Comparison of serum and whole blood levels of cytomegalovirus and Epstein-Barr virus DNA

The monitoring of viral DNA levels after transplantation is crucial for prevention of complications from cytomegalovirus (CMV) or Epstein-Barr virus (EBV) infection but there is no consensus as to which matrix is the most adequate. To compare serum and whole blood (WB) as specimens for measuring viral DNA, clinical samples from a 3-year period were studied, with focus on cases where serum and WB were drawn on the same day. In 1896 paired serum and WB samples, CMV DNA was detected in both specimen types in 472 samples with 0.18 log higher levels (P < 0.001) in WB than in serum (median level 2.73 vs. 2.56 log copies/mL), and in only either serum or WB in 127 and 108 samples, respectively, generally at levels below 1000 copies/mL. In 664 paired samples, EBV DNA was detected in both serum and WB in 160 samples, with 1.48 log higher levels (P < 0.001) in WB (median 4.2 vs. 2.4 log copies/mL), in only WB in 227 cases with a median at 3.0 log copies/mL, and only in serum in 14 samples at low levels. The correlation between serum and WB DNA levels was weaker for EBV than for CMV (R-2 0.31 vs. 0.74). We conclude that either serum or WB may be used for monitoring CMV and EBV DNA levels, that EBV DNA is detected post transplant in > 50% of WB samples and at 30 times higher levels than in serum, and that post-transplantation lymphoproliferative disorder (PTLD) may develop without further increase of EBV DNA in WB. Identification of PTLD may require EBV DNA testing in both specimen types or complementary tests.