Combined Oropharyngeal/Nasal Swab is Equivalent to Nasopharyngeal Sampling for SARS-CoV-2 Diagnostic PCR

Abstract

Background: Early 2020, the COVID-19 epidemic became a public health emergency of international concern. To address this pandemic broad testing with an easy, comfortable and reliable testing method is of utmost concern. Nasopharyngeal (NP) swab sampling is the reference method though hampered by international supply shortages. A new oropharyngeal/nasal (OP/N) sampling method was investigated using the more readily available throat swab.Methods: In this prospective observational study 36 COVID-19 patients were tested with both a NP and combined OP/N swab for SARS-CoV-2 RNA by PCR. In hospitalized suspect patients, who tested negative on both swabs, extensive retesting was performed. The sensitivity of NP versus combined OP/N swab sampling on admission and the correlation between viral RNA loads recovered was investigated.Results: 35 patients were diagnosed with SARS-CoV-2 by means of either NP or OP/N sampling. The paired swabs were both positive in 31 patients. The one patient who tested negative on both NP and OP/N swab on admission, was ultimately diagnosed on bronchoalveolar lavage fluid. A strong correlation was found between the viral RNA loads of the paired swabs (r = 0.76; P < 0.05). The sensitivity of NP and OP/N analysis in hospitalized patients (n = 28) was 89.3% and 92.7% respectively.Conclusions: This study demonstrates equivalence of NP and OP/N sampling for detection of SARS-CoV-2 by means of rRT-PCR. Sensitivity of both NP and OP/N sampling is very high in hospitalized patients.