Anti-streptolysin O
Encyclopedia
Anti-streptolysin O is the antibody made against streptolysin O, an immunogenic, oxygen-liable hemolytic toxin produced by most strains of group A and many strains of groups C and G streptococci
. The O in the name stands for oxygen-labile; the other related toxin being oxygen-stable streptolysin-S. The main function of streptolysin O is to cause hemolysis (the breaking open of red blood cells) in particular, beta-hemolysis.
or scarlet fever
. Its importance in this regard has not diminished.
Since these antibodies are produced as a delayed hypersensitive reaction to the above mentioned bacteria, there is no normal value. Any presence of these antibodies indicates an exposure to these bacteria. However, as many people are exposed to these bacteria and remain asymptomatic, the mere presence of ASO does not indicate disease.
Acceptable values, where there is no clinical feature of rheumatism are as follows:
This titre (value) has a significance only if it is greatly raised, or if a rise in titre can be demonstrated in paired blood samples taken days apart.The antibody levels begin to rise after 1 to 3 weeks of strep infection,peaks in 3 to 5 weeks and falls back to insignificant levels in 6 months.
Values need to be correlated with a clinical diagnosis.
methods like latex agglutination or slide agglutination. ELISA
may be performed to detect the exact titre value.
To detect the titre value, by a non-ELISA method, one has to perform the above agglutination using a serial dilution technique.
) and hence attack the cellular matrix of various organs, mainly the heart, joints, skin, brain, etc.
) antistreptolysin O antibodies used in blood test
s for the diagnosis of a streptococcal infection
or indicate a past exposure to streptococci.
The ASOT helps direct the antimicrobial
treatment and is used to assist in the diagnosis of scarlet fever
, rheumatic fever
and post infectious glomerulonephritis
.
A positive test usually is >200 units/mL, but normal ranges vary from laboratory to laboratory and by age.
The false negatives rate is 20-30%. If a false negative is suspected, then an anti-DNase B titre should be sought. False positives can result from liver disease
and tuberculosis
.
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
. The O in the name stands for oxygen-labile; the other related toxin being oxygen-stable streptolysin-S. The main function of streptolysin O is to cause hemolysis (the breaking open of red blood cells) in particular, beta-hemolysis.
Significance
When the body is infected with streptococci, it produces antibodies against the various antigens that the streptococci produce. ASO is one such antibody. So, a raised or rising levels can indicate past or present infection. Historically was one of the first bacterial markers used for diagnosis and follow up of rheumatismRheumatism
Rheumatism or rheumatic disorder is a non-specific term for medical problems affecting the joints and connective tissue. The study of, and therapeutic interventions in, such disorders is called rheumatology.-Terminology:...
or scarlet fever
Scarlet fever
Scarlet fever is a disease caused by exotoxin released by Streptococcus pyogenes. Once a major cause of death, it is now effectively treated with antibiotics...
. Its importance in this regard has not diminished.
Since these antibodies are produced as a delayed hypersensitive reaction to the above mentioned bacteria, there is no normal value. Any presence of these antibodies indicates an exposure to these bacteria. However, as many people are exposed to these bacteria and remain asymptomatic, the mere presence of ASO does not indicate disease.
Acceptable values, where there is no clinical feature of rheumatism are as follows:
- Adults: less than 200 units
- Children: less than 300 units
This titre (value) has a significance only if it is greatly raised, or if a rise in titre can be demonstrated in paired blood samples taken days apart.The antibody levels begin to rise after 1 to 3 weeks of strep infection,peaks in 3 to 5 weeks and falls back to insignificant levels in 6 months.
Values need to be correlated with a clinical diagnosis.
Estimation
It is done by serologicalSerology
Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...
methods like latex agglutination or slide agglutination. ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
may be performed to detect the exact titre value.
To detect the titre value, by a non-ELISA method, one has to perform the above agglutination using a serial dilution technique.
Mechanism of action
These antibodies produced against the bacteria cross react with human antigens (mainly collagenCollagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
) and hence attack the cellular matrix of various organs, mainly the heart, joints, skin, brain, etc.
Antistreptolysin O titre
Antistreptolysin O titre (AS(L)O titre or AS(L)OT) is a titre of (serumBlood plasma
Blood plasma is the straw-colored liquid component of blood in which the blood cells in whole blood are normally suspended. It makes up about 55% of the total blood volume. It is the intravascular fluid part of extracellular fluid...
) antistreptolysin O antibodies used in blood test
Blood test
A blood test is a laboratory analysis performed on a blood sample that is usually extracted from a vein in the arm using a needle, or via fingerprick....
s for the diagnosis of a streptococcal infection
Streptococcus
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning...
or indicate a past exposure to streptococci.
The ASOT helps direct the antimicrobial
Antimicrobial
An anti-microbial is a substance that kills or inhibits the growth of microorganisms such as bacteria, fungi, or protozoans. Antimicrobial drugs either kill microbes or prevent the growth of microbes...
treatment and is used to assist in the diagnosis of scarlet fever
Scarlet fever
Scarlet fever is a disease caused by exotoxin released by Streptococcus pyogenes. Once a major cause of death, it is now effectively treated with antibiotics...
, rheumatic fever
Rheumatic fever
Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...
and post infectious glomerulonephritis
Glomerulonephritis
Glomerulonephritis, also known as glomerular nephritis, abbreviated GN, is a renal disease characterized by inflammation of the glomeruli, or small blood vessels in the kidneys...
.
A positive test usually is >200 units/mL, but normal ranges vary from laboratory to laboratory and by age.
The false negatives rate is 20-30%. If a false negative is suspected, then an anti-DNase B titre should be sought. False positives can result from liver disease
Liver disease
Liver disease is a broad term describing any single number of diseases affecting the liver.-Diseases:* Hepatitis, inflammation of the liver, caused mainly by various viruses but also by some poisons , autoimmunity or hereditary conditions...
and tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...
.
External links
- Antistreptococcal antibody titres - GPnotebook.co.uk.
- Antistreptolysin O Titer - medterms.com.
- Antistreptolysin O Titer, Serum
- Streptococcal antibody tests - healthAtoZ.com