There has been immense publicity in the last few days that one million home testing kits for coronavirus could be sent out in a matter of weeks. These kits are based upon the analysis of a small sample of blood, taken by finger prick, to detect the immunoglobulins IgM and IgG, antibodies that arise some time after symptoms appear. So, because the tests are detecting the immune response and not the virus itself, they inform if a person has had the condition, if indeed there is a period of immunity after having contracted the disease.  It might be, then, that those who have had the virus could return to their normal routines. 

These tests are performed by immunochromatography, usually using test cassettes just like the many currently available pregnancy test kits used at home and throughout the health care system.

However, it is vital to ensure that such test kits are reliable. Today (27 March 2020), The Guardian reports that the Spanish government has withdrawn 9,000 coronavirus testing kits from use after it emerged that they had an accurate detection rate of just 30%. Similarly, studies have shown that, for qualitative faecal immunochemical tests based on this technique, about two thirds of the commonly used products performed acceptably but some had low sensitivity and specificity and probably should not be used for bowel screening.

It is highly likely that a range of home COVID-19 (SARS-CoV-2) test kits will soon be marketed in chemists and, more especially, by online retailers. All are urged to wait until such tests have been rigorously evaluated using approved protocols, and then assessed as satisfactory against agreed performance specifications.  As the Chief Medical Adviser to the UK Government, Professor Chris Whitty, said: “The one thing worse than no test is a bad test”.

Further information can be found in a very readable article in The Telegraph (27 March 2020) – 

Professor Callum Fraser, Centre for Research into Cancer Prevention and Screening, University of Dundee