Comparison of CMV ELISPOT and CMV Quantiferon™ interferon-γ releasing assays in assessing risk of CMV infection in kidney transplant recipients.

Background.Assessing the CMV specific cell-mediated immunity (CMI) represents an appealing strategy to detect transplant recipients at risk of infection. In this study we compared two interferon gamma-releasing assays (IGRAs), CMV Quantiferon and CMV ELISPOT, in predicting protective CMV specific T-cell responses.Methods.221 Quantiferon and ELISPOT tests were conducted on 120 adult KTR (including 100 R+ and 20 D+/R-). As control cohort 39 adult healthy subjects (including 33 CMV seropositive and 6 CMV seronegative) were enrolled. CMV IgG serology was used as reference for both tests.Results.In CMV seropositive individuals, ELISPOT and Quantiferon provided 46% concordance with serology, 12% discordance, 18% disagreement between ELISPOT or Quantiferon with serology and 24% grey areas when one or both tests resulted weak positive. None of CMV seronegative subjects showed detectable responses in ELISPOT and Quantiferon. In transplant recipients, both ELISPOT and Quantiferon positively correlated with each other and negatively correlated to CMV DNAemia in a significant way (p-value <0.05). During the antiviral prophylaxis, all 20 D+/R- KTRs examined displayed undetectable Quantiferon and ELISPOT and there was no evidence of CMV seroconversion. The ROC statistical analysis revealed similar specificity and sensitivity in predicting detectable viremia (AUC 0.66 and 0.62 for Quantiferon and ELISPOT respectively). ELISPOT and Quantiferon values above 150 spots/200000 PBMCs and <1-6 IU IFN-g were associated with protection from CMV infection (OR 5 and 8.75 respectively).Conclusion.In transplants both tests displayed similar ability in predicting CMV infection. Both ELISPOT and Quantiferon require several ameliorations to avoid false nagative results.