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Antistreptolysin O titer
ASO titer; ASLO
Antistreptolysin O (ASO) titer is a blood test to measure antibodies against streptolysin O, a substance produced by group A streptococcus bacteria. Antibodies are proteins our bodies produce when they detect harmful substances, such as bacteria.
Antibodies
An antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. Examples of antigens include micr...
How the Test is Performed
A blood sample is needed.
How to Prepare for the Test
DO NOT eat for 6 hours before the test.
How the Test will Feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick. After the test, you may have some throbbing at the site.
Why the Test is Performed
You will need the test if you have symptoms of a previous infection by group A streptococcus. Some illnesses caused by this bacteria are:
- Bacterial endocarditis, an infection of the inner lining of your heart
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A kidney problem called
glomerulonephritis
Glomerulonephritis
Glomerulonephritis is a type of kidney disease in which the part of your kidneys that helps filter waste and fluids from the blood is damaged....
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Rheumatic fever
, which can affect the heart, joints, or bones
Rheumatic fever
Rheumatic fever is a disease that may develop after an infection with group A streptococcus bacteria (such as strep throat or scarlet fever). It can...
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Scarlet fever
Scarlet fever
Scarlet fever is caused by an infection with bacteria called A streptococcus. This is the same bacteria that cause strep throat.
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The ASO antibody may be found in the blood weeks or months after the strep infection has gone away.
Normal Results
A negative test result means that you do not have strep infection. Your health care provider may do the test again in 2 to 4 weeks. At times, a test that was negative the first time may be positive (meaning it finds ASO antibodies) when done again.
Normal value ranges may vary slightly. Talk to your provider about the meaning of your test results.
What Abnormal Results Mean
An abnormal or positive test result means you recently had a strep infection, even if you had no symptoms.
Risks
Veins and arteries vary in size from person to person, and from one side of the body to the other. Because of this, it may be harder to get a blood sample from some people than it is from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding where the needle is inserted
- Fainting or feeling lightheaded
- Hematoma (blood buildup under the skin)
- Infection (a slight risk any time the skin is broken)
References
Bryant AE, Stevens DL. Streptococcus pyogenes. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases . 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 199.
Comeau D, Corey D. Rheumatology and musculoskeletal problems. In: Rakel RE, Rakel DP, eds. Textbook of Family Medicine . 9th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 32.
Low ED. Nonpneumoccal streptococcal infections and rheumatic fever. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine . 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 290.
Nussenbaum B, Bradford CR. Pharyngitis in adults. In: Flint PW, Haughey BH, Lund V, et al, eds. Cummings Otolaryngology: Head & Neck Surgery . 6th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 9.
Shulman ST, Bisno AL. Nonsuppurative poststreptococcal sequelae. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases . 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 200.
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Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
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Blood test - illustration
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.
Blood test
illustration
Review Date: 1/10/2016
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.
