α1-Microglobulin as a promising marker of cadmium-induced tubular dysfunction, possibly better than β2-microglobulin

Abstract

The purpose of the present study was to evaluate the validity of α1-microglobulin (α1-MG) in comparison with popularly used β2-microglobulin (β2-MG). A database on 8975 cases of never-smoking adult women was revisited; the data were based on spot urine samples from the women in 10 prefectures all over Japan. The validity of α1-MG was examined following essentially the same protocol as β2-MG was examined in a previous study. Comparisons were made for α1-MG as observed (e.g. α1-MGob), as corrected for creatinine (CR or cr) (e.g. α1-MGcr) and as corrected for a specific gravity (SG or sg) of 1.016 (e.g. α1-MGsg). A cut-off value of 5.0mg α1-MG/g cr or l was deduced from 400μg β2-MG/g cr taking advantage of the regression equation between α1-MG and β2-MG. The prevalence of α1-microglobulinuria as corrected for a specific gravity of 1.016 (or α1-MGsg-uria in short) was essentially unchanged irrespective of SG, except for in very dense or very thin urine samples. α1-MGcr-uria prevalence decreased at higher CR. Comparison of the present observation with previous findings on β2-MG-uria prevalence showed that the variation in prevalence of MG-uria as a function of urine density was smaller for α 1-MGsg whereas it was substantially larger for β 2-MGcr, and thus it appeared prudent to consider α1-MGsg rather than β2-MG cr as a marker of tubular dysfunction. © 2003 Elsevier Ireland Ltd. All rights reserved.