[Advanced Testing and Laboratory for HBV, HCV, and HIV Infection]

Most target substances for immunoassay of infectious disease are antigens or antibodies which do not exist in the human body. Therefore, the method to set reference values is different from chemistry or hematology testing. High sensitivity is required for infectious disease testing, particularly for screening. Also, its reference values (cut-off values) are set as low as possible. Therefore, a false-positive reaction can be caused due to slightly non-specific reactions in infectious disease reagents. The specificities for infectious disease reagents were evaluated with 9 kinds of HCV antibody test kit and 9 kinds of HIV screening kit. The frequencies of false-positive results were 0.2-1.8 and 0.2-1.3%, respectively, and even a kit with a high specificity showed a false-positive result for 1 in 500 samples. The sensitivities for infectious disease reagents were evaluated with a newly developed super-high- sensitive HBs antigen assay kit and 8 kinds of chemiluminescence HBs antigen assay kit which are highly sensitive conventional kits. As a result, the super-high-sensitive kit was 10 to 40 times more sensitive than conventional kits. After introducing the super-high-sensitive kit to routine assays, 16 HBV-infected patients, who were not identified with the conventional kits, were detected for six months. On the other hand, we confirmed false-positive results due to contamination between specimens after introducing the super-high-sensitive kit. It is recommended to use the super-high-sensitive kit in a well-controlled environment to prevent contamination between specimens in order to generate highly reliable test results.