A longitudinal prospective study of cytomegalovirus pp65 antigenemia in renal transplant recipients.

Cytomegalovirus (CMV)-encoded pp65 antigen in peripheral blood leukocytes (CMV antigenemia) was investigated in 1017 serial samples from 64 patients for 16 weeks after renal transplantation in a prospective study. In 110 samples from 24 patients, at least one antigen-positive leukocyte was identified. The median number of stained cells was 4 (range 1-1000) per 4 x 10(5) leukocytes. Twenty-one of 24 patients with serological signs of an active CMV infection were antigen-positive (sensitivity 87.5%), whereas 3 patients with antigenemia did not show serological signs of infection during the observation period (specificity 92.5%). Positive results were obtained 19 days (median) before serological response and 9 days (median) before the onset of CMV syndrome. The sensitivity in defining a CMV syndrome was 100% (n = 8). In all patients who presented with CMV syndrome, antigenemia was present prior to the onset of symptoms or on the same day. In contrast, serological monitoring rendered the diagnosis of CMV infection possible at the onset of clinical symptoms in only two of eight patients. We conclude that (1) insufficient results obtained with the CMV antigenemia assay by other investigators are mainly due to technical problems that can easily be overcome by the protocol presented and (2) the detection of CMV pp65 antigen in peripheral blood leukocytes is an excellent tool for rapid and early diagnosis of CMV infection.