Strep (Direct)

A screening test for a strep antigen (Strepto-Direct) is used as a first-line test for throat infections and can detect the presence of strep A on a throat swab within a few minutes. A positive result indicates the presence of Group A Streptococcus, and an antibiotic can be prescribed immediately.

 

However, a negative result does not eliminate the possibility of a bacterial infection, and all Strepto-Direct negative specimens must be confirmed in the laboratory.

 

It is a highly specific test. As compared to throat culture, rapid antigen detection tests (RADTs) offer diagnosis at the point of care within five to 10 minutes. (1)

The traditional technique for confirmation is a 48-hour bacterial culture. An initial observation is made after 24 hours to identify rapidly positive cultures. 24-hour negative cultures are re-examined after 48 hours to obtain a final negative or positive result.

Figure 1: Specificity and Sensitivity of RADT (3)

 

The antibiotic prescription is often delayed by 24 or even 48 hours. Group C and G streptococci are also detected.

Available evidence suggests that clinical prediction rules for triage children who should undergo Group A Streptococcus testing are not sufficiently accurate. Implementing Rapid Antigen Detection Tests into clinical practice has an important impact on antibiotic prescription rates, with a reduction of about 30 %. (2)

 

 

 

 

References:

Strep-Direct

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