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Old 05-27-2012
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Warning! Gosh! MTB appears wrong here...

Is MTB-CK wrong?

mtb states that

negative Rapid streptococcal antigen test= no antiobitcs needed

positive Rapid streptococcal antigen test=
positive pharyngeal culture
that means to go for throat culture
however uptodate says
A positive RSAT is useful in establishing the diagnosis of GAS pharyngitis, but a negative test does not rule out GAS.

that means postive RSAT means treatment and negative RSAT means culture throat
also kaplan medicine states
Diagnosis. Rapid Streptococcal antigen test are 60-100% sensitive but are >95% specific. A
positive test can be considered the equivalent of a positive culture, whereas a negative test
should be confirmed with a culture.
so what is the conclusion?
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Old 05-27-2012
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RSAT have a specificity of ≥95 percent and a sensitivity that varies between 65 and 90 percent [1,35,38-43]. Given the high specificity and limited sensitivity of the available tests, a positive RSAT is useful in establishing the diagnosis of GAS pharyngitis, but a negative RSAT does not rule out GAS. Because some RSAT may miss as many as 35 percent of cases of GAS pharyngitis, we recommend that throat culture be performed in children and adolescents with negative RSAT

If the rapid test is negative, a follow-up culture (which takes 24 to 48 hours) might be performed.

Negative antigen test misses <5% of strep pharyngitis, While it is reasonable to rely on a variety of strategies to exclude strep throat in average-risk patients, high-risk patients with a negative rapid antigen test should have an additional rapid strep test or a throat culture to exclude strep with a certainty of greater than 95%

sometimes MTB love to make things simple by giving General rules to detailed things ?? !! which is just to remember, but can be wrong

so at the end, if high risk culture or repeat, if intermediate risk i think u can rule it out
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The above post was thanked by:
doc s.j (12-01-2012), patelMD (05-28-2012)


Kaplan-Medical, USMLE-Books

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