Hello researchers!
Can anyone help explain each of the lines/curves exist in this figure about "detection of SARS‑CoV‑2"
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@Majd Hello,
The lines in the figure represents few different parameters. One is the PCR detection of the viral nucleic acids in nasopharyngeal swab, fecal swab and bronchoalveolar lavage fluid. It shows that before symptoms the nasopharyngeal swab offer the best way to detect a active COVID-19 patient. This is followed by BALF and anal swab well into the symptomatic phase. The solid Red line shows that viral isolation from patients is possible only during the -1 and + 1 week of symptoms. The dotted lines primarily indicate the SARS CoV 2 antibodies that are detectable in the patients blood. IgA appears first followed by IgM followed by IgG.
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I concur with Arup Acharjee's analysis.
I find the early spike of IgA quite curious. The figure does not say where the IgA was detected, but I am presuming it was in blood? as opposed to saliva?
IgM is produced 1st in an immune response, and that is followed by IgG and IgA. The IgM levels decay by 6 weeks, and this is normal. The sustained IgG levels are also normal. But the very early rise and loss of IgA is puzzling. That suggest a potential cross-reaction with previously generated antibodies that is easily cleared by binding to corona virus as the viral load increase, but is not protective.
Thank you Mr. Gary for addition I also suppose the IgA rise was detected in blood
Dr. Acharjee's interpretation of the data is correct. As regards the IgA peak, it is intended as a serum peak. However, it was recently demonstrated that IgA can be also detected in saliva samples or oropharyngeal swabs. However, IgA detection showed a lower sensitivity compared to IgG and IgM detection.
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