No Association Between Ct Value and COVID-19 Severity and Mortality in Qatar

The association between the cycle threshold (Ct) which reflects the SARS-CoV-2 viral load and the severity of COVID-19 is still not clear. We investigated the association between Ct values, symptoms and the risk of ICU admission and mortality from COVID-19 in Qatar.

This case-control study used data of hospitalized individuals with confirmed COVID-19 during the period March to September 2020. Cases were defined as individuals with confirmed COVID-19 who were admitted to the intensive care unit (ICU) or died and controls as those who were not admitted to the ICU. The association between Ct value, symptoms, ICU admission and mortality was investigated using Ct value as a categorical variable (below and above 25) in multivariable regression models and adjusted for relevant confounders.

A total of 622 participants with median age 53 (IQR: 53-63), of which 69% were males, were included. There were 236 ICU admissions and 111 deaths. When categorized, Ct value (<25 vs ≥25) had no association with the odds of ICU admission (OR 0.85, 95% CI 0.56 to 1.29) or odds of mortality (OR 1.21, 95% CI 0.71 to 2.08). Respiratory (OR 2.95, 95% CI 1.57 to 5.56) and gastrointestinal symptoms (OR 1.99, 95% CI 1.18 to 3.35) were associated with higher odds of ICU admission. Similarly, respiratory (OR 4.96, 95% CI 1.10 to 22.43) and gastrointestinal symptoms (OR 3.17, 95% CI 1.29 to 7.84) were associated with higher odds of mortality.

Although RT-PCR Ct has good diagnostic value, its prognostic value appears to be unreliable. Respiratory and gastrointestinal symptoms are associated with COVID-19 criticality and mortality in this setting.