Vol. 101 November 15, 2013 Sore Throat: Strep or Not ?!

hub“What’s the difference between a cold and a strep throat?”
“About $75.”

A strep throat diagnosis has always required an office visit and a swab of the throat because clinical features alone can not reliably distinguish between group A strep and a viral sore throat.

For decades physician researchers have been seeking a way to make the correct diagnosis of strep pharyngitis vs a viral cold based on clinical findings only. During my training in the 60’s a pediatric group practice in Rochester, N.Y. compared their strep throat culture results to each physicians’ prediction based on clinical findings only (fever,  absent cough, tonsil appearance, etc.). They batted about 50% at best, with errors in both directions, false positives and false negatives.

That may change soon.

A team of Boston research physicians have recently come up with a potential APP for that!

These physicians combined two clinical findings that the patient could recognize with real-time data about the occurrence of positive strep tests in the community in the past 14 days to generate a “Home Score”.(1)  The addition of this community prevalence data, “real-time biosurveillance data”, according to the authors, increases the reliability of the prediction of “strep or no strep” for patients over 15 years old. One with a low-risk “home score” could safely skip going to the doctor. In the U.S. 12 million people a year visit a clinician for a sore throat, and the authors speculate that a “home score” could reduce those visits by 230,000 to 780,000. Of course, electronic “real-time biosurveillance data” is not available in most places. In the office where I work our “real-time biosurveillance” is distinctly less high tech and consists of a question to our nurse, “Joan, have we had a lot of positive streps this week?”

Why all the fuss about strep? Multiple studies show that treatment of strep throat with penicillin merely shortens the duration of symptoms by only about 24 hours in most cases compared to treatment with just increased fluids, temperature control, and rest. But, in people over 3 years of age (some say 6 yrs.) a strep infection can cause some people to develop complications of kidney (glomerulonephritis) or heart (rheumatic fever) inflammation . That is the reason we treat step throats with antibiotics. Children under 6 yrs. rarely develop those complications.

The American Academy of Pediatrics recommends strongly that anyone under 15 yo. be examined and have a strep test done. That strep test is now a Rapid Strep Test (RST) rather than a culture. It detects the presence of the bacteria by antigen reactions, not culture growth, and gives a result in 5 minutes. A throat culture for strep takes 18 to 48 hours. A small percentage of the RSTs may be falsely negative, so the AAP recommends that negative RSTs be double-checked with a back-up strep culture.

There may soon be a home kit for that!

Improvements in RST have reduced false negatives to a very small number. So small, that other physician researchers in Boston are ready to test a home-based, patient-administered RST. A positive home-based RST would be enough to initiate treatment and prevent complications. Such a reliable home-based test could greatly reduce visits to the pediatrician, ER, or urgent care setting, but communication with a health care provider would still be necessary to start appropriate antibiotic treatment.

So, in the near future you might be able to self-diagnose a “non-strep” sore throat using a smart phone APP (if over 15 years old) or a strep throat with a home-based RST kit and get timely, appropriate treatment without a visit to a health care provider.

I assume the APP will be free or $1.99 at most. I wonder what the home RST test kit will cost?

Of course, nothing in medicine is 100%, even death and taxes now-a-days.* About 12% of people who have a strep throat and are treated with penicillin will still carry the strep asymptomatically for a long time, not develop complications, and will have a positive RST with just a viral cold or even when healthy.

* The Obamacare penalty for not being insured was determined to be a tax by a 5 to 4 vote of the Supreme Court. Past ethical controversy about “brain death” has been superseded by equally lively discussions of “heart death”.

References:
1.  Ann Intern Med. 2013;159:577-583, 5 Nov

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