Purpose: Low cardiorespiratory fitness (CRF) increases the risk of postoperative morbidity and mortality following major surgery. Assessing CRF preoperatively, by measuring peak oxygen uptake (VO_2peak) during cardiopulmonary exercise testing (CPET), is valuable yet not widely available. This study aimed to assess whether questionnaires could be used preoperatively to identify high-risk surgical patients.

Methods: Healthy participants and patients who underwent CPET completed the FitMáx, Duke Activity Status Index (DASI), the modified 4-questions DASI (M-DASI-4Q), Veterans-Specific Activity Questionnaire (VSAQ), and Metabolic Equivalents of Task (MET) questionnaire. Questionnaire-VO_2peak was compared with CPET-VO_2peak. Overall performance of the questionnaires was assessed by the area under the curve (AUC) of receiver operating characteristic (ROC) curves. Furthermore, corresponding to the Youden index or pre-specified levels, sensitivity, specificity, and predictive values were determined.

Results: In total, 361 participants were included. All questionnaires showed high AUC values to identify high-risk patients, defined on the basis of CPET-VO_2peak thresholds. FitMáx and VSAQ demonstrated superior results compared to the other questionnaires. Based on the Youden index, the optimal questionnaire-VO_2peak cut-off values were 20.6, 21.3, and 26.1 ml·kg^-1·min^-1 for the FitMáx and 16.3, 18.2, and 20.4 ml·kg^-1·min^-1 for the VSAQ corresponding to the VO_2peak thresholds 16.0, 18.2 and 24.5 ml·kg^-1·min^-1 respectively.

Conclusion: The ability to identify high-risk surgical patients preoperatively (defined by the CPET-VO_2peak thresholds) by the FitMáx and the VSAQ indicates that they could be used to identify high-risk surgical patients. Patients with a poor predicted VO_2peak ≤ 21.3 and ≤ 18.2 ml·kg^-1·min^-1, respectively for FitMáx and VSAQ, should be referred to formal preoperative (cardiopulmonary) exercise testing.

Purpose: The FitMáx© was developed as a questionnaire-based instrument to estimate Cardiorespiratory Fitness (CRF) expressed as oxygen uptake at peak exercise (VO_2peak). Test-retest reliability is a clinometric measurement property, which defines stability over time if multiple measurements are performed (i.e. reliability). The present study aimed to assess the test-retest reliability of the FitMáx©-questionnaire in different patient groups.

Patients and methods: A total of 127 cardiac, pulmonary and oncology patients and healthy subjects aged 19-84 years who completed the questionnaire twice within an average of 18 days were included for analysis. Participants were in a stable clinical situation (no acute disease or participating in a training program). To determine the test-retest reliability, the Intraclass Correlation Coefficient (ICC) and Standard Error of the Measurement (SEM) was calculated between the first (T₀) and second (T₁) administration of the questionnaires.

Results: An excellent agreement was found between the FitMáx©-questionnaire scores at T₀ and T₁, with an ICC of 0.97 (SEM 1.91) in the total study population and an ICC ranging from 0.93 to 0.98 (SEM 1.52-2.27) in the individual patient groups.

Conclusion: The FitMáx©-questionnaire proves to be reliable and stable over time to estimate CRF of patients and healthy subjects. Trial registration NTR (Netherlands Trial Register), NL8846. Registered 25 August 2020, https://trialsearch.who.int/Trial2.aspx?TrialID=NL8846.

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.