Clinical relevance of direct quantification of pp65 antigenemia using flowcytometry in solid organ and stem cell transplant recipients

A total of 1,305 blood samples from 85 solid organ transplant (SOT) recipie nts and 25 stem cell transplant (SCT) recipients at risk for cytomegaloviru s (CMV) infection were prospectively collected and tested using the shell v ial assay (SVA) and a leukocytic qualitative PCR (q-PCR). Of these, 462 spe cimens were further tested by direct quantification of CMV antigenemia by f low cytometry (FC-Ag), 125 were tested with a quantitative competitive PCR, and 200 were tested for pp65 antigenemia using the slide method (S-Ag), La boratory data were statistically analyzed according to the presence of CMV- related symptoms. In SOT and SCT recipients, active CMV infection occurred in 63.5 and 36%, respectively, and CMV disease occurred in 53 and 24%, resp ectively. FC-Ag results correlated better with q-PCR and S-Ag than with SVA . The first test found to be positive during follow-up was FC-Ag in 73% of cases. In SOT recipients, FC-Ag showed the highest sensitivity and negative predictive value for the diagnosis of any grade of CMV disease. For FC-Ag, the threshold beyond which CMV disease was highly probable seemed to lie a t 0.20% positive polymorphonuclear leukocytes. FC-Ag appears to be a useful test for the early detection of CMV infection and the prediction of CMV di sease.