Group A Streptococcal Disease

Group A streptococci (Streptococcus pyogenes) cause a broad spectrum of disease and are the primary bacterial cause of exudative tonsillitis and pharyngitis. Rheumatic fever, a resulting complication of untreated streptococcus infection, may develop 2-4 weeks after a streptococcal throat infection. In serious cases, rheumatic fever can cause heart disease.

Tabs Content

Clinical Overview

Diagnosis

Indications for Testing

Sore throat, fever, and lymphadenopathy

Laboratory Testing

Consider Centor score when testing for group A strep in patient with sore throat

Modified Centor criteria for management of sore throat

Modified Centor Criteria for Management of Sore Throat
Criteria	Points
Absence of cough	1
Swollen and tender anterior cervical nodes	1
Temperature >100.4ºF (38ºC)	1
Tonsillar exudates or swelling	1
Age
3-14 years	1
15-44 years	0
≥45 years	-1
Cumulative Score	Suggested Management
≤0	No testing
1	Risk <10% Test if high suspicion or recent contact
2-3	Rapid testing or throat culture
≥4	Treatment without testing
Recommended by Centers for Disease Control (CDC), American College of Physicians (ACP), and American Academy of Family Physicians (AAFP) Not recommended by Infectious Diseases Society of America (IDSA) or American Heart Association (AHA) – approach results in unnecessary prescribing of antibiotics

Rapid antigen detection with reflex to culture for initial negative antigen testing in children
- Sensitivity – 70-90%
- Specificity – >95%
Swabbing posterior pharynx increases sensitivity of both rapid antigen test and culture
Positive rapid test confirms strep infection in presence of clinical syndrome
Throat culture – sensitivity 90-95%
Occurrence of strep infection in adults is low (10%); follow-up culture of negative rapid antigen not usually indicated
Antibody tests (antistreptolysin O [ASO] and anti-DNase-B) – provide serologic evidence of prior and current infection in suspected poststreptococcal glomerulonephritis or rheumatic fever (Parks, 2015)
- May be indicated for
  - Patients with suspected acute rheumatic fever and poststreptococcal glomerulonephritis in high-risk settings
    - Either titer (ASO, anti-DNase-B) may be used for glomerulonephritis antibody
    - Both antibody tests should be used to exclude rheumatic heart disease
  - Patients with suspected rheumatic fever and poststreptococcal pharyngitis in low-risk settings – negative or low ASO usually sufficient to rule out disease
- Not useful in diagnosing acute streptococcal disease (titers rise 7-14 days after infection and peak in 2-3 weeks) – convalescent titers with rise are best evidence of antecedent streptococcal infection
Elevated serum ASO titers – found in about 85% of individuals with acute rheumatic fever
- ASO and anti-DNase-B antibodies – elevated titers in 90-95% of acute rheumatic fever patients
- Skin infections with group A streptococci
  - Often associated with a poor ASO response
  - Anti-DNase-B titers are increased after skin infection

Differential Diagnosis

Viral
- Epstein-Barr virus
- Rhinovirus
- Adenovirus
- Influenza virus
- Cytomegalovirus
- Respiratory syncytial virus
- Enterovirus
  - Coxsackievirus
  - Echovirus
- Herpes simplex virus
- HIV
Bacterial
- Group C or G streptococci
- Corynebacterium diphtheriae
- Arcanobacterium haemolyticum
- Neisseria gonorrhoeae
- Mycoplasma pneumoniae
- Yersinia enterocolitica (rare)
- Chlamydophila pneumoniae
- Oropharyngeal tularemia
- Epiglottis
- Retropharyngeal abscess
Malignant
- Head and neck cancer – tonsillar
Lymphadenitis
- Bacterial
  - Atypical mycobacteria
  - Secondary to head and neck infections
- Fungal
  - Histoplasmosis
  - Coccidiomycosis
- Viral
- Malignant
  - Head and neck cancer
  - Metastatic cancer

Background

Epidemiology

Prevalence
- Streptococcal pharyngitis
  - Represents 1-2% of primary care visits
  - 1 of the top 20 reported diseases
- Rheumatic fever poststreptococcal pharyngitis – 1-2/100,000
Age – usually <20 years
- Rare in children <3 years old
Transmission – direct contact with nasal discharge
- Seasonally most common in winter and/or early spring

Organism

Streptococcus pyogenes bacteria are gram-positive cocci
May evoke cross-reacting immune response with human tissue leading to the postinfection sequelae of
- Acute rheumatic fever (including rheumatic heart disease) – associated with streptococcal pharyngitis
- Acute glomerulonephritis – associated with both streptococcal pharyngitis and skin disease
Causes a range of human disease
- Pharyngitis
- Impetigo
- Scarlet fever
- Invasive infections

Risk Factors

Young age
Crowded conditions

Clinical Presentation

Primary symptoms – sudden onset sore throat, fever (>100.4°F), headache
Constitutional symptoms – nausea, vomiting, abdominal pain
Clinical findings – pharyngeal erythema, exudative tonsillitis, anterior cervical adenopathy, palatine petechiae
- Presence of cough, hoarseness, pharyngeal ulcers, diarrhea, and/or conjunctivitis are more suggestive of viral pharyngitis
- Fine papular erythematous (sandpaper) rash – scarlet fever
Complications
- Peritonsillar abscess
- Toxic shock syndrome – almost exclusively associated with soft tissue infections
- Rheumatic fever – rheumatic heart disease
- Poststreptococcal glomerulonephritis
- Poststreptococcal reactive arthritis

