Exploratory Factor Analysis of NRG Oncology's University of Washington Quality of Life Questionnaire—RTOG Modification
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CONTEXT: The 15-item University of Washington Quality of Life questionnaire-Radiation Therapy Oncology Group (RTOG) modification (UW-QOL-RTOG modification) has been used in several trials of head and neck cancer conducted by NRG Oncology such as RTOG 9709, RTOG 9901, RTOG 0244, and RTOG 0537. OBJECTIVES: This study is an exploratory factor analysis (EFA) to establish validity and reliability of the instrument subscales. METHODS: EFA on the UW-QOL-RTOG modification was conducted using baseline data from NRG Oncology's RTOG 0537, a trial of acupuncture-like transcutaneous electrical nerve stimulation in treating radiation-induced xerostomia. Cronbach α coefficient was calculated to measure reliability; correlation with the University of Michigan Xerostomia Related Quality of Life Scale was used to evaluate concurrent validity; and correlations between consecutive time points were used to assess test-retest reliability. RESULTS: The 15-item EFA of the modified tool resulted in 11 items split into four factors: mucus, eating, pain, and activities. Cronbach α ranged from 0.71 to 0.93 for the factors and total score, consisting of all 11 items. There were strong correlations (ρ ≥ 0.60) between consecutive time points and between total score and the Xerostomia Related Quality of Life Scale total score (ρ > 0.65). CONCLUSION: The UW-QOL-RTOG modification is a valid tool that can be used to assess symptom burden of head and neck cancer patients receiving radiation therapy or those who have recently completed radiation. The modified tool has acceptable reliability, concurrent validity, and test-retest reliability in this patient population, as well as the advantage of having being shortened from 15 to 11 items.
