Responsiveness of the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire in lumbar surgery and its threshold for indicating clinically important differences.

BACKGROUND CONTEXT

Introduced in 2007, the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) has been widely used, but its psychometric properties have not been well studied.

PURPOSE

The objective of this study was to assess the responsiveness of the JOABPEQ in lumbar surgery and its threshold for indicating clinically important differences.

STUDY DESIGN

This is a prospective study.

PATIENT SAMPLE

Two hundred three consecutive patients underwent lumbar surgeries between July 2013 and November 2015 in a single hospital. Of the 203 patients, 181 patients who completed 1 year of follow-up were included.

OUTCOME MEASURES

Before and after surgery, the patients were asked to complete the questionnaire, including JOABPEQ, the 8-Item Short Form Health Survey (SF-8), and EuroQol-5D (EQ-5D). The participants were divided into five anchoring groups, ranging from "much better" to "much worse," according to reports from both physicians and patients.

MATERIALS AND METHODS

The responsiveness of measures was compared among five domains of the JOABPEQ ("low back pain," "walking ability," "lumbar function," "social function," and "mental health"), two domains of the SF-8 (the physical component summary [PCS] and the mental component summary [MCS]), and the EQ-5D. The responsiveness was assessed by the paired t test, the effect size, and the standardized response mean. The Spearman rank correlation coefficient and the receiver operating characteristic (ROC) curve were assessed using the five anchoring groups as external criteria. The clinically important differences, based on the ROC curve, were assessed.

RESULTS

Walking ability was most responsive, followed by low back pain and the PCS. The MCS was least responsive, followed by mental health and lumbar function. Social function and the EQ-5D had intermediate-level responsiveness. The substantial clinically important differences occurred at 20 points for low back pain and lumbar function, 23 points for walking ability, 14 points for social function, and 8 points for mental health.

CONCLUSIONS

The JOABPEQ domains are responsive measures in patients who undergo lumbar surgery. For physical function, the threshold for substantial clinically important differences was approximately 20 points for the JOABPEQ.