RT-PCR Ct values combined with age predicts invasive mechanical ventilation and mortality in hospitalized COVID-19 patients in a MERS-CoV-endemic country

BACKGROUND: Several risk factors have been used to predict severity of coronavirus disease 2019 (COVID-19), real-time reverse transcriptase polymerase chain reaction (RT-PCR) cycle threshold (Ct) values have not been included. METHODS: A retrospective analysis of laboratory-confirmed COVID-19 patients who were hospitalized between March 2 and September 1, 2020, in an academic hospital in Riyadh that serves as a Middle East respiratory syndrome coronavirus (MERS-CoV) referral center was conducted. Nasopharyngeal (NP) and endotracheal (ET) samples were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by RT-PCR, and viral load (VL) was determined based on the Ct values of E genes. The Ct values were distributed into four groups, with group Ct1 (≤19) indicating the highest VL and Ct4 (≥31) indicating the lowest VL. Univariate logistic regression was used to analyze age, gender, and comorbidities in relation to Ct groups for a primary endpoint of either invasive mechanical ventilation (IMV) or mortality. Significant variables were further analyzed by multivariate logistic regression. RESULTS: The analysis included 728 patients hospitalized with COVID-19 (38% female; median age = 53 years; 41.3% diabetic; 39.4% hypertensive). Overall, 13.6% of these patients required IMV, and the in-hospital mortality rate was 15.5%. The IMV rate was higher in the Ct1 and Ct2 groups (15.2% and 15.5%, respectively) than in the Ct4 group (6.4%; p = 0.01). The mortality rate was also higher in the Ct1 and Ct2 groups (19.4% and 18.9%, respectively) than in the Ct4 group (8.9%; p = 0.02). The univariate analysis showed that lower Ct values and increasing age were associated with an increased risk of IMV (OR: 1.03; 95% CI: 1.01, 1.04; P < 0.0001) and mortality (OR: 1.04; 95% CI: 1.03, 1.06; P < 0.0001). The multivariate analysis showed that Ct1 was associated with the highest risk of mortality (OR: 2.29; 95% CI: 1.16, 5.52; P = 0.016), while Ct2 was associated with the highest risk of IMV (OR: 3.1; 95% CI: 1.47, 6.53; P = 0.003). CONCLUSION: The SARS-CoV-2 RT-PCR Ct values of hospitalized COVID-19 patients can be used as predictors of IMV and mortality, and this effect increases when combined with age. Clinicians could use these predictors to triage older patients for risk stratification and allocate IMV.