Determination of β2-microglobulin in human urine and serum by latex immunoassay

Abstract

This highly sensitive method for determination of β2-microglobulin (β2-m) in human urine or serum is based on direct agglutination by β2-m of latex particles on which an antibody against β2-m is adsorbed. The agglutination is quantified by counting the remaining unagglutinated particles, or by turbidimetry. A novel aspect of this method is the capability to prevent nonspecific agglutination of the antibody-coated particles by diluting them with an albumin solution of well-defined characteristics (pH, freshness, concentration) just before the assay. The assayable concentration range is 1-32 μg/L, the detection limit 0.5 μg/L. Within-assay CV, based on 10 determinations of β2-m in urine and serum at two different dilutions, ranged from 4.6 to 8.7%. Between-assay CV, calculated from 10 determinations of β2-m in urine and serum, was 10 and 8.4%, respectively. Analytical recovery of β2-m in urine averaged 97% and in serum 104% (n = 10). No component of urine of serum interfered. Coefficients of correlation for β2-m in urine or serum as measured by radioimmunoassay and latex immunoassay were 0.97 and 0.93, respectively. Concentrations of β2-m in serum and urine from 33 healthy men (ages 20 to 67 years) averaged 1.5 mg/L and 54 μg/g of creatinine, respectively.