key: cord-0913949-0osh17w1
authors: Döhla, Manuel
title: On the usefulness of point-of-care antibody tests for SARS-CoV-2 in community screening settings
date: 2020-05-25
journal: Public Health
DOI: 10.1016/j.puhe.2020.05.031
sha: 8cb9e06eb7f36eddff0808bcb3c31c0a87fc1b24
doc_id: 913949
cord_uid: 0osh17w1

nan

Dear Editors, we are pleased with the discussion of our paper [1] and would like to take the opportunity to discuss the benefits of antibody testing in screening scenarios in more detail.

SARS-CoV-2 is a particularly complex pathogen, since especially mild forms of the disease are often non-specific or asymptomatic [2] and therefore symptom-based risk management is not possible.

The present letter to the editor reports a PCR sensitivity of about 70%; but of course this depends on whether RNA-negative persons are also defined as COVID-19 cases based on certain symptoms. However, this definition is country-specific and has been updated several times during the pandemic.

PCR is the gold standard for acute infections, and we agree with the comment that an antibody test based on IgG is not suitable for adequately testing the immune response due to the time course of the immune reaction.

But a screening of asymptomatic or unspecifically symptomatic SARS-CoV-2-infected persons by means of IgM-antibodies seems to be worthwhile considering the relevance of investtigational speed [3] .

As mentioned and shown in Figure 1 of our study, we could not see a single "IgM only" response in our rapid tests, nor a single "IgG only" response. It could be that we happen to see only freshly infected people before IgM antibodies are formed as well as infected people in antibody class swap. However, there could also be a technical problem with the test on the IgM band.

Therefore, besides the development of suitable rapid tests based on PCR or antigens with high sensitivity for screening and quarantine decisions, it should be considered whether rapid antibody tests could be useful as an addition to PCR.

In our study, 11 individuals with positive rapid test would have been quarantined, 3 would have been released after negative PCR. 14 more people would have been quarantined 24 hours later after a positive PCR. We would have reduced the transmission possibilities for 24h by 36.4%, with opportunity costs of 3 false positives at an extremely high prevalence of 44.9% (by today's case numbers). With a lower prevalence and therefore a lower PPV, these costs would even increase. Therefore, we summarize our statement that antibody tests should not be used in community screenings to derive public health measures like quarantine. This is without prejudice to the importance of antibody testing for the decision to lift quarantine or other de-escalation measures.

Rapid point-of-care testing for SARS-CoV-2 in a community screening setting shows low sensitivity

Characteristic Temporary Loss of Taste and Olfactory Senses in SARS-CoV-2-positive-Individuals with Mild Symptoms

Quantifying SARS-CoV-2 transmission suggests epidemic control with digital contact tracing