[Evaluation of two beta 2-microglobulin reagents by turbidimetric immunoassay]

An increased level of beta 2-microglobulin (beta 2M) is seen in diseases such as lymphoproliferative diseases, renal diseases, solid tumors, liver diseases, certain viral infection, or chronic inflammatory diseases, etc. In this study, we evaluated a quantitative beta 2M assay for precision and linearity using an automated turbidimetric immunoassay (TIA) by Hitachi 7600-110 (Hitachi High Technologies Co., Japan). The TIA of beta 2M was compared with a chemiluminescent immunoassay (CLIA) by Immulite 2000 (Diagnostic Products Corporation, USA).

Two TIAs, the Hitachi 7600-110 with Roche reagent (Roche-TIA) and the Hitachi 7600- 110 with HBI reagent (HBI-TIA), were evaluated for within-run precision, within-day precision, betweendays precision, and linearity. With 68 serum samples, two TIAs were compared with Immulite 2000 using DPC reagent (DPC-CLIA). These data were analyzed by Passing-Bablok analysis and Bland- Altman analysis.

The coefficients of variation (CVs) of within-run precision, within-day precision, and between- days precision were less than 7% in all groups. The linearity tests of the two TIAs were maintained well (Roche-TIA: R2=0.9952; HBI-TIA: R2=0.9946). The comparison study indicated good correlations (Roche-TIA/DPC-CLIA: r=0.9738, y=0.9625x-0.0375; HBI-TIA/DPC-CLIA: r=0.9725, y= 1.1000x-0.3100). In Bland-Altman analysis, less than 2SD differences were observed between the two groups.

Both Roche-TIA and HBI-TIA showed a good precision and excellent correlations with DPC-CLIA; therefore, TIA could be used in the routine laboratory to determine a quantitative analysis of beta 2M.