Energy expenditure estimates in chronic kidney disease using a novel physical activity questionnaire

Background Physical activity (PA) levels are low in patients with advanced chronic kidney disease (CKD), and associate with increased morbidity and mortality. Reliable tools to assess PA in CKD are scarce. We aimed to develop and validate a novel PA questionnaire for use in CKD (CKD-PAQ). Methods In phase 1, a prototype questionnaire was developed based on the validated Recent Physical Activity Questionnaire (RPAQ). Structured feedback on item relevance and clarity was obtained from 40 CKD patients. In phase 2, the questionnaire was refined in 3 iterations in a total of 226 CKD patients against 7-day accelerometer and RPAQ measurements. In phase 3, the definitive CKD-PAQ was compared with RPAQ in 523 CKD patients. Results In the final iteration of phase 2, CKD-PAQ data were compared to accelerometer-derived and RPAQ data in 60 patients. Mean daily Metabolic Equivalent of Task (MET) and Total Energy Expenditure (TEE) levels were similar by all methods. Intraclass correlation coefficients showed fair agreement (MET) and good (TEE) between accelerometry and both CKD-PAQ and RPAQ. Agreement between questionnaires was excellent. For mean daily MET bias was 0.035 (SD 0.312) for CKD-PAQ and 0.018 (SD 0.326) for RPAQ. For TEE bias was 91 (SD 518) for CKD-PAQ and 44 (SD 548) kcal for RPAQ. Limits of agreement were wide for both parameters, with less dispersion of CKD-PAQ values. In phase 3, agreement between questionnaires was good (MET) and excellent (TEE). Bias of CKD-PAQ-derived mean daily MET from RPAQ-derived values was 0.031 (SD 0.193) with 95% limits of agreement -0.346 to 0.409. Corresponding values for TEE were 48 (SD 325) and -588 to 685 kcal/day. CKD-PAQ appeared to improve discrimination between low activity groups. Conclusions CKD-PAQ performs comparably to RPAQ though is shorter, easier to complete, may better capture low level activity and improve discrimination between low-activity groups.