Screening and case finding for major depressive disorder using the Patient Health Questionnaire (PHQ-9): a meta-analysis

Abstract

Objective

The Patient Health Questionnaire (PHQ-9) is a widely used screening tool for major depressive disorder (MDD), although there is debate surrounding its diagnostic properties. For the PHQ-9, we aimed to:

1. Establish the diagnostic performance at the standard cutoff point (10).

2. Compare the diagnostic performance at the standard cutoff point in different clinical settings.

3. Assess whether there is selective reporting of cutoff points other than 10.

Methods

We searched three databases — Embase, MEDLINE and PSYCHInfo — and performed a reverse citation search in Web of Science. We selected for inclusion studies of any design that assessed the PHQ-9 in adult populations against recognized gold-standard instruments for the diagnosis of either Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases criteria for major depression. Included studies had to report sufficient information to calculate 2*2 contingency tables. Data extraction and synthesis were performed independently by two researchers. For the included studies, we calculated pooled sensitivity, pooled specificity, positive likelihood, negative likelihood ratio and diagnostic odds ratio for cutoff points 7 to 15.

Results

Thirty-six studies (21,292 patients) met inclusion criteria. Pooled sensitivity for cutoff point 10 was 0.78 [95% confidence interval (CI), 0.70–0.84], and pooled specificity was 0.87 (95% CI, 0.84–0.90). At this cutoff, the PHQ-9 is a better screener in primary care than secondary care settings. No conclusions could be drawn at cutoff points other than 10 due to selective reporting of data.

Conclusions

For MDD, the PHQ-9 has acceptable diagnostic properties at cutoff point 10 in different settings. We recommend that future studies report the full range of cutoff points to allow exploration of optimal cutoff points in different settings.

Introduction

Major depressive disorder (MDD) has a high prevalence in the general population and is associated with considerable morbidity, as well as a high financial cost to society [1]. The Patient Health Questionnaire (PHQ-9) is a self-report tool for screening and case finding for MDD and is based on the Primary Care Evaluation of Mental Disorders, a diagnostic tool developed in the mid-1990s. It is widely used in both clinical and research settings. An indication of its importance comes from its recommendation as a measurement tool for depressive symptoms by the most recent iteration of the Diagnostic and Statistical Manual of Mental Disorders (DSM, Fifth Edition).

Four systematic reviews and meta-analyses previously evaluated the diagnostic properties of the PHQ-9. One of these [2] evaluated how the instrument performs in primary care settings and compared the algorithm scoring method with the summed score ≥ 10. A meta-analysis published in 2015 by Manea et al. examined the psychometric properties of the PHQ-9 using the algorithm scoring method and compared this scoring method in different settings with the summed score method at cutoff point of 10 [3]. Another review conducted by Gilbody et al. (published in 2007) summarized the diagnostic properties of the PHQ-9 in different settings [4]. The authors of this review also attempted to summarize the psychometric properties of the PHQ-9 at alternative cutoff points; however, not enough validation studies were found at the time. This analysis was subsequently carried out by Manea et al. in 2012 [5]. This diagnostic meta-analysis has suggested that the performance of the instrument at cutoff point 10 may be lower than that observed in the original validation study. The authors also suggested that different cutoff points may be required for different settings. It is therefore important to examine the performance of other cutoff points which is one of the aims of this review. The review by Manea et al. also highlighted the possibility that there may be selective reporting of cutoff points and that this may artificially inflate the observed diagnostic performance of the measure, at least for cutoff points other than the standard one, which tends to be reported by all studies.

On the basis of this, the current review has three aims: firstly, to establish the diagnostic performance of the PHQ-9 at the standard cutoff point (given the popularity of the PHQ-9, the number of studies available to assess this has grown rapidly since the previous review); secondly, to compare the diagnostic performance of the PHQ-9 at the standard cutoff point in different clinical settings; thirdly, to assess whether there is selective reporting of cutoff points for cutoffs other than 10.