314.9: COVID-19 in Kidney and Kidney-Pancreas Transplantation. Clinical Utility of PCR Cycle Threshold

Abstract

Introduction: COVID-19 is diagnosed with a polymerase chain reaction (RT-PCR) test analyzing respiratory samples, with a positive or negative result. Cycle threshold (Ct) values of an RT-PCR assay refer to the number of cycles needed to amplify viral RNA to reach a detectable level. The clinical implications of Ct values are not yet fully understood either for the general population or solid organ transplant recipients. Objective: To describe the correlation of Ct values with the outcome of a group of transplant (TX) and immunocompetent (IC) patients (Ps). Methods: Prospective study of TX and IC Ps diagnosed with COVID-19 as confirmed by PCR testing between the 1st and 7th day (mean 2.85) after the onset of symptoms. The Ct of the specific gene for SARS-CoV-2 from the PCR tests was considered. A poor outcome was defined for patients with hypoxemia, mechanical ventilation or progressing to death. A logistic regression analysis, where the dependent variable was the patient’s outcome, was performed. Data were processed with the R Studio v.4.0.5 software (2021). Results: One hundred and eighty Ps with COVID-19 diagnosis were analyzed: 123 IC and 57 TX; 51% were women and the average age was 49±14, without differences between groups. The mean Ct level of the specific gene was 22.3 ± 6 for TX vs. 25.02 ± 7.1 for IC (p=0.009). The predominant comorbidity in the IC group was diabetes mellitus (DM) in 25%, followed by obesity in 22%, while in the TX group it was high blood pressure (HBP) in 82%, followed by DM in 19%. A significant association between comorbidities and IC was found (Chi2 = 9.34; p = 0.002). In a bivariate analysis, the specific gene and the TX and/or IC status were not associated with outcome. Age, sex, presence of comorbidities, C-reactive protein (CRP) and ferritin values were associated with outcome (Table 1). In a multiple analysis, two models were developed: one using CRP and the other ferritin as inflammatory markers. In both models, all the variables were associated with outcome, except for specific gene. The likelihood of a poor outcome increased with older age, higher ferritin and CRP levels, comorbidities, in female Ps and the IC group vs. the TX one (Table 2). Conclusion: No association between Ct value and outcome was found. The Ct value was lower in the TX group; however, no association was found when analyzing it separately either. Comorbidities and inflammatory markers were associated with a poor outcome. The poorer outcome in the IC group could be accounted for by a higher prevalence of comorbidities and an older average age in this group.