VAS SRM = 1.6. For unchanged patients NRS SRM = 1.0 and VAS SRM = − 0.5.

In chronic pain, for improved patients NRS SRM = 1.1 and VAS SRM = 0.4. For unchanged patients NRS SRM = − 0.2 and VAS SRM = 0.1.

Skovlund et al. 2005 [27]

VAS: 100 mm line anchored at no pain/discomfort and pain/discomfort 4-point VRS: none, mild, moderate, severe

Sensitivity of scales with multiple simulations

Cross-sectional analyses with multiple simulations to understand the sensitivity of scales.

The VAS consistently gave higher power to detect true differences in pain ratings than the 4-point VRS.

Chanques et al. 2010 [16]

11-point NRS 5-point VRS (no pain, mild pain, moderate pain, severe pain, extreme pain) VAS: 10-cm line anchored at no pain and extreme pain

ES Type of ES (Cohen’s d or SRM) not provided in the reference

Patients identified NRS was the easiest, most accurate and preferred scale in comparison with 5-point VRS and VAS. NRS demonstrated the best sensitivity (96.6%) and negative predictive value (89.6%) whereas VRS demonstrated the best specificity (70.7%) and positive predictive value (86.3%). VAS demonstrated the lowest performance, except for the negative predictive value, which was comparable to VRS

ES for 11-point NRS: 1.18

ES for 5-point VRS: 0.94

ES for VAS: 1.13 (vertical orientation)

Dogan et al. 2012 [28]

Faces scale: 7-point horizontal scale that defines feels due to pain. First face represents no pain and the last face represents the worst possible pain VAS: 10-cm horizontal line anchored at no pain and severe pain.

Calculated ES (SRM)

Faces scale ES = 1.78

VAS ES = 1.36

Chien et al. 2013 [17]

11-point NRS (several different BPI scales)

6-point VRS - PPI (no pain, mild, discomforting, distressing, horrible, excruciating)

6-point VRS - ODI (no pain, very mild, moderate, fairly severe, very severe, the worst imaginable)

SRM

Results for all participants:

11-point NRS SRM: ranged from 0.17 to 0.42

6-point VRS SRM: ranged from 0.27 to 0.29

Gonzalez-Fernandez et al. 2014 [29]

VAS (100 mm line)

NRS: (gLMS = VAS with the addition of numbers)

Between group difference

The mean (SD) VAS score was 6.13 (2.27) and the mean (SD) NRS score (after scaling to a 0–10 scale) was 4.35 (2.52), with medians of 7 and 4, respectively.

The mean difference between the two scores (VAS and NRS) was + 1.78 (P < 0.0001).