CMV loads observed in patient serum may be significantly lower than those observed in plasma. (A) Plasma containing citrate (C), plasma containing EDTA (E), and serum (S) obtained in parallel from the same patient (subject A in Table 2) were subjected to Q-PCR (in duplicate). (B) Plasma containing citrate (C), plasma containing EDTA (E), and serum (S) obtained from a CMV-negative healthy volunteer and the serum from the patient (S+) were seeded to 750 CMV particles/ml, and the CMV loads were determined by Q-PCR. nc, negative controls (reference plasma).