Covid-19: Two antibody tests are “highly specific” but vary in sensitivity, evaluations find
Elisabeth Mahase
Abstract
Covid-19: Two antibody tests are "highly specific" but vary in sensitivity, evaluations find Elisabeth MahaseThe BMJ Two tests for covid-19 antibodies developed by the drug companies Roche and Abbott are "highly specific" but one was found to have lower sensitivity than was previously reported by the company, evaluation by Public Health England has shown.Abbott had reported that its assays had a sensitivity of 100% (the true positive rate) 14 days after symptom onset.However, PHE found that it had a sensitivity of 93.4% at 14 days, respectively.PHE published the reports after experts called for transparency in relation to the evaluation results, so that any claims could be fully scrutinised. 1 Now that the evaluations have been made public, experts have said it is not clear whether these tests are any better than other available antibody tests and emphasised that the evaluations did not meet the standard needed for accreditation.Roche's Anti-SARS-CoV-2 serology assay was tested between 5 and 7 May by the PHE diagnostic support group, 2 which used 93 serum samples from convalescent patients and 472 negative samples.The team reported that all negative samples tested negative, giving a specificity of 100%, while the overall sensitivity was 83.87%, rising to 87.0% at 14 days after onset of symptoms, 87.7% 21 days after, and 100% more than 40 days after.Abbott's SARS-CoV-2 IgG kit was tested between 4 and 7 May, 3 with 96 samples from convalescent patients and 759 negative samples.The assay was found to be 99.63%specific, with a sensitivity of 93.90% at 14 days after symptom onset, dropping to 93.40% at 21 days and 87.5% at 40 days.