The minimal important change of the gambling symptom assessment scale among individuals experiencing gambling problems who underwent self-help internet interventions

The Gambling Symptom Assessment Scale (G-SAS) is one of the most common treatment outcome measures to assess gambling symptom severity. For clinicians and patients to interpret whether the observed changes in G-SAS scores are meaningful, we need to determine the minimal important change (MIC)–the smallest change in score that patients perceive as important. To estimate the MIC of G-SAS, we analyzed data from 281 participants in two randomized controlled trials of Internet interventions for problem gambling. Participants completed the G-SAS both at baseline and 1 week later and rated their perceived change in gambling symptoms. We estimated the MIC using four approaches based on mean change scores, receiver operating characteristic curves, predictive modeling, and adjusted predictive modeling. When asked the anchor question about symptom changes 1 week after baseline, 52% of participants reported improvement. The MIC estimates ranged from 2.1 to 7.0 points across different approaches. Based on the predictive MIC (3.8, 95% CI 3.2 to 4.4) and adjusted predictive MIC (3.8, 95% CI 2.6 to 4.8), which are expected to be more unbiased than the others, we recommend a four-point reduction as the MIC of the G-SAS.