IDCM Issue 5: Does My Adult Patient Have Strep Throat?

Post Date: 
2016-05-19
Author: 
Natasha Chida, MD, MSPH

     
How common is streptococcal pharyngitis (strep throat) in adults

    
Sore throat is a common outpatient condition; in the United States (US) it is the third most common reason for people to visit a doctor in the ambulatory setting.1Caused by group A streptococcus (GAS), strep throat is the most common cause of pharyngitis globally, affecting 500,000,000 persons every year. It primarily occurs persons aged 5-15.2-3 Most sore throats in adults are due to viruses, and in the US it is estimated that only 5-15% of adult cases of pharyngitis are caused by GAS (unless the adult is in contact with school-age children).3-4Despite this, 75% of adults who present with a sore throat receive antibiotics.5
 
What physical exam findings are common in strep throat? 
    
In one systematic review, the most useful positive physical exam findings for strep throat were: tonsillar exudates (likelihood ratio [LR] 3.4); pharyngeal exudate (LR 2.1); and exposure to someone with strep throat in the prior 2 weeks (LR 0.6).1 The most useful negative physical exam findings were: the absence of tender anterior cervical lymph nodes (LR 0.6); the absence of tonsillar enlargement (LR 0.63); and a lack of tonsillar exudate (LR 0.74).1 The presence of isolated fever, non-tender cervical lymphadenopathy, pharyngeal injection, or palatal petechial were not helpful physical exam findings.
 
Importantly, one single finding can “rule out” or “rule in” strep throat. Therefore, scoring systems have been developed for the assessment of strep throat; 2 of the most commonly used scores are the Centor Criteria (Figure 1) and the McIssac Score.2 These criteria have been validated in developed nations in settings such as emergency departments, urgent care centers, outpatient clinics, etc. The McIssac Score is the same as the Centor Criteria but also adjusts by age.2 The Centor Criteria are more commonly used.


Figure 1

Centor Criteria1
(1 point per finding)

Fever

Tonsillar exudates

Tender anterior cervical lymphadenopathy

Absence of cough

 
Since strep throat is uncommon in adults, what is the best way to diagnose it?
    
Physicians often overestimate GAS as a cause of sore throat.3 Therefore, in the US a combination of a symptom screen and laboratory testing is used in order to decrease overdiagnosis and overtreatment (of note, recommendations for diagnosing strep throat differ by country).3-4 The US Centers for Disease Control and Prevention (CDC) recommends first screening adults with the Centor Criteria; if fewer than 2 criteria are present, CDC recommends NO testing and NO treatment, as the likelihood of strep throat is low (Table 1).4 If 2 or more criteria are present, CDC recommends administering a rapid streptococcal antigen test. If the rapid test is negative, no treatment is recommended, again because of the low incidence of the infection in adults. If test results are positive, treatment is recommended, because the test is highly specific (approximately 95%).4,6 In adults it is not necessary to confirm a negative rapid test with a throat culture, due to the low likelihood of diagnosis, and because the risk of ARF is low.


Table 1

Likelihood Ratio of Strep Throat
by Centor Criteria Points1

0

0.16

1

0.3

2

0.75

3

2.1

4

6.3

 

The Infectious Disease Society of America (IDSA) endorses CDC’s approach, but also notes that if a patient has a sore throat and strong evidence of a viral process (cough, rhinorrhea, hoarseness, oral ulcers) there is no need to evaluate for strep throat.3 In addition, it is not recommended to use of anti-streptococcal antibody titers to diagnose strep throat, as these titers don’t reach a maximum level until 3-8 weeks after infection and can remain elevated for months.3, 7

 
What are the complications of strep throat?
   
Suppurative complications of strep throat include: peritonsillar abscess; retropharyngeal abscess; cervical lymphadenitis; bacteremia; otitis media; and mastoiditis. Non-suppurative complications include acute rheumatic fever ([ARF], occuring 1-5 weeks after strep throat) and post-streptococcal glomerulonephritis.Complications from strep throat in adults are rare, including ARF.4
 
 
What is the best treatment for strep throat in adults?
 
The symptoms of untreated strep throat last approximately 8-10 days. Patients are infectious during illness and up to 1 week after. The predominant reason to treat strep throat is to prevent the suppurative and nonsuppurative complications associated with the disease (particularly rheumatic fever).3-4 Of note, the incidence of post-streptococcal glomerulonephritis is not affected by treatment.3 If treated within 9 days of symptom onset, ARF can be prevented.3 Treatment also shortens the duration of illness by 1-2 days if started within 2-3 days of symptom onset, and can also reduce infectivity by a few days.1
 
In the US it is recommended to treat confirmed strep throat with amoxicillin or penicillin V X 10 days; there has never been a report of penicillin-resistant GAS.3 A single dose of IM penicillin G is also acceptable. If the patient has a non-anaphylactic allergy to penicillin an alternative is a first-generation cephalosporin X 10 days. Alternatively, clindamycin X 10 days, clarithromycin X 10 days, and azithromycin X 5 days are also acceptable. It is NOT recommended to use tetracyclines (due to the high prevalence of resistant strains), trimethoprim-sulfamethoxazole (which does not eradicate GAS), or fluoroquinolones (which are unnecessarily broad).3-4


Bottom Line: Strep throat in adults is not common; use the Centor Criteria to determine if testing is needed, and only treat if a rapid streptococcal antigen is positive.
   

References

 
  1. Abell MH, Smith MA, Barry HC, Ives K, Carey M. The rational clinical examination. Does this patient have strep throat? JAMA. 2000; 284(22):2912-8. PMID: 11147989.
  2. Fine AM, Nizet V, Mandl KD. Large-scale validation of the Centor and McIsaac scores to predict group A streptococcal pharyngitis. Arch Intern Med. 2012; 172(11):847-52. PMID: 22566485.
  3. Centers for Disease Control and Prevention. https://www.cdc.gov/getsmart/community/materials-references/print-materials/hcp/adult-acute-pharyngitis.html. Accessed 2015-05-18.
  4. Shulman ST, Bisno AL, Clegg HW, 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; 55(10):1279-82. PMID: 23091044.
  5. Linder JA, Chan JC, Bates DW. Evaluation and treatment of pharyngitis in primary care practice: the difference between guidelines is largely academic. Arch Intern Med 2006; 166:1374–9. PMID: 16832002.
  6. Gerber MA, Shulman ST. Rapid diagnosis of pharyngitis caused by group A streptococci. Clin Microbiol Rev. 2004;17(3):571-80. PMID: 15258094.
  7. Johnson DR, Kurlan R, Leckman J, Kaplan EL. The human immune response to streptococcal extracellular antigens: clinical, diagnostic, and potential pathogenetic implications. Clin Infect Dis 2010; 50:481–90. PMID: 20067422.

 

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