Determination of urinary low molecular weight proteins for the diagnosis of tubular damage.

The low molecular weight proteins alpha-1-microglobulin, beta-2-microglobulin and retinol binding protein were estimated in 32 healthy children and compared to 81 urine samples of children with tubular damage. Tubular damage was diagnosed clinically and established on polyacrylamide gel electrophoresis. Means for healthy children were: beta-2-microglobulin (b2m) 109 +/- 77 micrograms/l, alpha-1-microglobulin (alpha-1-m) 0.39 +/- 0 mg/dl, retinol binding protein (rbp) 0.49 +/- 0 mg/dl. Means for children with tubular damage were: b2m 16952 +/- 20057 micrograms/l, alpha-1-m 3.51 +/- 2.09 mg/dl and rbp 2.75 +/- 2.83 mg/dl. Comparing the groups using Student's t test revealed significant differences between healthy children and those with tubular disorders for each of the methods applied (b2m: t = 4.73, p = less than 0.0001, alpha-1-m: t = 8.43, p = less than 0.05, rbp: t = 4.5, p = less than 0.0001). The three methods did not correlate significantly to each other. Alpha-1-microglobulin showed tubular damage in 71 out of 81 patients, beta-2-microglobulin in 64 out of 81 and retinol binding protein in 41 out of 81 children with tubular disorders. The determination of b2m and alpha-1-m is useful for screening and diagnosis of tubular disorders in contrast to the estimation of the retinol binding protein. Cost/time effectiveness is being discussed.