"I Think I Have Strep Throat"

One of the most common maladies in our urgent care practice is a sore throat.  The actual chief complaint that is  frequently stated is “strep throat”.  It is a common misperception that “strep” throat and sore throat are interchangeable and synonymous terms.  There are many causes of a sore throat; most of the time it is not caused by “strep”, that is, the streptococcal bacteria, at all.

Strep throat stands out among all the other causes mainly because it is the one that can lead to serious consequence of rheumatic fever, an immune response that can cause heart, kidney, and brain disease.  Strep throat demands antibiotic treatment for the main reason of preventing rheumatic fever.  The fact that patients will feel better faster and lose their contagiousness is merely a bonus.

But what about a sore throat not caused by strep?  Most are caused by viruses for which antibiotics are useless and will get better without treatment.  In fact using an antibiotic for a viral infection can cause more problems than it solves for it is not uncommon a rash to develop with these viral infections.  If an antibiotic is being used  at the time, this has the consequence of creating a situation where the victim will be incorrectly labeled as “allergic” to that antibiotic and a potentially useful medication will no longer be available  to that person forever more.

So how can one tell the difference?  Clinically, the afflicted individual really can’t tell for certain.  Worse,  the clinician, despite many caregivers claim to the contrary, can’t tell reliably either!  Several well conceived investigations to judge physicians ability in correctly diagnosing strep throat by interview and physical examination only have determined that we can accurately diagnose strep throat in approximately 50 per cent  of the cases.  In case you aren’t aware, that is exactly the same accuracy of correctly calling the flip of a coin!  That is why testing is essential for proper treatment and use of antibiotics.

The “gold standard” test for strep is the throat culture.  In this test the throat is swabbed then this is smeared on a culture medium for incubation.  The quickest result by this method is about 24 hours, but may take up to 3 days!  In response  to the delay of diagnosis, the rapid antigen tests, or rapid step tests were developed.  Using antibody reactions to detect the presence of the telltale chemical marker, or antigen, of strep, the diagnosis can now be established in less than ten minutes.  A properly performed test approaches the accuracy of culturing and is fairly reliable; but, unfortunately it is not infallible.   Therefore, many doctors will perform a culture if the rapid test is negative for strep.

Strep throat, technically called streptococcal pharyngitis, is highly contagious so will tend to spread in environments of close contact or questionable hygiene, namely households and schools.  Still, more often than not, that “step throat” that the kids bring home will be caused by an agent that is something other than strep.

– Michael J. Varney, M.D.