How to carry out widal test

WIDAL TEST: Aim: to detect presence of salmonella antibodies in patient’s blood serum, the causative agent of typhoid fever. Material: febrile antigen kit, disposable stirrers, Pasteur pipette, a tile, test tube, centrifuges. Principle: The Widal test is a serological technique which test for the presence of salmonella antibodies in a patient plasma, this test is done to check the bacteria salmonella Typhi which courses typhoid. When investigating typhoid, the patient’s serum is tested for O and H antibodies (agglutinations) against the following antigen suspension:- S-Typhi O antigen suspension S-Typhi H antigen suspension Anti-febrile antigens are suitable for both the rapid slide and tube agglutination tests against human sera for the detection of this agglutination. Anti-stained antigens suspensions are killed, bacteria stained antigens are specific to the flagella H antigens. The Widaltest kit contains attenuated typhoid antigens which react specifically with the body’s antibody to form an agglutination reaction. Procedure: Whole blood was collected from the patient using a sterile syringe. Blood was placed into an EDTA container and was centrifuged in order to separate blood from supernatant (plasma). A dropper pipette was used to dispense out the plasma into eight different spot on the tile. The salmonella antigen reagents were shaken well and a drop of undiluted antigen suspension was added to each plasma aliquot made earlier(i.e. TyphiOand H, S. Paratyphi AO and AH, S. Paratyphi BO and BH, and S. Paratyphi CO and CH on each serum spot respectively). A stirring rod was used to mix or smear the antigen and plasma properly, the tile is rotated for at least 2 minutes and agglutination is observed. Clinical Importance: Non-reactive: smooth suspension with no visible agglutination, indicates absence of salmonella species in the serum. Reactive: any degree of agglutination visible microscopically indicates the presence of salmonella species. When viewed, the significant of titres are noted e.g. 1/20, 1/40, 1/80, 1/160, 1/320. The significant titres is >_1/80. Below are different salmonella species: TITRE O TITRE H Salmonella TYPHI O H Salmonella Paratyphi Ao Ah Salmonella Paratyphi Bo Bh Salmonella Paratyphi Co Ch Table 2: Different Salmonella Species used for screening test SEROLOGY TITRE TITRE O TITRE H Salmonella Typhi A 1/20 1/160 Salmonella Paratyphi B 1/40 1/80 Salmonella Paratyphi C 1/80 1/320 Salmonella Paratyphi D 1/60 1/40 Table 3: Result of screening test carried out on a given sample. From the result above, it is observed that the samples result which was rated based on the degree of agglutinations observed has a titre value of 1/80 and above. This implies or shows that the sample has the presence of salmonella antibodies in its body system and consequently typhoid fever.