Biomolecular Features of COVID-19 in Hodeidah, Yemen

Background: The biomolecular technique namely Real-Time Polymerase Chain Reaction (RT-PCR) is very important in confirmation of coronavirus disease 2019 (COVID-19) but in progressive infection and predication of the illness severity is not used.

Objective: Therefore, the study aimed to determine the relationship between the viral load of COVID-19 infection and the severity of illness based on cycle threshold (Ct).

Methodology: The research was designed in a case series study. The study included 60 patients that were confirmed by the RT-PCR test with COVID-19 and divided into two major groups. The first major group was mild and moderate cases (n:20) that were treated at home (outpatient) and the second major group was severe and critical cases (n:40) that were treated in the isolation center (inpatient).

Results: The results showed no relationship between the viral load and severity of illness, where the minimum Ct was 14, and the maximum Ct was 36. The mean of Ct was 22 ± 7. On the other hand, the low Ct (high viral load) was reported in early detection cases. In addition , 60% (36 cases) of patients had low Ct (high viral load ; Ct ≤ 15 and ≤ 25 ) 40% of patients (24 cases) had high Ct (low viral load ; Ct ≤ 26 and ≤ 39 ) that was more than 25 Ct and less than 39 cycles . On the other mean , 95 % of first group cases (mild and moderate cases ) had high viral load based on Ct -values and 42.5 % of second group (severe and critical) had low viral load based on Ct -values. On the other hand, kinetic of viral load–based Ct where the viral load was reported in the first week as very high (low Ct 21) with a longitudinal assessment of RT-PCR test results in individuals requiring third –fourth weeks to clear COVID-19 RNA showed a significant reduction of the viral load in samples (Ct values > 30).

Conclusion: The study concluded that several factors can affect the Ct of RT-PCR (onset date, collection technique, type of swab, sampling method). Briefly, the COVID-19 RT-PCR test cannot be used as a predictor of the severity of illness.