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The Essence: The Best of April 2020

By Anne-Margaret Olsson posted 05-06-2020 13:40

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 “Are Early Serological Markers Necessary?” to “Should We Test Surgery Patients for COVID-19 on a Pre-op Basis?”. Read on for our editor’s picks of the best discussions on the Artery in April.

Pneumatic Tube System for COVID Samples
Initiated by @Kathryn Lloyd, MD, ABB

Should pneumatic tube systems be used for delivering COVID-19 specimens to the lab? CDC’s website advises against transporting respiratory COVID-19 specimens via pneumatic tube, while in a call, the agency advised against using tube systems to transport any specimens from COVID-19 positive patients. In light of this, one respondent’s lab has been asking for hand-delivery of all specimens. On the flipside, a few other labs are continuing to use the tube system as long as samples are properly packaged (e.g., in a sealed biohazard bag). One of these labs is also considering double bagging specimens as a further precaution against contamination.

Are Early Serological Markers Necessary?
Initiated by @David Grenache, PhD, DABCC, MT (ASCP)

One respondent thinks that IgM/IgA testing may determine whether convalescent patients can donate plasma, but the original poster thinks IgG is better suited to this purpose. Another respondent points out that the Royal College of Pathologists of Australia recommends against using IgG/IgM rapid tests to diagnose COVID-19 because these tests miss people in the early infectious stage of the disease. With respect to POC serology tests in particular, WHO also recommends that labs only use these tests in research settings.

Algorithms for the Use of COVID Ab Testing
Initiated by @Tammy Farley, MT(ASCP)

A lab professional is wondering if anyone can share an algorithm for the use of COVID antibody testing. Most respondents agree, however, that until the question of immunity is answered (i.e. is the antibody response protective from re-infection and for how long?), antibody tests for SARS-CoV-2 have limited clinical utility. Currently, these tests’ main clinical uses are: 1) as a complementary test to a negative PCR in a critically ill patient and 2) for identifying recovered patients who could be convalescent plasma donors.

COVID-19 Word Problem
Initiated by @Jennifer Matera, MT (ASCP)

One poster is asking if her institution should test surgery patients for COVID-19 on a pre-op basis to determine whether surgeons need PPE. Her community has a disease prevalence of 2.5%, and her institution’s test has a sensitivity of 65% and a specificity of 95%. Based off of these numbers, a respondent calculated that there is only a 1% chance of false negatives using this test. If this false negative rate is low enough for the surgeons, the respondent recommends providing pre-op COVID-19 testing. However, if surgeons plan to wear PPE regardless of the test results, then the test isn’t needed.