The study investigates the dynamics of SARS-CoV-2 viremia

In a recent prospective study posted in medRxiv* Preprint server, researchers evaluated the dynamics of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) viremia.

The 2019 coronavirus disease (COVID-19) caused by SARS-CoV-2 usually presents with mild symptoms, but in some cases it can develop into severe disease and become fatal. It is important to identify patients who develop severe illness and have the potential to improve management.

Elevated interleukin (IL) -6 levels are some of the poor prognostic factors that help stratify risk in patients with COVID-19.

Reverse transcription-polymerase chain reaction (RT-PCR), which detects viral ribonucleic acid (RNA), remains the gold standard for diagnosing COVID-19. Nevertheless, there is no relationship between the viral load of the nasopharyngeal swab and the clinical severity of the disease.

the study

In the current study, researchers used quantitative and qualitative RT-PCR methods to analyze viremia kinetics in patients with COVID-19. The study was conducted at the Hospital Universitario de La Princesa in Madrid, Spain, between November 2020 and January 2021. Approximately 57 patients with COVID-19 confirmed by RT-PCR were followed longitudinally.

In addition to sociodemographic variables, the authors obtained clinical features and outcome data such as intensive care unit (ICU) requirements and hospital mortality. Poor (clinical) results were associated with one of the early (ICU or mortality) factors. In addition, they collected data on hospitalization, symptoms, and death. Blood samples were taken 24-36 hours after admission, 48-72 hours in the first week, and twice a week until discharge.

Two RT-PCR tests qualitatively processed all specimens – the TaqPath ™ COVID-19 CEIV DRT-PCR kit and the Cobas® SARS-CoV-2 test. A QuantStudio ™ 5 real-time PCR system (qTaqPath test) was used for quantitative analysis.

Survey results

Four samples (median) were collected for each patient, with a median age of participants of 64 years. About 61% of the cohort were men. Eight patients (14%) were admitted to the ICU during hospitalization, and five patients (9%) had fatal consequences. There were 10 patients with a median age of 60.5 years and poor outcomes.

The researchers investigated 298 and 300 plasma samples. Consistent results were obtained with the two qualitative RT-PCR tests, and both the Cobas and TaqPath tests showed higher positive detections in statistically significant plasma samples. The qTaqPath test was used to quantify the viral load in 41 serum samples and 50 plasma samples. The median viral load of plasma samples was 462.88 copies / ml and that of serum samples was 370 copies / ml. The difference between the two sample types was not statistically significant.

Two qualitative (RT-PCR) tests were able to detect three targets for the N, S, and ORF genes in 64.3% of patients and at least two targets in 79% of cases. Researchers have observed three different patterns of viremia. a) Persistent viremia (PV) with viremia observed in two or more consecutive tests, b) Sporadic viremia (SV), detectable viremia in isolated samples, c) Negative Viremia, viremia during hospitalization. There were 16 (28%) patients with PV, 34 (60%) with SV, and 7 (12%) with NV. PV persisted for a short period of time, with a median plasma sample of 5 days and a median serum sample of 4.5 days.

In the case of PV, viremia clearance was spontaneous during hospitalization. Of the PV patients, 9 had initially high viral load and then decreased. Six patients showed reduced viral load. Patients who died had increased viral load levels until they died. All patients with poor outcomes during hospitalization showed PV, while patients with SV or NV had poor outcomes. Viral load was lower in SV patients compared to PV patients. Median viral load in SV patients was 77.3 copies / ml for plasma and 59.4 copies / ml for serum. The viral load in PV patients was fairly high, 558 copies / ml for plasma and 370.4 copies / ml for serum.

Conclusion

The authors stated that patients with poor outcomes, such as ICU admission or death, showed PV, but SV or NV was not associated with poor outcomes. These findings indicate that PV patients are more likely to have poor clinical outcomes at admission.

Both quantitative and qualitative RT-PCR methods have shown similar patterns of viremia kinetics. In particular, plasma samples gave higher positive test results than serum samples. Therefore, the researchers suggested using the viral load results from plasma samples for viremia analysis. In conclusion, PV may indicate a poor prognosis in patients with COVID-19, so both qualitative and quantitative RT-PCR methods are suitable for determining SARS-CoV-2 viremia.

*Important Notices

medRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.