Toward standardization of Epstein-Barr virus DNA load monitoring: Unfractionated whole blood as preferred clinical specimen

Epstein-Barr virus (EBV) DNA load monitoring in peripheral blood has been s hown to be a useful tool for the diagnosis of aberrant EBV infections. In t he present study we compared the relative diagnostic values of EBV DNA load monitoring in unfractionated whole blood and simultaneously obtained serum or plasma samples from Burkitt's lymphoma (BL) patients, transplant recipi ents, human immunodeficiency virus (HIV)infected individuals, and infectiou s mononucleosis (IM) patients by a quantitative competitive PCR (Q-PCR). Th e EBV DNA load in BL patients was mainly situated in the cellular blood com partment (up to 4.5 x 10(6) copies/ml). EBV DNA loads in unfractionated who le blood and parallel serum samples showed no correlation. In transplant re cipients, IM patients, and HIV-infected patients, the EBV burden in the cir culation was almost exclusively restricted to the cellular blood compartmen t, because serum or plasma samples from these patients yielded negative res ults by Q-PCR, despite high viral loads in corresponding whole-blood sample s. A 10-fold more sensitive but qualitative BamHI-W-repeat PCR occasionally revealed the presence of EBV at <2,000 copies of EBV DNA per mi of serum. Spiking of 100 copies of EBV DNA in samples with negative Q-PCR results exc luded the presence of inhibitory factors in serum or plasma that influeuced the Q-PCR result. Serum samples from all populations were often positive f or <beta>-globin DNA, indicating cell damage in vivo or during serum prepar ation. We conclude that serum is an undesirable clinical specimen for EBV D NA load monitoring because it omits the presence of cell-associated virus a nd uncontrolled cell lysis may give irreproducible results or overestimatio n of the DNA load, Unfractionated whole blood is strongly preferred since i t combines all blood compartments that may harbor EBV and it best reflects the absolute viral burden in the patient's circulation.