Comparison of cytomegalovirus loads in plasma and leukocytes of patients with cytomegalovirus retinitis

Cytomegalovirus (CMV) DNA loads in paired leukocyte and plasma samples from 199 patient visits by 66 patients with CMV retinitis were determined. Leukocyte CMV load determinations had a greater range of values (mean, 24,587 copies/10⁶ leukocytes; maximum, 539,000) than did plasma CMV load determinations (mean, 10,302 copies/ml; maximum, 386,000), and leukocyte vital loads were detectable in a greater proportion of patients at the time of diagnosis of CMV retinitis prior to initiation of anti-CMV therapy (82%) than were plasma viral loads (64%) (P = 0.0078). Agreement with CMV blood cultures was slightly better for plasma (κ = 0.68) than for leukocytes (κ = 0.53), due to a greater proportion of patients with detectable vital loads in leukocytes having negative blood cultures.