In a five-year prospective follow-up study of 115 psychiatrically hospitalized patients, interinterview reliability for depressive symptoms was 94%. Specific interrater diagnostic reliability was 80%, using explicit diagnostic criteria. Disagreement was solely on degree of certainty within a specific diagnosis, not between different diagnoses. Interrater reliability was 100% for presence or absence of affective disorder.
Follow-up was blind. Of 52 patients initially diagnosed by explicit criteria as having primary affective disorder, 43 were followed up. Blind diagnostic agreement was 86%. An additional 9% not concordant by blind diagnosis fell within the usual clinical concept of primary affective disorder. Only two patients (5%) had a course incompatible with the natural history of primary affective disorder. To our knowledge this is the first blind, prospective validation of criteria for the diagnosis of primary affective disorder.
Murphy GE, Woodruff RA, Herjanic M, Fischer JR. Validity of the Diagnosis of Primary Affective DisorderA Prospective Study With a Five-Year Follow-up. Arch Gen Psychiatry. 1974;30(6):751–756. doi:10.1001/archpsyc.1974.01760120017003