The Essence: The Best of October 2020

By Anne-Margaret Olsson posted 29 days ago

  
The Artery is your community for finding solutions to your day-to-day clinical chemistry questions. Last month, several answers were found to questions ranging from "For what length of time do SARS-CoV-2-positive patients continue to shed virus?" to “What would a CAP inspector do if a lab were not following the manufacturer’s SOP/recommendations for molecular SARS-CoV-2 methods with FDA EUAs”. Read on for our editor’s picks of the best discussions on the Artery in October.

Drug Testing in Oral Fluid
Initiated by @Paul Davis, ABFT, NRCC

When labs test for cocaine in oral fluid, should they test for cocaine, benzoylecgonine (BE), or both? One respondent says BE only, because cocaine degrades very quickly in oral fluid and he has rarely seen cocaine-positive samples that don’t have detectable BE. However, another respondent counters that this approach is outdated. Research from a few years ago shows that nearly 25% of oral fluid samples that test positive in cocaine/BE screening only have cocaine in them.

COVID Viral Shedding
Initiated by @Linda England, MT (ASCP)

For what length of time do SARS-CoV-2-positive patients continue to shed virus? Most respondents have seen persistent shedding of SARS-CoV-2 RNA sufficient for detection for at least 100-plus days. If a patient continues to test positive for viral RNA after 10 days post-symptom onset, however, CDC recommends considering the patient non-infectious. Testing for IgM after this timepoint could also potentially help determine if such a patient is non-infectious, but not all respondents agree on this point.

COVID-19 Molecular Methods and CAP Inspections
Initiated by @Roberto Alegre, BSc-Biochemistry, MT-C (AMT), Supervisor (FL-CL

What would a CAP inspector do if a lab were not following the manufacturer’s SOP/recommendations for molecular SARS-CoV-2 methods with FDA EUAs? Even in the case of tests with EUAs, the lab must follow the method’s IFU. If the lab chooses to make any kind of modification, the test is now considered an LDT and the lab must then follow all standards for an LDT. If the lab doesn’t, the CAP inspector will likely cite multiple deficiencies. However, if the only modification a lab makes is adding or changing a specimen type, then the lab can simply do a bridging study.


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