ImplemeNting SARS-CoV-2 Rapid antigen testing in the Emergency wArd of a Swiss univErsity hospital: the INCREASE study

  1. Giorgia Caruana
  2. Antony Croxatto
  3. Eleftheria Kampouri
  4. Antonios Kritikos
  5. Onya Opota
  6. Marylin Foerster
  7. René Brouillet
  8. Laurence Senn
  9. Reto Lienhard
  10. Adrian Egli
  11. Giuseppe Pantaleo
  12. Pierre-Nicolas Carron
  13. Gilbert Greub
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Abstract

Background

While facing a second wave in SARS-CoV-2 pandemic, in November 2020 the Swiss Federal Office of Public Health (FOPH) authorized the use of rapid antigen tests (RATs) in addition to the gold-standard reverse transcription-polymerase chain reaction (RT-PCR).

Methods

We implemented the use of RAT in the emergency ward of our university hospital for rapid patients’ triaging and compared performances of four different antigen tests. All results were compared to SARS-CoV-2 specific RT-PCR (reference standard).

Results

Triaging patients using RAT in association with RT-PCR allowed us to isolate promptly positive patients and to save resources, in a context of rapid RT-PCR reagents shortage. Among 532 patients with valid results, overall sensitivities were 48.3% for One Step Exdia and 41.2% for Standard Q ® , Panbio−and BD Veritor. All four antigen tests exhibited specificity above 99%. Sensitivity increased up to 74.6%, 66.2%, 66.2% and 64.8% for One Step Exdia, Standard Q, Panbio, and BD Veritor respectively, when considering viral loads above 10 5 copies/ml, up to 100%, 97.8%, 96.6% and 95.6% for viral loads above 10 6 copies/ml and 100% (for all tests) when considering viral loads above 10 7 copies/ml. Sensitivity was significantly higher for patients presenting with symptoms onset within 4 days (74.3%, 69.2%, 69.2% and 64%, respectively) versus patients with evolution of symptoms for more than 4 days (36.8%, 21.1%, 21.1% and 23.7%, respectively). Sensitivities of all RAT assays were of only 33% among hospitalized patients without COVID-19 symptoms.

Conclusion

RAT might represent a useful epidemiological resource in selected clinical settings as a complementary tool to the molecular tests for rapid patients triaging, but the lower sensitivity compared to RT-PCR, especially in late presenters and subjects without COVID-19 symptoms, must be taken into account in order to correctly use RAT for triaging.

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