Validation of the 4DSQ Somatization Subscale in the Occupational Health Care Setting as a Screener

Lars de Vroege, Wilco H. M. Emons, Klaas Sijtsma, Rob Hoedeman, Christina M. van der Feltz-Cornelis

Purpose Somatoform disorders (physical symptoms without medical explanation that cause dysfunction) are prevalent in the occupational health (OH) care setting and are associated with functional impairment and absenteeism. Availability of psychometric instruments aimed at assessing somatoform disorders is limited. In the OH setting, so far only the Patient-Health-Questionnaire 15 has been validated as screener for somatoform disorder, and has been shown to have moderate validity. The Four-Dimensional Symptom Questionnaire (4DSQ) is frequently used in the OH setting but the Somatization subscale is not validated yet. The aim of this study is to validate the 4DSQ Somatization subscale as screener for DSM-IV somatoform disorder in the OH setting by using the MINI interview as gold standard. Methods Employees absent from work due to physical symptoms, for a period longer than 6 weeks and shorter than 2 years, were asked to participate in this study. They filled out the 4DSQ and underwent a MINI interview by telephone for DSM-IV classification. Specificity and sensitivity scores were calculated for all possible cut-off scores and a receiver operator curve was computed for the Somatization subscale. 95 % confidence intervals (95 % CIs) were calculated for sensitivity and specificity. Results The Somatization subscale of the 4DSQ has an optimal cut point of 9, with specificity and sensitivity equal to 64.3 % [95 % CI (53.6; 73.7 %)] and 60.9 % [95 % CI (40.8; 77.8 %)], respectively. Receiver operator curves showed an area under the curve equal to 0.61 [SE = 0.07; 95 % CI (0.48; 0.75)] for the Somatization subscale of the 4DSQ. Conclusion The 4DSQ Somatization subscale is a questionnaire of moderate sensitivity and specificity.