Comparison of the Factor Structure of the Patient Health Questionnaire for Somatic Symptoms (PHQ-15) in Germany, the Netherlands, and China. A Transcultural Structural Equation Modeling (SEM) Study

Abstract

Background: Persistent somatic symptoms are associated with psychological distress, impaired function, and medical help-seeking behavior. The Patient Health Questionnaire (PHQ)-15 is used as a screening instrument for somatization and as a monitoring instrument for somatic symptom severity. A bifactorial model has been described, with one general factor and four orthogonal specific symptom factors. The objective of the present study was to assess and to clarify the factor structure of the PHQ-15 within and between different countries in Western Europe and China.Method: Cross-sectional secondary data analysis performed in three patient data samples from two Western European countries (Germany N = 2,517, the Netherlands N = 456) and from China (N = 1,329). Confirmatory factor analyses (CFA), and structural equation modeling (SEM) analysis were performed.Results: The general factor is found in every sample. However, although the outcomes of the PHQ-15 estimate severity of somatic symptoms in different facets, these subscales may have different meanings in the European and Chinese setting. Replication of the factorial structure was possible in the German and Dutch datasets but not in the dataset from China. For the Chinese dataset, a bifactorial model with a different structure for the cardiopulmonary factor is suggested. The PHQ-15 could discern somatization from anxiety and depression within the three samples.Conclusion: The PHQ-15 is a valid questionnaire that can discern somatization from anxiety and depression within different cultures like Europe or China. It can be fitted to a bifactorial model for categorical data, however, the model can only be recommended for use of the general factor. Application of the orthogonal subscales in non-European samples is not corroborated by the results. The differences cannot be ascribed to differences in health care settings or by differences in concomitant depression or anxiety but instead, a cultural factor involving concepts of disease may play a role in this as they may play a role in the translation of the questionnaire. Further research is needed to explore this, and replication studies are needed regarding the factorial structure of the PHQ-15 in China.

Are comparisons of mental disorders between Chinese and German students possible? An examination of measurement invariance for the PHQ-15, PHQ-9 and GAD-7

“…The possible reason for this could be that the samples included in our study have a greater difference in cultural background. Our result corresponded with the findings of an earlier crosscultural study [32], which also could not confirm measurement invariance of the PHQ-15 between Chinese and German samples of outpatients. In our study, the pattern of variant items at the level of metric and scalar invariance across groups was mixed.…”

“…In previous studies, measurement invariance of the PHQ-15 with a bifactor model (one general somatic symptom factor and four orthogonal-specific symptom factors of pain, gastroenterology, cardiovascular and fatigue symptoms) could be confirmed with samples of college students from Germany and Switzerland [30], between German and migrants [31] and between patient samples from Germany and the Netherlands, but not between Chinese patient samples and Western (German and Dutch) patient samples [32]. Measurement invariance with a one-factor model was confirmed between primary care patients of native-born Germans, Russianspeaking immigrants and native-born Russians [33].…”

Psychometric Properties of the Chinese Version of the Cognitions About Body and Health Questionnaire

“…Among the dimensions of somatic symptoms, PHQ-15, a questionnaire measuring the level of somatic distress, was found to have distinct structures in Chinese and European samples. 30 Second, using only CABAH is not suitable for diagnosing SSD; the questionnaire SSD-12 should be the better option for this purpose. 31 Different from the previous construct somatoform disorders, the concept “medically unexplained“ has been removed in SSD; therefore, SSD may co-exist in patients with medical comorbidity.…”

Assessment of the structured clinical interview (SCID) for DSM-5 for somatic symptom disorder in general hospital outpatient clinics in China

“…The PHQ-15 was validated in Chinese for somatic symptoms [14,15]. The SSS-8 is a self-rating scale used to quantify the somatic symptom burden of patients in the past week and has been validated in Chinese patients [16].…”