Group A Streptococcal Screen

Strep screen, rapid strep screen, direct strep screen.

To detect a group A streptococcal infection such as strep throat.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings
(Method: Enzyme immunoassay or latex agglutination) Negative.

Critical Findings and Potential Interventions


(Study type: Body fluid, throat swab [two swabs should be submitted so that a culture can be performed if the screen is negative]; related body system: Immune and Respiratory systems.) Rheumatic fever is a possible sequela to an untreated streptococcal infection. Early diagnosis and treatment appear to lessen the seriousness of symptoms during the acute phase and overall duration of the infection and sequelae. The onset of strep throat is sudden and includes symptoms such as chills, headache, sore throat, malaise, and exudative gray-white patches on the tonsils or pharynx. The group A streptococcal screen should not be ordered unless the results would be available within 1 to 2 hr of specimen collection to make rapid, effective therapeutic decisions. A positive result can be a reliable basis for the initiation of therapy. A negative result is presumptive for infection and should be backed up by culture results. In general, specimens showing growth of less than 10 colonies on culture yield negative results by the rapid screening method. Evidence of group A streptococci disappears rapidly after the initiation of antibiotic therapy. A nucleic acid probe method has also been developed for rapid detection of group A streptococci.


  • Assist in the rapid determination of the presence of group A streptococci.

Interfering Factors

Factors that may alter the results of the study

  • Polyester (rayon or Dacron) swabs are favored over cotton for best chance of detection. Fatty acids are created on cotton fibers during the sterilization process. Detectable target antigens on the streptococcal cell wall are destroyed without killing the organism when there is contact between the specimen and the fatty acids on the cotton collection swab. False-negative test results can be obtained on specimens collected with cotton tip swabs. Negative strep screens should always be followed with a traditional culture.

Other Considerations:

  • Sensitivity of the method varies among manufacturers.
  • Adequate specimen collection in children may be difficult to achieve, which explains the higher percentage of false-negative results in this age group.

Potential Medical Diagnosis: Clinical Significance of Results

Positive Findings In:

  • Rheumatic fever
  • Scarlet fever
  • Strep throat
  • Streptococcal glomerulonephritis
  • Tonsillitis

Nursing Implications

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

  • Inform the patient this test can assist in identifying a streptococcal infection.
  • Explain that a throat swab is needed for the test. Address concerns about pain and explain that there may be some discomfort during the swabbing procedure.

Potential Nursing Actions

  • Vigorous swabbing of both tonsillar pillars and the posterior throat enhances the probability of streptococcal antigen detection.
  • Obtain a history of prior antibiotic therapy.

After the Study: Potential Nursing Actions

Treatment Considerations

  • Infection prevention and treatment are important during any illness. Emphasize the value of good hand hygiene and assist with hygiene as needed. Adhere to standard precautions and obtain ordered cultures. Monitor and trend temperatures and associated laboratory values (white blood cells, C-reactive protein).
  • Serious throat infection and inflammation can impinge on airway patency. A key intervention to decrease this risk is to administer ordered antibiotics and emphasize the importance of completing the entire course of antibiotic therapy even if no symptoms are present. Other potential interventions are to assess respiratory rate, rhythm, depth, and accessory muscle use and to administer prescribed oxygen with humidification and pulse oximetry to evaluate oxygenation.

Followup Evaluation and Desired Outcomes

  • Collaborates with health-care provider to develop a plan of care that supports health, including adherence to the recommended medication regime and adherence to follow-up appointments.

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