Monitoring coronavirus disease progression and clinical impact through quantitative viral load testing

Chih-Kai Chang; Chi-Sheng Chen; Ming-Jr Jian; Hsing-Yi Chung; Feng-Yee Chang; Jung-Chung Lin; Shan-Shan Hsieh; Sheng-Hui Tang; Cherng-Lih Perng; Chien-Wen Chen; Chun-Hsiang Chiu; Hung-Sheng Shang

doi:10.1016/j.cca.2024.119731

Monitoring coronavirus disease progression and clinical impact through quantitative viral load testing

Clin Chim Acta. 2024 May 15:560:119731. doi: 10.1016/j.cca.2024.119731. Online ahead of print.

Affiliations

¹ Division of Clinical Pathology, Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China.
² Division of Infectious Diseases and Tropical Medicine, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China.
³ Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China.
⁴ Division of Clinical Pathology, Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, Republic of China. Electronic address: iamkeith001@gmail.com.

PMID: 38754576
DOI: 10.1016/j.cca.2024.119731

Abstract

Background: The viral load (VL) in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals is critical for improving clinical treatment strategies, care, and decisions. Several studies have reported that the initial SARS-CoV-2 VL is associated with disease severity and mortality. Cycle threshold (Ct) values and/or copies/mL are often used to quantify VL. However, a multitude of platforms, primer/probe sets of different SARS-CoV-2 target genes, and reference material manufacturers may cause inconsistent interlaboratory interpretations. The first International Standard for SARS-CoV-2 RNA quantitative assays has allowed diagnostic laboratories to transition SARS-CoV-2 VL results into international units per milliliter (IU/mL). The Cobas SARS-CoV-2 Duo quantitative assay provides VL results expressed in IU/mL.

Materials and methods: We enrolled 145 and 50 SARS-CoV-2-positive, hospitalized and 50-negative individuals at the Tri-Service General Hospital, Taiwan from January to May 2022. Each participant's electronic medical record was reviewed to determine asymptomatic, mild, moderate, and severe cases. Nasopharyngeal swabs were collected using universal transport medium. We investigated the association of SARS-CoV-2 VL with disease severity using the Cobas SARS-CoV-2 Duo quantitative assay and its functionality in clinical assessment and decision making to further improve clinical treatment strategies. Limit of detection (LOD) was assessed.

Results: All 50 SARS-CoV-2-negative samples confirmed negative for SARS-CoV-2, demonstrating 100 % specificity of the Cobas SARS-CoV-2 Duo assay. Patients with severe symptoms had longer hospital stays, and the length of hospital stay (30.56 days on average) positively correlated with the VL (8.22 ± 1.21 log₁₀ IU/mL). Asymptomatic patients had the lowest VL (5.54 ± 2.06 log₁₀ IU/mL) at admission and the shortest hospital stay (14.1 days on average).

Conclusions: VL is associated with disease severity and duration of hospitalization; therefore, its quantification should be considered when making clinical care decisions and treatment strategies. The Cobas SARS-CoV-2 Duo assay provides a commutable unitage IU/mL for interlaboratory interpretations.

Keywords: Cobas SARS-CoV-2 Duo assay; Severe acute respiratory syndrome coronavirus 2; Viral load.