Lab Test

Strep Screen, Group A

Throat, Pharynx, Pharyngitis, Rapid Strep Test, Rapid Strep A Screen, Rapid Strep A Screen Antigen, Strep A Screen (Rapid), Strep Screen, Group A Strep (Rapid Antigen Test)

Test Codes




Specimen Collection Criteria

Collect: Throat swab. Carefully swab the posterior pharynx and both tonsils, then place in a transport system with Amies media, e.g. Culturette, ESwabs, etc

Physician Office/Draw Specimen Preparation

Maintain swab specimens at room temperature (20-26°C or 68-78.8°F) until transport. Refrigerate (2-8°C or 36-46°F) the specimen if delays (>8 hours) in transport are expected.

Preparation for Courier Transport

Transport: Swab transport system, at room temperature (20-26°C or 68-78.8°F) or refrigerated (2-8°C or 36-46°F).

Rejection Criteria

  • Specimens collected with calcium alginate swabs.
  • Specimens submitted in amies charcoal.

In-Lab Processing

A negative result for Strep Screen, Group A, will reflex to Group A Strep by NAA (EPIC LAB6907) for patients less than 16 years of age.


Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 8 hours
Refrigerated (2-8°C or 36-46°F): 48 hours
Frozen (-20°C/-4°F or below): Unacceptable

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Dearborn Microbiology Laboratory
Farmington Hills Microbiology Laboratory
Grosse Pointe Microbiology Laboratory 
Lenox Main Laboratory
Livonia Main Laboratory
Royal Oak Microbiology Laboratory
Taylor Microbiology Laboratory
Trenton Microbiology Laboratory
Troy Microbiology Laboratory
Wayne Microbiology Laboratory 


Sunday – Saturday, 24 hours a day.
STAT results available within 1 hour of receipt in the Laboratory.
Routine results available within 24 hours of receipt in the Laboratory.

Reference Range


Test Methodology

Rapid Chromatographic Immunoassay.


  • Rapid Strep Screen testing has been reported to detect 70-85% of cases of Group A Streptococcus (GAS).
  • A negative Strep Screen result will reflex to Group A Strep by NAA (LAB6907) for patients less than 16 years of age. 

Clinical Utility

Detection of Streptococcus pyogenes (Group A) antigen in pharyngeal specimens aids in the rapid diagnosis of pharyngitits due to Group A Streptococcus.

Clinical Disease

  • Streptococcus pyogenes is the most common bacterial pathogen implicated in pharyngitis. The principal manifestations of S. pyogenes are strep throat, scarlet fever, and skin infections (impetigo and cellulitis). Necrotizing fasciitis (the so called flesh-eating bacterial infection) has also been caused by S. pyogenes. Rapid diagnosis and treatment of S. pyogenes infections are necessary to prevent complications associated with these infections. The most common complications include acute rheumatic fever and acute glomerulonephritis. Rheumatic fever may occur after strep throat in about 2-3% of cases. Glomerulonephritis may follow either pharyngeal or skin infection. The most common symptoms of streptococcal pharyngitis include an abrupt onset of sore throat, malaise, headache, and a fever greater than 101°F. The throat is red and may have a grayish-white exudate on the tonsils. Additionally, children with strep throat often complain of a stomachache.
  • Scarlet fever is caused by an exotoxin produced by some beta-hemolytic Group A Streptococcus. The symptoms include a skin rash on the upper chest beginning on the second day of illness. The rash fades within a week and the skin may peel.
  • Impetigo is a superficial cutaneous infection characterized by crusted lesions. It typically occurs in late summer or early fall. It is most common in tropical or semitropical climates.
  • Necrotizing fasciitis is a life-threatening, and sometimes fatal disease that affects previously healthy patients. Symptoms include fever, severe pain, redness and swelling at the wound site. People with chronic illness are at higher risk of acquiring invasive disease. Cuts, wounds, and chickenpox provide an opportunity for bacteria to enter.
  • Toxic Shock Syndrome is usually caused by toxin 1 of S. aureus. Rarely Streptococcus pyogenes may also cause Toxic Shock Syndrome.


Streptococcal pharyngitis occurs year-round in temperate climates, but the incidence peaks in the winter and spring months. Infections can occur in any age group but most cases occur among school-age children.


Streptococcal infections are spread from person to person via inhalation of S. pyogenes laden respiratory droplets. Food-borne and milk-borne transmission has also been described. A number of individuals, particularly school-age children, carry S. pyogenes without signs of illness. Carriers are culture positive and seronegative.


  1. Spellerberg, B. and C. Brandt. 2015. Streptococcus. Manual of Clinical Microbiology. 11th edition. ASM Press. Washington, D.C.

CPT Codes

LOINC:  18481-2


Last Updated


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