Validation of the patient health questionnaire (PHQ)-9 and PHQ-2 in patients with COPD in China

Patient Health Questionnaire (PHQ-9) and PHQ-2 are commonly used screening tools for depression but have not been validated in Chronic obstructive pulmonary disease (COPD) patients. We aimed to validate PHQ-9 and PHQ-2 among COPD patients in China.

Stable COPD patients were assessed using a PHQ-9 questionnaire and then assessed by a senior psychiatrist to confirm the diagnosis of major depressive disorder (MDD) according to the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition. Receiver operating characteristic curve analysis was performed to validate the PHQ-9/PHQ-2.

Out of 265 COPD patients, 11.7% were diagnosed with MDD. The Cronbach's α-coefficient for PHQ-9 was 0.751. Both PHQ-9 and PHQ-2 showed good correlations with COPD symptoms and quality of life. The AUC values of PHQ-9 and PHQ-2 were 0.848 and 0.736, respectively, for identifying MDD. Based on the highest Youden index, the optimal cut-off scores were PHQ-9 ≥ 7 and PHQ-2 ≥ 2, with a sensitivity of 74.2% and 58.1% and specificity of 89.7% and 89.3%, respectively.

PHQ-9 score ≥ 7 and PHQ-2 score ≥ 2 should be used as the optimal cut-offs for COPD patients in China. PHQ-9 is a valid tool for detecting MDD in COPD patients, while PHQ-2 (score < 2) is more useful for quickly excluding MDD.