We use a CE marked Roche coronavirus antibody test called the Elecsys Anti-SARS-CoV-2 S assay. The manufacturer (Roche) carried out a study to support the CE mark submission of this test. The study used blood samples from patients with a positive coronavirus infection. Roche did not use samples from people without symptoms, so the results may have differed if the study had included these people.
Test sensitivity is the ability of a test to correctly detect a positive result when testing samples from people known to have had a coronavirus infection. Sensitivity can increase from the point of diagnosis because antibody levels increase in response to an infection. This means that from 21 days after a positive diagnosis (the earliest point at which we recommend testing), the test returned a positive result in 98.3% of cases. After 28 days, sensitivity is 100%, based on Roche’s study.
Test specificity is the ability of a test to correctly produce a negative result when testing samples from people known not to have had a coronavirus infection. Roche used 5,991 negative samples (which were collected before October 2019). The test produced only one false-positive result – giving the test a specificity of 99.98%.
This test may not accurately detect antibodies in people who have compromised immune systems because their antibody response may be slower or weakened. This includes people with immunodeficiency diseases, infections such as HIV, or those who take medications that suppress the immune system. This may also affect the sensitivity and specificity of the test.