Rapid Strep Test

Anatomy of a Sore Throat Natural Cold Flu Remedies Slideshow The Common Cold Slideshow

Medical Author: John Mersch, MD, FAAP
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

• Overview of streptococcal throat infection
• What is a rapid strep test?
• Why is identification of streptococcal infection important?
• What is the traditional test for strep throat?
• Why is the rapid test better?
• How is a rapid strep test done?
• What are the limitations of the rapid strep test?

Overview of streptococcal throat infection

The incidence of sore throats (pharyngitis) varies with season, age of the patient, and geographic area. Sore throats can be caused by infection from either viruses or bacteria. Fewer than a third of all pharyngitis is bacterial, the most common bacteria being Group A streptococcus (GAS) . Children 5 years to 15 years of age are the most common age group affected. Infection is most likely during the winter/early spring season. This is most likely due in part to the seasonal variation of Strep bacteria concentration in the community as well as the higher likelihood of close proximity due to either weather conditions and/or school attendance during winter months.

The pediatric population may have different presentations of GAS infection:

1. Infants (< 1 year of age) low grade fever (< 101 F, 38 C), fussiness, decreased appetite, often following exposure to either daycare or older infected siblings
   
   
2. Children (< 3 years of age) prolonged purulent nasal discharge, low grade fever, and enlarged and tender lymph nodes in the neck area
   
   
3. Children (> 3 years of age) sudden onset sore throat, moderate fever (> 101 F, 38 C), headache, upset stomach, and enlarged and tender lymph nodes in the neck area.

The majority of sore throats (70% - 85%) are caused by viruses. Representative examples are:

• EBV (Ebstein-Barr virus) and CMV (cytomegalic inclusion virus) which may produce a mononucleosis symptom complex (sore throat, fever, disproportionate fatigue, tender and swollen neck lymph nodes, and commonly enlargement of the spleen and liver;
  
  
• adenovirus (which may be associated with conjunctivitis ("pink eye");
  
  
• influenza; and
  
  
• miscellaneous others - herpes, rhinovirus (cause of the common "cold"), etc.

Unfortunately, no single characteristic element of either the patient's history or physical exam discriminates between GAS and non-strep pharyngitis. Thus, the importance of laboratory evaluation since strep throat should be treated with antibiotics, while relief of symptoms remains the mainstay of treatment for viral sore throats.