Coronavirus: NHS staff found to be given inconsistent tests for Covid-19
22 April 2020, 09:09 | Updated: 22 April 2020, 09:30
Inconsistent tests for coronavirus have been administered on NHS staff working during the pandemic, according to a leaked government memo.
The Public Health England (PHE) document, released on 11 April, said "some discordant results" had been found in the in-house test, and advised a change to commercial kits.
It said this followed on from the Medicines and Healthcare products Regulatory Agency's "derogation" to use the original tests while the latter became available.
Among the issues with in-house testing listed in the document was "considerable diversity" of molecular platforms, reagents used, testing kits and the performance conditions in various labs.
"Quality assurance difficulties" were also cited, while "shortages of wards and transport medium" were said to have led to "local variations".
Enzyme performance in the tests were also listed as becoming "degraded" in comparison to the original performance.
The document went on to acknowledge some labs would need to continue using the in-house test while waiting for commercial tests to become available and listed several precautionary measures to take.
According to Open Democracy, which spoke to a leading pathologist with knowledge of the ongoing situation, the in-house test would miss around a quarter of positive cases of COVID-19.
However, PHE says this claim was "incorrect", and that the test had a 95% sensitivity when it was originally developed.
It said that further analysis of 1,144 samples tested in a lab revealed 35 "discrepant samples". After updating a component, it said the rate fell to 15 such inconsistent samples.
PHE added: "These differences may be due to either the test giving an incorrect result and are not quantified as either false negatives or positives, but rather discordant results between different test systems at a rate of less than 2%."
In a statement, Professor Sharon Peacock, the director of the National Infection Service at PHE, said: "No diagnostic test is 100% sensitive. Following a rigorous evaluation, we learned the PCR test produced different results to alternative tests in less than 2% of samples and we issued immediate actions to laboratory staff to ensure the continued reliability of the test.
"It is inaccurate to claim that the PHE diagnostic test provides false negative results 25% of the time.
"The test is regularly and thoroughly reviewed to make sure it remains reliable and effective. It is standard practice to move to commercial test kits once available, and this work is already underway."
Meawhile, care minister Helen Whately told Sky News on Wednesday that some of the early tests "weren't effective enough".
She added that those who were subject to these early tests had been contacted to let them know, and to offer them another test.