Screening for major depression in cancer outpatients: the diagnostic accuracy of the 9-item patient health questionnaire

Abstract

Background: Systematic screening for depression has been recommended for patients who have medical conditions like cancer. The 9-item Patient Health Questionnaire (PHQ-9) is becoming widely used, but its diagnostic accuracy has not yet been tested in a cancer patient population. In this article, the authors report on the performance of the PHQ-9 as a screening instrument for major depressive disorder (MDD) in patients with cancer.

Methods: Data obtained from a depression screening service for patients who were attending clinics of a Regional Cancer Centre in Edinburgh, United Kingdom were used. Patients had completed both the PHQ-9 and a 2-stage procedure to identify cases of MDD. Performance of the PHQ-9 in identifying cases of MDD was determined using receiver operating characteristic (ROC) analysis.

Results: Data were available on 4264 patients. When scored as a continuous measure, the PHQ-9 performed well with an area under the ROC curve of 0.94 (95% confidence interval [CI], 0.93-0.95). A cutoff score of ≥ 8 provided a sensitivity of 93% (95% CI, 89%-95%), a specificity of 81% (95% CI, 80%-82%), a positive predictive value (PPV) of 25%, and a negative predictive value (NPV) of 99% and could be considered optimum in a screening context. The PHQ-9 did not perform as well when it was scored using an algorithm with a sensitivity of 56% (95% CI, 55%-57%), a specificity of 96% (95% CI, 95%-97%), a PPV of 52%, and an NPV of 97%.

Conclusions: The PHQ-9 scored as a continuous measure with a cutoff score of ≥ 8 performed well in identifying MDD in cancer patients and should be considered as a screening instrument in this population.