Group A Strep Culture
Test Code
CXGRA
Description
Group A Strep culture is used to determine if Streptococcus pyogenes is the causative agent of a throat infection. Negative Strep A antigen tests reflex to Group A Strep culture.
Only S. pyogenes is evaluated in this test, which is the primary bacterial pathogen associated with throat infections and the preferred test. Other causes of bacterial pharyngitis are rare; for these infrequent cases, a general throat culture may be considered.
Collect
Swab the posterior pharynx, tonsillar area, and inflamed areas of the throat. Place gentle pressure on the tongue with a tongue depressor. Extend 2 sterile swabs between the tonsillar pillars and behind the uvula avoiding the tongue, buccal mucosa, and uvula. Sweep the swab back and forth across the infected area. Do not obtain a specimen if the epiglottis is inflamed, as sampling may trigger life-threatening respiratory obstruction.
One swab is used for the point of care Strep antigen testing. If this is negative, the remaining swab needs to be sent to the laboratory for culture. The swab transport system can be a dry or moist swab with or without silica gel.
Patient Prep
Avoid antibiotic administration prior to sample collection.
Unacceptable Conditions
- Specimens received outside of temperature storage requirements
- Specimens received outside of stability time frame
- Specimens in non-sterile swabs
- Specimens in expired transport media
- Specimens from a source not acceptable for this testing
- Mislabeled or unlabeled specimen
Stability
- For optimal recovery of potential pathogens, specimens should arrive within 2 hours at room temperature (20-25°C)
- If transportation is delayed, specimens may remain at room temperature (20-25°C) for a maximum of 24 hours
Performed
7 days a week from 8am to 6pm
Methodology
Screen for beta-hemolytic colonies followed by biochemical testing and MALDI-TOF mass spectrometry.
Turnaround Time
2 days
Department
Microbiology Lab
Synonyms
Streptococcus (group A) Culture
Study Offerings
CAP/CLIA
Reference Interval
No Streptococcus Group A isolated
Interpretation
- A positive will be reported as: Streptococcus pyogenes (Group A)
- A negative will be reported as: No Streptococcus Group A isolated
CPT Code
87081
New York Approved
Standard
FDA
Standard Method