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 Streptococcal Infections Streptococci are gram-positive aerobic organisms that cause many disorders, including pharyngitis, pneumonia, wound and skin infections, sepsis, and endocarditis. Symptoms vary with the organ... read more .)
In patients with tonsillopharyngitis Tonsillopharyngitis Tonsillopharyngitis is acute infection of the pharynx, palatine tonsils, or both. Symptoms may include sore throat, odynophagia, cervical lymphadenopathy, and fever. Diagnosis is clinical, supplemented... read more , a throat swab may need to be tested primarily to diagnose:
Group A beta-hemolytic streptococci (GABHS) infection
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:
Fever (on examination or by history)
Absence of cough
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 Coronaviruses and Acute Respiratory Syndromes (MERS and SARS) Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more is suspected.
The swab may cause brief, minor gagging.
Light source; flexible lamp or head-mounted light
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.
The tonsils are located along the sides of the posterior oropharynx. They lie between the anterior and posterior pillars of the throat.
Sitting position with head tilted back slightly
Step-by-Step Description of Procedure
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.
Follow-up on test results.
Warnings and Common Errors
Touching the swab to the tongue or sides of the mouth
Not swabbing all 3 sites in the pharynx
Tips and Tricks
Proceed swiftly because the patient will likely gag.
Having the patient stick out the tongue actually stiffens it and can make it harder to see the pharynx.