Context: Depressive disorders are highly prevalent in the general population, but recognition and accurate diagnosis are made difficult by the lack of a simple confirmatory test.
Objective: To review the accuracy and precision of depression questionnaires and the clinical examination for diagnosing clinical depression.
Data sources: We searched the English-language literature from 1970 through July 2000 using MEDLINE, a specialized registry of depression trials, and bibliographies of selected articles.
Study selection: Case-finding studies were included if they used depression questionnaires with easy to average literacy requirements, evaluated at least 100 primary care patients, and compared questionnaire results with accepted diagnostic criteria for major depression. Eleven questionnaires, ranging in length from 1 to 30 questions, were assessed in 28 published studies. Reliability studies for the clinical examination required criterion-based diagnoses made by at least 2 clinicians who interviewed the patient or reviewed a taped examination. Fourteen studies evaluated interrater reliability.
Data extraction: Pairs of authors independently reviewed articles. For case-finding studies, quality assessment addressed sample size and whether patients were selected consecutively or randomly, the criterion standard was administered and interpreted independently of and blind to the results of the case-finding instrument, and the proportion of persons receiving the criterion standard assessment was less than or more than 50% of those approached for criterion standard assessment. For reliability studies, quality assessment addressed whether key patient characteristics were described, the interviewers collected clinical history independently, and diagnoses were made blinded to other clinicians' evaluations.
Data synthesis: In case-finding studies, average questionnaire administration times ranged from less than 1 minute to 5 minutes. The median likelihood ratio positive for major depression was 3.3 (range, 2.3-12.2) and the median likelihood ratio negative was 0.19 (range, 0.14-0.35). No significant differences between questionnaires were found. For mental health care professionals using a semistructured interview, agreement was substantial to almost perfect for major depression (kappa = 0.64-0.93). Nonstandardized interviews yielded somewhat lower agreement (kappa = 0.55-0.74). A single study showed that primary care clinicians using a semistructured interview have high agreement with mental health care professionals (kappa = 0.71).
Conclusions: Multiple, practical questionnaires with reasonable performance characteristics are available to help clinicians identify and diagnose patients with major depression. Diagnostic confirmation by mental health care professionals using a clinical interview or by primary care physicians using a semistructured interview can be made with high reliability.