Determination of β2-microglobulin in serum by a microparticle-enhanced nephelometric immunoassay

Abstract

This fully automated nephelometric immunoassay to quantify β2-microglobulin in human serum measures the light-scattering signal produced by agglutination of commercially available latex microparticles (diameter 0.1 μm) coated with specific F(ab')2 against β2-microglobulin. The calibration curve, generated by serial dilutions of a β2-microglobulin standard of known concentration, is used to calculate β2-microglobulin concentrations in serum samples by the logit-log function and linear-regression analysis. The assay range (sample dilution 400-fold) extends from 0.3 to 40.0 mg/L No antigen excess appears at β2-microglobulin concentrations up to 320 mg/L. Within-run CVs ranged from 1.0% to 3.4%, and between-days from 1.2% to 2.8%. Total imprecision (CV) was <5%. Analytical recovery averaged 99.5% ± 2.8%. Rheumatoid factor, complement, bilirubin (up to 340 μmol/L), and hemoglobin (up to 2.0 g/L) do not interfere. Strongly turbid lipemic samples must be cleared before analysis. Standard curve linearity was very good in samples covering the clinical useful range of concentrations. Results of the method correlated well with those of radioimmunoassay and micropartcle enzyme-linked immunoassay (r = 0.979 and 0.975, respectively). The reference interval (nonparametric estimation) in apparently healthy adults (n = 303) was 0.87 (0.80-0.94) to 2.42 (2.28-2.45) mg/L; the median value was 1.54 mg/L.