SARS-CoV-2 viral load
Quantitative detection of SARS-CoV-2 RNA from the nasal wash of all the clinical samples was done by performing rtRT-PCR using Simplexa™ COVID-19 Direct kit (DiaSorin) as per the manufacturer’s instructions. Reactions were run on the LIAISON® MDX instrument (DiaSorin). The DiaSorin Molecular Simplexa™ COVID-19 Direct assay system is a real-time RT-PCR system that enables the direct amplification of Coronavirus SARS-CoV-2 RNA from nasal wash (NW) specimen. The data is analyzed with LIAISON® MDX Studio Software. The assay targets two different regions of the SARS-CoV-2 genome, ORF1ab S gene14. The sample was considered SARS-CoV-2 positive when one of the target genes in the same sample was positive and negative if both the genes were negative. The Ct values for both the genes were nearly similar. In this study, we used the Ct value of ORF1ab from nasal wash for the comparisons. The Ct value is inversely correlated with RNA copy number of the virus. Ct value < 40 was considered COVID-19 positive.