External quality assurance in diagnostic immunology: a twenty-year experience in Korea

Abstract

External Quality Assurance (EQA) Program in diagnostic immunology was founded in 1982 in Korea, starting from proficiency testing for HBsAg and serological tests for syphilis. Proficiency testing for antisteptolysin O (ASO) and Widal tests was started in 1983, rheumatoid factor (RF), C-reactive protein (CRP) and anti-HBs tests in 1986, anti-HIV in 1992, and anti-HCV in 1993, now assessing total nine immunological tests. EQA surverys are performed twice annually and about 400 laboratories have been participating now. Over 75% of participating laboratories have used immunoassays including enzyme immunoassay for HBsAg, anti-HBs, anti-HCV and anti-HIV, and less than 20% of laboratories used hemagglutination tests. Overall error rate for HBsAg was less than 5%, those for anti-HBs and anti-HCV about 3% and anti-HIV less than 0.5%. Only negative samples are now used for anti-HIV proficiency testing and two levels (negative and weakly positive or positive) of samples should be included in proficiency testing to assure the results. Thirty-five to forty-five percentages of participating laboratories have used nephelometry or turbidimetric immunoassay for CRP, RF and ASO. When comparing two kinds of nephelometry reagents most popularly used in Korea, quantitative results for CRP and RF by one kind were statistically different from the other. The reason for these discrepancies was not clear yet, however, standardization should be required. In the future, EQA in diagnostic immunology in Korea not only includes laboratory performance evaluation, but also evaluation of method performance and reagent evaluation.