Estimating the minimum clinically important difference (MCID) of the five-repetition sit-to-stand test in patients with lumbar disc herniation

The impact of surgical interventions on lumbar disc herniation (LDH) is often assessed using objective functional impairment (OFI) tests like the five-repetition sit-to-stand (5R-STS) test. This study calculates the minimum clinically important difference (MCID) for 5R-STS improvement in patients with LDH one year after surgery.

Adult patients with LDH scheduled for surgery were prospectively recruited from a Dutch short-stay spinal clinic. The 5R-STS time, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), Numeric Rating Scale for back and leg pain, EQ-5D-3L health-related quality of life questionnaire and EQ5D-VAS were recorded preoperatively, at 6-weeks and 1-year post-operatively. The MCID was calculated using anchor-based methods (within-patient change; between-patient change; and receiver-operating characteristic approaches) and distribution-based methods (0.5 standard deviation (SD); effect size; standard error of measurement; standardized response mean; and 95% minimum detectable change (MDC)). The final MCID value was based on the “gold standard”: an averaging of the anchor-based methods using ODI and RMDQ as the closest available anchors.

We prospectively recruited 134 patients. One-year follow-up was completed by 103 (76.8%) of patients. The MCID values derived using different methods varied from 0.7 to 5.1 s (s). The final, averaged, anchor-based MCID for improvement was 3.6 s. Within distribution-based methods, 95% MDC and 0.5SD approach, yielded an MCID of 3.0 and 3.8 s, respectively, aligning closely with the overall anchor-derived MCID for 5R-STS.

In a patient with LDH, an improvement in 5R-STS performance of at least 3.6 s can be regarded as a clinically relevant improvement.