BALTIMORE—The Sleep Condition Indicator (SCI), a brief clinical screening tool, may be a highly sensitive and specific method for identifying patients with insomnia disorder, according to research presented at the 27th Annual Meeting of the Associated Professional Sleep Societies. The eight-item scale appears to correlate well with the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI). A short form of the SCI, which includes two questions, may be useful for rapid screening, reported Simon Kyle, PhD, Lecturer in Clinical and Health Psychology at the University of Manchester, UK, and Colin Espie, PhD, Professor of Clinical Psychology at the University of Oxford, UK.
A Multistudy Evaluation of the SCI
Dr. Kyle and colleagues based the SCI on the criteria for insomnia disorder that were proposed for inclusion in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5). The scale includes two quantitative items that assess sleep continuity (ie, problems with initiating and maintaining sleep), two qualitative items about patient satisfaction with sleep quality, two quantitative items regarding the severity of the sleep complaint, and two qualitative items about the patient’s daytime dysfunction. In contrast to the PSQI and the ISI, higher scores on the SCI indicate better sleep condition.
The investigators evaluated the SCI in five studies using online surveys and in the context of a randomized controlled trial of online cognitive behavioral therapy for insomnia. The group assessed the SCI’s internal consistency, sensitivity and specificity, concurrent validity with standard measures of insomnia, and responsiveness to change. To create the short form of the SCI, the researchers conducted logistic regression modeling to identify the subset of items that best explain the SCI total score.
High Sensitivity and Specificity
The SCI had highly significant and strong negative correlations with the PSQI and the ISI. Trials of a small, healthy sample suggested that the SCI had small, negative correlations with depression, anxiety, and stress. Dr. Kyle and colleagues also found that having a better sleep condition was positively associated with better physical and mental health. For a version of the SCI in which responses are given on a scale of 0 to 10, a total score lower than 4.6 correctly identified 92% of people who met DSM-5 criteria for insomnia disorder. A score higher than 4.6 correctly identified 87% of individuals who did not meet DSM-5 criteria for insomnia disorder.
Two of the researchers’ largest data sets indicated that the SCI had a satisfactory to good level of internal consistency. Logistic regression analysis identified two of the eight items on the SCI that predicted 82% of the variance in total SCI scores. Results of the short, two-item version of the SCI correlated strongly with SCI total score.
The SCI is not intended to replace the PSQI or the ISI, but it contributes to the range of measures that assess sleep with the latest criteria, said Dr. Kyle. “The SCI provides a brief, intuitive scale based on DSM-5. It’s been extensively tested on large samples and has good psychometric properties,” he concluded.
—Erik Greb
Senior Associate Editor