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

Abstract

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 (T₀) and after (T₁) 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 T₀ to examine criterion validity, and between changes in questionnaire-VO_2peak and CPET-VO_2peak (ΔT₀-T₁) 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 T₁ were available for 58 participants (83%). Mean CPET-VO_2peak significantly improved at T₁ (Δ1.6 mL·kg^{- 1}·min^{- 1} or 8%). Agreement between questionnaire-VO_2peak and CPET-VO_2peak at T₀ 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.

Keywords: Cardiopulmonary exercise test; Cardiorespiratory fitness; Exercise rehabilitation; Patient-reported outcome measures; Psychometric properties.

Fig. 1

Participant inclusion flowchart Abbreviations: CPET, cardiopulmonary exercise test; n, number of subjects

Fig. 2

AD. Criterion validity with identity line for relation between questionnaire-VO_2peak and CPET-VO_2peak at T₀. A) FitMáx-VO_2peak compared with CPET-VO_2peak. B) FitMáx-VO_2peak without cycling compared with CPET-VO_2peak. C) VSAQ-VO_2peak compared with CPET-VO_2peak. D) DASI-VO_2peak compared with CPET-VO_2peak. Abbreviations: CPET, cardiopulmonary exercise test; DASI, duke activity status index; ICC, intraclass correlation coefficient; kg, kilograms; mL, milliliters; min, minute; VO_2peak, peak oxygen uptake; VSAQ, veterans specific activity questionnaire

Fig. 3

 A-D. Bland-Altman plots for the agreement between questionnaire-VO_2peak and CPET-VO_2peak at T₀. The dashed lines represent the 95%-LoA, from − 1.96 SD to + 1.96 SD. The solid line represents ratio bias and the dotted line represents the zero bias line. A) FitMáx-VO_2peak compared with CPET-VO_2peak. B) FitMáx-VO_2peak without cycling compared with CPET-VO_2peak. C) VSAQ-VO_2peak compared with CPET-VO_2peak. D) DASI-VO_2peak compared with CPET-VO_2peak. Abbreviations: CPET, cardiopulmonary exercise test; DASI, duke activity status index; kg, kilograms; mL, milliliters; min, minute; VO_2peak, peak oxygen uptake; VSAQ, veterans specific activity questionnaire</fig>

Fig. 4

AD. Scatterplots for the relation between changes (Δ) in questionnaire-VO_2peak and CPET-VO_2peak from T₀-T₁. A) ΔFitMáx-VO_2peak compared with ΔCPET-VO_2peak. B) ΔFitMáx-VO_2peak without cycling compared with ΔCPET-VO_2peak. C) ΔVSAQ-VO_2peak compared with ΔCPET-VO_2peak. D) ΔDASI-VO_2peak compared with ΔCPET-VO_2peak Abbreviations: CPET, cardiopulmonary exercise test; DASI, duke activity status index; ICC, intraclass correlation coefficient; kg, kilograms; mL, milliliters; min, minute; VO_2peak, peak oxygen uptake; VSAQ, veterans specific activity questionnaire

Fig. 5

ROC-curves for the ability of questionnaires to detect a true improvement in CPET-VO_2peak Abbreviations: DASI, duke activity status index; ROC-curve, receiver operating characteristics curve; VSAQ, veterans specific activity questionnaire