ARUP Lab Tests

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Streptococcus (Group A) Culture 0060126
Method: Culture/Identification

Recommended Use

Gold standard for confirming group A streptococcal infection

Order when rapid testing is negative and suspicion of streptococcus is moderately high

DNase-B Antibody 0050220
Method: Quantitative Nephelometry

Recommended Use

Confirm current or recent group A streptococcal infection in patients suspected of having a nonsuppurative complication such as acute glomerulonephritis (AGN) or acute rheumatic fever (ARF)

DNase-B and antistreptolysin O (ASO) antibody tests are generally ordered concurrently

Preferred test for rheumatic chorea since it remains elevated longer

Streptolysin O Antibody (ASO) 0050095
Method: Quantitative Nephelometry

Recommended Use

Confirm a prior infection with group A streptococcus in patients suspected of having a nonsuppurative complication such as AGN or ARF

DNase-B and ASO antibody tests are generally ordered concurrently

Medical Experts

Delgado, Julio, MD, MS, Chief Medical Officer; Director of Laboratories; Chief, Division of Clinical Pathology at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

Fisher, Mark A., PhD, D(ABMM), Medical Director, Bacteriology, and Special Microbiology, Antimicrobial Susceptibility Testing, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

References

Guidelines

U.S. Department of Health and Human Services, Centers for Disease Control and Prevention. Group A Streptococcal (GAS) Disease. Centers for Disease Control and Prevention. Atlanta, GA [Last updated: Sep 2016; Accessed: Oct 2017]
Shulman ST, Bisno AL, Clegg HW, Gerber MA, Kaplan EL, Lee G, Martin JM, Van Beneden C, Infectious Diseases Society of America. 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): e86-102. PubMed

General References

Alcaide ML, Bisno AL. Pharyngitis and epiglottitis. Infect Dis Clin North Am. 2007; 21(2): 449-69, vii. PubMed

Choby BA. Diagnosis and treatment of streptococcal pharyngitis. Am Fam Physician. 2009; 79(5): 383-90. PubMed

Clerc O, Greub G. Routine use of point-of-care tests: usefulness and application in clinical microbiology. Clin Microbiol Infect. 2010; 16(8): 1054-61. PubMed

Kalra MG, Higgins KE, Perez ED. Common questions about streptococcal pharyngitis. Am Fam Physician. 2016; 94(1): 24-31. PubMed

Kociolek LK, Shulman ST. In the clinic. Pharyngitis. Ann Intern Med. 2012; 157(5): ITC3-1 - ITC3-16. PubMed

Parks T, Smeesters PR, Curtis N, Steer AC. ASO titer or not? When to use streptococcal serology: a guide for clinicians. Eur J Clin Microbiol Infect Dis. 2015; 34(5): 845-9. PubMed

Wessels MR. Clinical practice. Streptococcal pharyngitis. N Engl J Med. 2011; 364(7): 648-55. PubMed

Zühlke LJ, Beaton A, Engel ME, Hugo-Hamman CT, Karthikeyan G, Katzenellenbogen JM, Ntusi N, Ralph AP, Saxena A, Smeesters PR, Watkins D, Zilla P, Carapetis J. Group A streptococcus, acute rheumatic fever and rheumatic heart disease: epidemiology and clinical considerations. Curr Treat Options Cardiovasc Med. 2017; 19(2): 15. PubMed

Resources from the ARUP Institute for Clinical and Experimental Pathology®

Martins TB, Augustine NH, Hill HR. Development of a multiplexed fluorescent immunoassay for the quantitation of antibody responses to group A streptococci. J Immunol Methods. 2006; 316(1-2): 97-106. PubMed

Martins TB, Hoffman JL, Augustine NH, Phansalkar AR, Fischetti VA, Zabriskie JB, Cleary PP, Musser JM, Veasy G, Hill HR. Comprehensive analysis of antibody responses to streptococcal and tissue antigens in patients with acute rheumatic fever. Int Immunol. 2008; 20(3): 445-52. PubMed

Martins TB, Veasy G, Hill HR. Antibody responses to group A streptococcal infections in acute rheumatic fever. Pediatr Infect Dis J. 2006; 25(9): 832-7. PubMed

Stockmann C, Ampofo K, Hersh AL, Blaschke AJ, Kendall BA, Korgenski K, Daly J, Hill HR, Byington CL, Pavia AT. Evolving epidemiologic characteristics of invasive group a streptococcal disease in Utah, 2002-2010. Clin Infect Dis. 2012; 55(4): 479-87. PubMed

Content Review:

October 2017

Last Update: June 2019

Group A Streptococcal Disease

Diagnosis

Indications for Testing

Laboratory Testing

Differential Diagnosis

Background

Epidemiology

Organism

Risk Factors

Clinical Presentation

ARUP Lab Tests

Medical Experts

References

Guidelines

General References

Resources from the ARUP Institute for Clinical and Experimental Pathology®

ARUP Laboratories

ARUP Websites

ARUP Consult


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	Group A Streptococcal Disease. ARUP Consult^©. Retrieved October 15, 2019, from: https://arupconsult.com/content/streptococcal-disease-group

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Group A Streptococcal Disease

Diagnosis

Indications for Testing

Laboratory Testing

Differential Diagnosis

Background

Epidemiology

Organism

Risk Factors

Clinical Presentation

ARUP Lab Tests

Medical Experts

References

Guidelines

General References

Resources from the ARUP Institute for Clinical and Experimental Pathology®

ARUP Laboratories

ARUP Websites

ARUP Consult