Why do primary care doctors diagnose depression when diagnostic criteria are not met?

Abstract This study examines predictors of false positive depression diagnoses by primary care doctors in a sample of primary care attendees, taking the patients' diagnostic status from a self‐report measure (Depression Screening Questionnaire, DSQ) as a yardstick against which to measure doctors' correct and false positive recognition rates. In a nationwide study, primary care patients aged 15–99 in 633 doctors' offices completed a self‐report packet that included the DSQ, a questionnaire that assesses depression symptoms on a three‐point scale to provide diagnoses of depression according to the criteria of DSM‐IV and ICD‐10. Doctors completed an evaluation form for each patient seen, reporting the patient's depression status, clinical severity, and treatment choices. Predictor analyses are based on 16,909 patient‐doctor records. Covariates examined included depression symptoms, the total DSQ score, number and persistence of depression items endorsed, patient's prior treatment, history of depression, age and gender. According to the DSQ, 11.3% of patients received a diagnosis of ICD‐10 depression, 58.9% of which were correctly identified by the doctor as definite threshold, and 26.2% as definite subthreshold cases. However, an additional 11.7% of patients not meeting the minimum DSQ threshold were rated by their doctors as definitely having depression (the false positive rate). Specific DSQ depression items endorsed, a higher DSQ total score, more two‐week depression symptoms endorsed, female gender, higher age, and patient's prior treatment were all associated with an elevated rate of false positive diagnoses. The probability of false positive diagnoses was shown to be affected more by doctors ignoring the ‘duration of symptoms’ criterion than by doctors not following the ‘number of symptoms’ criterion for an ICD or DSM diagnosis of depression. A model selection procedure revealed that it is sufficient to regress the ‘false positive diagnoses’ on the DSQ‐total score, symptoms of depressed mood, loss of interest, and suicidal ideation; higher age; and patient's prior treatment. Further, the total DSQ score was less important in prediction if there was a prior treatment. The predictive value of this model was quite good, with area under the ROC‐curve = 0.86. When primary care doctors use depression screening instruments they are oversensitive to the diagnosis of depression. This is due to not strictly obeying the two weeks duration required by the diagnostic criteria of ICD‐10 and DSM‐IV. False positive rates are further increased in particular by the doctor's knowledge of a patient's prior treatment history as well as the presence of a few specific depression symptoms. Copyright © 2000 Whurr Publishers Ltd.