Covid-19 antibody test detects whole blood serum levels of IgM and IgG antibodies following an infection. The antibody development varies by patient and can take 4-23 days. IgM antibodies are less specific than IgG antibodies as these are faster to develop compared with more specific IgG antibodies.
There are a number of tests have been developed and are specific to Covid-19 IgM/IgG antibodies. All use similar technology. Recently Abbott home testing kits were withdrawn from home testing for demonstrating false positives. It is not clear why this is the case.
One conspiracy theory is that tests proved accurate on laboratory tests, which demonstrated the effectiveness of such tests with 99-100% accuracy. However, the tests were not designed or approved for home testing. Accuracy may have been affected when used as a home test as sample kits were sent via the post. Patients were expected to take blood themselves. Samples were then sent back in the post to a laboratory for testing. At the time of the launch in the UK there was an early heat wave, with temperatures reaching late 20s/early 30 degrees Centigrade. Having worked in the clinical homecare market where products are transported across the country at 2-8C in temperature-controlled transport or temperature-controlled packaging, uncontrolled packaging, even in a white van can exceed 40 degrees Centigrade. Samples unless protected correctly will cook! The MHRA stopped the home sampling of these kits.
Global Health Clinics use Biopanda-19 rapid tests. The tests are produced in the UK and are MHRA approved and CE marked. These have not been withdrawn by MHRA and are now in fact endorsed by the National Pharmacy Association and The Tony Blair Institute for Global Change.
These tests can only be performed by trained clinicians in clinic or surgery or pharmacy environments which are generally temperature controlled.
The tests are sophisticated and work by a blood sample being placed on a test strip which contains recombinant SARS-CoV-2 antigen conjugated with coloured particles. If IgM/IgG antibodies are present they combine with the coloured antigen. An added buffer solution takes the antibody/coloured antigen particles along the test slide. At detection points antihuman IgM or antihuman IgG are located on the slide and these combine with the IgM or IgG now coloured article and concentrate the colour which shows up as a coloured test line. Simply if you have antibodies you will develop a line. These lines are very specific giving 99-100% accuracy. A test line shows that the solution has run the length of the test strip validating a working test. The test runs for 10 to 15 minutes.
The tests are qualitative not quantitative. This means that they show antibodies present, not how many. However, we have found patients who were heavily infected which may have resulted in hospitalisation produce strong lines well within the 10-minute test.
For more help or advice talk to our lead clinician. Tests are available in the Surrey and Berkshire through our Longcross clinic close to the Woking, Chertsey, Ascot, Windsor, Cobham and Walton areas.
Note if you have antibodies present it does mean you still have to take care and not spread any infection found on hard surfaces. Although not infected yourself you could still be a pollinator and can physically pass the infection on to loved ones or other members of the public.