Monitoring aerobic capacity in cancer survivors using self-reported questionnaires: criterion validity and responsiveness

BACKGROUND: Evaluating the criterion validity and responsiveness of the self-reported FitMáx©-questionnaire, Duke Activity Status Index (DASI) and Veterans Specific Activity Questionnaire (VSAQ) to monitor aerobic capacity in cancer survivors. METHODS: Cancer survivors participating in a 10-week supervised exercise program were included. The FitMáx©-questionnaire, DASI, VSAQ and a cardiopulmonary exercise test (CPET) were completed before (T(0)) and after (T(1)) the program. Intraclass correlation coefficients (ICC) were calculated between VO(2peak) estimated by the questionnaires (questionnaire-VO(2peak)) and VO(2peak) measured during CPET (CPET-VO(2peak)), at T(0) to examine criterion validity, and between changes in questionnaire-VO(2peak) and CPET-VO(2peak) (ΔT(0)-T(1)) to determine responsiveness. Receiver operating characteristic (ROC) analyses were performed to examine the ability of the questionnaires to detect true improvements (≥ 6%) in CPET-VO(2peak). RESULTS: Seventy participants were included. Outcomes at T(1) were available for 58 participants (83%). Mean CPET-VO(2peak) significantly improved at T(1) (Δ1.6 mL·kg(− 1)·min(− 1) or 8%). Agreement between questionnaire-VO(2peak) and CPET-VO(2peak) at T(0) was moderate for the FitMáx©-questionnaire (ICC = 0.69) and VSAQ (ICC = 0.53), and poor for DASI (ICC = 0.36). Poor agreement was found between ΔCPET-VO(2peak) and Δquestionnaire-VO(2peak) for all questionnaires (ICC 0.43, 0.19 and 0.18 for the FitMáx©-questionnaire, VSAQ and DASI, respectively). ROC analysis showed that the FitMáx©-questionnaire was able to detect improvements in CPET-VO(2peak) (area under the curve, AUC = 0.77), when using a cut-off value of 1.0 mL·kg(− 1)·min(− 1), while VSAQ (AUC = 0.66) and DASI (AUC = 0.64) could not. CONCLUSION: The self-reported FitMáx©-questionnaire has sufficient validity to estimate aerobic capacity in cancer survivors at group level. The responsiveness of the FitMáx©-questionnaire for absolute change is limited, but the questionnaire is able to detect whether aerobic capacity improved. The FitMáx©-questionnaire showed substantial better values of validity and responsiveness compared to DASI and VSAQ.