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The Essence: The Best of July 2020

By Anne-Margaret Olsson posted 08-03-2020 13:24

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 “How Effective Would it be to Implement Antigen-Based COVID-19 Point-of-Care Testing for Airport Arrivals?” to “What Do Other Lab Professionals Think About Preheating COVID-19 Serum Samples Prior to Running Serology IgG and IgM?”. Read on for our editor’s picks of the best discussions on the Artery in July.

Antigen-based POC COVID-19 Test
Initiated by @Vivek Pant, MD

How effective would it be to implement antigen-based COVID-19 point-of-care testing for airport arrivals? Although antigen tests are very specific for the virus, one respondent points out that they are not as sensitive as molecular PCR tests. This means that there is a higher chance of false negatives with antigen testing and negative results may need to be confirmed with a PCR test. Therefore, pooled PCR testing might be a better option for airport screening.

Gabapentin Nonlinear Calibration Curve
Initiated by @Dan Wang, PhD, DABCC

One lab has had a LC-MS/MS serum gabapentin quantification assay since 2015, but recently the calibration curve became quadratic instead of linear. What could have caused this? One respondent suggests several potential reasons, from an aging detector to an inadvertent change in the curve weighting setting that could make a curve appear to fit better with a quadratic rather than a linear equation. To try to pinpoint the cause, he suggests comparing the gabapentin and ISTD raw signal areas before and after the problem started.

African Countries Need Cheaper COVID-19 Tests
Initiated by @Mustafa Barbhuiya, PhD, ASCP, NRCC

With African countries lagging far behind in COVID-19 testing, one lab professional is making the case for low- and middle-income countries (LMICs) to adopt lateral flow antigen tests for COVID that don’t require instrumentation. One respondent asked if pooled PCR testing would be a better option for LMICs, since antigen tests are not as sensitive as PCR tests. The original poster then explained that in areas with no electricity or running water, any kind of PCR testing is unfeasible, and an imperfect antigen test is better than nothing.

COVID-19 Preheating Serology
Initiated by @Jeri Rubendall, MT (ASCP)

What do other lab professionals think about preheating COVID-19 serum samples prior to running serology IgG and IgM? All respondents so far have said that they don’t preheat for safety and instead rely solely on PPE. One respondent also added that labs should be careful about heat-inactivating specimens for use with EUA methods. An EUA is not a full FDA approval, and therefore it’s her understanding that modifications are not allowed without the testing site filing another, specific EUA.