id	author	title	date	pages	extension	mime	words	sentences	flesch	summary	cache	txt
cord-285527-1mceq6v0	Kinloch, Natalie N	Suboptimal biological sampling as a probable cause of false-negative COVID-19 diagnostic test results	2020-06-28		.txt	text/plain	1910	127	55	To investigate suboptimal sample collection as a possible cause of false-negative test results, we quantified human DNA levels recovered on nasopharyngeal swabs submitted to a single laboratory for COVID-19 testing, hypothesizing that human DNA could serve as a stable molecular marker of specimen collection quality. Human DNA levels were quantified using droplet digital PCR (ddPCR), a technique where each sample is fractionated into 20,000 nanolitre-sized water-in-oil droplets prior to PCR amplification with sequence-specific primers and fluorescent probes, and where Poisson detection sensitivity compared to the original real-time RT-PCR assay, we re-tested the 40 suspected false-negative specimens by nested RT-PCR. Overall, we observed significantly lower human DNA levels in the suspected false-negative nasopharyngeal swab samples compared to a panel of consecutive samples submitted for testing during the same period, though overlap between groups was still substantial (Figure 1, p<0.001) . Our observations strongly support suboptimal biological sampling, but not PCR sensitivity for SARS-CoV-2 RNA detection, as a contributing cause of false-negative COVID-19 test results.	./cache/cord-285527-1mceq6v0.txt	./txt/cord-285527-1mceq6v0.txt