Associations between Physical Function Questionnaires and VO2Peak in Patients on Hemodialysis

Background: Cardiopulmonary exercise testing (CPET) is well-recognized as the gold standard tool for quantifying cardiovascular functional capacity (as assessed by oxygen uptake at peak exercise, VO2Peak). VO2Peak is a strong predictor of survival in patients with chronic kidney disease (CKD). It is currently unknown whether physical function questionnaires can reliably predict VO2Peak in patients with advanced CKD. Herein, we sought to assess the predictive value of the International Physical Activity Questionnaire (IPAQ) and Patient Reported Outcomes Measurement Information System (PROMIS) evaluations for VO2Peak in patients on hemodialysis. Methods: We analyzed data from the “Effects of long interdialytic intervals on Cardiovascular Functional Capacity (ECON)” study, a randomized crossover trial of patients on hemodialysis. All participants underwent CPET and completed questionnaires on a non-dialysis day. A total of 31 patients completed ECON, however 2 patients were excluded in this analysis due to incomplete questionnaire data. Multiple linear regression analysis was used to assess the association between IPAQ and PROMIS results with VO2Peak. Results: 29 patients were dichotomized based on the median VO2Peak value of 11.3 mL/min/kg into a High group (n=15, 11 [73%] men, age=53 [11]; VO2Peak=14.9 [12.2-16.5] mL/min/kg) and a Low group (n=14, 4 [50%] men, age=54 [12] ]; VO2Peak=10.2 [9.3-10.8] mL/min/kg ). The High group had a lower BMI (26.7 [23.5-27.5] kg/m2) compared to the Low group (33.2 [27.8-38.9] kg/m2; P=0.021). No group differences were observed in age, sex, race/ethnicity, dialysis vintage, hypertension, or diabetes (all P’s>0.05). The High group had a higher median number of days walked per week (P=0.037) on the IPAQ and a higher average score on the PROMIS Mobility questionnaire (P=0.006). The PROMIS Function questionnaire and all other IPAQ results were not statistically different between groups (P>0.05). The number of days walked per week (P=0.15) and PROMIS Mobility questionnaire (P=0.06) were not significantly associated with VO2Peak after adjusting for age and sex. Conclusion: Our results indicate that physical function questionnaires are not effective for predicting VO2Peak in dialysis patients. CPET is therefore recommended to objectively determine cardiovascular functional capacity and exercise intolerance. Funding: Private Foundation Support