Evaluation of CLINITEST® Rapid Covid-19 + Influenza antigen test in a cohort of symptomatic patients in an emergency department

Rapid management of patients with respiratory tract infections in hospital emergency departments is one of the main objectives since the concurrent circulation of respiratory viruses following the SARS-CoV-2 pandemic. The use of new combined point-of-care antigen tests for detecting influenza A/B and SARS-CoV-2 represents an advantage in response time over the molecular tests. The objective was to evaluate the suitability of the CLINITEST® Rapid Covid-19 + Influenza Antigen test (Siemens Healthineers, Germany) (RCIA test) by measuring the sensitivity, specificity, Cohen’s kappa, and cut-off values.

Nasopharyngeal samples were collected from a randomised group of symptomatic patients of all ages at emergency department during January–February 2023. In parallel, these patients were screened for influenza A/B, and SARS-CoV-2 using RT-PCR. The Ct (cycle threshold) values were collected for positive [RT-PCR (+) /RCIA test (+)] and false negative [(RT-PCR (+) /RCIA test (-)] samples. A subanalysis was performed in the paediatric population (< 16 years-old).

We included 545 patients (55.8% females) with a median age of 7 years-old (IQR: 1–66.5). The RCIA test showed a sensitivity of 59.7% [95%CI: 46.9–67.33] for influenza A, 65.6% [95%CI: 49.5–80.3] for influenza B, and 76.9% [95%CI: 45.8–84.8] for SARS-CoV-2. The specificity was between 90.7%-99.7% with a moderate/high level of agreement with RT-PCR (kappa score: 0.6–0.8) for the three respiratory viruses included in the RCIA test.

The sensitivity of the RCIA test is insufficient for screening of patients, including patients with low Ct values (Ct > 20). Despite its good specificity and Cohen’s kappa value, its use as a screening test is not comparable to RT-PCR systems in the ED environment with a high number of false negative results.