Monitoring of CD38high expression in peripheral blood CD8+ lymphocytes in patients after kidney transplantation as a marker of cytomegalovirus infection.

Background: Cytomegalovirus (CMV) infection is a life-threatening complication after solid organ transplantation. It usually appears in the first months after transplantation as a consequence of immunosuppression. The goal of this study was to evaluate the clinical significance of CD38(high)/CD3(+)8(+) percentages in the detection of CMV infection in patients after kidney transplantation.

Methods: In this retrospective study, 269 patients were monitored 2-3 months after renal transplantation for the percentage of CD38(high)/CD3(+)8(+) lymphocytes estimated by flow cytometry and for the number of CMV DNA copies in peripheral blood using a real-time polymerase chain reaction.

Results: CMV infection was diagnosed in 12 (4.5%) patients between the 31st and 63rd days after transplantation, and all of them had percentages of CD38(high)/CD3(+)8(+) T lymphocytes above 20%. In 4 of them, CMV DNAemia in peripheral blood was not detected, and 2 of these suffered from tissue-invasive CMV disease. In 7 patients with CMV DNAemia, the CD38(high)/CD3(+)8(+) T lymphocyte percentage did not exceed 20%, and these patients did not develop CMV infection requiring antiviral treatment. In 23 additional patients, a CD38(high)/CD3(+)CD8(+) percentage above 20% was recorded without CMV DNAemia. All of the remaining 234 patients never exceeded the arbitrary limit of 20%. The estimated sensitivity and specificity were 100% and 91% using clinical decision on the presence of CMV infection as a reference value, respectively. The estimated negative predictive value was 100%; however, the estimated positive predictive value was quite low (34%).

Conclusions: The CD38(high)/CD3(+)8(+) lymphocyte percentage seems to be a useful additional diagnostic marker for CMV infection in patients after kidney transplantation, especially when patients are in the risk of a tissue-invasive disease when CMV DNA copies may not be detectable in peripheral blood.