Association Between RT-PCR Cycle Threshold and Outcomes of Individuals Hospitalized for COVID-19

Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can lead to a wide spectrum of clinical severity. The gold standard diagnosis of infection is reverse transcription polymerase chain reaction of nasopharyngeal swabs, which also provides a semiquantitative assessment of viral loads by measuring cycle threshold (CT) values.

To assess whether CT values at admission can predict mortality and oxygen needs among individuals hospitalized for coronavirus disease 2019 (COVID-19).

The retrospective study included adults hospitalized for COVID-19 between 1 August 2020 and 30 April 2021 at Barzilai University Medical Center. Patients were categorized according to initial CT values as high (≥ 25) or low (< 25) values. The primary outcome was the association between CT values during admission and overall mortality.

The study group included 636 patients, with a mean age of 67.2 years, 54.4% males. Overall mortality of patients with CT values < 25 was significantly higher (odds ratio for mortality 1.78 vs. patients with CT ≥ 25, P = 0.002). Significantly more patients in the low CT group required oxygen support than in the high CT group, 50% vs. 31.9% (P < 0.001). An inverse association between CT values and mortality rates remained significant in multivariate regression analysis, such that a 1-unit decrease in CT was associated with a 6% increased mortality.

Lower CT values at admission were associated with increased mortality among patients hospitalized for COVID-19. CT values can be used to predict outcomes among such patients.