Validity of the Patient Generated Index as a Quality-of-Life Measure in Radiation Oncology

Abstract

To evaluate psychometric properties of an instrument designed to measure individualized health-related quality of life (HRQOL). Repeated measures of self-reported quality of life. An outpatient radiation therapy department in the western part of the United States. 86 adults with cancer receiving their first course of radiation therapy. The Patient Generated Index (PGI), the National Comprehensive Cancer Network's Distress Thermometer (DT), and the European Organisation for Research and Treatment of Cancer Quality-of-Life Questionnaire-Core-30 (QLQ-C30). Convergent validity, responsiveness, sensitivity, and response shift. PGI scores were inversely correlated with scores on the DT (r = -0.49, -0.55, -0.44; p < 0.001), as well as the role (r = 0.31, 0.4, 0.38; p < 0.01), emotional (r = 0.33, 0.41, 0.33; p < 0.01), social functioning (r = 0.27, 0.49, 0.42; p < 0.05), pain (r = -0.29, -0.39, -0.39; p < 0.01), and fatigue (r = -0.35, -0.25, -0.47; p < 0.05) QLQ-C30 subscales at all measurement times. The PGI was responsive to those reporting high or low DT scores (t = 4.42, 3.32, 2.9; p < 0.05). A small-to-moderate effect size was detected in those who had an increase (effect size = 0.51) or decrease (effect size = 0.38) in HRQOL over time. Participants reconceptualized HRQOL over time. Data supported the PGI as a valid measure of individualized HRQOL. The PGI potentially provides a more patient-centered measure of HRQOL in patients with cancer. Additional testing is needed in larger, more diverse groups.