Relationship Between HSV-1 Serostatus and HSV-2 IgG Confirmation Results using an Inhibition Assay

Abstract

Abstract Background: Approximately 2% of HerpeSelect Herpes Simples Virus type 2 (HSV-2) IgG enzyme immunoassay (screen assay) sera positive samples do not confirm using an HSV-2 IgG inhibition assay. Of these, roughly 1.33% are confirmed negative and a small proportion (0.2%) are indeterminate due to inhibition observed with HSV-1 and HSV-2 lysate. The objective of this study was to assess the relationship between HSV-1 IgG serostatus and HSV-2 IgG confirmation results using the HSV-2 IgG inhibition assay. Methods: This study included consecutive HSV-2 IgG screen-positive specimens regardless of index value. Specimens were also tested for HSV-1 IgG. The HSV-2 IgG confirmation results from the inhibition assay were evaluated to assess the relationship between inhibition results and HSV-1 serostatus. Results: Of the 21,006 positive HSV-2 IgG specimens, 13,237 (63%) were also positive for HSV-1 IgG. The proportion of HSV-1 IgG-positive samples among inhibition-indeterminate samples (33/40, 83%) was higher than among inhibition-negative (167/279, 60%) and inhibition-positive (13,041/20,691, 63%) samples. Among HSV-1 IgG-positive samples, the median HSV-1 IgG index was also significantly higher for the inhibition-indeterminate group (median = 48.8) than for the inhibition-negative (median = 30.7) and inhibition-positive groups (median = 31.2) (P = 0.00013 and P = 3.1e-05, respectively). Conclusion: These findings suggest that HSV-2 IgG inhibition-indeterminate, but not inhibition-negative, results are associated with higher index values of HSV-1 IgG. Further studies are needed to understand other factors associated with inhibition-indeterminate results.