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The Essence: The Best of September 2020

By Anne-Margaret Olsson posted 10-01-2020 14:13

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 to Determine if a [COVID-19] Positive Result is False?' to “[Does] Anyone Use Separate Reference Ranges for Serum and Whole Blood Ionized Calcium?”. Read on for our editor’s picks of the best discussions on the Artery in September.

False Positives Rapid Testing in Hospital
Initiated by @Gerard Abate, MD

One Artery user has a COVID-19 patient who, after three weeks of hospitalization, tested negative for SARS-CoV-2 in the central lab, but tested positive with a rapid test. He is wondering how to determine if the positive result is false and if he should retest the patient. A respondent pointed out that CDC no longer recommends a test-based strategy for discontinuing transmission-based precautions, even for hospitalized patients, because persistence of SARS-CoV-2 PCR positivity does not generally correlate with infectiousness. Instead, CDC recommends using symptom- and time-based determinations to determine if a patient is still infectious. 

Minimum Qualifications for the High Complexity Testing Personnel
Initiated by @Jagadish Ulloor, PhD

A lab professional is wondering what the minimum educational and work experience qualifications are for testing personnel performing high complexity testing. Respondents say that these qualifications actually vary depending on the accrediting agency, as well as the state the lab is located in, because several states have personnel requirements that differ from CLIA. In light of this, when trying to determine the qualifications for testing personnel, labs should check the requirements for their state, for any other states whose patients they test, and for each of the accreditations the lab holds. 

Ionized Calcium Reference Ranges
Initiated by @Martin Abrams, BS.MS

One lab professional wants to know if anyone uses separate reference ranges for serum and whole blood ionized calcium or if other labs just use the same range for both. One respondent’s lab uses different reference intervals because his lab uses different instruments for serum vs. whole blood that don’t run the same. He added, though, that each lab will need to determine on their own whether their instruments for serum and whole blood need to be interpreted using different reference intervals, or whether the same interval can be used for both.