Relationship of the cycle threshold values of SARS-CoV-2 polymerase chain reaction and total severity score of computerized tomography in patients with COVID 19

Abstract

Aim: Studies analyzing viral load in COVID-19 patients and any data that compare viral load with chest computerized tomography (CT) severity are limited. This study aimed to evaluate the severity of chest CT in reverse transcriptase polymerase chain reaction (RT-PCR)-positive patients and factors associated with it. Methodology: SARS-CoV-2 RNA was extracted from nasopharyngeal swab samples by using Bio-speedy viral nucleic acid buffer. The RT-PCR tests were performed with primers and probes targeting the RdRp gene (Bioexen LTD, Turkey) and results were quantified as cycle threshold (Ct) values. Chest CT of SARS-CoV-2 RNA-positive patients (n = 730) in a period from 22 March to 20 May 2020 were evaluated. The total severity score (TSS) of chest CT ranged 0–20 and was calculated by summing up the degree of acute lung inflammation lesion involvement of each of the five lung lobes. Results: Of the 284 patients who were hospitalized, 27 (9.5%) of them died. Of 236 (32.3%) patients, there were no findings on CT and 216 (91.5%) of them were outpatients (median age 35 years). TSS was significantly higher in hospitalized patients; 5.3% had severe changes. Ct values were lower among outpatients, indicating higher viral load. An inverse relation between viral load and TSS was detected in both groups. CT severity was related to age, and older patients had higher TSS (p < 0.01). Conclusion: Viral load was not a critical factor for hospitalization and mortality. Outpatients had considerable amounts of virus in their nasopharynx, which made them contagious to their contacts. Viral load is important in detecting early stages of COVID-19, to minimize potential spread, whereas chest CT can help identify cases requiring extensive medical care.

Keywords

• SARS-CoV-2
• Viral load
• CT value
• Chest tomography
• Total severity score
• Mortality