*Purpose: To assess the diagnostic performance and clinical utility of the Viracor CMV T-cell Immunity Panel (CMV-TCIP), which measures both CMV-specific Cd4+ and Cd8+ T-cell responses using flow cytometry and intracellular cytokine staining, to predict clinically significant CMV events in solid organ transplant (SOT) recipients.

*Methods: We enrolled SOT recipients receiving care at either Brown University or University of Maryland affiliated hospitals between 04/2017 and 10/2018 who had CMV-TCIP results and at least one subsequent assessment for CMV DNAemia. A CMV event was defined as CMV DNAemia prompting initiation of treatment. We built CMV-protection relative operating curves (ROC) for CMV-specific %Cd4+ and %Cd8+ T-cells as well as for absolute lymphocyte count (ALC).

*Results: We analyzed 28 samples from 21 SOT recipients [20(16) kidney, 6(3) heart, 2 lung; 10(8) CMV R+, 18(13) D+/R-]. The CMV-protection ROC-AUC was significant for %CMV-specific Cd4+ and Cd8+ T-cells, but not for ALC (Figure). At a cut-off of 0.22% CMV-specific Cd4+ T-cells, PPV was 80% (95% CI 51-96%) and NPV was 77% (95% CI 45-95%). The 3 patients with “false positive” %CMV-specific Cd4+ T-cells were classified as such because of valganciclovir initiation, but none had symptoms due to CMV; in 2 of these patients, CMV DNAemia was decreasing before treatment.

*Conclusions: In this small observational study the CMV-TCIP, but not the ALC, was useful in predicting subsequent CMV events deemed significant by the treating physicians. The clinical utility of this commercially available assay merits further validation in a blinded prospective study.

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