Objective: To provide documentation for the diagnostic validity of the Athens Insomnia Scale (AIS), a self-assessment psychometric tool which has previously shown high consistency, reliability and external validity for the evaluation of the intensity of sleep difficulty.
Methods: The AIS was administered to a total of 299 subjects (105 primary insomniacs, 100 psychiatric outpatients, 44 psychiatric inpatients and 50 nonpatient controls) who were also assessed for the ICD-10 diagnosis of "nonorganic insomnia" blindly in terms of the AIS scores.
Results: 176 subjects were identified as insomniacs and 123 as noninsomniacs. Logistic regression of AIS total score against the ICD-10 diagnosis of insomnia demonstrated that a score of 6 is the optimum cutoff based on the balance between sensitivity and specificity. When diagnosing individuals with a score of 6 or higher as insomniacs, the scale presents with 93% sensitivity and 85% specificity (90% overall correct case identification). For this cutoff score, in the general population, the scale has a positive predictive value (PPV) of 41% and a negative predictive value (NPV) of 99%. For the same cutoff score, among unselected psychiatric patients, the PPV was found to be 86% and the NPV 92%. Other cutoff scores can be also considered, however, depending on the importance of avoiding false positive or false negative results; for example, for a cutoff score of 10, the PPV in the general population reaches about 90% without the NPV becoming lower than 94%.
Conclusion: The AIS can be utilized in clinical practice and research, not only as an instrument to measure the intensity of sleep-related problems, but also as a screening tool in reliably establishing the diagnosis of insomnia.