Contribution of rapid lateral flow assays from capillary blood specimens to the diagnosis of COVID-19 in symptomatic healthcare workers: a pilot study in a university hospital, Paris, France.

BACKGROUND: This study aimed to assess, by rapid tests, the immune status against COVID-19 among Healthcare Workers (HCW) with history of symptoms, and for whom SARS-CoV-2 detection was either not documented or negative. METHODS: Whole blood by finger prick and serum samples were taken from HCW for use with 2 rapid lateral flow tests and an automated immunoassay. RESULTS: Seventy-two HCWs were included, median duration between symptoms onset and serology sampling was 68 days. Anti-SARS-CoV-2 antibodies were detected by rapid test in 11 HCW (15.3%) and confirmed in the 10 with available serum by the automated immunoassay. The frequency of ageusia or anosmia was higher in participants with SARS-CoV-2 antibodies (P = 0.0006 and P = 0.029, respectively). CONCLUSIONS: This study, among symptomatic HCW during the first wave in France, showed that 15% had IgG anti-SARS-CoV-2, a higher seroprevalence than in the general population. Rapid lateral flow tests were highly concordant with automated immunoassay.

Performance evaluation of two SARS-CoV-2 IgG/IgM rapid tests (Covid-Presto and NG-Test) and one IgG automated immunoassay (Abbott).

The aim of this study was to assess the analytical performances, sensitivity and specificity, of two rapid tests (Covid- Presto® test rapid Covid-19 IgG/IgM and NG-Test® IgM-IgG COVID-19) and one automated immunoassay (Abbott SARS-CoV-2 IgG) for detecting anti- SARS-CoV-2 antibodies. This study was performed with: (i) a positive panel constituted of 88 SARS-CoV-2 specimens collected from patients with a positive SARS-CoV-2 RT-PCR, and (ii) a negative panel of 120 serum samples, all collected before November 2019, including 64 samples with a cross-reactivity panel. Sensitivity of Covid-Presto® test for IgM and IgG was 78.4% and 92.0%, respectively. Sensitivity of NG-Test® for IgM and IgG was 96.6% and 94.9%, respectively. Sensitivity of Abbott IgG assay was 96.5% showing an excellent agreement with the two rapid tests (κ = 0.947 and κ = 0.936 for NGTest ® and Covid-Presto® test, respectively). An excellent agreement was also observed between the two rapid tests (κ = 0.937). Specificity for IgM was 100% and 86.5% for Covid-Presto® test and NG-Test®, respectively. Specificity for IgG was 92.0%, 94.9% and 96.5% for Covid-Presto®, NGTest ®, and Abbott, respectively. Most of the false positive results observed with NG-Test® resulted from samples containing malarial antibodies. In conclusion, performances of these 2 rapid tests are very good and comparable to those obtained with automated immunoassay, except for IgM specificity with the NG-Test®. Thus, isolated IgM should be cautiously interpreted due to the possible false-positive reactions with this test. Finally, before their large use, the rapid tests must be reliably evaluated with adequate and large panel including early seroconversion and possible cross-reactive samples.