Prednisone dosing per body weight or body surface area in children with nephrotic syndrome: is it equivalent?

The current guidelines recommend a dosage of prednisone of 60 mg/m(2) body surface area per day (BSA PRED) for the initial therapy of nephrotic syndrome (NS). Alternatively, a dosage of 2 mg/kg body weight per day (W PRED) can be used. We hypothesized that the BSA PRED and W PRED are not equivalent and analyzed the differences between BSA PRED calculated with various formulas for body surface area (BSA), W PRED and the dose of prednisone prescribed for our patients. We performed a retrospective chart review of the patients at their initial presentation of NS. Thirty-three children were included, of median age 3.34 years at presentation. The W PRED was significantly lower than BSA PRED (P < 0.05), with a median W PRED:BSA PRED ratio of 0.85 [interquartile range (IQR) 0.8 to 0.9]. The difference between W PRED and BSA PRED decreased proportionally to patients' weights up to 30 kg. No differences were noted between the various BSA formulas using both weight and height for the calculation of BSA. The Bland-Altman analysis showed a proportional error between W PRED and BSA PRED up to the average daily dose of 60 mg, with a mean bias of 0.86 (95% limits of agreement = 0.68 to 1.05). Ten out of the 33 patients (30%) were given a lower than recommended BSA PRED dose by more than 5 mg/day. In conclusion, the dosage of prednisone at 2 mg/kg per day versus 60 mg/m(2) per day is not equivalent for patients with weights <30 kg and/or dose <60 mg/day.