Covid-19 antibody tests: a briefingBMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m2284 (Published 24 June 2020) Cite this as: BMJ 2020;369:m2284
All rapid responses
Thank heavens for an unambiguous criticism of these tests by Dr Pushpa-Rajah (rapid response).
I challenge anyone medically qualified to disagree.
Starting from here, I go on to say:
1. Nobody knows how many persons in any discrete population have had Covid - 19 infection eliciting antibody reaction in the host.
2. Nobody knows how many individuals in such population inhaled Covid -19, or were infected mucosally by Covid-19, and were too strong ( ? Cellular immunity) to develop an antibody reaction, with or without clinical disease.
The implications for the value to be attributed to vaccines will be a matter for conjecture.
Competing interests: No competing interests
It was unfortunate that Baraniuk reported uncritically the accuracy of the SARS-CoV-2 antibody tests made by Abbott and Roche.  Armstrong did contextualise those claims but the wide confidence intervals went unmentioned. 
According to Public Health England’s evaluation the Roche assay is 86.7% sensitive (95% confidence interval 76.8 to 93.4) at 21 days after onset of symptoms.  The Abbott assay is 93.5% sensitive (95% confidence interval 85.5 to 97.9) at the same time point.  Particularly concerning is that Public Health England despite stating its “methodology was of a high standard” has not specified how many unique patients were involved in the assessment of either test. [2–4]
Additional publicly available data in individual patients rather than samples have been published by both Roche and Abbott in their respective manufacturer’s “Instructions for Use” documentation. Roche demonstrated 80% sensitivity in five recovered patients at 24-26 days after diagnosis was confirmed with a viral swab.  Abbott reported 69% sensitivity overall when it assessed the test serially over time in 13 patients.  A stark difference compared to the effusive language used when antibody testing was initially proposed for use. 
The Medicines and Healthcare Products Regulatory Agency has specified (in consensus with industry and clinicians) “minimally acceptable” performance requirements to be met for a test to be suitable for the Government’s plan for mass antibody testing. This requires at least 98% sensitivity (95% confidence interval 96 to 100%) on samples collected after twenty days since first symptoms, and performed in a sample size of 200 patients.  Neither test has achieved this in any setting.
Recently published meta-analyses support the conclusions drawn from the insufficient quantity of manufacturers’ data that were available but never well publicised. [9–11] There are already several questions concerning the utility of antibodies tests, and poor transparency regarding their accuracy will make them even harder to justify. 
1 Baraniuk Chris. Covid-19 antibody tests: a briefing BMJ 2020; 369 :m2284
2 Armstrong Stephen. Why covid-19 antibody tests are not the game changer the UK government claims BMJ 2020; 369 :m2469
3 Public Health England. Evaluation of Roche Elecsys AntiSARS-CoV-2 serology assay for the detection of anti-SARS-CoV-2 antibodies. 11 June 2020. https://assets.publishing.service.gov.uk/government/uploads/system/uploa...
4 Public Health England. Evaluation of the Abbott SARS-CoV-2 IgG for the detection of anti-SARSCoV-2 antibodies. 8 June 2020. https://assets.publishing.service.gov.uk/government/uploads/system/uploa...
5 Roche. Elecsys® Anti-SARS-CoV-2. Package Insert 2020-07, V3.0; Material Numbers 09203095190 and 09203079190. US Food and Drug Administration
6 Abbott. Abbott ARCHITECT SARS-CoV-2 IgG Instructions for Use. H14806R01. April 2020. US Food and Drug Administration
7 Government of the United Kingdom. Prime Minister’s statement on coronavirus (COVID-19): 19 March 2020. https://www.gov.uk/government/speeches/pm-statement-on-coronavirus-19-ma...
8 Medicines & Healthcare Products Regulatory Agency. Target Product Profile. Antibody tests to help determine if people have immunity to SARS-CoV-2. https://assets.publishing.service.gov.uk/government/uploads/system/uploa...
9 Deeks JJ, Dinnes J, et al. Antibody tests for identification of current and past infection with SARS-CoV-2. Cochrane Database Syst Rev 2020; doi:10.1002/14651858.cd013652
10 Lisboa Bastos Mayara, Tavaziva Gamuchirai, Abidi Syed Kunal, Campbell Jonathon R, Haraoui Louis-Patrick, Johnston James C et al. Diagnostic accuracy of serological tests for covid-19: systematic review and meta-analysis BMJ 2020; 370 :m2516
11 EUnetHTA. The current role of antibody tests for novel coronavirus SARS-CoV-2 in the management of the pandemic. Collaborative Assessment. EUnetHTA 2020.
12 Andersson Monique, Low Nicola, French Neil, Greenhalgh Trisha, Jeffery Katie, Brent Andrew et al. Rapid roll out of SARS-CoV-2 antibody testing—a concern BMJ 2020; 369 :m2420
Competing interests: No competing interests