Association of SARS CoV-2 cycle threshold (Ct) with outcomes in COVID-19: Hospital-based study

Background and Objective: Burden of SARS-CoV-2 estimated by PCR cycle threshold (Ct) may have prognostic importance. To evaluate association of COVID-19 Ct with clinical features and outcomes we performed a hospital based study. Methods: Successive virologically confirmed patients were recruited and demographic and clinical details recorded. Cohort was classified according to Ct into three: Group 1 >30.0, Group 2 25.0-29.9 and Group 3 <25.0. Descriptive statistics are presented. Results: 873 adults (men 651, women 222) were enrolled. The mean age in men was 38.2±18y and women 41.2±19y. Group 3 patients were significantly older (42.4±19y) than Group 2(39.5±18) and Group 1(39.3±17y). Co-morbiditieshypertension, diabetes, obstructive lung disease- were more in Group 3 as were shortness of breath at admission and lymphopenia. In Group 3 vs. Group 2 and Group 1, the average time to virus negativity (9.8±4.1 vs 8.6±3.3 and 8.4±3.4 days) and duration of hospitalization (10.5±5.4 vs 9.8±3.7 and 9.5±3.3 days) were greater. Odds ratios and 95% confidence intervals (OR, 95% CI) in Groups 2 and 3 vs. Group 1 for oxygen requirement were 5.47(CI 2.98-10.07) and 4.48(1.69-11.91), non-invasive ventilation 3.43(1.47-8.05) and 9.81(2.93-32.76), and invasive ventilation 10.81(4.68-24.79) and 63.10(16.90-235.52) (p<0.001). Multivariate analyses showed that compared to Group 1, mortality was significantly greater in Group 2(OR 8.78, 1.95-39.63) and Group 3(OR 34.71, 7.01-171.78) and in Group 3 vs. Group 2(OR 2.27, 1.66-3.12). Conclusions: Hospitalized COVID-19 patients with low SARS CoV-2 cycle threshold are older, have greater comorbidities and lymphopenia. They have greater need for oxygenation, non-invasive and invasive ventilation and have significantly greater mortality. Ct values provide important prognostic information. © 2021 Journal of Association of Physicians of India. All rights reserved.