Psychiatry and Primary CareDiagnostic accuracy of the mood module of the Patient Health Questionnaire: a systematic review☆
Introduction
Detection of depression, especially in primary care, is far from optimal [1], [2], [3]. Both underdiagnosis and overdiagnosis have been reported, resulting in inadequate treatment. Underdiagnosis is related to the fact that patients present to their family physician with atypical symptoms either because they are too ashamed to discuss psychological problems or because subjective somatic symptoms are the main reason for their consultation. Family physicians may have difficulty with asking patients frankly about psychological symptoms. Sometimes, they do not know how to introduce the idea that depression may be an explanation for patients' physical complaints [4]. Overdiagnosis may occur among patients with subclinical depression or in psychological distress who are known to have had earlier episodes of depression [5]. Underdiagnosis carries the risk that patients do not get effective psychiatric treatment or are inappropriately treated for physical symptoms. Conversely, overdiagnosis carries the risk for unnecessary and therefore ineffective psychiatric treatment of minor and self-limiting problems. An instrument to detect a major depressive episode (MDE) should ideally have both a high sensitivity and a high specificity in order to reduce the number of false-negatives and false-positives.
A number of screening instruments to detect depressive episodes have been developed. Recently, these instruments were evaluated by Williams et al. [6] in a literature synthesis reporting similar operating characteristics but differences in administration time, ease of scoring and the ability to serve additional purposes, such as monitoring severity and screening for conditions other than depression. Of these instruments, only the Patient Health Questionnaire (PHQ) was developed for screening and diagnosis as well as monitoring of depression severity. It was developed in 1999 as a self-report version of the Primary Care Evaluation of Mental Disorders (PRIME-MD) [7] aimed at criteria-based diagnosis not only of depressive episodes but also of other mental disorders commonly encountered in primary care. Nowadays, the PHQ is used all over the world and has been translated into more than 25 languages, including German [8], French [9], Spanish [10], Italian [11], Arabic [12], Bengali [13], Turkish [14], Flemish [15] and Dutch [16].
The nine-item depression module of the full PHQ is called the PHQ-9 [17]. In contrast to other depression questionnaires, the PHQ-9 evaluates the nine Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for MDE [18]. The diagnosis of MDE can be made by a categorical algorithm using these nine items. By calculating a summary score, the severity of an episode can be assessed. Several studies have reported on the diagnostic accuracy of this instrument, but so far, the results have not been synthesized. We systematically reviewed the literature on the diagnostic accuracy of the self-report version of the PHQ-9. We further performed a meta-analysis to calculate its summary sensitivity and specificity.
Section snippets
Data sources
We performed a systematic search of literature dating between 1999 (PHQ issued) and July 2006 using the databases EMBASE, PubMed and PsycINFO with the terms “PHQ” and “Patient Health Questionnaire,” both as MESH headings and as text words. In addition, we checked the references of all included articles for relevant studies.
Study selection
Articles were included if their titles and abstracts were focused on the diagnostic accuracy of the PHQ-9 for MDE. Furthermore, the PHQ had to have been compared with a
Study selection
We found 223 articles, of which 40 were selected for detailed reading. Twenty-eight articles were excluded because (1) they did not concern the self-administered version of the PHQ-9 (n=5), (2) the study did not validate the complete mood module of the PHQ (n=4), (3) the PHQ-9 was only used for detecting any depressive episode and not specifically MDE (n=3), (4) the article was not a diagnostic accuracy study on the PHQ-9 (n=14) or (5) the data had been previously published in articles by the
Discussion
Our meta-analysis, in which we used the random effects model to calculate the summary sensitivity and specificity of four primary care studies, shows that the PHQ-9 has a high specificity of 0.94 (range=0.90–0.97) when used with the algorithm. This indicates that the PHQ-9 is a reliable tool if the user wants to avoid overdiagnosis. On the other hand, the chance of missing a patient with a depressive disorder in an unselected primary care sample (estimated prevalence of MDE=10%) is substantial
Acknowledgments
The authors thank Rob J.P.M. Scholten, MD, PhD, for his statistical advice and for constructing Figure 3 of this article.
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K. Wittkampf had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.