Prognostic Value of “Cycle Threshold” in Confirmed COVID-19 Patients
Narmada Aluru, Boggu Rajyalakshmi, Purushottam Reddy
Abstract
Objective: To study the correlation between the cycle threshold (CT) of reverse transcription-polymerase chain reaction (RT-PCR) test in confirmed COVID-19 patients and the severity of disease. Background: RT-PCR test is a standard method for the diagnosis of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections. This test is based upon the amplification of the fluorescent signal. The number of cycles that the fluorescent signal undergoes to reach the threshold is called "cycle threshold. " It is inversely related to the nucleic acid content of the sample. Patients and methods: This is a single-centered, retrospective observational study. We have included a total of 192 patients. SARS-CoV-2 infection was confirmed by the RT-PCR test. Entire data have been collected from the electronic medical records. The primary outcome was 28-day mortality, whereas the secondary outcomes were intensive care unit (ICU) admission, invasive ventilation, acute kidney injury, renal replacement therapy, shock, and COVID-19 reporting and data system (CO-RADS) score on high-resolution computed tomography of the chest, total length of stay in the hospital, and the number of ICU days and ventilator days. Results: We have calculated the mean CT value for all groups and calculated the p-value for statistical significance. For the total length of stay in the hospital and the number of ICU days and ventilator days, we applied the Pearson correlation coefficient. The p-value was statistically significant for mortality, ICU admission, and shock groups. The CT values and the length of ICU stay were inversely correlated with the statistically significant p-value. Conclusion: Low CT value is associated with increased ICU admission, high mortality, shock, and increased length of ICU stay.