Clinical utility of Patient Health Questionnaire-9 (PHQ-9) in memory clinics

Background. Both dementia and depression may produce complaints of memory impairment. Differential diagnosis may be difficult, but has practical implications regarding choice of appropriate treatment. Aim. To assess the clinical utility of the Patient Health Questionnaire-9 (PHQ-9), a validated instrument for measurement of depression severity, in differentiating patients with and without dementia, referred with complaints of memory impairment to dedicated memory clinics. Methods. Pragmatic prospective study of consecutive referrals (n=113) to two dementia clinics, diagnosed using standard clinical diagnostic criteria for dementia (DSM-IV) and also administered the PHQ-9. Results. PHQ-9 proved acceptable to patients, and was quick and easy to use. Using traditional parameters of diagnostic utility (sensitivity, specificity, positive predictive value, likelihood ratios), PHQ-9 performance was modest for the diagnosis of dementia. However, pragmatically PHQ-9 scores proved helpful in deciding which patients, both with and without dementia, required a trial of antidepressant medication. Conclusions. PHQ-9 proved useful as a brief screen for depression in patients attending dementia clinics with a complaint of memory impairment.