Evaluation of external quality assessment results for HIV testing laboratories in Korea using current analytical methods

Background: This report presents HIV External Quality Assessment (EQAS) results by the KCDC from the 17 HIV testing laboratories that also performed HIV-1 western blot testing of the 585 laboratories. Method: The HIV EQAS panel consisted of 10 undiluted plasma samples from donors who were 3 positive, four indeterminate and 3 negative for HIV antibody. The results were analyzed by traditional methods (mean ± 2 SD), robust statistics (median), and Youden plots (99% coverage). Results: The sensitivities for the HIV antigen and antibody ELISAs were 94.1% and 98.3%, respectively, with the inconsistent 1.7% caused by indeterminate, weakly positive samples. The specificities of HIV antigen and antibody ELISAs were 93.3% and 100%, respectively. The traditional method detected 2 laboratories as outliers for HIV antigen testing and 3 laboratories as outliers for HIV antibody testing. The robust statistics method showed better discrimination of outliers, detecting seven laboratories as outliers for HIV antigen testing and six for HIV antibody testing. The outliers detected by the Youden plot were differentiated as six systematic and 2 random errors. Conclusion: Therefore, the design of reliable EQAS based on HIV panels with varied and specified titers is prerequisites for quality improvement of HIV testing laboratories.