Use of the single-item Patient Global Impression-Severity scale as a self-reported assessment of insomnia severity.

We evaluated a single-item Patient Global Impression-Severity (PGI-S) scale for assessing insomnia severity during the clinical development programme for suvorexant. The analyses used data from two randomised, double-blind, placebo-controlled, 3-month, Phase III clinical trials of suvorexant in patients with Diagnostic and Statistical Manual of Mental Disorders IV criteria insomnia. Patients assessed insomnia severity during the previous week using the PGI-S, a one-item questionnaire containing six response options ranging from 0 (none) to 5 (very severe), at baseline and at Week 2, and Months 1, 2, and 3 after randomisation. The seven-item Insomnia Severity Index (ISI) and other subjective and objective assessments were also completed by patients. PGI-S responses were compared primarily with the ISI using descriptive statistics and correlations. The PGI-S demonstrated favourable measurement characteristics (validity, reliability, responsiveness and sensitivity). PGI-S scores decreased from baseline to Month 3 in a similar pattern to the ISI total score, and the Spearman correlation coefficient between PGI-S and the ISI was .73. An improvement of ≥2 points on the PGI-S defined a treatment responder, based on comparison to the ISI definition of a responder (improvement of ≥6 points). Our present findings suggest that the PGI-S is a simple but valid, reliable, responsive, sensitive, and meaningful patient-reported assessment of insomnia severity. The PGI-S may be particularly useful as a companion outcome to sleep monitoring using wearable sleep devices or smartphones in at-home settings.