Minimal (clinically) important differences for the Fatigue Assessment Scale in sarcoidosis

Summary Objective The usefulness of any questionnaire in clinical management and research trials depends on its ability to indicate a likelihood of treatment success during follow-up. The Minimal Clinically Important Difference (MCID) reflects a clinically relevant change score. The aim of this study was to estimate the MCID for the Fatigue Assessment Scale (FAS) in patients with sarcoidosis. Methods Outpatients ( n = 321) of the ild care team of the Department of Respiratory Medicine of the Maastricht University Medical Centre, The Netherlands, participated in this prospective follow-up study. Anchor-based and distribution-based methods were used to estimate the MCID. Based on the anchor Physical Quality of Life, a Receiver Operating Characteristic (ROC) was obtained. The distribution-based methods consisted of the Effect Size and Standard Error Measurement (SEM). Results The anchor-based MCID found with ROC was 3.5. The distribution-based methods showed that the corresponding change scores in the FAS for a small effect was 4.2. The SEM criterion was 3.6 points change in the FAS. Conclusions Based on the anchor-based and distribution-based methods, the MCID is a 4-point difference on the FAS. This MCID can be used in the follow-up of fatigue (FAS) in clinical trials and in the management of individual sarcoidosis cases.