Editor’s note: Centor’s Corner is a new Paging MDCalc column featuring our favorite pharyngitis guru, blogger extraordinaire, and Scientific Advisory Board member Dr. Robert Centor, with regular insights from Dr. Centor on the applications of evidence to practice and musings from an experienced clinician. To comment on Centor’s Corner articles, please e-mail the editor at firstname.lastname@example.org or tweet directly to Dr. Centor @medrants.
On Twitter recently, several British tweeters discussed whether they should use the FeverPAIN Score or the Centor Score. Obviously I have a bias here, but I will try to discuss this issue dispassionately.
I downloaded the PRISM study, where the authors proposed FeverPAIN. The goal of FeverPAIN is to increase the patient cohort not needing testing or antibiotics. As I studied FeverPAIN, I found one important advance, but another point of naïveté.
To frame the discussion, the FeverPAIN study used all sore throat patients over 3 years old. They used positive testing for group A, C or G beta-hemolytic streptococci as their dichotomous outcome. They developed a 5-point scale (1 point of each):
|Fever in past 24 hours|
|Absence of cough or coryza|
|Symptom onset within 3 days|
|Severe tonsil inflammation|
Contrast this with the Centor Score (again 1 point each):
|Swollen, tender anterior cervical nodes|
The two scores are measuring the same concepts and thus will have a high correlation. Bacterial infections, both group A and group C/G streptococci and (in our recent study) Fusobacterium necrophorum cause an inflammatory response (exudates, swelling, adenopathy), a fever response and a lack of a viral response (lack of cough or coryza). Since both scores include two inflammatory response variables, one fever, and one viral variable, they are quite similar.
FeverPAIN includes an interesting variable: symptom onset at three days or less. As one studies pharyngitis, one notes that acute pharyngitis needs a very careful definition that includes short symptom onset. I like this inclusion but caution against disregarding patients with longer symptom duration. If the patient has worsening symptoms past three days, they no longer have acute pharyngitis, but rather need a careful evaluation for either suppurative complications (peritonsillar abscess or Lemierre syndrome), or one should consider significant viral infections in adults, like infectious mononucleosis and acute HIV. Thus, FeverPAIN has the advantage of noting that acute pharyngitis patients more likely have a bacterial infection.
The other problem that I have with the FeverPAIN analysis is the lack of distinction between preadolescents and adolescent/young adults. We have written about this problem, both in Medrants.com and in this article – Adolescent Pharyngitis: A Review of Bacterial Causes1.
The streptococcal carrier rates for pre-adolescents are much higher than for adolescents and young adults. In several studies in which I participated, adolescents and young adults had carrier rates around 1-2%. This older age group has group A strep less commonly, group C/G strep more commonly, and Fusobacterium necrophorum much more commonly.
So what should clinicians do in 2017?
I would suggest to the FeverPAIN authors that they reanalyze their data using an age cutoff of approximately 14 or 15. I suspect they will find very different findings in the pre-adolescent and older age cohorts.
We should pay great attention to the symptom onset as a criterion for even considering the patient has acute pharyngitis. If the patient presents at four days or later, we should likely not use an algorithm and scoring rule, but rather focus on the clinical course and worry about a broader differential.
We should also diagnose and treat pre-adolescents differently from adolescents and young adults. The older patients have more severe symptoms and more often develop suppurative complications.
With either scoring system, low scores likely allow us to avoid antibiotics or testing. But using a score without understanding a larger differential diagnosis in patients with persistent or especially worsening symptoms can result in serious diagnostic errors.
This comparison raises several interesting questions about prediction scores in general. We should understand the assumptions of the score prior to using that score. In the sore throat example, FeverPAIN adds an important qualification: duration of symptoms. But some patients with longer symptoms deserve very careful investigation.
We should label both the Centor score and FeverPAIN as useful for acute pharyngitis (symptoms less than three days). We should discourage their use for patients with worsening symptoms longer than three days. At that point, the differential diagnosis changes dramatically and the prediction rule no longer applies, because the patient does not have acute pharyngitis.
The pharyngitis guidelines do not seem to address this issue. Applying any guideline to the wrong presentation can lead to major errors. Too often we default to guideline medicine because it makes our practice easier. But guidelines have dangers when they do not accurately specify the assumptions behind the guideline.
For sore throat patients, applying one of these two scores or performing a rapid group A strep test only makes sense when the patient has short duration pharyngitis. Guidelines should specify short duration and make clear that longer duration or worsening pharyngitis has an entirely different differential diagnosis. Too often physicians assume that a sore throat is just a sore throat, and disregard thinking even when the presentation runs outside the normal acute sore throat.
Could we combine these two scores for acute pharyngitis to get a better prediction? We cannot because they measure the same attributes. Physicians should pick one. They may need a different score for pre-adolescents and adolescents.
To summarize, both scores define groups that need neither testing nor antibiotics. If physicians would follow that common guideline, we would greatly decrease unnecessary antibiotic usage. We should consider adolescents and young adults differently than pre-adolescents. We should use neither scores nor rapid tests in patients (especially the older age group) whose symptoms are worsening. They do not have acute pharyngitis. They deserve careful consideration of a broader differential diagnosis including: peritonsillar abscess, Lemierre syndrome, infectious mononucleosis, and acute HIV.