Performing nasopharyngeal swabs—Guidelines based on an anatomical study

Abstract

Nasopharyngeal swabs are performed to collect material for diagnosing diseases affecting the respiratory system, such as Covid-19. Yet, no systematic anatomical study defines concrete prerequisites for successfully targeting the nasopharyngeal mucosa. We therefore aim at simulating nasopharyngeal swabs in human body donors to characterize parameters allowing and supporting to enter the nasopharynx with a swab, while avoiding endangering the cribriform plate. With the aid of metal probes and commercial swabs a total of 314 nasopharyngeal swabs in anatomical head/neck specimens stemming from 157 body donors were simulated. Important anatomical parameters were photo-documented and measured. We provide information on angles and distances between prominent anatomical landmarks and particularly important positions the probe occupies during its advancement through the nares to the upper and lower parts of the nasopharynx and cribriform plate. Based on these data we suggest a simple and safe three-step procedure for conducting nasopharyngeal swabs. In addition, we define easily recognizable signals for its correct performance. Evaluations prove that this procedure in all specimens without deformations of the nasal cavity allows the swab to enter the nasopharynx, whereas a widespread used alternative only succeeds in less than 50%. Our data will be the key for the successful collection of nasopharyngeal material for detecting and characterizing pathogens, such as SARS-CoV-2, which have a high affinity to pharyngeal mucosa. They demonstrate that the danger for damaging the cribriform plate or olfactory mucosa with swabs is unlikely, but potentially higher when performing nasal swabs.