To the Editor: Dr Segev and colleagues1 studied trends in selection and outcome of 80 347 persons drawn from a mandated US registry of live kidney donors between 1994 and 2009. The authors used a matched cohort that was drawn from 9364 participants of the third National Health and Nutrition Examination Survey (NHANES III) conducted between 1988 and 1994,2 a period of time that ended at the start of their donor cohort study period. The matched cohort was one-eighth the size of the live donor cohort after appropriate exclusions. The authors discussed the larger sample size caused by oversampling for the purposes of standard error estimates but did not consider the study limitation due to the time lag between the donor and the matched cohorts.
Matuchansky C. Perioperative Mortality and Long-term Survival in Live Kidney Donors. JAMA. 2010;303(22):2248-2250. doi:10.1001/jama.2010.727