Quality of life is one of the essential aspects to be assessed in patients with low back pain (LBP). For its measurement, SF-12 (a survey) is the most extensively used method, but its Minimal Clinically Important Difference (MCID) was not known.

A multicenter, prospective, cohort study was performed with an objective to assess the MCID for the physical (PCS) and mental (MCS) component summaries of Short Form SF-12 (SF-12), in patients with low back pain (LBP).

In this study, patient (n-458) with subacute and chronic LBP were consecutively recruited across 21 practices. Upon recruitment and 12 months later, specific criteria like LBP, referred pain, disability, PCS and MCS were evaluated. The external standard used were self-reported health status change between baseline and 12 month-assessment. Estimation of MCID for SF-12 was done following four anchor-based methods for which the Area Under the Curve (AUC) was calculated. These methods include minimal detectable change (MDC); average change (AC); change difference (CD); and receiver operating characteristic curve (ROC). The effect on MCID values of pain duration and baseline scores were also assessed.

The findings of the study revealed the values for PCS: MDC: 0.56, AC: 2.71, CD: 3.29, ROC: 1.14. Values for MCS, were: MDC: 3.77, AC: 3.54, CD: 1.13, ROC: 4.23. AUC values were < 0.7. Values of MCID were found to be smaller among chronic patients and those with better baseline quality of life.

Therefore, it can be concluded that calculating MCID through different methods leads to different results. In subacute and chronic LBP patients, improvements > 3.77 in MCS and > 3.29 in PCS, can be considered clinically relevant. MCID was noted to be smaller in patients having longer pain duration and better baseline quality of life.