Strep is a bacterium meaning that it has a cell membrane, cytoplasm, DNA, and can replicate independently thereby rendering it susceptible to a host of antibiotics including penicillin. Viruses, on the other hand, lacking these same attributes do not respond to routine antibiotics. There are many varieties of strep including S. pneumoniae, the most common cause of pneumonia, but for the remainder of this post when I use the word strep, I am referring to group A beta-hemolytic strep, the bug that causes strep throat.
Everybody, at one time or another, has awakened with a horrible sore throat, the feeling that you’re swallowing razor blades, and the fever and achiness that accompanies it–to use a sophisticated medical term, “Yecchh!” Sore throats are responsible for more than 15 million doctor visits annually. But how many of these sore throats are caused by strep and how many of them need antibiotics?
Strep is rare before age 3 and uncommon after age 45. The peak incidence occurs in children between the ages of 5 and 15 with a seasonal prevalence that peaks during the winter months, although sporadic cases occur year round. It’s the bug that keeps on giving, as you can get strep over and over again. Recurrent strep infection is the leading indication for tonsillectomy in children. The incubation period (i.e. the time when a patient is not outwardly symptomatic but has active infection and is contagious to others) lasts for 2 to 5 days. About 10% of school age children harbor Strep pyogenes in their throats during winter months that will falsely trigger a + strep test.
But here’s the rub; most sore throats aren’t caused by strep. In school-age children, strep is the source in just 30 to 40% of sore throats, while in adults the number drops to just 5 to 15%. So why are antibiotics still being used in two-thirds of kids and more than half the adults who visit their doctor for sore throat?
When confronting sore throats there are 5 treatment options: 1) treat everybody, 2) treat nobody, 3) treat only those with clinical symptoms suggestive of strep, 4) treat only those with + strep tests, 5) use a combination of selected strep testing and empiric treatment. And here’s where the controversy heats up as the recommendations put forth by the Infectious Diseases Society of America, the American Heart Association, and the American Academy of Pediatrics don’t jibe with those of the CDC, the American College of Physicians, and the American Association of Family Practice, whose recommendations differ markedly from most European nations.
Here are my thoughts:
Regarding the first option of treating everybody with a sore throat; this makes no sense since we know that the majority of patients with sore throat don’t have strep. Although some patients will benefit, overall there will be more harm due to antibiotic side-effects and antibiotic resistance.
The second option of treating nobody with a simple sore throat actually does make sense since the overwhelming majority of sore throats are self-limited and resolve on their own. But failing to treat strep here in the States doesn’t go over well with patients or parents despite the fact that penicillin reduces the total duration of strep throat symptoms by less than a day. More than 90% of both treated and untreated patients are asymptomatic by a week. The benefit of penicillin in symptom reduction is likely the same as doing simple things like taking ibuprofen, drinking plenty of fluids, and gargling with salt water.
How about the third option of only treating those with symptoms strongly suggestive of strep? Dr. Robert Centor noted that certain symptoms increase the likelihood that a sore throat will be strep-related. They include: the presence of fever; exudate (yucky white stuff on the throat or tonsils); swollen, tender lymph nodes in the neck; and the absence of cough. Several large prospective studies have looked at the accuracy of these predictors and found that if none of the findings are present then the likelihood of strep is low, on the order of 1 to 2% while if all the criteria are present that number increases to between 51 to 53%. While the strategy of treating based on clinical symptoms alone does reduce the use of unnecessary antibiotics in patients with viral sore throats, it also guarantees that some patients with strep will go untreated. Is that a big deal?
It used to be. Back in the 1940’s, during a particularly horrific outbreak of strep at Warren Air Force Base, more than 2% of those infected ended up developing rheumatic fever, a particularly dangerous complication involving the heart and other organ systems, sometimes leading to destruction of the mitral valve. Treating strep throat with penicillin for 10 days reduces the risk of this complication by roughly 75%, and for decades afterward this provided the rationale for testing and treating strep throat. But the run-of-the-mill strep we see today is not our grandparents’ strep. Over time the germ has become decidedly less virulent (wherein virulence is defined as the capacity of an organism to cause disease). While 120 years ago, outbreaks of scarlet fever had a mortality rate as high as 30% in kids, it’s now just strep throat with a rash. Similarly, the incidence of rheumatic heart disease following a routine strep infection now stands at less than 1 per 100,000, a number so low that the CDC stopped tracking this complication more than 20 years ago. While some bacteria, like the skin staph known as MRSA, have become more virulent, strep has moved in the other direction. To prevent 1 case of rheumatic heart disease today requires treating more than 133,000 kids with penicillin, a number expected to result in more than 13,000 cases of diarrhea and 2 to 3 deaths due to fatal allergic reactions. Nor has treatment been shown to reduce the incidence of kidney complications associated with strep. Treatment in my daughter didn’t prevent her from developing glomerulonephritis as a 13-year old (an illness from which she eventually recovered after blowing up like a toad).
