Precision of the Kalon Herpes Simplex Virus Type 2 IgG ELISA: An international inter-laboratory assessment

Background: The commercial Kalon HSV-2 IgG ELISA is currently recommended for research use in sub-Saharan Africa because of its superior accuracy compared to other serologic assays. However, there are no data on key precision parameters of Kalon such as inter-operator variation, repeatability, and reproducibility, thus contributing to a barrier for its acceptance and use in clinical trials in sub-Saharan Africa. We evaluated the analytical and field precision of the Kalon HSV-2 IgG ELISA. Methods: A total of 600 HIV-infected and uninfected serum samples from South Africa and Zambia, previously tested by the gold standard University of Washington HSV western blot (UW-WB), were tested using Kalon by two technologists in an United States reference laboratory. Aliquots of 183 samples were retested using Kalon by an on-site technologist in a South African laboratory and a Zambian laboratory. Results: Intra-assay variation was below 10%. Intra-assay, intra-laboratory, and inter-laboratory correlation and agreement were significantly high (p<0.01). In comparison to the UW-WB, accurate performance of Kalon was reproducible by each operator and laboratory. Receiver operating characteristic curve analysis indicated high selectivity of Kalon in the overall study population (area under the curve=0.95, 95%CI=0.92-0.97). Discussion: Kalon is a robust assay with high precision and reproducibility. Accordingly, operator errorlikely does not contribute to the variability observed in Kalon's specificity throughout sera from sub-Saharan Africa. Conclusions: In populations with optimal diagnostic accuracy, Kalon is a reliable stand-alone method for on-site HSV-2 IgG antibody detection.