Rethinking of the clinical utility of the cycle threshold value of the RT-qPCR of COVID-19 in decision-making and prediction of the patients’ outcomes

Background: The cycle threshold (Ct) values derived from real-time quantitative PCR (RT-qPCR) testing for COVID-19; a widely utilized diagnostic tool hold the potential as a prognostic marker. However, its clinical utility in guiding decision-making and improving patients’ outcomes is questioned. Aim: This study critically examined the Ct values’ role in assessing COVID-19 severity, and outcomes, addressing gaps and inconsistencies in the current interpretations and applications of this test, to contribute in decreasing the morbidity and mortality of the disease. Subjects, materials, and methods: This cross-sectional, prospective, single-center study was done on 158 COVID-19 patients divided into three groups based on Ct values; moderate to high viral load (Ct < 30), low viral load (Ct =30 -40) and undetectable (Ct >40 or not detected). Patients’ data including demographics, symptoms, risk factors, vital signs, disease severity, and laboratory investigations were all collected. Results: Non-significant association was detected in the three groups between Ct values and factors such as age, sex, clinical symptoms, smoking habits, or disease severity, notably headache and renal diseases were more frequent in the low viral load group while total white blood cells and lymphocytes counts were significantly lower in positive groups than in the undetectable group, also Ct values weren't significantly correlated with patient outcomes. Conclusion: Ct values of the RT-PCR testing, which are negatively associated with viral load, are not a convincing COVID-19 indicator for severity and outcome, despite some correlations being found.