Validation of a New Physical Activity Instrument Against Pedometers Among Dialysis Patients

Abstract

The newly developed Low Physical Activity Questionnaire (LoPAQ) was designed to capture the low activity level among typically sedentary patients undergoing dialysis and correlated well with a physical activity questionnaire used in the general population. However, this instrument has not been validated against a more objective measure. We recruited patients receiving dialysis for ≥3 months from 3 dialysis facilities in San Francisco. Spontaneous walking activity was measured by pedometers over 7days including a weekend and used as the standard reference. Patients were instructed to record their activities and step count readings. Study coordinators administered the LoPAQ during a dialysis session (hemodialysis [HD]) or clinic visit (peritoneal dialysis [PD]). The LoPAQ ascertains time and energy expended in walking activity, as well as light, moderate, and vigorous activity, and total physical activity during a 1-week recall period with 11 simple questions and requires approximately 10minutes to administer. The LoPAQ also asks about time spent in sitting activities over 1week. Spearman correlation was used to determine whether the LoPAQ results correlate with step counts. Sixty dialysis patients (HD=48, PD=12) completed the LoPAQ and wore a pedometer for 1week. Mean age was 58.0±12.7years, 78.3% were men, and median dialysis vintage was 3.1 (IQR, 1.1-5.8) years. Median step count was 2,630.5 (1,270.7-5,137) steps/day. Most patients (82.8%) reported walking activity around the neighborhood, for transportation, and/or for fitness or pleasure, with a median of 595 (70-1,566.3) kcal/week. Total kilocalories per week of physical activity reported on the LoPAQ were 655 (422.8-2,336.8). Participants reported an average of 5 (3-8) sedentary hours per day. Energy expenditure in walking by the LoPAQ was highly correlated with weekly step counts (rho=0.53, P<.001). In addition, the overall activity reported on the LoPAQ correlated with weekly pedometer readings (rho=0.35, P=.01) and did not differ between HD and PD patients. The LoPAQ was easier and less time-consuming than previously validated physical activity questionnaires. LoPAQ demonstrated a good correlation with objective pedometer step counts among dialysis patients, similar to other physical activity instruments used in healthier and more active populations.