Explained: How to combine antibody and PCR tests for better results

Cambridge University researchers have now developed a point-of-care test that combines the two kinds. They describe it in Cell Reports Medicine.

Health workers prepare for Covid-19 antigen tests in New Delhi. (AP Photo: Manish Swarup)

In testing for novel coronavirus infection, the PCR test and rapid antibody test come with limitations. A PCR test, which screens nasal and throat swabs, may miss the virus if it has already moved away from the nose and throat and reached the lungs by the time the test is done.

Antibody tests look for antibodies, but these appear days after infection.

Cambridge University researchers have now developed a point-of-care test that combines the two kinds. They describe it in Cell Reports Medicine.

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The approach was tried in 45 patients They provided nose/throat swabs and blood serum. The authors designed a gold standard test of two parts, either of which could be positive to confirm Covid-19.

In the first part, artificial SARS-CoV-2 viruses were mixed with serum from patients to see whether the serum had antibodies. The second part was the standard PCR test. Using this gold standard, 24 of the patients had Covid-19.

Overall, the nucleic acid tests could identify eight out of ten patients with Covid-19, but when combined with the rapid antibody tests, 100% of the Covid-19 patients were correctly identified.

Source: University of Cambridge

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