Minimal detectable change of the Patient Health Questionnaire-9, Patient Health Questionnaire-8, and Patient Health Questionnaire-2: individual patient data meta-analysis.

Abstract

To estimate the minimal detectable change (MDC) for the Patient Health Questionnaire-9 (PHQ-9) and its eight item (PHQ-8) and two item (PHQ-2) versions including differences by participant and study characteristics. Individual participant data meta-analysis. Medline, Medline In-Process and other non-indexed citations, PsycInfo, and Web of Science, 1 January 2000 to 9 May 2018. Datasets from articles in any language if participants were aged ≥18 years, were recruited from any non-psychiatric setting, and were not recruited because they were seeking mental healthcare. Eligible datasets had a classification for major depressive disorder or major depressive episode based on a validated semi-structured or fully structured interview conducted within two weeks of administering the PHQ-9, PHQ-8, or PHQ-2. Pooled MDCs across studies were estimated for the PHQ-9, PHQ-8, and PHQ-2 with random effects meta-analysis for 95% (MDC95), 90% (MDC90), and 67% (MDC67) confidence that change beyond measurement error occurred. PHQ-9, PHQ-8, and PHQ-2 analyses included 42 548 participants (94 studies), 42 592 participants (94 studies), and 44 085 participants (98 studies), respectively. Mean participant age was 49 years (standard deviation 17), and 60% of participants were women. Overall, 10% of participants had major depression (range 1-57% across studies). MDC95 was 5.72 points (95% confidence interval (CI) 5.54 to 5.90, 95% prediction interval (PI) 4.00 to 7.44) for the PHQ-9, 5.51 points (95% CI 5.33 to 5.68, 95% PI 3.87 to 7.15) for the PHQ-8, and 2.26 points (95% CI 2.15 to 2.37, 95% PI 1.20 to 3.32) for the PHQ-2. For the PHQ-9, MDC95 was highest in inpatient healthcare settings at 6.48 (95% CI 6.05 to 6.92) points. MDC95 for the PHQ-9 increased by 0.40 (95% CI 0.25 to 0.55) points for each 10% increase in the proportion of participants with major depression. Sex and age had minimal or no association. Subgroup and meta-regression findings were similar for the PHQ-8 and PHQ-2. Based on the pooled estimate, a six point difference on the PHQ-9, the PHQ version most used in clinical practice, could be an appropriate MDC threshold in general practice. A higher threshold may be preferred in specialty mental healthcare. MDC67 or MDC90 thresholds would provide less certainty that change has occurred. Alternative strategies, such as using the upper end of a prediction interval, would provide more certainty but a greater likelihood of not recognising change. PROSPERO CRD42014010673.