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Lab Manual for UCSF Clinical Laboratories

Lab Manual for SFGH

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Item Value
Available Stat? No
Test code ASAG
Performed by? Microbiology
Sendout? no
Price range $$$
In House Availability 24 hours/ 7 days; culture will be done on all specimens negative by the antigen test.
Principle The Directigen EZ Group A Strep Test is a qualitative, lateral flow immunoassay for the detection of Strep A carbohydrate antigen in a throat swab. In this test, antibody specific to Strep A carbohydrate antigen is coated on the test line region of the strip. During testing, the extracted throat swab specimen reacts with an antibody to Strep A that is coated onto particles. The mixture migrates up the membrane to react with the antibody to Strep A on the membrane and generates a red line in the test region. The presence of this red line in the test region indicates a positive result, while its absence indicates a negative result. To serve as a procedural control, a red line will always appear in the control region indicating that proper volume of specimen has been added and membrane wicking has occurred.
Interpretation The rapid Strep A Test is intended for use in determining the presence of group A streptococcus antigen in a pharyngeal swab specimen. The test is not intended for distinguishing whether the specimen is from a colonized or an infected individual. A negative result may indicate either that the specimen obtained was negative for the presence of group A streptococci, the swabbing was not efficient, or the amount of antigen extracted from the specimen was less than the analytical sensitivity of the assay. The rapid Strep A Test result should be interpreted in conjunction with other clinical and laboratory data available to the clinician. An additional follow-up culture will be done by the clinical Microbiology Laboratory if the rapid Strep A Test result is negative. In our laboratory, the sensitivity of this test as compared to culture is approximately 86%; specificity is approximately 95%.
Container type Double Swab Kit for Rapid Group A Strep Test (These swab kits are available through Laboratory Support Services, 206-8199. )
Collection Instructions To collect specimen, swab the back of the throat and any inflamed tonsil area. Avoid swab contact with teeth, gums, tongue, or cheek surfaces Excess blood or mucus on the swab may interfere with testing and cause false positive results.
Sample type Swab
Special instructions Do not use transport media containing gelatin, agar or charcoal. Swab must arrive in laboratory within 24 hours of time of collection.
Normal range No antigen detected.
Synonyms Streptococcal Antigen From Throat Swabs;
Stability 24 hours at room temperature.
References 1. Murray PR, et al. Manual of Clinical Microbiology, 9th Ed. ASM Press, Washington, D.C., 2007.

2. BD Directigen(TM) EZ Goup A Strep Test Product Insert 11558096102 (02). Becton Dickinson and Co., Sparks, MD, 21152. 2007/01.
CPT coding 87430
Last Updated 11/20/2010 1:53:49 PM
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