Classification characteristics of the Patient Health Questionnaire-15 for screening somatoform disorders in a primary care setting

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Abstract

Background

This study examines how effectively the Patient Health Questionnaire-15 (PHQ-15), a self-administered screening instrument, recognizes somatoform symptoms and somatoform disorders in a German primary care setting.

Methods

A selected sample of 308 patients (mean age 47.2 years, 71.4% women) from two regular primary care practices was screened with the PHQ-15 and additionally examined with structured interviews. Their primary care physicians rated symptoms reported in the interview as either “medically explained” or “medically unexplained.”

Results

Seventy-six percent of the symptoms were judged as medically unexplained. The PHQ-15 correlated significantly with the total number of symptoms as well as the number of somatoform symptoms (both r=0.63; P≤.001). A comparison between the most frequently reported symptoms in the interview and the 15 items of the PHQ-15 revealed that even though the PHQ-15 does not differentiate between medically explained and medically unexplained symptoms, it does catch many somatoform symptoms. When used to predict the diagnosis of a somatoform disorder, a cutoff of 10 points in the PHQ-15 was identified as optimal, resulting in a sensitivity of 80.2% and specificity of 58.5%. However, the cutoff has to be adjusted according to specific research or clinical purposes.

Conclusion

Several previous results could be confirmed, and under consideration of some limitations, the PHQ-15 seems to be a valuable tool for identifying somatoform symptoms and disorders in primary care.

Introduction

Medically unexplained symptoms (MUSs) and somatoform disorders (SFDs) are a prevalent phenomenon in the primary care setting [1], [2], [3], [4]. Although effective therapeutic strategies for treating this patient group exist [5], [6], [7], diagnostic instruments and screening methods are needed for a reliable case detection. The Patient Health Questionnaire-15 (PHQ-15) was developed for this purpose [8]. It is an economical, self-administered screening instrument that has been used as a tool in a number of studies. Moreover, it has been suggested by the DSM-V Workgroup on Somatic Symptom Disorders as a measure of symptom severity for the current proposal of a revised SFD classification [9]. The general purpose of the present study is to further validate the PHQ-15 and to test its screening and classification characteristics. We attempt to replicate previous results and provide new data.

The PHQ-15 is a screening instrument for somatic symptom severity (SSS) and has been developed from its precursors, the “Primary Care Evaluation of Mental Disorders” (PRIME-MD) [10] and the “PRIME-MD Patient Health Questionnaire” (PRIME-MD PHQ) [11], [12]. These methods aim at economically detecting mental disorders and have been used and validated in a variety of studies [8], [13], [14], [15], [16], [17], [18], [19], [20]. Validity, classification characteristics and responsiveness to change have been reported by these studies. However, to the best of our knowledge, the analyses of classification characteristics were always focused on the PHQ-15′s precursor, the PRIME-MD PHQ, but not on the PHQ-15 itself. One exception is a study by van Ravesteijn et al. [20]. However, after conducting a factor analysis, they eliminated two items and thus only studied 13 instead of 15 items. Therefore, in our study, we want to examine the PHQ-15′s validity in its most commonly used complete 15-item version.

As with every instrument currently used to screen MUSs and SFDs, the PHQ-15 does not differentiate between medically unexplained and medically explained symptoms. To judge this, a medical examination and physicians' opinions are needed. However, it is possible to assess whether a screening instrument is able to capture those symptoms that are most likely medically unexplained and that most often occur in patients with SFD. This is another aim of the current study. We also want to test the assumption of Kroenke et al. that the symptoms inquired about in the PHQ-15 are the most prevalent symptoms reported in the outpatient setting [8], [21].

In summary, based on these existing findings, we aim at answering the following questions: (a) Is the PHQ-15 able to capture physical symptoms in general as well as somatoform symptoms — needed to diagnose an SFD — in particular? What symptoms are reported most often by patients, and is the PHQ-15 able to capture these symptoms? (b) Is the PHQ-15 a good predictor of the existence of an SFD according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) [22]? What is the optimal threshold to further consider the diagnosis of an SFD?

To answer these questions, the present study focuses on the primary care setting because, for most patients with MUSs, their primary care physician is the first point of contact.

Section snippets

First step

Screening and interviews took place between February and September 2008 within two primary care practices in Mainz, Germany. Both practices are part of the regular German health system with two general practitioners (GPs) working at each practice.

In a first step, 614 general medical outpatients were screened consecutively with the PHQ-15 questionnaire. We wanted to recruit at least 600 patients with the final goal of sampling a sufficiently high number of patients with a high risk of having an

Prevalence rates

The 308 patients achieved a mean PHQ-15 score of 9.82 (S.D.=5.09, range 0–28) and reported a total of 2838 symptoms in the subsequent interview (9.21 symptoms per patient, S.D.=6.21, range 0–37). According to the physicians' ratings, 2218 of these symptoms (78.2%) were labeled as somatoform (7.20 symptoms per patient, S.D.=5.98, range 0–35) and 516 (18.2%) as somatic. One hundred four symptoms (3.7%) could not be rated due to lack of information. Adjustment to the original number of 614

Discussion

The main intention of the present study was to assess the psychometric properties of the PHQ-15 as a screening instrument for MUS and SFD in the primary care setting. The finding of a proportion of 76.0% of somatoform symptoms in the total symptom count is similar to the results of previous studies. For example, Aiarzaguena and colleagues [28] reported a ratio between somatic and somatoform symptoms of 1 to 4 and Kroenke and Mangelsdorff [29] a ratio of 1 to 3. These results confirm the high

References (44)

  • KroenkeK

    Somatoform disorders and recent diagnostic controversies

    Psychiatr Clin North Am

    (2007)
  • De WaalMWM et al.

    Somatoform disorders in general practice: prevalence, functional impairment and comorbidity with anxiety and depressive disorders

    Br J Psychiatry

    (2004)
  • van der Feltz-CornelisCM et al.

    Randomised controlled trial of a collaborative care model with psychiatric consultation for persistent medically unexplained symptoms in general practice

    Psychother Psychosom

    (2006)
  • KroenkeK et al.

    The PHQ-15: validity of a new measure for evaluating the severity of somatic symptoms

    Psychosom Med

    (2002)
  • American Psychiatric Association

    DSM-5 development — complex somatic symptom disorder [Internet]. Arlington: American Psychiatric Association

  • SpitzerRL et al.

    Utility of a new procedure for diagnosing mental disorders in primary care: the PRIME-MD 1000 Study

    JAMA

    (1994)
  • SpitzerRL et al.

    Validation and utility of a self-report version of PRIME-MD: the PHQ Primary Care Study

    JAMA

    (1999)
  • Diez-QuevedoC et al.

    Validation and utility of the Patient Health Questionnaire in diagnosing mental disorders in 1003 general hospital Spanish inpatients

    Psychosom Med

    (2001)
  • EscobarJI et al.

    Effectiveness of a time-limited cognitive behavior therapy-type intervention among primary care patients with medically unexplained symptoms

    Ann Fam Med

    (2007)
  • GerberMR et al.

    Intimate partner violence exposure and change in women's physical symptoms over time

    J Gen Intern Med

    (2008)
  • KroenkeK et al.

    Venlafaxine extended release in the short-term treatment of depressed and anxious primary care patients with multisomatoform disorder

    J Clin Psychiatry

    (2006)
  • BeckerS et al.

    Screening for somatization and depression in Saudi Arabia: a validation study of the PHQ in primary care

    Int J Psychiatry Med

    (2002)
  • Cited by (0)

    1

    Present address: “salus klinik" Hospital, Friedrichsdorf, Germany.

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