Antibodies against SARS-CoV-2 verification of commercially available assays and a nuanced sustainable approach

Important results from the project

The aim of this project was to do independent verifications of rapid tests for antibodies (serology) and antigens (viruses), since data on sensitivity and specificity may vary by operator and selection of samples. One of the objectives was to contribute to increasing the availability of rapid tests for home use, which was considered impossible at the beginning of the pandemic, but which is now accepted. We evaluated the sensitivity and specificity of 19 serology rapid tests and 11 salivary antigen rapid tests and were able to identify false positives and varying degrees of sensitivity.

Expected long term effects

Data on sensitivity and specificity rarely corresponded to what the manufacturer reports. For serology tests, a false positive signal was detected for patients with chronic inflammatory disease, which would give them a false reassurance of immunity. Also for antigen tests, some false positive tests were identified for saliva samples negative for viruses by PCR. The evaluation of the serology tests showed that all tests are able to detect antibodies in samples that have a high titer, but not for those samples with lower antibody concentration.

Approach and implementation

The verification of the serology tests could be carried out partly with serum and saliva samples already collected before the pandemic and stored in the biobank and which by definition then were negative for SARS-CoV-2 specific antibodies and antigens. We also recruited 431 individuals who donated blood and saliva, and performed repetitive tests for antigen in saliva. The serology response was compared with quantitative measurements using a method developed at SciLifeLab. Saliva tests were verified against dilution series of positive controls in a biosafety level 3 laboratory.