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

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 <= 0.01). 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. (C) 2011 Elsevier Inc. All rights reserved.