What about the fourth option of only treating those with + strep tests? The newer rapid tests are pretty accurate but falsely positive in kids colonized with strep, and falsely negative in kids where not enough strep is collected on the swab. I must add that kids don’t like having their throats swabbed, and it’s tough to get a thorough swipe in a kicking, crying, puking, 3-year old. Knowing this, some guidelines recommend that all negative rapid tests be followed by a formal throat culture, whose results typically come back in 1 to 3 days.
Is it worth it? Walgreens’ Healthcare Clinics charge $17 for a rapid strep test; CVS’s Minute Clinics charge $30; while most urgent care centers charge between $40 and $50. The cost is even higher in the ER where a rapid strep will set you back $130. If the rapid test is negative and the doctor adds a formal throat culture to the list (as per recommendations from the Infectious Diseases Society of America) then add another $140 to the bill. This doesn’t include the physician or facility charges. According to the website Wise Bread, typical urgent care centers charge $111 to treat strep throat, while the average ER bill comes to $531. Wow!—that’s a lot of dough to decide whether or not to allocate $4 for penicillin to treat a self-limited condition that almost always goes away on its own.
So let’s consider the last option; empirically treating those with all 4 of the Centor criteria (fever, exudate, swollen lymph nodes, and no cough), not treating those with none of the criteria, and selectively using strep testing in the rest. This makes the most sense to me, although I would argue that formal throat cultures costing hundreds of dollars are never indicated for routine sore throat. In this case, I disagree with all of the US medical societies and believe the Brits have it right. Their guideline recommends treating based on the history, age of the patient, and the presence of clinical symptoms alone, with no routine strep testing.
Modified Centor Criteria:
- Fever (temperature greater than 100.4F) = 1 point
- Swollen and/or tender lymph nodes in the anterior neck = 1 point
- Tonsillar swelling and/or exudate (“white stuff”) = 1 point
- Absence of cough and runny nose = 1 point
- Age: 3-15 = 1 point; age 15-45 = 0 point; age 45 and older = minus 1 point
Risk of strep: score 0 to -1 = 1-2.5%; 1 point = 5-10%; 2 points = 11-17%; 3 points = 28-35%; 4-5 points = 51-53%
(Adapted from NEJM 2011; 364: 648)
If your doctor does decide to treat you, there’s no evidence that the fancy, new, more expensive antibiotics work better than penicillin. Strep is a dumb bug with a resistance rate of about 10%, nearly the same as 50 years ago. If you’re penicillin allergic then clindamycin or Keflex are suitable alternatives. Although Zithromax is frequently prescribed for Strep throat, it is not a first-line agent, requires a higher dose than for ear infections, and carries with it an unacceptably high rate of resistance.
Final thoughts: If you have a bad sore throat, go ahead and see your doctor, even get a rapid strep test if you want, but know that using penicillin (even the shot) will get you better only marginally faster than simply gargling with salt water, drinking plenty of fluids, and taking fever medicine. If your throat is so swollen that you can’t swallow, there’s good evidence that a single dose of steroid will help.
Here’s the breakdown:
And here’s what happens when the treatment recommendations of the Infectious Diseases Society of America are followed:
1) 100 kids with a sore throat.
2) 100 rapid strep tests: 37 will be (+) and 63 will be (-).
Treatment in 37 kids: 27 kids appropriately treated, 10 kids colonized with strep inappropriately treated (27% of the total). Initial screening and treatment charges: $5,148.00**
3) No initial treatment in 63 kids. Here the IDSA recommends follow up throat cultures for all kids with (-) rapid screening tests.
4) 63 throat cultures: 3 will be (+), 60 will be (-).
Appropriate treatment in 3 more kids. Additional charges: $8,832.00**
5) Total screening and treatment costs of 100 kids with sore throat to correctly treat 30 children with strep and to incorrectly treat 10 children colonized with strep: $13,980.00. This is nuts!!
**Assuming an average urgent care charge of $50 per rapid strep test, $140 per throat culture, and $4 per penicillin prescription. This does not include physician and facility charges of at least $100 per patient screened. Note that ER charges will be 2-3x’s higher.
- Michael Wessels, “Streptococcal Pharyngitis,” NEJM 2011; 364: 648-55.
- Stanford Shulman et al., “Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America,” Clinical Infectious Diseases 2012; 55: e86-e102.
- Beth Choby, “Diagnosis and Treatment of Streptococcal Pharyngitis,” Am Family Physician 2009; 79 (5): 383-90.
- Daan Van Brusselen et al., “Streptococcal Pharyngitis in Children: To Treat or Not to Treat?” Eur Journal Pediatrics 2014; 173: 1275-83. (* best single review *)
- Elena Chiappini et al., “Analysis of Different Recommendations From International Guidelines for the Management of Acute Pharyngitis in Adults and Children,” Clinical Therapeutics 2011; 33: 48-58.
- Jeremie Cohen et al., “Selective Testing Strategies for Diagnosing Group A Streptococcal Infection in Children with Pharyngitis: A Systematic Review and Prospective Multicentre External Validation Study,” Canadian Med Assoc Journal 2015; 187 (1): 23-32.
- Anneliese Spinks et al., “Antibiotics For Sore Throat,” The Cochrane Collaboration 2014, John Wiley & Sons, Ltd