The efficiency of some home antigen test kits in detecting Covid-19 appears to have declined with the advent of the Omicron variant, a new study shows.
He finds in the British Medical Journalare based on three widely used rapid antigen tests and show improved performance when tests used both nasal and throat samples compared to nasal samples alone.
However, only one test met World Health Organization (WHO) standards of at least 80% sensitivity – the ability to correctly identify a true positive sample.
It also achieved a specificity of 97 percent, where it correctly identified a true negative sample in people with symptoms.
Rapid antigen tests were not advocated by senior health officials in Ireland well into the pandemic, on the grounds that they were not as good as PCR lab tests at detecting the virus. A negative result could give someone with symptoms a false sense of security.
However, rapid antigen tests have long since become an important part of the Covid-19 response.
The new study, conducted during the Omicron phase of the pandemic in the Netherlands, involved researchers evaluating the performance of three commercially available rapid antigen tests – Flowflex (Acon Laboratories), MPBio (MP Biomedicals) and Clinitest (Siemens-Healthineers). – compared.
The analysis by researchers from Utrecht University is based on 6,497 people with Covid-19 symptoms aged 16 and over who presented for testing at three public health Covid-19 testing sites between December 21 and February 10.
All symptomatic individuals were subjected to a reference PCR test by a staff member and asked to complete a rapid antigen test within three hours of their on-site visit, followed by an online questionnaire.
Nasal self-sampling was used during the emergence of omicron and when omicron was responsible for more than 90 percent of infections. Combined throat and nose self-sampling was used when Omicron was responsible for more than 99 percent of infections.
The researchers found that the sensitivities of the three tests performed with nasal self-sampling decreased during the launch of Omicron, from 87 to 81 percent for Flowflex, from 80 percent to 73 percent for MPBio, and from 83 percent to 70 percent for clinical test. However, the decrease was only statistically significant for Clinitest.
When a throat test was added to a nose test, sensitivity improved from 70 to 83 percent for MPBio and from 70 to 77 percent for Clinitest. No throat test was performed for Flowflex.
Only the MPBio self-collection ear-nose test met WHO standards for rapid antigen testing in people with Covid-19 symptoms.
These are observational results, and the researchers point out some limitations.
They suggest that manufacturers of rapid antigen tests should consider expanding their instructions to include combined throat-nose self-assays, although it’s unclear how many are suitable for expanded use.
Researchers said serial tests that use them more than once may perform better.
https://www.independent.ie/irish-news/health/antigen-home-test-kits-declined-in-performance-as-omicron-variant-of-covid-emerged-41990287.html The performance of antigen home test kits declined when Covid’s Omicron variant emerged