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    Chief Complaint


    Organ System


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    Centor Score (Modified/McIsaac) for Strep Pharyngitis

    Estimates probability that pharyngitis is streptococcal, and suggests management course.


    Use only in patients with recent onset (≤3 days) acute pharyngitis.

    When to Use
    Why Use

    Children with pharyngitis, primarily; the risk of GAS decreases significantly with age into adulthood.

    • The Centor Score correlates directly with risk of positive throat culture for GAS (Group A Streptococcus).
    • New 2012 guidelines from the IDSA (Infectious Disease Society of America) no longer recommend empiric treatment for patients alone; they recommend testing patients that are at higher risk for strep pharyngitis, but not giving antibiotics until a rapid test is positive or a throat culture is positive.
    • The modified criteria by McIsaac et al include an age component, along with tonsillar swelling, as part of the rule. GAS is incredibly rare in patients under 3 and less common in older adults, so this can help clinicians risk stratify patients.
    • Most cases of pharyngitis are viral in origin, and with the rare incidence of rheumatic fever, along with the questionable benefits of early antibiotics to prevent sequelae like peritonsillar abscess, antibiotics are prescribed much less often. Steroids (like dexamethasone) and NSAIDS often provide similar pain relief and resolution of symptoms to antibiotics.
    • Most pharyngitis is viral and does not respond to antibiotic treatment. The Centor Score attempts to predict which patients will have culture-confirmed streptococcal infections of their pharynx to help determine which patients to test in the first place.
    • The newer FeverPAIN Score is similar, but the Centor Score has the distinguishes between adolescents and young adults from pre-adolescents—important because strep carrier rates are higher in preadolescents than adolescents/young adults, and older patients are more likely to have severe symptoms and develop suppurative complications (Mitchell 2011).


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    Next Steps
    Creator Insights


    Steroids and NSAIDS improve symptoms; antibiotics are often indicated in streptococcal pharyngitis, but do not prevent its suppurative complications, like peritonsillar abscess.

    Critical Actions

    • Carefully consider patients with symptom duration longer than 3 days, even though the Centor Score does not apply.
    • While symptoms are not compatible with a diagnosis of acute pharyngitis, these patients require evaluation for suppurative complications (peritonsillar abscess or Lemierre syndrome), or viral infections in adult patients (infectious mononucleosis or acute HIV) (Centor 2017).


    Addition of the selected points:




    3-14 years


    15-44 years


    ≥45 years


    Exudate or swelling on tonsils





    Tender/swollen anterior cervical lymph nodes





    Temp >38°C (100.4°F)






    Cough present


    Cough absent



    Facts & Figures


    Centor Score

    Probability of strep pharyngitis




    No further testing or antibiotics.





    Optional rapid strep testing and/or culture.



    Consider rapid strep testing and/or culture. Note: IDSA and ASIM no longer recommend empiric treatment for strep based on symptomatology alone.



    Evidence Appraisal

    The original study by Centor et al was done in 1981 to develop criteria to diagnose GAS infection in adult patients presenting to the emergency department with sore throat (Centor 1981). The original model designated four criteria: tonsillar exudates, swollen tender anterior cervical nodes, absence of a cough, and history of fever. Patients exhibiting all four variables had a 56% probability of a Group A beta strep positive culture; three variables, 32%; two variables, 15%; one variable, 6.5%; and zero variables, 2.5%.

    The Centor Score was later modified to include age (McIsaac 1998) and validated (McIsaac 2004) for use in both children and adults presenting with sore throat. McIsaac et al (1998) determined that using the Centor Score would reduce the number of unnecessary initial antibiotic prescriptions by 48%, without an increase in throat culture use.

    The Centor Score and its modifications were derived in relatively small samples (n=286 and n=521, respectively). In order to more precisely classify the risk of GAS infection, Fine et al (2012) performed a national-scale validation of the score on a geographically diverse population of over 140,000 patients presenting in a clinical setting. The study was carried out over the course of more than a year, mitigating any impact of seasonality of GAS incidence on the results. This analysis provided more precise interpretations of risk for each category of the Centor Score; these still fell within the 95% confidence interval of Centor's original study with a much smaller sample size.

    In their comparison of the Centor Score with other identification and treatment strategies, McIsaac et al (2004) found that use of the score resulted in fewer overall tests (cultures and rapid tests) per person but more throat cultures (96.1% of adults) than other strategies. As a result, the Centor Score represented a compromise, requiring the least diagnostic testing, providing 100% sensitivity and greater than 90% specificity in both children and adults, and producing significant reductions in unnecessary use of antibiotics, compared to other strategies.

