PLEXUS EPSTEIN-BARR VIRUS (EBV) IGG AND IGM MULTI-ANALYTE DIAGNOSTICS: MULTIPLEX BEAD-BASED ASSAYS FOR EBV SERUM ANTIBODY DETECTION

Session ID:	S13
Author Name:	Heather Gregson, Nanmei Liu, Tommy Truong, Xin Su, and Lilly Kong Focus Diagnostics, Inc, Cypress, CA.
Country:	US
Conference Session:	Session I

Background: Epstein-Barr virus (EBV) is a common virus associated with a wide variety of presentations, from asymptomatic to severe infectious mononucleosis. EBV serology methods include IFA, ELISA, and multiplex tests for antibody detection. We describe here results from clinical trials that used Plexus EBV IgG and IgM multiplex assays based on the xMAP^® technology (Luminex^® Corporation, Austin, TX) for EBV serology testing. The Plexus EBV IgG assay detects antibodies for VCA, EA-D, and EBNA-1. The Plexus EBV IgM assay detects antibodies for VCA and heterophile.

Methods: Performance of the Plexus EBV IgG and IgM kits* was tested against FDA-cleared ELISA and heterophile rapid tests. Testing and collection of samples were performed at 3 United States testing sites: a hospital laboratory located in the Northeast, a pediatric hospital laboratory located in the Midwest, and Focus Diagnostics reference laboratory. A total of 623 prospectively collected sera submitted for EBV testing from adults and children and 250 retrospectively collected sera from patients with presumed acute EBV infection (as identified by investigators) were tested. The Plexus EBV IgG tests were run in conjunction with the Plexus EBV IgM tests for an antibody profile. The results were classified as to EBV infection status (acute, no infection, past infection, or indeterminate) based on results of the FDA-cleared ELISA and heterophile rapid tests. Cross-reactivity was evaluated with sera positive for antibodies to various related pathogens, childhood diseases, or positive for anti-nuclear antibody (ANA).

Results: The sensitivity and specificity of the Plexus EBV IgG assay and the Plexus VCA IgM assay was compared to ELISA. The Plexus IgM heterophile assay was compared to a heterophile rapid test.

	Plexus EBV IgM		Plexus EBV IgG
	VCA IgM	Heterophile	VCA IgG	EA IgG	EBNA IgG
Sensitivity	91.1%	87.4%	96.3%	85.4%	90.5%
Specificity	96.3%	98.9%,	73.6%	95.1%	99.2%

Cross-reactivity was not observed in the Plexus tests for heterophile and VCA IgM, EA IgG, or EBNA IgG, whereas cross-reactivity was observed in the Plexus VCA IgG assay with serum positive for rubella or Varicella-Zoster (VZV) antibodies, 3/14 and 3/10 samples respectively. The 3 cross-reactive samples rubella and VZA are the same samples. In addition, 2 of the 3 samples were classified as acute EBV infections based on positive results for VCA IgM and heterophile. In EBV serology, VCA IgG antibodies are usually present during the acute infection. Therefore, these two samples may contain VCA IgG antibodies detected by the Plexus EBV IgG assay but not detected by the VCA IgG ELISA.

Conclusions: The Plexus EBV IgG and IgM Multi-Analyte Diagnostic tests demonstrated good sensitivity and specificity and low cross-reactivity compared to single-analyte ELISA assays and heterophile rapid tests.