Covid-19 test results could mislead public | Letters

Dr Michael Browning is concerned by the limitations of the Roche antibody test, while Dennis Sherwood is worried about the reliability of self-administered swabs

Public Health England's report on its validation of the Roche Covid-19 antibody test (which the government is promoting for widespread use) reveals a number of limitations that were not mentioned in the public briefings (Public Health England approves Roche test for coronavirus antibodies, 13 May). The test showed inadequate levels of sensitivity for detecting antibodies to Covid-19 until 40 days after the onset of symptoms, so will only be useful from six weeks after the start of infection, and cannot be used for the diagnosis of acute infections; the validation process did not include controls from patients with other coronavirus infections (eg Sars/Mers) to exclude potential cross-reactions with these; it did not address how long antibodies persist following infection; and does not inform whether an individual is protected against reinfection, and therefore does not indicate whether they are safe to return to work, nor whether they are suitable for an immunity passport".

While the availability of antibody testing undoubtedly represents an important step in the fight against Covid-19, limitations such as these mean that these tests are not as clinically useful as the public has been led to believe.
Dr Michael Browning
NHS consultant immunologist, Pickwell, Leicestershire