Defining the minimal clinically important difference (MCID) of the Heinrichs-carpenter quality of life scale (QLS)

To determine the Minimal Clinically Important Difference (MCID) of the Heinrichs-Carpenter Quality of Life Scale (QLS). Data from the "Schizophrenia Trial of Aripiprazole" (STAR) study were used in this analysis. The MCID value of the QLS total score was estimated using the anchor-based method. These findings were substantiated/validated by comparing the MCID estimate to other measurements collected in the study. Half of the patients (49%) showed improvement in Clinical Global Impressions of Severity (CGI-S) during the trial. The estimated MCID of the QLS total score was 5.30 (standard error: 2.60; 95% confidence interval: [0.16; 10.43]; p < 0.05). Patients were divided into two groups: "QLS improvers" (QLS total score increased ≥ six points) and "non-improvers". The QLS improvers had significantly better effectiveness and reported significantly higher levels of preference for their current medications. There was a statistically significant difference between the two groups in the change in two of the four domains of QLS; "Interpersonal relations" and "Intrapsychic foundations" domains during the study. These findings support the value of the estimated MCID for the QLS and may be a useful tool in evaluating antipsychotic treatment effects and improving long-term patient outcomes in schizophrenia. Copyright © 2015 John Wiley & Sons, Ltd.