Two-point normalized protein catabolic rate overestimates nPCR in pediatric hemodialysis patients

Normalized protein catabolic rate (nPCR) calculation depends on estimating the urea generation between consecutive hemodialysis (HD) treatments. Two-point nPCR using blood urea nitrogen (BUN) before and after the same HD treatment has not been validated in pediatric patients, who typically receive a more intense HD dose than adults. This study aimed to compare nPCR calculated with a two-point vs. a three-point nPCR model in pediatric HD patients.

Pediatric patients receiving HD at 2 units were enrolled. Three BUN measurements were obtained around a midweek HD treatment: one prior to HD (preBUN1), one 30 s after HD (30sBUN), and one prior to the subsequent HD (preBUN2). The two-point nPCR model was calculated using preBUN1 and 30sBUN and the three-point nPCR model was calculated using preBUN2 and 30sBUN.

Seventy-six BUN sets from 35 patients were analyzed. Mean age was 16.4 ± 3.5 years. Mean dry weight was 51.4 ± 17.1 kg. Mean spKt/V was 1.54 ± 0.23. Mean preBUN2 was significantly lower than mean preBUN1 (60.2 ± 18.6 vs. 64.0 ± 18.9 mg/dl, p = 0.0001). nPCR obtained from the three-point model was significantly lower than nPCR obtained from the two-point model (1.07 ± 0.31 vs. 1.17 ± 0.31 g/kg/day, p = 0.00001). Seven of 76 (9.2 %) paired comparisons yielded three-point nPCR <1 vs. two-point nPCR >1.

Our data show that in pediatric patients receiving HD, the ((1) two-point and three-point models lead to significantly different nPCRs, and (2) inaccurate protein intake assessment may result from reliance on a two-point model for nPCR estimates.