ASOT test ...

موضوع: ASOT test ... الجمعة أكتوبر 31, 2008 11:09 pm

Name of test Antistreptolysin- O titer The test Code S01
Alternate abbreviations ASOT
Pages 2
Department Serology Date of issue 4 /2007

Prepared by 1- Kamal al najeili References 1- Lab kit
2-Awatif Abdelkader 2-Randox
3-Kayed Ahmad 1_1753.htm
3-
Scope The group A β-hemolytic streptococci produces various toxins that can acts as antigens, one of these exotoxins is streptolysin O. a person infected with this type of bacteria produces specific antibodies against these exotoxins, the quantity of this antibody (ASOT) in serum will reflect the degree of infection.

The test principle ASOT method is based on an immunological reaction between streptococci exotoxins bound to biologically inert latex particles and streptococcal antibodies in the test sample , visible agglutination occurs when increased antibody level , are present in the serum

Clinical application
in diagnosis of rheumatic fever and streptococcal infection.

Patient preparation and
Specimen requirements Fresh serum. stable 48 hours at 2-8c or 3 months at -20c
The sample with particle or fibrin should be centrifuged to eliminate them.

Type of specimen Serum
Collection site Routine vein puncture
Sample volume 5 ml adult - 3 ml child ( whole blood)
Collection materials and container Syringes, needles , tourniquet, alcohol swabs , plain tubes, or vacutainer collection system
Criteria for rejection • Incorrectly labeled specimen
• Inappropriate specimen
• Reject haemolised or lipemic sample

Sample handling and processing Insure complete clot formation has taken place , then centrifuge to have serum free of fibrin and red blood cells

Materials and equipment Mechanical rotator with adjustable speed 80-100 r. p. m.
General lab equipment.
Latex reagent
Positive control
Negative control

Reagent preparation Reagent is ready to use , no need for preparation
Test procedure 1. Allow the reagent and sample to reach room temperature.
2. Place 50micron of the sample and one drop of each Positive and Negative control into separate circles on the slid test.
3. shake the ASOT latex reagent gently before using and add a drop of this reagent next to the sample to be tested
4. Mix both drops with stirrer, spreading them over the entire surface of the circle, used different stirrers for each sample.
5. Rotate the slid with mechanical rotator at 80-100 r.p.m. for false positive result could appear if the test is read later than two min.
Calculations Any positive sample has ASOT concentration equal or more than 200.0 IU / ml, so serial dilutions must be done to semi-quantitative determinations
Quality control Positive and negative controls are recommended to monitor the performance of procedure as well as comparative pattern for better result interpretation.
Reference intervals <200.0 IU / ml
Procedure limitations Don’t use grossly hemolysed sample , sample can be stored at -20 for 3 months , avoid repeated freezing and thawing , and mix thoroughly after thawing by low speed vortexing