COVID-19: Guidance on Antibody Tests / N95 Sterilization / Loss of Smell & Taste / Prevalence in OB Patients

NEJM Journal Watch

By Amy Orciari Herman

Edited by David G. Fairchild, MD, MPH, and Lorenzo Di Francesco, MD, FACP, FHM

Some of the latest developments in novel coronavirus disease (COVID-19):

CDC guidance on antibody testing: The CDC has issued interim guidance on testing for SARS-CoV-2 antibodies. Among the recommendations: serologic assays that have received emergency use authorization from the FDA are preferred; the test’s positive predictive value should be high (e.g., choose a test with a specificity of 99.5% or greater if possible); and testing can be used to aid in the diagnosis of COVID-19 in patients who present late (e.g., 9–14 days after symptom onset), when the sensitivity of polymerase chain reaction testing is waning. See the full recommendations at the first link below.

N95 sterilization: Irradiating N95 masks with gamma radiation reduces their ability to filter air particles — even when relatively low doses are used — according to a study in JAMA Network Open. Researchers irradiated three different models of N95 masks (doses ranged from 1 to 50 kGy of 1.3 MeV gamma radiation). After irradiation, all masks passed a fit test. The masks were then placed in an air duct, through which ambient particulate matter was passed. The masks’ filtration efficiency was significantly reduced by all radiation doses. The researchers note: “These findings suggest that a qualitative fit test alone is unable to fully assess mask integrity and that at the doses required for sterilization, gamma radiation degrades the filtration efficiency of N95 masks.”

Loss of smell & taste: Loss of smell and taste in COVID-19 patients may be more common than previously reported, an Annals of Internal Medicine study finds. Roughly 2000 European patients with mild-to-moderate COVID-19 answered questionnaires about their symptoms on the day they were discharged from the hospital or, for ambulatory patients, after their symptoms resolved. Some 87% reported experiencing loss of smell; most said it developed at the same time as, or after, other COVID-19 symptoms. (In a subset of some 90 patients who underwent objective olfactory testing, smell dysfunction was confirmed in over 60%.) Loss of smell was not associated with nasal obstruction, rhinorrhea, or postnasal drip. Overall, about one third of patients had recovered their sense of smell by the time of the questionnaire; loss of smell lasted, on average, 8 days. Additionally, 56% of patients reported impaired taste.

COVID-19 prevalence in OB patients: Some 3% of asymptomatic pregnant women who were tested for SARS-CoV-2 at presentation for delivery at three southern Connecticut hospitals in April tested positive for the virus, researchers report in JAMA. This is far lower than previous estimates from hard-hit New York City. Among all women screened (including those with symptoms), the prevalence was slightly higher, at 4%. The researchers conclude, “Approaches to care that balance screening and testing of patients combined with a rationalized approach to use of PPE should be considered for obstetric units.”