BCQ-: A Body Constitution Questionnaire to assess Yin-Xu. Part II: evaluation of reliability and validity

Based on the Traditional Chinese Medicine (TCM) theory and guided by the principles of modern medicine (MM), we aimed to develop an effective and reliable diagnostic tool using self-reported data in order to assess the Yin-Xu body constitution. In this study, we further evaluated a provisional 22-item version of the Yin-Xu Body Constitution Questionnaire (BCQ-) previously derived from the Delphi process.

A total of 1,272 eligible participants aged between 20 and 60 years was recruited. The participants had received health examination in teaching hospitals and had not shown any disease onset in the prior month. The factor structure of the BCQ- was explored, and the reliability and validity of each derived factor (scale) were evaluated.

Exploratory factor analysis revealed 5 factors corresponding to the manifestations of the diminishing Yin-Xu level in 5 different body areas: head, 4 limbs, gastrointestinal tract, body surface, and abdominal cavity. 3 items with low factor loading (<0.4) were dropped, resulting in a 19-item BCQ-. Cronbach's α ranged from 0.57 to 0.85, and the intra-class correlation coefficients were greater than 0.7 for most items. The diagnoses of Yin-Xu by both the BCQ- and experienced TCM doctors were consistent. The concurrent validity showed that higher Yin-Xu scores were associated with lower hemoglobin.

The final BCQ- measures the Yin-Xu constitution of 5 different body areas. The questionnaire is a reliable, valid, and potentially useful instrument for evaluating the Yin-Xu constitution in clinical research and practice.