    Harris et al (2016) encourage the use of the Centor Score primarily to identify patients with a low probability of Group A streptococcal pharyngitis who do not warrant further testing, citing the criteria's low positive predictive value.


    Other References

    Research Paper Shulman ST, et. al. Clinical Practice Guideline for the Diagnosis and Management of Group A Streptococcal Pharyngitis: 2012 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2012 Nov 15;55(10):1279-82. doi: 10.1093/cid/cis847.Research PaperHarris AM, Hicks LA, Qaseem A, for the High Value Care Task Force of the American College of Physicians and for the Centers for Disease Control and Prevention. Appropriate Antibiotic Use for Acute Respiratory Tract Infection in Adults: Advice for High-Value Care From the American College of Physicians and the Centers for Disease Control and Prevention. Ann Intern Med. 2016 Jan 19. doi: 10.7326/M15-1840.Research PaperMitchell MS, Sorrentino A, Centor RM. Adolescent pharyngitis: a review of bacterial causes. Clin Pediatr (Phila). 2011;50(12):1091-5.
    Dr. Robert M. Centor

    From the Creator

    Why did you develop the Centor Score? Was there a clinical experience that inspired you to create a this tool for clinicians?
    In 1979, while working in the "non-acute" adult emergency room, a resident asked me how to evaluate a sore throat patient. Having just finished my residency, I started to give a definitive answer, but had a moment of humility and told him that I did not know. We made a treatment decision at the time, and I went to the library to learn more. A wonderful microbiologist agreed to do some throat cultures for us, and I developed a questionnaire. Our goal was to see if clinical findings could stratify the probability that an adult (16 and older in our ER) patient had group A Strep.

    What pearls, pitfalls and/or tips do you have for users of the Centor Score? Are there cases when it has been applied, interpreted, or used inappropriately?
    We studied adults, and thus have always been wary of applying it to children. More recently, we have published a review that shows that pre-adolescent pharyngitis has many differences from adolescent/young adult pharyngitis. McIsaac has developed an adjustment for age which might be appropriate for pre-adolescents.

    Please do not use this score if the patient does not have a recent onset acute pharyngitis (3 days or less). Some have erred in using this for any throat discomfort.

    What recommendations do you have for health care providers once they have the Centor Score result? Are there any adjustments or updates you would make to the score given recent changes in medicine?
    Our recent research suggests that our Score stratifies not just group A strep, but also groups C&G strep and Fusobacterium necrophorum. Because we believe that we should treat all of these bacteria, we favor narrow antibiotics (preferably penicillin, amoxicillin or a narrow spectrum cephalosporin) for scores of 3 or 4. Depending on clinical assessment, we sometimes will also treat the 2s. Zeros and 1s need no testing or antibiotics. All patients should be told that pharyngitis is generally self limited and should improve over the next 2-5 days. If symptoms worsen, then the differential diagnosis broadens and the score is not longer relevant. Major red flags include rigors and inability to swallow secondary to pain. These patients need further evaluation, and likely hospitalization.

    Any further research you're working on related to resource utilization and sore throat?
    We continue to study the importance of Fusobacterium necrophorum, an obligate anaerobe that causes endemic pharyngitis in adolescents and young adults. This bacteria is very important because it is the most common cause of peritonsillar abscess in the 15-30 age group, and the primary cause of Lemierre Syndrome.

    About the Creator

    Robert M. Centor, MD, is the retired regional dean for the Huntsville Regional Medical and professor of medicine in the Division of General Internal Medicine at the University of Alabama at Birmingham. He researches medical decision-making and has published widely in the diagnosis and management of adult sore throats. Dr. Centor is also Chair Emeritus of the Board of Regents for the American College of Physicians.

    To view Dr. Robert M. Centor's publications, visit PubMed

    Dr. Warren McIsaac

    About the Creator

    Warren McIsaac, MD, MSc, is a family physician and an associate professor in the department of family and community medicine at the University of Toronto. He is also the research director of the Granovsky Gluskin Family Medicine Centre. Dr. McIsaac’s research interests include antibiotic resistance, antimicrobial stewardship, and prescribing decisions in primary care.

    To view Dr. Warren McIsaac's publications, visit PubMed

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