Xiao L, Lv N, Rosas LG, Au D, Ma J., Obesity (Silver Spring). doi: 10.1002/oby.21737. [Epub ahead of print], 2017 Jan 06
OBJECTIVE: To validate clinic weights in electronic health records against researcher-measured weights for outcome assessment in weight loss trials.
METHODS: Clinic and researcher-measured weights from a published trial (BE WELL) were compared using Lin's concordance correlation coefficient, Bland and Altman's limits of agreement, and polynomial regression model. Changes in clinic and researcher-measured weights in BE WELL and another trial, E-LITE, were analyzed using growth curve modeling.
RESULTS: Among BE WELL (n = 330) and E-LITE (n = 241) participants, 96% and 90% had clinic weights (mean [SD] of 5.8 [6.1] and 3.7 [3.9] records) over 12 and 15 months of follow-up, respectively. The concordance correlation coefficient was 0.99, and limits of agreement plots showed no pattern between or within treatment groups, suggesting overall good agreement between researcher-measured and nearest-in-time clinic weights up to 3 months. The 95% confidence intervals for predicted percent differences fell within ±3% for clinic weights within 3 months of the researcher-measured weights. Furthermore, the growth curve slopes for clinic and researcher-measured weights by treatment group did not differ significantly, suggesting similar inferences about treatment effects over time, in both trials.
CONCLUSIONS: Compared with researcher-measured weights, close-in-time clinic weights showed high agreement and inference validity. Clinic weights could be a valid pragmatic outcome measure in weight loss studies.