Variability in instructions for performance of nasopharyngeal swabs across Canada in the era of COVID-19 – what type of swab is actually being performed?

Abstract

Background The primary method of surveillance for the presence of SARS-CoV-2 is with nasopharyngeal swabs. Given the significant demand for nasopharyngeal swabs, a large number of previously untrained and unfamiliar staff are now performing this test. It was noted that there was significant heterogeneity in instructions for performing nasopharyngeal swabs in Canada, in contrast to the guidance provided by the Centers for Disease Control and Prevention (CDC), and the Pan American Health Organization (PAHO). The objective of this study was to review the instructions provided across Canada and contrast them to those of the CDC and PAHO. Methods A standard series of steps for nasopharyngeal swab performance was outlined based on the CDC, PAHO, and New England Journal of Medicine instructions. A comprehensive search was performed in August 2020 to identify nasopharyngeal swab guidelines provided by public health in the provinces and territories of Canada. Regional health authority guidance was also collected. Instructions provided were contrasted against the standardized steps. Results Instructions were identified for all provinces and territories, and for 81 regional health authorities. From the provincial and territorial guidelines, 10/13 (77%) cleared the nasal passages before swab insertion, 11/13 (85%) tilted the patient’s head back slightly, 12/13 (92%) inserted the swab parallel to the palate, but only 3/13 (23%) inserted the swab to at least a depth of two-thirds the distance between the patient’s nose and ear. A clear majority (81%) of regional health authority guidelines followed their respective provincial guidelines. For depth of insertion, Quebec provided a pictogram but no distance or technique for estimation. Six provinces and territories - Northwest Territories, Nunavut, Ontario, Saskatchewan, Prince Edward Island and Alberta - recommended 4 cm or one-half the distance from nostrils to ear. British Columbia and Manitoba recommended a 7 cm depth of insertion. Nova Scotia recommended one-half to two-thirds the distance from nose to ear. Lastly, Newfoundland, New Brunswick and the Yukon recommended an insertion from nose to the external ear canal. Conclusion There is significant heterogeneity in guidance for nasopharyngeal swab performance across Canada. The instructions provided by the majority of provinces and territories in Canada would not be effective in reaching the nasopharynx. Graphical abstract

The microbiome of the nasopharynx

“…Accurate sampling of the NP tract remains a challenge to establishing a baseline NP microbiome. Despite the technique of nasopharyngeal swabbing and washes being standardized by the World Health Organization (WHO), considerable heterogeneity had been noted within clinical practice during the COVID-19 pandemic [104][105][106][107]. The nasopharynx is defined as a subcomponent of the upper throat or posterior nasal cavity.…”

“…The nasopharynx is defined as a subcomponent of the upper throat or posterior nasal cavity. However during a recent systematic review of the scientific literature using risk-ofbias assessments and quality checklists, the anterior nares and posterior oropharyngeal wall have been found to be included within the term 'nasopharynx' [108,109]. Accuracy is important: alpha diversity indices for brushings of the inferior turbinate was increased vs. washings of the whole nasal cavity; whether this was due to a richer sampled environment or removal of pathogens with a greater range of mucosal adhesion is difficult to assess [110].…”

Der Nasen- oder Rachenabstrich in der COVID-19-Pandemie – Aspekte für den HNO-Arzt/die HNO-Ärztin – SARS-CoV-2, Coronavirus, Nasenabstrich, Rachenabstrich, Komplikationen

“…Die genannten Abstriche werden von unterschiedlichem Personal bestenfalls nach ausführlicher Instruktion durchgeführt: ▪ durch HNO-Ärzte/-Ärztinnen ▪ durch Ärzte/Ärztinnen anderer Fachgebiete ▪ durch medizinisches Fachpersonal (Pflegekräfte, Sanitäter, Medizinstudenten, Medizinische Fachangestellte etc.) ▪ durch nicht medizinisch vorgebildetes, aber gezielt instruiertes Personal ▪ durch Probanden/Probandinnen selbst, teils auch im Schulalter Anleitungen für die Durchführung von Abstrichen liegen in Gebrauchsanleitungen typischerweise schriftlich vor, werden jedoch auch kritisch bewertet [25]; Instruktionen werden auch in produktbezogenen oder allgemeinen Videos gegeben. Die Qualität solcher Instruktionen wurde in Studien unterschiedlich eingeschätzt.…”

Optimal Insertion Depth for Nasal Mid-Turbinate and Nasopharyngeal Swabs

“…The clinical specimens obtained are typically tested with either a real-time reverse-transcription polymerase chain reaction (RT-PCR) or the “rapid” antigen tests for SARS-CoV-2 infection [ 4 ]. There is considerable disagreement in guidelines with respect to the recommended insertion depth of nasopharyngeal swabs [ 5 ]. The suggested insertion depth ranges anywhere from 4 to 10 cm [ 5 , 6 , 7 , 8 , 9 ].…”

“…There is considerable disagreement in guidelines with respect to the recommended insertion depth of nasopharyngeal swabs [ 5 ]. The suggested insertion depth ranges anywhere from 4 to 10 cm [ 5 , 6 , 7 , 8 , 9 ]. The CDC does not describe the insertion depth for nasopharyngeal swabs, but instead states that the swab should be inserted until resistance is encountered equivalent to the posterior nasopharyngeal wall [ 10 ].…”