Validation and refinement of the Questionnaire for Lung Transplant Patients

CONTEXT: The Questionnaire for Lung Transplant Patients was designed to assess symptoms and activity tolerance in lung transplant recipients during their post-transplant evaluations. The initial psychometric evaluation determined that the questionnaire was clinically useful, reliable, and valid. OBJECTIVE: To report the results of further psychometric analyses in a new, expanded sample of lung transplant recipients and to demonstrate the iterative manner by which instruments are refined and tested. METHODS: Internal consistency, test-retest stability, convergent validity, factorial validity, and group differences attributable to age, gender, and transplant type were determined in a pooled sample of 177 lung transplant recipients. Sensitivity to change over time was measured in a subsample (n = 51) who provided repeated measures data. RESULTS: The Questionnaire for Lung Transplant Patients and its subscales were internally consistent (Kuder Richardson reliability of 0.73-0.95). Test-retest stability was high (intraclass correlations >0.70). Symptoms showed a significant curvilinear pattern with a tendency to decrease over time before rising again at the 12-month measurement for the total questionnaire (F=6.8, P=.012) and 2 subscales--Respiratory (F=5.6, P=.022) and Activities of Daily Living (F=19.7, P<.001). Convergent construct validity correlations ranged from 0.29 to 0.53 and were consistent with theoretical expectations. Factorial analysis confirmed 3 domains that coincided with the Respiratory, General, and Activities of Daily Living subscales. CONCLUSIONS: The Questionnaire for Lung Transplant Patients is a reliable and valid measure for assessing physical symptoms and activity intolerance after lung transplantation in individual recipients, recipients in aggregate, and comparison groups, on one occasion and serially over time. These results will guide future refinement and testing of the Questionnaire for Lung Transplant Patients.