Clinimetric analysis of the numeric pain rating scale, Oswestry disability index, and the Roland-Morris disability questionnaire in patients with lumbar spinal stenosis treated with conservative interventions.

BACKGROUND CONTEXT: The numeric pain rating scale (NPRS), Oswestry disability index (ODI) and the Roland-Morris disability questionnaire (RMDQ) are commonly used patient-reported outcome measures (PROMs) in patients with low back pain. However, there is a paucity of evidence supporting the reliability, validity, and responsiveness of these PROMs in patients with lumbar spinal stenosis (LSS) treated with conservative interventions including spinal manipulation, electrical dry needling, joint mobilization, and exercise.

PURPOSE: To establish the reliability, construct validity, responsiveness, minimal detectable change (MDC), and minimum clinically important difference (MCID) of the NPRS, ODI, and RMDQ in patients with LSS.

STUDY DESIGN/

SETTING

Clinimetric analysis of a prior randomized clinical trial.

PATIENT SAMPLE: One hundred twenty-eight (n = 128) patients with LSS treated with outpatient physical therapy, including manual therapy, exercise and electrical dry needling.

OUTCOME MEASURES: PROMs included the NPRS, ODI, RMDQ, and the global rating of change scale (GROC).

METHODS

The MDC (90 % and 95 % confidence interval) and MCID was established for "improved" (GROC: +3 to + 7) and "much-improved" (GROC: +5 to + 7) patients at 3-months follow-up. The intraclass correlation coefficient (ICC2,1) was analyzed at 2 weeks, 6 weeks and 3-months. Pearson's correlation (r) was also calculated.

RESULTS

The NPRS (ICC2,1 = 0.55; [95 % CI: 0.19-0.79]) exhibited moderate reliability, while the ODI (ICC2,1 = 0.86; [95 % CI: 0.70-0.94]) and RMDQ (ICC2,1 = 85; [95 % CI: 0.64-0.94]) exhibited good reliability at the 3-month follow-up. All PROMs exhibited acceptable responsiveness (area under the curve range 0.73 to 0.92; p < 0.001) and strong construct validity (Pearsons r: range 0.51 to 0.72; p < 0.001). The MDC95 was 2.3 points for the NPRS, 8.5 points for the ODI, and 6.1 points for the RMDQ. The MCID exceeded measurement error in the "much improved" patients for the NPRS (2.8 points) and the ODI (8.5 points), but did not for the RMDQ (4.5 points).

CONCLUSIONS

All three PROMs demonstrated suitable clinimetric properties in patients with LSS. Based on this analysis, patients who are "much improved" should have at least a 2.8-point reduction on the NPRS, and an 8.5-point reduction on the ODI to be considered clinically meaningful, and to exceed the measurement error. The MCID of the RMDQ did not exceed measurement error in either improvement category.