Laboratory Diagnosis and Monitoring the Viral Shedding of SARS-CoV-2 Infection

Abstract

The global pandemic of Coronavirus Disease 2019 (COVID-19) is now ongoing. Rapid and accurate detection of the causative virus SARS-CoV-2 is vital for the treatment and control of COVID-19. In this study, the comparative sensitivity of different respiratory specimens were retrospectively analyzed using 3552 clinical samples from 410 Guangdong CDC (Center for Disease Control and Prevention) confirmed COVID-19 patients. Except for BALF, the sputum possessed the highest positive rate (73.4%∼87.5%), followed by nasal swabs (53.1%∼85.3%) for both severe and mild cases during the first 14 days after illness onset (d.a.o). Viral RNA could be detected in all BALF from the severe group collected as early as 4 days after illness onset (d.a.o) and lasted up to 46 d.a.o., while none of BALF samples from mild group. Moreover, although viral RNA was negative in the upper respiratory samples, it was also positive in BALF samples in most cases from severe group during treatment. Despite of typical ground-glass opacity observed via computed tomographic (CT) scans, no viral RNA was detected in the first 3 or all upper respiratory tract specimens from some COVID-19 patients. In conclusion, sputum is most sensitive for routine laboratory diagnosis of COVID-19, followed by nasal swabs. Detection of viral RNAs in BLAF improves diagnostic accuracy in severe COVID-19 patients.

Fast Screening and Primary Diagnosis of COVID-19 by ATR–FT-IR

“…SARS-CoV-2 RNA can be detected in both upper and lower respiratory specimens including nasal swab, oropharyngeal swab, sputum, and bronchoalveolar lavage fluid (BALF). 2 , 3 Despite BALF, which is not a requisite for COVID-19 diagnosis because of the harder sampling, the sputum was reported to have the highest positive rate (74.4–88.9%), followed by nasal swabs (53.6–73.3%) during the first 14 days after onset (d.a.o.). 3 The positive rate for throat swab was reported to be around 60%.…”

“… 2 , 3 Despite BALF, which is not a requisite for COVID-19 diagnosis because of the harder sampling, the sputum was reported to have the highest positive rate (74.4–88.9%), followed by nasal swabs (53.6–73.3%) during the first 14 days after onset (d.a.o.). 3 The positive rate for throat swab was reported to be around 60%. 3 , 4 Viral RNA is also detected in serum samples with a percentage of 0% (0/31), 5 8% (1/12), 6 or 15% (6/41).…”

Practical challenges to the clinical implementation of saliva for SARS-CoV-2 detection

“…Diagnostic testing is a cornerstone of the COVID-19 pandemic response strategy [1], yet the establishment of laboratory testing which is accurate, practical, and scalable to meet the demand for public health surveillance measures has been a considerable challenge. Nasopharyngeal swabs are the preferred specimen type over throat swabs due to superior sensitivity [2,3], and over nasal aspirates due to lower risk of aerosol generation. Flocked nasopharyngeal swabs are designed to maximize mucosal contact and more efficiently release contents into the testing medium [4,5]; however, due to global demand during the pandemic response, a reliable supply of high-quality, flocked swabs and appropriate viral transport medium has been difficult to procure.…”

Comparison of three methods for detection of anti-SARS-CoV-2 antibodies

“…They also pointed out that, for severe cases, most required is detection of virus in bronchoalveolar lavage. 5 Serological tests detect antibodies to SARS-CoV-2 and in that way identify individuals who were in contact with virus. It was even suggested that combining RT-PCR with serological tests is optimal for diagnosis of suspected patients.…”