Comparison of scoring methods for the Brief Insomnia Questionnaire in a general population sample

The Brief Insomnia Questionnaire (BIQ) is a lay-administered, structured interview to derive insomnia disorders according to the Diagnostic and Statistical Manual, Fourth Edition, Text Revision (DSM-IV-TR), International Classification of Diseases, Tenth Edition (ICD-10) and research diagnostic criteria/International Classification of Sleep Disorders, Second Edition (RDC/ICSD-2). The concordance between diagnoses derived from the BIQ and clinical interviews was only moderate and the prevalence estimates based on the BIQ were significantly different from estimates based on clinical interviews. We hypothesized that a modification of the scoring algorithm closer to the diagnostic criteria would improve the performance of the BIQ.

Probability subsample of population-based epidemiological survey respondents (n=2011) completed clinical reappraisal (n=176) interviews. We compared the modified scoring with the original scoring in sensitivity, specificity, positive and negative predictive values, areas under the characteristic curve, and Cohen's kappa to detect DSM-IV-TR, ICD-10 and RDC/ICSD-2 insomnia diagnoses by the BIQ against clinical interviews.

The diagnostic accuracy was improved with the modified scoring. The areas under the receiver operating characteristic curve for the DSM-IV-TR, ICD-10, RDC/ICSD-2 and any of the insomnia diagnoses ranged from 0.76 to 0.87. Using the modified scoring, there was no significant difference between prevalence estimates based on the BIQ classification and clinical interviews.

The BIQ with modified scoring enhanced case detection and produced more accurate prevalence estimates of DSM-IV-TR, ICD-10 and RDC/ICSD-2 insomnia disorders. With scoring algorithms now extended to DSM-5 and ICSD-3 diagnoses, the BIQ should be more widely used in clinical and research settings.