Kidney function following recovery from TTP. GFR, estimated by the CKD-EPI equation^13,14  in all 57 patients at the time of their most recent serum creatinine measurement (median follow-up, 5.3 years; range, 0.1 to 15.7 years), was not different from the expected prevalence based on age, race, gender, and BMI-specific rates from the NHANES US reference population (P = .397). The albumin/creatinine ratio was measured in 2011 on 37 (80%) of 46 surviving patients (median follow-up, 5.9 years; range, 1.1 to 15.7 years); it was also not different from the expected prevalence based on age, race, gender, and BMI-specific rates from the NHANES US reference population (P = .793).