Beta-trace protein--a marker of kidney function in children: "Original research communication-clinical investigation".

Objectives: To determine the pediatric reference interval for serum beta-trace protein (beta-TP) and to compare beta-TP with established LMW markers of GFR, i.e., cystatin C (CysC) and beta(2)-microglobulin (beta(2)-M).

Design And Methods: All three LMW markers were measured immunonephelometrically. In 106 children above the age of 2 years without evidence of kidney disease, non-parametric reference intervals were calculated. The relative rise of the GFR marker concentrations above the upper reference was studied in 107 samples from 96 patients covering the entire GFR range.

Results: Above 2 years, the reference range of beta-TP was constant at 0.43-1.04 mg/L. With decreasing Schwartz-GFR, there was a comparable rise in beta-TP and beta(2)-M, while CysC rose less in the group with GFR below 30 mL/min/1.73 m(2) (278+/-49% [CysC] versus 336+/-65% [beta-TP] and 342+/-76% [beta(2)-M]; p=0.043 and 0.027, respectively).

Conclusions: These data confirm the potential of ss-TP as an endogenous GFR marker in children.