Identifying depression with the PHQ-2: A diagnostic meta-analysis.

Area of Science:

• Psychiatry
• Clinical Psychology
• Diagnostic Test Evaluation

Background:

• Brief screening instruments are valuable for identifying depression in busy clinical settings.
• The Patient Health Questionnaire-2 (PHQ-2) is a two-question instrument assessing core depression symptoms: low mood and loss of interest.
• The PHQ-2 offers a rapid assessment of potential depressive symptoms.

Purpose of the Study:

• To systematically review and meta-analyze the diagnostic performance of the PHQ-2 for detecting major depressive disorder.
• To evaluate the PHQ-2's accuracy at recommended (≥3) and alternative (≥2) cutoff scores.

Main Methods:

• A systematic literature search was conducted across Embase, MEDLINE, PsychINFO, and grey literature.
• Studies were included if they used the standard PHQ-2 scoring, compared it to a gold-standard diagnostic interview, and reported performance data for cutoff scores ≥3 or ≥2.
• Bivariate diagnostic meta-analysis was employed to pool sensitivity, specificity, and likelihood ratios, accounting for heterogeneity.

Main Results:

• Twenty-one studies (N=11,175) were included, with 1529 diagnosed with major depressive disorder.
• At a cutoff of ≥3, pooled sensitivity was 0.76 and specificity was 0.87, with substantial heterogeneity (I²=81.8%).
• At a cutoff of ≥2, pooled sensitivity was 0.91 and specificity was 0.70, with lower heterogeneity (I²=43.2%).

Conclusions:

• A PHQ-2 cutoff of ≥2 demonstrates higher sensitivity, potentially better for minimizing missed depression diagnoses.
• However, the lower specificity at ≥2 may lead to a high false-positive rate in low-prevalence populations.
• The choice of cutoff (≥2 vs. ≥3) depends on the clinical context and the balance between sensitivity and specificity, with caution advised due to potential reporting bias.