Responsiveness, Reliability, and Minimally Important and Minimal Detectable Changes of 3 Electronic Patient-Reported Outcome Measures for Low Back Pain: Validation Study

Abstract

Background: The Roland Morris Disability Questionnaire (RMDQ), visual analog scale (VAS) of pain intensity, and numerical rating scale (NRS) are among the most commonly used outcome measures in trials of interventions for low back pain. Their use in paper form is well established. Few data are available on the metric properties of electronic counterparts.

Objective: The goal of our research was to establish responsiveness, minimally important change (MIC) thresholds, reliability, and minimal detectable change at a 95% level (MDC₉₅) for electronic versions of the RMDQ, VAS, and NRS as delivered via iOS and Android apps and Web browser.

Methods: We recruited adults with low back pain who visited osteopaths. We invited participants to complete the eRMDQ, eVAS, and eNRS at baseline, 1 week, and 6 weeks along with a health transition question at 1 and 6 weeks. Data from participants reporting recovery were used in MIC and responsiveness analyses using receiver operator characteristic (ROC) curves and areas under the ROC curves (AUCs). Data from participants reporting stability were used for analyses of reliability (intraclass correlation coefficient [ICC] agreement) and MDC₉₅.

Results: We included 442 participants. At 1 and 6 weeks, ROC AUCs were 0.69 (95% CI 0.59 to 0.80) and 0.67 (95% CI 0.46 to 0.87) for the eRMDQ, 0.69 (95% CI 0.58 to 0.80) and 0.74 (95% CI 0.53 to 0.95) for the eVAS, and 0.73 (95% CI 0.66 to 0.80) and 0.81 (95% CI 0.69 to 0.92) for the eNRS, respectively. Associated MIC thresholds were estimated as 1 (0 to 2) and 2 (-1 to 5), 13 (9 to 17) and 7 (-12 to 26), and 2 (1 to 3) and 1 (0 to 2) points, respectively. Over a 1-week period in participants categorized as "stable" and "about the same" using the transition question, ICCs were 0.87 (95% CI 0.66 to 0.95) and 0.84 (95% CI 0.73 to 0.91) for the eRMDQ with MDC₉₅ of 4 and 5, 0.31 (95% CI -0.25 to 0.71) and 0.61 (95% CI 0.36 to 0.77) for the eVAS with MDC₉₅ of 39 and 34, and 0.52 (95% CI 0.14 to 0.77) to 0.67 (95% CI 0.51 to 0.78) with MDC₉₅ of 4 and 3 for the eNRS.

Conclusions: The eRMDQ was reliable with borderline adequate responsiveness. The eNRS was responsive with borderline reliability. While the eVAS had adequate responsiveness, it did not have an attractive reliability profile. Thus, the eNRS might be preferred over the eVAS for measuring pain intensity. The observed electronic outcome measures' metric properties are within the ranges of values reported in the literature for their paper counterparts and are adequate for measuring changes in a low back pain population.

Keywords: Roland Morris Disability Questionnaire; electronic patient-reported outcome measures; minimal detectable change; minimally important change; numerical rating scale; reliability; responsiveness; validation; visual analog scale.

Figure 1

Electronic visual analog scale for pain intensity showing 63 units of pain intensity.

Figure 2

Electronic Roland Morris Disability Scale showing a part score of 3 units.

Figure 3

Electronic numerical rating scale for pain intensity showing a part score of 6 units.

Figure 4

Histogram of patient age at baseline.

Figure 5

Flowchart showing completion rates at 1 and 6 weeks, chronicity status, and the incidence of self-reported recovery using the health transition question for participants who also completed the electronic numerical rating scale, and electronic Roland Morris Disability Questionnaire, and electronic visual analog scale measurement.

Figure 6

Graphs showing minimally important change bootstrap standard error convergence from simulations with increasing replication numbers. MIC: minimally important change, NRS: numerical rating scale, RMDQ: Roland Morris Disability Questionnaire, VAS: visual analog scale.