• Reference [2]
ETIOLOGY OF PHARYNGITIS
Viruses - viruses account for the majority of throat infections
Adenovirus
  • Causes syndrome of fever, sore throat, cough, and conjunctivitis
Herpes simplex 1 virus
  • Gingivostomatitis
  • Causes painful oral ulcers
Coxsaskievirus
  • Hand, foot, mouth disease
  • Painful sores develop in the mouth (herpangina)
  • Red spots develop on hands and soles of feet
Rhinovirus
Coronavirus
  • Common cold viruses
  • Sore throat is a common feature
Influenza
Parainfluenza
  • Sore throat is a common feature of a flu syndrome
Epstein-Barr Virus
Cytomegalovirus
  • Cause a syndrome of fever, sore throat, lymphadenopathy, and fatigue
  • Also called infectious mononucleosis
Bacteria
Group A Streptococcus
  • Most common bacterial cause of pharyngitis
  • Accounts for 20 - 30% of pharyngitis in children and 5 - 15% in adults
Group C Streptococcus
  • More common in adults and college students
  • May occur in outbreaks from contaminated food (e.g. unpasteurized milk)
  • No clear link to rheumatic fever or glomerulonephritis
  • No clear evidence that antibiotic treatment is beneficial
Group G Streptococcus
  • No clear link to rheumatic fever or glomerulonephritis
  • No clear evidence that antibiotic treatment is beneficial
Neisseria gonorrhoeae
  • May occur in sexually active people
Corynebacterium diphtheriae
  • May form thick coat in back of throat
  • Vaccine is part of the standard childhood vaccination schedule
  • Also part of TdaP vaccine (tetanus, diphtheria, pertussis)





  • Reference [1, 2, Manufacturer's PI]
DIAGNOSTIC TESTS FOR STREP THROAT
Test Accuracy Other
Rapid antigen testing
  • Sensitivity: > 90%
  • Specificity: > 90%
  • Performed in office. Takes about 5 minutes to get results.
  • Antibodies to strep antigen are coated on the test strip. If strep antigen is present in throat swab, it binds antibody causing the strip to change color.
  • Older versions of rapid antigen testing had lower sensitivities (70 - 90%). Most manufacturers of kits used today report sensitivities > 90%.
  • Some versions of rapid antigen testing use different markers (e.g. immunofluorescence) that are read by a machine
Direct DNA probe tests
  • Sensitivity: > 90%
  • Specificity: > 90%
  • Sample collected in office and sent to lab for processing
  • If Strep RNA is present in sample, complementary DNA in the test kit will form a complex with it. DNA:RNA complexes are then detected by a machine.
  • More expensive than rapid antigen testing
PCR testing
  • Sensitivity: > 90%
  • Specificity: > 90%
  • Sample collected in office. May be sent to lab. Some office-based machines are available.
  • Strep DNA in the sample is amplified and then detected through polymerase chain reaction (PCR) techniques
  • More expensive than rapid antigen testing
Culture
  • Considered reference standard
  • Sample collected in office and then sent to lab where it is cultured on a plate
  • Prior antibiotics may cause false-negative result
  • Takes 1 - 3 days to get results



  • Reference [2,4,5,6]
COMPLICATIONS OF GROUP A STREP (GAS) PHARYNGITIS
Rheumatic fever
  • Inflammatory autoimmune reaction that occurs 2 - 4 weeks after GAS infection
  • Symptoms included arthritis (35 - 88%), carditis (50 - 78%), erythema marginatum (< 6%), subcutaneous nodules (1 – 13%), and fever
  • Treatment involves prolonged antibiotic prophylaxis and NSAIDs
Rheumatic heart disease
  • Sequelae of rheumatic fever carditis
  • Thought to occur from antibodies that cross-react with streptococcal proteins and heart tissue
  • Mitral valve is most commonly affected. Mitral regurgitation is most common disorder while mitral stenosis is pathognomonic.
Otitis media
Peritonsillar abscess
  • Symptoms include dysphagia, ipsilateral ear pain, rancid breath, and drooling
  • Physical findings include swollen tonsil that is displaced medially and inferiorly, uvula deviation, difficulty opening mouth, and muffled voice
  • Treatment includes abscess drainage, antibiotics, and airway support
Post-streptococcal glomerulonephritis
  • May occur 1 - 6 weeks after GAS infection
  • Symptoms include hematuria, proteinuria, edema, hypertension, and reduced kidney function
  • Antibiotic therapy for GAS infections does not appear to prevent post-streptococcal glomerulonephritis
  • Treatment is mostly supportive (e.g. diuretics, blood pressure management, fluid restriction)
  • Most children have complete resolution within weeks while adults are more likely to have residual kidney disease



First-line (non-penicillin allergic) - IDSA recommendations
Medication Pediatric dosing Adult dosing Duration / Price
Penicillin
(Pen VK®)
250 mg twice daily or 3 times daily 250 mg 4 times daily or 500 mg twice daily 10 days ($)
Amoxicillin 50 mg/kg once daily (max 1000 mg) OR 25 mg/kg (max 500 mg) twice daily 1000 mg once a day or 500 mg twice a day 10 days ($)
Penicillin G benzathine
(Bicillin L-A®)
  • < 27 kg - 600,000 units IM
  • ≥ 27 kg - 1,200,000 units IM
1,200,000 units IM 1 dose ($$-$$$)
Penicillin allergic
Cephalexin*
(Keflex®)
20 mg/kg/dose twice daily (max 500 mg/dose) 500 mg twice a day 10 days ($)
Cefadroxil*
(Duricef®)
30 mg/kg once daily (max 1000 mg) 1000 mg once a day 10 days ($)
Clindamycin
(Cleocin®)
7 mg/kg/dose 3 times daily (max 300 mg/dose) 300 mg three times a day 10 days ($-$$$)
Azithromycin
(Zithromax®)
12 mg/kg once daily (max 500 mg) 500 mg once a day 5 days ($)
Clarithromycin
(Biaxin®)
7.5 mg/kg/dose twice daily (max 250 mg/dose) 250 mg twice daily 10 days ($-$$)
  • * Do not use in patients with immediate type hypersensitivity to penicillin
  • Pricing based on a standard course of therapy in a child or adult. $ = 0-$50, $$ = $51-$100, $$$ = $101-$150, $$$$ = > $150
  • Reference [2]