Cycle Threshold Values Predict COVID-19 Severity and Mortality but Are not Correlated with Laboratory Markers

Many studies have evaluated the possible utility of cycle threshold (Ct) values as a predictor of Coronavirus disease 2019 (COVID-19) severity and patient outcome. Given the inconsistent results, we aimed to evaluate the association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Ct values and disease severity, inflammatory markers, and outcomes in Iranian patients with COVID-19. A retrospective study of 528 patients with COVID-19 hospitalized from September 2020 to October 2021 was conducted. Demographic, clinical, and laboratory data of patients were retrieved from electronic medical records. Ct values were analyzed as a continuous variable after subcategorizing into 3 groups: low (Ct values<20), medium (Ct values 20 to 30), and high (Ct values>30). Of the 528 patients (45.1% female) aged 13 to 97 years, 109 patients had low Ct values, 312 patients had medium, and 107 patients had high Ct values. Patients with low Ct values were more likely to present with critical COVID-19, require invasive mechanical ventilation and develop complications such as acute respiratory distress syndrome and pneumonia. Furthermore, patients with low or medium Ct values were more likely to die compared to patients with high Ct values. Multivariate analysis showed that patients with low or medium Ct values were more likely to have severe COVID-19 compared with patients with high Ct values. The multivariate analysis also showed a higher risk of mortality in patients with low Ct values compared to patients with high Ct values, although this was not statistically significant. Our findings revealed that Ct values were an independent predictor of COVID-19 severity. The risk of mortality was higher in patients with low Ct values. However, further investigation is needed to address the correlation between Ct values and inflammatory factors.