Development of the fluorometric ELISA method for determination of alpha1-microglobulinuria in a cadmium-polluted area in Japan.

摘要

OBJECTIVES: To evaluate the usefulness of a newly developed fluorometric enzyme-linked immunosorbent assay (fluorometric ELISA) method for quantification of alpha1 -microglobulin (alpha1-m, protein HC) in an epidemiological study. METHODS: Urinary alpha1-m in 37 female inhabitants in a cadmium-polluted area, including seven cases with Itai-itai disease, and ten inhabitants in a non-polluted area in Japan were examined. The alpha1-m was measured by both the fluorometric ELISA and a commercially available enzyme immunoassay (EIA) method to evaluate correlation of the two measurements. Concentration of beta2-microglobulin (beta2-m) was also determined in the same samples. RESULTS: The detection limit of this method was 3 ng/ml or less of alpha1-m. A significant, high positive correlation was obtained between the alpha1-m concentrations measured with the fluorometric ELISA and that of EIA (r = 0.95, P < 0.0001). A significant association was also shown between the alpha1-m and beta2-m concentrations in the urine samples. The concentrations of urinary alphal-m of the inhabitants in the cadmium-polluted area (mean: 6.21 mg/l, 95% confidence interval (95% CI): 4.06-9.50 mg/l) were significantly higher than those of the reference area (mean: 2.19 mg/l, 95% CI: 1.90-2.67 mg/l). The urinary alpha1-m level of the Itai-itai patients was shown to be highest at 39.63 mg/l (95% CI: 28.27 55.55 mg/l). When the cut-off value of 10 mg/l was employed, alpha1-m had a sensitivity of 100% and specificity of 100% for Itai-itai disease. CONCLUSION: These results suggest that this fluorometric ELISA is a useful tool to determine urinary alpha1-m in the epidemiological survey of renal tubular dysfunction, especially in the cadmium-polluted area of Japan.