How To Swab a Throat for Testing
Testing may involve traditional culture on sheep blood agar (GABHS) or Thayer-Martin medium (gonorrhea), rapid antigen testing (GABHS), or nucleic acid amplification testing (gonorrhea, COVID-19).
(See also Streptococcal Infections.)
In patients with tonsillopharyngitis, a throat swab may need to be tested primarily to diagnose:
Gonococcal pharyngitis may be suspected in patients with known or possible exposure to gonorrhea (eg, recent oral-genital contact).
Criteria suggestive of need for testing for GABHS pharyngitis include the presence of ≥ 2 of the following:
Threshold for GABHS testing may be lower in patients at increased risk because of diabetes or immunocompromise.
Throat swabs are also sometimes tested if COVID-19 is suspected.
Use swabs supplied with the specific test kit being used or by the facility's laboratory. If none are supplied, use a swab with a plastic or wire shaft and a rayon, Dacron, or calcium alginate tip. Avoid swabs with wooden shafts and/or cotton tips because these materials may interfere with certain tests.
Explain the procedure to the patient, including that they may gag briefly.
Wear gloves and eye protection, and if COVID-19 is under consideration, gown, N95 respirator, and face shield.
Position the patient and light source to illuminate the posterior oropharynx.
Have the patient open the mouth and relax the tongue by saying "aaaah."
Press the tongue down using a tongue depressor.
Gently rub the swab against both tonsils and the posterior pharynx.
Place the swab in the culture medium, transport medium, or sterile test tube.