COVID-19 Diagnostics: Performing a Nasopharyngeal and Oropharyngeal Swab
It is essential to follow proper infection control measures when samples are collected
from patients with a suspected Coronavirus infection. Among other things, the examiner
should wear an N95 respirator mask, gown, protective goggles, and gloves. To save resources,
we will refrain from using each of these items in this video and instead only show the technical
details of sample collection.
Let’s begin with the nasopharyngeal swab.
The patient should be alert and cooperative. Allow them to first blow their nose. The patient
should sit in a relaxed and comfortable position during the sample collection process. Tilt
the patient’s head back slightly and support it with your non-dominant hand. If necessary,
lean the patient’s head against a wall to minimize jerky movements. Stand slightly offset
from the patient to avoid the risk of contamination in case of sudden cough or sneeze.
Be sure to advise the patient of potential discomfort during sample collection, and let
the patient know that they are welcome to close their eyes.
Sample collection should only be completed using sterile swabs made from artificial cotton
with flexible plastic shafts.
Calcium alginate swabs or swabs with wooden shafts must not be used. These materials can
inactivate viral particles or inhibit PCR tests. Furthermore, wooden shafts are more
likely to cause patient injury.
Hold the swab like a pen between the thumb, index, and middle fingers. Maintain a loose
grip that allows the swab to accommodate any resistance encountered during sample collection,
to reduce the risk of injury. Avoid using the following hand position during
sample collection. Let’s begin with the nasopharyngeal swab,
the preferred method of sample collection.
Start by inserting the swab horizontally into the left or right nostril. Carefully advance
the swab while maintaining a course that is close to both the septum and the floor of
the nose, parallel to the palate.
Do not advance the swab upwards, but instead straight back until resistance is felt as
the swab reaches the posterior nasopharynx. When collecting samples from an adult patient,
this corresponds to a travel distance of approximately 5-6 centimeters or 2 inches. The swab should
reach a depth equal to half the distance between the nostrils and the outer opening of the
Leave the swab at this depth for a few seconds while gently wiping the wall by twisting the
swab shaft. Slowly and gently remove the swab.
Immediately insert the swab into the sample collection tube, which may contain 2-3 mL
of viral transport media. If a nasopharyngeal swab cannot be collected
for any reason, an oropharyngeal sample can also be collected through the mouth. Again,
inform the patient that the smear will feel uncomfortable for a short time and may trigger
a gag reflex.
Ask the patient to open their mouth wide, protrude their tongue forward, and say “Ah.”
Depress the patient’s tongue using a tongue depressor. Gently insert the swab into the
oral cavity without touching the lips, teeth, tongue, hard palate, or soft palate. These
surfaces should be avoided as they are often colonized by a wide range of microbes.
Collect the sample from the back wall of the throat. Twist the swab shaft gently but thoroughly,
sampling the oropharyngeal wall.
Just as with the nasopharyngeal swab, the oropharyngeal swab should now be placed into
the sample collection tube and sent to the laboratory as quickly as possible.