Anti-streptolysin O
Anti-streptolysin O(ASO or ASLO) is the antibody made againststreptolysin O,an immunogenic, oxygen-labilestreptococcalhemolyticexotoxinproduced by most strains of group A and many strains of groups C and GStreptococcusbacteria. The "O" in the name stands foroxygen-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.
Increased levels of ASO titre in the blood could cause damage to the heart and joints. In most cases, penicillin is used to treat patients with increased levels of ASO titre.
Clinical significance
[edit]When the body is infected with streptococci, it producesantibodiesagainst the variousantigensthat the streptococci produce. ASO is one such antibody. A raised or rising levels can indicate past or present infection. Historically it was one of the first bacterial markers used for diagnosis and follow up ofrheumatic feverorscarlet fever.Its importance in this regard has not diminished.[citation needed]
Since these antibodies are produced as a delayed antibody reaction to the above-mentioned bacteria, there is no normal value. The 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.
A titre has significance only if it is greatly elevated (> 200), but a rise in titre demonstrated in paired blood samples taken days apart is more informative for diagnosis. 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.[citation needed] The aim is to convert it.
Estimation
[edit]It is done byserologicalmethods like latex agglutination or slide agglutination.ELISAmay 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.[citation needed]
Mechanism of action
[edit]These antibodies produced against the bacteria cross-react with human antigens (mainlycollagen) and hence attack thecellular matrixof various organs, mainly the heart, joints, skin, brain, etc.[citation needed]
Antistreptolysin O titre
[edit]Antistreptolysin O titre (AS(L)O titerorAS(L)OT) is a measure of the blood plasma levels of antistreptolysin Oantibodiesused in tests for the diagnosis of astreptococcal infectionor indicate a past exposure to streptococci. The ASOT helps directantimicrobialtreatment and is used to assist in the diagnosis of scarlet fever, rheumatic fever, andpost infectious glomerulonephritis.[citation needed]
A positive test usually is > 200 units/mL,[1]but normal ranges vary from laboratory to laboratory and by age.[2]
Thefalse negativesrate is 20 to 30%.[1]If a false negative is suspected, then ananti-DNase Btitre should be sought.False positivescan result fromliver diseaseandtuberculosis.[1]
References
[edit]- ^abcAntistreptococcal antibody titres. gpnotebook. URL:http://www.gpnotebook.co.uk/cache/-1630535637.htmArchivedJanuary 26, 2007, at theWayback Machine.Accessed on: March 31, 2007.
- ^Danchin M, Carlin J, Devenish W, Nolan T, Carapetis J (2005). "New normal ranges of antistreptolysin O and antideoxyribonuclease B titres for Australian children".J Paediatr Child Health.41(11): 583–6.doi:10.1111/j.1440-1754.2005.00726.x.PMID16398843.S2CID9111180.
External links
[edit]- Antistreptococcal antibody titres- GPnotebook.co.uk.
- Antistreptolysin O TiterArchived2013-03-21 at theWayback Machine- medterms.com.
- Antistreptolysin O Titer, Serum
- Streptococcal antibody tests- healthAtoZ.com