Suppression of non-specific binding in serological Luminex assays.

Bead-based suspension array technology (xMAP, Luminex Corp.) permits the simultaneous analysis of antibodies with specificities for up to 100 different antigens in a single reaction and the high through-put screening of up to 1,000 sera per day. Therefore, this technology is becoming more and more popular for serological analyses, replacing ELISA techniques at least for epidemiological purposes. However, a major intrinsic problem of Luminex technology is that human sera may contain antibodies that directly bind to the beads, resulting in intolerably high non-specific background. The proportion of such "bead binders" in different serum panels frequently exceeds 5% and is therefore a severe problem. We screened for background inhibitors and found that serum pre-incubation with polyvinylalcohol, polyvinylpyrrolidone and a proprietary reagent (Super ChemiBlock, Chemicon) significantly reduced non-specific background, whereas use of Luminex SeroMap beads only partially solved the problem.