Abstract
COVID-19 serology interpretation can be challenging, especially in front of IgM+/IgG− profile. With the emergence of SARS-CoV-2, physicians managed to learn how to prescribe new laboratory assays for its diagnosis: PCR and serology. Indications for prescription are different. Interpreting results may be challenging, especially in serology. As any immunoassay technique, interferences may exist in serology which can be a cause of errors. An IgM+/IgG− profile, even with negative PCR, associated with symptoms suggestive of COVID-19 requires isolation measures and the continuation of additional tests. However, the persistence of IgM+/IgG− profile alone 1 month after symptom onset does not lead to a conclusion of seroconversion, since seroconversion is defined by the appearance of specific IgGs. Faced with atypical serology profiles, a clinical-biological dialogue should be initiated. The biologist is trained on the analytical performances of the technique he has previously evaluated. He may complete investigations with additional techniques and counsel the physician.