A RAPID TURBIDIMETRIC IMMUNOASSAY FOR SERUM ANTISTREPTOLYSIN-O

We designed a rapid, quantitative turbidimetric immunoassay for serum antistreptolysin‐O (ASO), based on the immunoprecipitating velocity with purified streptolysin‐O (SLO), which can be measured turbidimetrically at 340 nm. The assay system involves polyoxy‐ethylene mono‐p‐nonylphenyl ether to accelerate and enhance the immunoprecipitation reaction. No antibody excess phenomenon is observed, up to 1,700 U/ml. Grossly icteric sera can be assayed. Patient sera gave acceptable results. Free cholesterol offers no interference. The standard curve is linear for values up to 800 U/ml. Results measured by the proposed method and those by the conventional microtitration method correlated well. Analytical recovery averaged 90.1% (80.3%‐102.5%). Within‐run and day‐to‐day CVs ranged from 2.1% to 3.5% and from 2.5% to 6.9% respectively. Working SLO is stable for at least 15 days at 4°C. The proposed method has proven to be superior to other available methods for measuring serum ASO. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company