ASOT (Anti-Streptolysin O Titer) Lab -4- PDF

‫جامعة تكريت‬ ‫كلية الطب‬ ‫فرع االحياء المجهرية الطبية‬ ‫م‪.‬م‪.‬جعفر جميل ابراهيم‬ ‫المرحلة الثانية‬ ‫مناعة عملي‬ ‫‪ASOT‬‬ ‫‪(Antistreptolysin O‬‬ ‫)‪Titer‬‬ ‫‪Lab -4-‬‬  Anti-streptolysin O...

‫جامعة تكريت‬ ‫كلية الطب‬ ‫فرع االحياء المجهرية الطبية‬ ‫م‪.‬م‪.‬جعفر جميل ابراهيم‬ ‫المرحلة الثانية‬ ‫مناعة عملي‬ ‫‪ASOT‬‬ ‫‪(Antistreptolysin O‬‬ ‫)‪Titer‬‬ ‫‪Lab -4-‬‬  Anti-streptolysin O (ASO or ASLO) is an antibody produced against a toxin "foreign Ag" produced by Lancefield group A streptococci "streptococcus pyogens". The toxin is called streptolysin O, the O stands for oxygen- labile; the other toxin that secreted is an oxygen-stable " streptolysin S". Significance of ASOT ASOT testing is a procedure that demonstrate the presence of antibodies generated by the body against infections by group A streptococcus (S. pyogen) mostly for Tonsillitis and Rheumatic fever, this microbe produces the toxin streptolysin O, which cause destruction of RBCs cell walls.  This toxin is immunogenic, that is, the body produces antibodies against it.  Note that :- Antibodies (IgG) begin to appear in patient serum 7-10 days after infection. The antibody may be detected in the blood for weeks or months after the primary source of infection has eradicated.  If the titer doesn't decrease with time; this means that a recurrent or chronic infection may exist. ASOT test It is a latex agglutination test for the qualitative screening and semi-quantitative determination of anti- streptolysin O antibodies in serum. Specimen should be Serum collected in plain tubes. Principle of the test: A stabilized buffered suspension of polystyrene latex particles have been coated with streptolysin O Ag when is mixed with a serum containing antibodies to streptolysin O, agglutination occur. The reaction will occur within minutes Results Interpretation At Direct agglutination step: No agglutination: Serial dilution is done to exclude probability of prozone phenomena. The result is written less than 200 IU/ml. Don't write negative result.  Agglutination is observed: This mean that ASO Level of 200 IU/ml or more, and so Serial dilution is done to detect the exact titer Results and Interpretation The serum ASO titer can be defined as the highest dilution showing a positive result. The approximate ASO level (IU/ml) present in the sample can be obtained by the following formula: ASO titer (IU/ml) = Highest dilution with positive reaction x Reagent sensitivity (200 IU/ml)  E.g. if the agglutination is present up to a titer 1:8, the approximate serum ASO level is 8 x 200 = 1600 IU/ml" Elevated levels may indicate: 1. Active streptococcal infection. 2. Sore throat. 3. Rheumatic fever. 4. Scarlet fever. 5. Post-streptococcal glomerulonephritis. 6. Bacterial endocarditis. Important notes about the test: False positive results(rise in titer) may occur in : 1. High fibrinogen 2. Gross hemolysis 3. High lipid in serum 4. Oxidized reagent 5. Bacterial contamination "dirty slide