Concurrent validity of kidney transplant questionnaire in US renal transplant recipients

BACKGROUND: Valid instrumentation in the assessment of health-related quality of life (HQoL) in renal transplant recipients is critical to identifying particular nuances and determinants of HQoL in this population. Therefore, the validity of disease-specific instruments to measure HQoL in renal transplant recipients, such as the Kidney Transplant Questionnaire (KTQ), needs further investigation. The objective of this study was to assess the concurrent validity of the KTQ in adult US renal transplant recipients using the well established SF-12 Health Survey version 2 (SF-12v2) as the comparison instrument. METHODS: One hundred and fourteen renal transplant recipients met the following inclusion criteria for this study, ie, were at least 21 years of age, more than two years post-transplant, and receiving immunosuppressant therapy. Subjects were asked to complete a series of HQoL instruments, ie, the KTQ and the SF-12v2 (physical component summary [PCS-12] and mental component summary [MCS-12]). Descriptive statistics were calculated, and correlational analyses were conducted to examine the concurrent validity of the HQoL instruments. RESULTS: Among 100 participants (87.7% response rate), the majority of participants were male (52%), had deceased donor transplants (63%), and received Medicare benefits (84%). PCS-12 was positively correlated with three of five KTQ subscales (P < 0.05), ie, KTQ-physical (r = 0.43), KTQ-fatigue (r = 0.42), and KTQ-uncertainty/fear (r = 0.2). MCS-12 was positively correlated with all KTQ subscales (P < 0.01), ie, KTQ-physical (r = 0.26), KTQ-fatigue (r = 0.48), KTQ-uncertainty/fear (r = 0.33), KTQ-emotional (r = 0.47), and KTQ-appearance (r = 0.28). CONCLUSION: The findings support the concurrent validity of the KTQ in US renal transplant recipients. Future studies should continue exploring the validity of the KTQ, as well as its practical and research utility in HQoL measurement in the renal transplant population.