Evaluation of commercial EBV RecombLine assay for diagnosis of nasopharyngeal carcinoma

BackgroundIn recent years a number of Epstein–Barr virus (EBV) proteins were defined as being immunodominant for either IgM, IgG or IgA immune responses, yielding promising markers for diagnostic serology. Specific reactivity patterns to these proteins have been described for infectious mononucleosis (IM), nasopharyngeal carcinoma (NPC), various types of lymphoma, and healthy EBV carriers.ObjectivesTo compare the NPC-related diagnostic value of EBV RecombLine test (Mikrogen, Germany) with a standardized immunoblot assay [Fachiroh J, Schouten T, Hariwiyanto B, Paramita DK, Harijadi A, Haryana SM, et al. Molecular diversity of Epstein–Barr virus IgG and IgA antibody responses in nasopharyngeal carcinoma: a comparison of Indonesian, Chinese, and European subjects. J Infect Dis 2004;190:53–62] and to define the diagnostic value of individual EBV marker proteins in a population with high incidence of NPC.ResultSera from Indonesian NPC patients taken at primary diagnosis (n = 108) were analyzed for IgG and IgA reactivity and compared with regional healthy blood donors (n = 62), non-NPC patient controls (n = 10) and IM patients (n = 10). Most NPC patients and controls showed strong IgG reactivity to VCA-p18, -p23, and EBNA1, limiting their diagnostic use. Few (<20%) healthy donors and patient controls showed IgG reactivity to EA proteins p47/54 and p138, yielding combined sensitivity/specificity and PPV/NPV values of 92.6%/98.3% and 99.0%/88.1%, for diagnosing NPC. NPC sera showed significantly more EBV reactive IgA antibody (>80% positive) than controls (<10% positive), although being less broadly reactive and significantly less strong compared to IgG. For IgA best results were observed for RecombLine EBNA1 with sensitivity/specificity and PPV/NPV values of 92%/89% and 93.4%/85.9%, respectively.ConclusionIn high incidence NPC regions with low incidence IM yet high prevalence of EBV infection, both RecombLine IgG and IgA tests provide a useful alternative to the more complex cell-extract based immunoblot assay as confirmation test for NPC diagnosis in particular when using EA and EBNA1 as discriminators in IgG and IgA testing, respectively.