The Constitutional Type Questionnaire: validation in the patient population of the Royal London Homoeopathic Hospital

In homeopathy the choice of a medicine is based on the total ‘picture’ presented by the patient. This picture includes ‘constitutional type’ which comprises personality, and general physical features. The Constitutional Type Questionnaire (CTQ) is designed to systematically assess constitutional types. This study examines the reliability and validity of the CTQ. Four hundred and seventy-two outpatients attending clinics at the Royal London Homoeopathic Hospital completed the CTQ, a 152-item scale rating features traditionally considered typical of 19 constitutional homeopathic medicine ‘pictures’ on 5-point frequency or severity scales. A subsample was retested after 1 week to measure the test–retest reliability. Another subsample was prescribed a medicine by a homeopathic doctor. Prescriptions were compared with the CTQ, to assess the content validity of the scale. The construct validity was measured by Grade of Membership (GOM) analysis. The scale demonstrated good test–retest reliability (r=0.73), internal consistency (r=0.95). The correlation between CTQ results and the medicine prescribed by the homeopathic doctor was 75.8%. The GOM analyses are reported by Davidson et al elsewhere in this issue of the journal. Although the CTQ could be improved, the scale displays good reliability and validity.