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arteriosclerosis obliterans.


abbreviation for antistreptolysin-O test.


1. Administrative services organization, see there.
2. Allele-specific–oligonucleotide hybridization.
3. Anti-streptolysin O, see there.

Antibodies, Antistreptolysin O

Synonym/acronym: Streptozyme, ASO.

Common use

To assist in the diagnosis of streptococcal infection.


Serum (1 mL) collected in a red-top tube.

Normal findings

(Method: Immunoturbidimetric) Adult/older adult: Less than 200 international units/mL; 17 yr and younger: Less than 150 international units/mL.


Group A β-hemolytic streptococci secrete streptolysin O,, a toxin which can hemolyze red blood cells. Circulating toxin stimulates the immune system to develop streptolysin O antibodies. These antistreptolysin O (ASO) antibodies form within 1 wk after the onset of a streptococcal infection and peak 2 to 3 wk later. The ASO titer usually returns to preinfection levels within 6 to 12 mo, assuming reinfection has not occurred. Up to 95% of patients with acute glomerulonephritis and up to 85% of patients with rheumatic fever demonstrate a rise in titer. ASO titer may not become elevated in some patients who experience sequelae involving the skin or kidneys, and the antideoxyribonuclease-B, streptococcal test may a better test for these patients.

This procedure is contraindicated for



  • Assist in establishing a diagnosis of streptococcal infection
  • Evaluate patients with streptococcal infections for the development of acute rheumatic fever or nephritis
  • Monitor response to therapy in streptococcal illnesses

Potential diagnosis

Increased in

  • Presence of antibodies, especially a rise in titer, is indicative of exposure.

  • Endocarditis
  • Glomerulonephritis
  • Rheumatic fever
  • Scarlet fever

Decreased in


Critical findings


Interfering factors

  • Drugs that may decrease ASO titers include antibiotics and corticosteroids because therapy suppresses antibody response.
  • False-positive ASO titers can be caused by elevated levels of serum β-lipoprotein (observed in liver disease)

Nursing Implications and Procedure


  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching:  Inform the patient this test can assist in documenting exposure to streptococcal bacteria.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex.
  • Obtain a history of the patient’s immune system, symptoms, and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values).
  • Review the procedure with the patient. Inform the patient that specimen collection takes approximately 5 to 10 min. Address concerns about pain and explain that there may be some discomfort during the venipuncture.
  • Sensitivity to social and cultural issues,   as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.


  • Potential complications: N/A
  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate specimen container with the corresponding patient demographics, initials of the person collecting the specimen, date, and time of collection. Perform a venipuncture.
  • Remove the needle and apply direct pressure with dry gauze to stop bleeding. Observe/assess venipuncture site for bleeding or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.


  • Inform the patient that a report of the results will be made available to the requesting health-care provider (HCP), who will discuss the results with the patient.
  • Administer antibiotics as ordered. Remind the patient of the importance of completing the entire course of antibiotic therapy even if signs and symptoms disappear before completion of therapy.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Answer any questions or address any concerns voiced by the patient or family.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include culture throat, group A streptococcal screen, and antideoxyribonuclease-B streptococcal.
  • See the Immune System table at the end of the book for related tests by body system.
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