Determination of anti-streptolysin O (ASLO) by agglutination method (LATEX)

The ASLO latex test is a rapid agglutination test on the blade for the qualitative and semi-quantitative detection of anti-streptolysin O in human serum samples. Group A hemolytic streptococcus, Group C hemolytic streptococcus or group G hemolytic streptococcus produces streptolysin, a haemolytic exotoxin to which the human body releases anti-streptolysin antibodies.

This detection method uses a suspension of streptolysin-coated latex particles (antigen) that will come into contact with the serum of the patient suspected of being infected (anti-streptolysin O antibodies). If the antibodies are present in the sample, the agglutination reaction occurs and the test is considered positive.

After 1-2 weeks of infection with Streptococcus, the anti-streptolysin antibody level can be detected, the maximum level reaching after 3-6 weeks.

 

INSTRUCTIONS FOR THE QUALITATIVE METHOD

 

MATERIAL PREPARATION

Place all the necessary materials at the room temperature on the work table. Read the working instructions. Use a 40μl pipette.

The number of the patient is noted on the card.

Samples to be tested should not be contaminated, haemolized or lipemic.

 

SAMPLE WORK

Easily shake the positive control

Place a positive control drop in the first circle

Place a negative control drop in the second circle

Place 40μl of patient samples in the rest of the circles

Gently stir the latex suspension

Place a drop of the latex suspension in each circle next to the test sample

Mix the test sample with the latex solution using the beater and spread over the entire surface of the circle. Use a new mixer at each sample

Mix the mixture by rotating the card with about 100 rpm for about 4 minutes and note the moment when the agglutination of the samples appears

If reading is done after 4 minutes, false positive results may occur.

 

INTERPRETATION

The presence or absence of agglutination is examined macroscopically. The presence of visible agglutination indicates an anti-streptolysin antibody content greater than or equal to 200 IU / ml (positive result).

 

Semi-quantitative method

This method uses serial dilutions with patient serum and saline solution. After the dilutions are made, place a drop of latex and mix.

 

Sources of errors

Bacterial contamination of controls and samples

Refrigeration / melting of reagents

The traces of detergent on the reaction plates after washing