SARS-CoV-2 detection using digital PCR for COVID-19 diagnosis, treatment monitoring and criteria for discharge

Renfei Lu; Jian Wang; Min Li; Yaqi Wang; Jia Dong; Weihua Cai

With dPCR assay, we were able to track the progress of the treatment by monitoring the viral load 254 from samples obtained on different dates. RT-PCR suffered from sporadic appearance of positive 255 result which puzzled clinicians. dPCR results, in contrast, faithfully reflected the onset and healing of 256 the disease, when examined together with relevant radiological evidence and treatment history. dPCR 257 showed evidences of higher sensitivity to detect low virus load in patients who showed mild symptoms 258 or have been treated for COVID-19 than We were also able to compare the viral load in different organs thanks to higher sensitivity of dPCR 260 assay. The dPCR assay provides quantitative information on the viral load of specimens collected from 261 different locations of the same patient. In all but one cases, the viral load is the highest in pharyngeal 262 samples, lower in stool samples and the lowest in serum. Interestingly, a considerable amount of virus 263 was found in the phlegm of one of the patients whose pharyngeal sample was negative. These 264 observations may provide valuable insight into the pathology of this emerging disease 20 . 265