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The Essence: The Best of June 2020

By Anne-Margaret Olsson posted 07-02-2020 11:18

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 “Should COVID Serology Positives Be Confirmed?” to “Do Any Labs Have Guidance or a Policy for Pooling Samples for SARS-CoV-2 PCR Testing?”. Read on for our editor’s picks of the best discussions on the Artery in June.

Should COVID Serology Positives Be Confirmed?
Initiated by @Charles Beavers, MD

Given the high probability of encountering false positives with serology, is anyone considering confirmation testing with another antigen (e.g. spike vs. nucleocapsid antibodies)? One respondent says that, especially in low prevalence areas, both FDA and CDC recommend that using two methods to detect antibodies will increase the accuracy of the positive result. Another respondent explains that CDC calls this the orthogonal testing algorithm and that, ideally, the assay with the highest sensitivity out of the two would be used to confirm.

Universal Hospital Admission Testing for COVID
Initiated by @Jeremy Hart, MD, MBA

Can anyone speak to their institution’s experience with universal admission testing for COVID-19? One large psychiatric hospital dedicates four units to isolating new admissions. This allows them to make sure all new patients—most of whom come from corrections facilities—test negative for COVID before they are moved to a “home” unit. The disadvantage of this, however, is that the hospital can no longer admit patients at the same rate it used to, all new patients are grouped together for about a week regardless of admission status, and they’ve now lost 4 high acuity units to admissions only.

IgG Antibody COVID
Initiated by @Guadalupe Rivera, PhD

Would it be possible for a COVID-19 patient who tests true positive via RT-PCR to never develop IgG antibodies to SARS-CoV-2? Respondents say that most individuals when challenged with SARS-CoV-2 will produce an antibody response. However, there does seem to be a subset of the population that does not make measurable antibodies. That could be due to a quirk of B-cell responsiveness or incomplete responses to mild/asymptomatic infections. It’s also likely that many qualitative assays simply have cutoffs that are too high to detect lower antibody levels.

SARS-CoV-2 Pooled Sample Testing
Initiated by @Denise Gaff, ASCP

Do any labs have guidance or a policy for pooling samples for SARS-CoV-2 PCR testing? One respondent says his lab is not pooling samples, but he shared a study that assessed this strategy. The study found that when the incidence rate of SARS-CoV-2 infection is 10% or less, group testing results in the saving of reagents and personnel time with an overall increase in testing capability of at least 69%.