PREFINAL LABORATORY L3: ASO LATEX AGGLUTINATION Flashcards
ASO kit is storage temperature
2-8C
principle of ASO test
latex particles coated with streptolysin O are agglutinated when mixed with samples containing ASO
describe ASO latex test
slide agglutination test for the qualitative and semi-quantitative detection of anti-streptolysin O
what kind of enzyme is streptolysin O
toxic immunogenic exoenzyme
what organisms produce streptolysin O
beta-hemolytic streptococci groups A, C, and G
disease associations of streptolysin O
rheumatoid fever
acute glomerulonephritis
streptococcal infections
describe rheumatic fever
inflammatory dse affecting connective tissue from several parts of human body
example of body parts affected by rheumatoid fever
skin, heart, joints
describe acute glomerulonephritis
renal infection that affects mainly renal glomerulus
reagents of ASO test kit
ASO latex antigen
positive control
negative control
components of ASO latex antigen
latex particles coated with streptolysin O, pH 8.2 preservative
components from human origin have been tested and found to be negative of what antigens/antibody
HBsAg, HCV, and antibody to HIV 1/2
ASO latex sensitivity is calibrated against what standard
ASO International Standard from NIBSC 97/662
T or F:
ASO test kits can be frozen
F
could change the functionality of test
vials must be kept at what position
vertical position
what should be done if vials are changed in position
gently mix to dissolve aggregates that may be present
what indicates the reagent deterioration
presence of particles and turbidity
additional equipment required in ASO test
mechanical rotator (80-100 rpm)
vortex mixer
50 ul pipette
sample used in ASO test
fresh serum
fresh serum is stable for how many days and at what temperature
7 days at 2-8C or 3 months at -20C
what should be done to samples with fribrin
centrifuged
specimens to be avoided
hemolyzed or lipemic
procedure for qualitative method
1) Allow the reagents and samples to reach room temperature.
2) Place 50 uL of the sample and one drop of each Positive and Negative controls into separate circles on the slide test.
3) Mix the ASO-latex reagent vigorously or on a vortex mixer before using and add one drop (50 uL) next to the sample to be tested
4) Mix the drops with a stirrer, spreading them over the entire surface of the circle. Use different stirrers for each sample.
5) Place the slide on a mechanical rotator at 80-100 rpm for 2 minutes.
what kind of results will show if read after 2 minutes
false positive
what can be reduced if samples and reagents are used at low temperatures
sensitivity of the test
first step of semi-quantitative method
make serial two-fold dilutions of sample in 9 g/L saline solution
the presence of agglutination indicates
ASO concentration equal or greater than 200 IU/mL
this is defined as the highest dilution showing a positive result in semi-quantitative method
titer
formula of approx ASO concentration
200 x ASO titer = IU/mL
reference values of ASO
up to 200 iU/mL (adults)
100 iU/mL (children <5 years old)
analytical sensitivity of ASO test
200 (+/- 50) IU/mL
prozone effect in ASO test
no prozone effect was detected up to 1500 IU/mL
diagnostic sensitivity of ASO test
98%
diagnostic specificity of ASO test
97%
substances that do not interfere with ASO test
bilirubin (20 mg/dL)
hgb (10 g/L)
lipids (10 g/L)
rheumatoid factors (300 IU/mL)
what can cause false negative results
early infx
children from 6 mos to 2 years
conditions that can cause false positive result
rheumatoid arthritis
scarlet fever
tonsilitis
several streptococcal infx
healthy carriers
titration at biweekly intervals during how many weeks are advisable for dse evaluation
4 or 6 weeks
