Specimen Collection for Suspected COVID-19

Pathlab has been receiving many queries regarding the appropriate specimen to collect for COVID-19 following the release of the recent MOH guidelines on 14th July which states “either nasopharyngeal and/or oropharyngeal swabs are appropriate for the collection of specimens for COVID-19 testing.”

Nasopharyngeal swab is still the preferred sample type

A subsequent message released by Dr Ashley Bloomfield on 23rd July has also clarified this. It is important to note that detection rate, sensitivity and viral load of an nasopharyngeal swab (NPS) is significantly higher than that of an oropharyngeal swab (OPS) (Wang H, Hu J, Zhou M et al, (2020), Nasopharyngeal swabs are more sensitive than Oropharyngeal swabs for COVID-19 Diagnosis and Monitoring the SARS-CoV-2 Load. Front. Med. 7:334).

OPS for COVID-19 testing can be considered in the community setting in those patients with acute symptoms who refuse an NPS. Due to the decreased sensitivity, OPS for COVID-19 testing should not be routinely offered to patients. However, a well collected OPS can be used if a NPS cannot be taken for any reason.

Recommended Specimen types in different contexts:

Context Swab Site
Symptomatic people < 7 days from onset form the community
(General Practice, Urgent care facilities,
Community based assessment centres,
and designated COVID testing practices)
NPS recommended
OPS accepted
Symptomatic people >= 7 days from onset from the community NPS only
All asymptomatic people NPS only
Managed Isolation facilities NPS only
Emergency departments, Hospital wards and clinics NPS only
Suspected outbreaks and Contact tracing NPS only
Work and Travel clearance NPS only