Latex investigations methods and reporting
principles of common
Latex investigations methods and reporting
Resources Needed:
· Flip chart, Marker pens
· Black/White board and chalk
· Handout with different types of diagrams
· Dispensing bottles with needles
· Disposable test cards
· Disposable dropper pipettes
· Rubber teats
· Disposable mixing sticks
· O-Antigens
· H-Antigens
· Controls – positive and negative
· Instruction manual
· Disinfectant
· Gloves
· Rotator
· Timer clock/stop watch
· Saline, 0.85%
· Disposal bucket
Describe specific Immunology / Serology investigations(Diagnostic procedures
List common specific immunology/serology investigation
· VDRL/RPR,
· HBs Ag,
· Cryptococcus serum test,
· Widal test,
· pregnancy test,
· rheumatoid factor test,
· ICT
· ASOT
Explain the principle and reporting of each common immunology/serology investigations according to SOP
SIGNIFICANCE OF INVESTIGATING TYPHOID FEVER
· To confirm diagnosis of typhoid fever
· To determine the carrier status who has recovered from typhoid fever.
· Pyrexia of unknown cause(persistent high temperature)
WIDAL TEST BY TILE METHOD,
Reagents
· O-Antigens
· H-Antigens
· Controls – positive and negative
Demonstration of the widal test by tile method according to the SOP
· Demonstrate of the pregnancy test according to the SOP.
Performance of the widal test by tile method(Qualitative analysis)
- Principle
Killed salmonella suspensions with O and H Ag reacts with corresponding Ab in the serum of the patient with infection and shows agglutation.
· Procedure
o Bring the test kit reagents to room temperature.
o Mix the reagents before use
o Pippette one drop of O-Ag and H-Ag on the circles on the tile or test cards.
o Using a rubber teat and dropper pipette, dispense 1 drop (0.05ml) of sample on one of the test card circles labeled O and H.
o Mix using the applicator stick
o Dispense the positive and negative control sera in the same way and mix.
o use your hands to rotate the test card for 1 minute..
o Read the results macroscopically in a good light and check for agglutination.
o Place all the materials in the bucket marked “INCINERATION”.
NB: Each laboratory must determine the time necessary to perform the procedure (turnaround time).
· Reporting results
o Visible Agglutination indicates presence of salmonella Antibodies. Proceed to quantitative test( tube titration method)
o No visible agglutination indicates absence of salmonella antibodies. Report as negative or non-reactive.
· Limitations:
o The test reagent must be stored at 2 – 8oC and when in use place at room temperature before use.
o Check carefully the expiry dates on the test kits.
· Quality control
o Always run positive and negative controls when performing the test, and make sure the control samples are reading correctly.
points for the widal test by tile method
· Store reagents at the correct temperature according to the manufacturer’s instructions.
· Check carefully the expiry dates on the test kits.
· Check that the catalogue numbers on the reagent containers match the numbers on the kit procedures in the package insert.
![](https://i.ytimg.com/vi/_ArW7CubWkw/hqdefault.jpg)
Evaluation
QUANTITATIVE WIDAL TEST BY TUBE METHOD
This is done to all reactive patients sample after tile method to determine the degree of antibodies(infection)
materials
· Disposable dropper pipettes
· Rubber teats
· Disposable mixing sticks
· O-Antigens
· H-Antigens
· Controls – positive and negative
· Instruction manual
· Disinfectant
· Test tubes
· Incubator or water bath(370c)
· Gloves
· Rotator
· Timer clock/stop watch
· Saline, 0.85%
· Disposal bucket
Method
1.Arrange a total of 16 test tubes, each row 8 tubes as shown below
2.Label the 2 rows as O and H
Test Tube no.
|
1
|
2
|
3
|
4
|
5
|
6
|
7
|
8
|
Saline (ml)
|
1.9
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
Patient serum
|
0.1(neat)
|
-
|
-
|
-
|
-
|
-
|
-
|
-
|
Mix& transfer(ml)
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
1.0
|
Discard
|
Dilution
|
1:20
|
1:40
|
1:80
|
1:160
|
1:320
|
1:640
|
1:1280
|
Saline control
|
3.Add one drop of O and H antigen in to the each of the row of test tube.
4.Mix well and incubate at 370c for 16-20 hrs.
5.check for agglutination. Titre is the highest dilution of the at which agglutination/flocculation is observed
Interpretation of results
- A titre of 1:80 or more is considered significant and rise in titre after a few days will confirm the diagnosis.
- Individuals with previous infection or with TAB vaccine will show H positive reaction. Culture the specimen to the diagnosis
- Chronic liver disease can also result to high O or H more than active typhoid fever.
References:
· Ivan M. Roitt & Peter J.Delves ROITTS ESSENTIAL IMMUNOLOGY, 10th Edition, (2004) Replika press Pvt.ltd ,india
· Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAl Countries, part 2, Edition (2003) Cambridge University press,international sales department.
· Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAL COUNTRIES, volume 2, Microbiology, Edition (1984) Cambridge University press.
· Warren Levinson. MD,PHD– Medical Microbiology & Immunology edition (2004) Mc Graw –HillCompanies
Satish Gupte THE SHORT TEXT BOOK FOR MEDICAL MICROBIOLOGY(including parasitology) 10th Edition, (2004) Replika press Pvt.ltd ,india
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