Nasal Swab Sampling for SARS-CoV-2: a Convenient Alternative in Times of Nasopharyngeal Swab Shortage

Nasopharyngeal swab is the reference sampling method to detect SARS CoV2, as recommended by world Health Organization (WHO) (1).….

KEYWORDS COVID-19, nasal swab, nasopharyngeal swab, RT-PCR, SARS-CoV-2, molecular diagnosis N asopharyngeal swab is the reference sampling method to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as recommended by the World Health Organization (WHO) (1). However, nasal specimens may have a slightly lower sensitivity than nasopharyngeal specimens (2,3). We herein validated an alternative procedure to collect nasal secretions with a swab routinely used in medical bacteriology for which there is no risk of supply disruption in order to perform the molecular diagnosis of SARS-CoV-2 infection.
Patients who were suspected of having coronavirus disease 2019 (COVID-19) attending the Hôpital Européen Georges Pompidou, Paris, France, were for their own care according to medical decision prospectively included and subjected to SARS-CoV-2 molecular testing using nasopharyngeal swab (Xpert nasopharyngeal sample collection kit; Cepheid, Sunnyvale, CA, USA) and nasal swab (Copan Transystem; Copan, Brescia, Italy).
Nasal and nasopharyngeal swabs were inserted in the nostril until they hit an obstacle (the inferior concha and the back of the nasopharyngeal cavity, respectively), rotated five times, and removed. The test was conducted in only one nostril per patient. After sampling, the nasopharyngeal swab was inserted into a vial containing 3 ml of virus transport medium (Xpert viral transport medium; Cepheid), and the nasal swab was placed in a 15-ml tube containing 3 ml of saline solution (0.9% NaCl). SARS CoV-2 was detected using Allplex 2019-nCoV assay (Seegene, Seoul, Korea).
A total of 44 patients were prospectively included up to the end of March 2020. Their median age was 63.0 years, ranging from 18 to 94 years. There were 23 (52.3%) male and 21 female patients. A total of 37 (84.1%) patients showed laboratoryconfirmed SARS-CoV-2 infection using nasopharyngeal swab, with 7 patients giving negative results (15.9%) ( Table 1).
Out of 37 patients that were positive for SARS-CoV-2 by nasopharyngeal swab testing, 33 also tested positive by nasal sampling. All SARS-CoV-2-negative patients with nasopharyngeal swabs (n ϭ 7) gave negative test results using nasal swabs (Table 1).
We herein report that the molecular detection of SARS-CoV-2 using nasal swab specimens was nearly equivalent to the detection using nasopharyngeal swab considered the gold standard. SARS-CoV-2 detection from nasal samples showed high sensitivity and specificity. Agreement and accuracy of test results using nasal sampling by reference to gold standard nasopharyngeal sampling were estimated as substantial and good, respectively. Taken together, these observations demonstrate that nasal sampling could be used to screen SARS-CoV-2 in times of nasopharyngeal swab shortage.