Table 2.
Key studies that support response scale selection for PRO instruments based on responsiveness
| Reference | Response Scale Type | Methods to Determine Responsivenessa | Summary of Resultsb |
|---|---|---|---|
| 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). |
PRO patient-reported outcome, NRS numeric rating scale, VAS visual analogue scale, SRM standardized response mean, VRS verbal rating scale, ES effect size, BPI Brief Pain Inventory, ODI Oswestry Disability Index, gLMS general Labeled Magnitude Scale, SD standard deviation
aSRM calculated by dividing the mean change by the standard deviation of the mean change scores. Effect size of 0.2 = small, 0.5 = moderate, and > 0.8 = large clinical change
bAll references provided direct evidence: Primary research that compares different response scales within study