Potential pitfalls of routine SARS-CoV-2 serology for mass screening.

To the Editor,

We have read with great interest the recent article on the evolving approach to the laboratory assessment of coronavirus disease 2019 (COVID‐19). Indeed, antibody tests for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) constitute one of the keys to fight the SARS‐CoV‐2 epidemic, in particular, to surpass the deconfinement period. Seropositivity to SARS‐CoV‐2 antigens would allow identifying previously infected individuals, a priori considered to be healed and protected against new reinfection. There are, however, potential concerns on the relevance of SARS‐CoV‐2 serology. Thus, the majority of SARS‐CoV‐2 infection is asymptomatic or paucisymptomatic with localized mucosal replication at the respiratory tract tissue and without a viremic phase. Seemingly, they only provide a slight stimulation of the immune system, inducing a weak rapidly decreasing systemic humoral immune response, as reported in the Middle East respiratory syndrome (MERS)‐CoV infection. The risk of false‐negativity implies that SARS‐CoV‐2 serology would then markedly underestimate the extent of mild and asymptomatic infection. Furthermore, possible cross‐reactivity with other phylogenetically related CoV's could result in false positivities. Finally, routine SARS‐CoV‐2 serology is not designed to detect the unique neutralizing antibodies considered as protective in convalescent COVID‐19 individuals, , and, thus, cannot identify patients unable to control the SARS‐CoV‐2 infection. Taken together, SARS‐CoV‐2 serology shows several potential pitfalls, which make it possibly less reliable in determining the level of protection of an individual, with the risk of poorly diagnosing an already infected asymptomatic person, the possibility of low specificity because of cross‐reactivities against CoV's antigen, and the lack of identification of protective antibodies. Routine SARS‐CoV‐2 serology for mass screening remains until now challenging and does not seem so simple to be used to overcome the SARS‐CoV‐2 epidemic.

FUNDING INFORMATION

This letter to the editor was supported by the Assistance Publique Hôpitaux de Paris (AP‐HP), Paris, France.

CONFLICT OF INTERESTS

The authors declare that there are no conflict of interests.