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. 2021 Aug 6;41(8):BSR20211238. doi: 10.1042/BSR20211238

Figure 3. Samples and methods for testing COVID-19.

Figure 3

Image (A) shows the two major categories of samples and corresponding methods for detection of COVID-19. Image (B) provide time relationship between viral load, symptoms, and positivity on sensitivity of diagnostic tests. After onset of symptoms (usually 5 days after exposure), the viral load could be below the threshold level for detection through RT-PCR (test may give false-negative results). The same pattern follows at the end of the disease when the patient is recovering. Seroconversion may usually be detectable between 5–7 and 14 days after the onset of symptoms. Thus, the serological tests are prone to give false-negative results in the first phase of the disease. Images adapted from [103] with permission from PeerJ under Creative Commons Attribution License, and [100] with permission from Elsevier under COVID-19 resource centre.