Psychometric properties of the Specific Thalassemia Quality of Life Instrument for adults

BACKGROUND: No specific questionnaire has been developed to assess the health-related quality of life of thalassemia patients. Thus, the main objective of this study was to develop, according to psychometric standards, a self-administered Specific Thalassemia Quality of Life Instrument (STQOLI) for adult patients. METHODS: First, a qualitative phase was conducted to generate items and identify domains using the critical analysis incident technique and a literature review. A list of easily comprehensible, non-redundant items was defined using the Delphi technique and a pilot study on ten thalassemia patients. This phase involved both patients and experts. The second step was a quantitative validation phase comprising a study of 128 thalassemia patients in a single hospital. It was designed to select items, identify dimensions, and measure reliability and internal and concurrent validity. The psychometric and scaling properties of the proposed 41-item Specific Thalassemia Quality of Life Instrument were then assessed among patients recruited from the Thalassemia Unit at the General Hospital of Nikaia, Greece. RESULTS: The final questionnaire had 41 items comprising four main domains and one global item about general health. The factorial structure was satisfactory (loading > 0.40 on each factor of the four domains for all items). Interscale correlations ranged from 0.06 to 0.78, Cronbach’s α-coefficients were 0.78 for the psychosocial domain, 0.77 for the chelation domain, 0.72 for the transfusion domain, 0.81 for the disease and symptoms domain, and 0.840 for the total score of the questionnaire. CONCLUSION: The 41-item Specific Thalassemia Quality of Life Instrument seems to be a valid tool for assessing health-related quality of life for patients with thalassemia. More research is needed to explore the universal properties of the questionnaire.