key: cord-0713040-i97qg46b
authors: Shah, Sweta; Singhal, Tanu; Davar, Namita; Thakkar, Pooja
title: Correlation between Ct values and severity of disease or mortality in patients with COVID 19 is confounded by the time of testing since onset of illness. Dos:20.7.20 DOA: 24.8.20
date: 2020-11-16
journal: Indian J Med Microbiol
DOI: 10.1016/j.ijmmb.2020.10.021
sha: 97132740fb89750c055d1a4b5a24802fd48d019a
doc_id: 713040
cord_uid: i97qg46b

There are several reports of Ct values of RT PCR assays for COVID 19 being associated with disease severity and infectivity. We studied the correlation between Ct values and disease severity and mortality at our hospital;. All patients with RT PCR diagnosed COVID 19 illness admitted at the study site and for whom Ct values were available were included in the study. The patients with mild disease had significantly lower Ct values than patients with severe disease but had also been tested significantly earlier in the illness than those with severe disease. The patients who died had significantly lower Ct values than patients who survived but here again they had significantly shorter duration of symptoms before testing. We therefore recommend that the time of testing since onset of symptoms should be controlled for while correlating Ct values with disease severity.

Currently available RT PCR methods for diagnosis of COVID 19 are able to give an estimate of 16 the viral load. [1] The cycle threshold (Ct) values of the PCR reaction correlate inversely with the 17 viral load; low Ct values indicate high viral loads and vice versa. [2] Furthermore, higher viral 18 loads have been seen to correlate with disease severity and infectivity. [3, 4] We therefore studied 19 the correlation of the Ct value of RT PCR for COVID 19 with severity of disease and mortality 20 in patients admitted with COVID 19 at our hospital. (summarized as median since data was not normally distributed) was significantly shorter in the group with mild disease (3 days) as compared to those with severe disease (5 days)Of the 113 46 patients with severe disease, 56 had died, 55 had been discharged and 2 had been transferred to other hospitals. . The Ct values of patients who died were significantly lower than those who 48 survived (Table 2 ). However the duration of illness prior to testing (summarized as median since 49 data was not normally distributed) in patients who died was significantly shorter (3 days) than 50 those who survived (5 days). 63 [3] In-hospital mortality was 35 % with a high viral load (Ct<25; n=220), 18% with a medium J o u r n a l P r e -p r o o f 

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