Strep Screen
Rapid antigen tests for group A Streptococcal pharyngitis are available. The major advantage of rapid diagnosis is that a patient can be diagnosed and treated at the same time. Early treatment is beneficial because it promptly relieves symptoms, decreases the likelihood of serious sequelae, and limits the spread of infection to others.
The sensitivities of these techniques depend not only on the methodology used but also on the numbers of streptococci present in the sample. A recent College of American Pathologists survey summarized results from several commonly used kits:
|
Methodology |
# Tested |
% Correct |
|
Abbott Testpack |
222 |
99 |
|
Abbott Testpack Plus |
760 |
99 |
|
BD Culturette 10MN LTX |
47 |
100 |
|
BD Directigen |
39 |
98 |
|
BD Directigen 123 |
619 |
96 |
|
BD Q Test Strep |
15 |
83 |
|
Biostar Strep A OIA |
150 |
100 |
|
DPC DX Strep A |
48 |
98 |
|
Hybritech Tandem Icon |
365 |
99 |
|
Kodak Surecell |
102 |
100 |
|
Wampole Clearview |
65 |
93 |
Obviously some kits perform better than others. Tests with an efficiency below 99% should be avoided. False negative results may occur with any test method if the specimen contains small numbers of streptococci. Therefore, a good throat swab is crucial. All antigen-negative swabs should have the negative result confirmed by culture.
Specimen requirement is a throat swab placed in clear liquid transport media.
Reference range is negative for group A Streptococcus by antigen detection.
