A study published in the Clinical Medicine Journal of the Royal College of Physicians in the United Kingdom by Robinson and others in March 2021 compared the use of the Roche and Abbott assay for antibodies amongst a large cohort of healthcare workers in Southern England.
The cohort study included data obtained from staff at the Western Sussex Hospital Trust and Brighton and Sussex University Hospitals during voluntary antibody testing using the Abbott and Roche SARS-CoV-2 antibody assays at each Trust respectively.
The observed seroprevalence level was 7.9% using the Abbott test at the Western Sussex Hospital and 13% using the Roche antibody test at the Brighton and Sussex University Hospital.
Based on a previous positive PCR, the study found that the false negative rate of the Abbott and Roche assays were respectively 60.2% and 19% respectively, which implied a sensitivity level of 39.8% and 81%.
Interestingly, in these cohorts seropositivity was most strongly associated with those of South Asian ethnicity, Allied Health professionals and male sex.
The study provided real world data on the efficacy of both the Abbott and Roche SARS-CoV-2 antibody assays.
Despite a higher incidence within the Western Sussex Hospital Trust cohort of PCR proven and COVID-19 infections and a higher case rate in the region, a far lower incidence of antibody positivity was seen at the Western Sussex Hospital Trust, 7.9% versus 13%.
Notably, the majority of staff who had had a prior positive PCR with Abbott actually had a negative antibody test, 60.2%. This figure was slightly improved in those who also reported symptoms with 54.7% demonstrating antibodies at the Western Sussex Hospital Trust compared with 87.5% at the Brighton University Hospital.
The study concluded that serum antibody tests on healthcare workers may not accurately reflect the seroprevalence in this population and are likely to have underestimated the true incidence of SARS-CoV-2 infection.
They also concluded that the two most widely used antibody tests in the UK, Roche and Abbott have a real world sensitivity of 81% and 39.8% respectively and they suggested that neither antibody tests performed to the specification level stated by the manufacturer.
At The London General Practice we provide an antibody test which is much more sensitive and specific, which has been developed with the researchers at Imperial College London.
Dr Paul Ettlinger
BM, DRCOG, FRCGP, FRIPH, DOccMed