Widal Test

Slide Widal
Tube widal

1. WIDAL TEST ANKUR VASHISHTHA

2. HISTORY It was developed by Farnand Widal in 1896. Widal test is one of the oldest and most widley used serological test for diagnosis of enteric fever. Salmonella antibodies start appearing in the serum at the end of first week of fever. A rising titer of antibodies is indicative of enteric fever.

3. Principle It is an agglutination test where H and O antibodies against S.typhi and S. Paratyphi A and B are detected.

4. ANTIGEN USED Four antigen are used. O antigen of S.Typhi (TO) H antigen of S.Typhi (TH) H antigen of S. Paratyphi A (AH) H antigen of S. Paratyphi B (BH)

5. METHODS OF WIDAL TEST Two types as follows:- Slide widal test (Rapid, Screening & Qualitative) Tube widal test (Quantitative)

6. Slide widal test Mix one drop of patient serum & one drop of Ag (O,H,AH,BH) in respective circle on slide. Mix properly & rotate for 1 min. Examine for clump. Put – ve & + ve control also.

7. Result Positive:- Clumps Negative:- No clump.

8. Interpretation of slide widal SERUM VOLUME ( In microlitres ) APPROXIMATE TUBE TEXT TITRE 80µl 1:20 40µl 1:40 20µl 1:80 10µl 1:160 5µl 1:320

9. Tube widal test Following are 4 main steps:- Master dilution Serial Dilution Final dilution Incubation

10. Master dilution Take one tube & prepare 1:10 dilution of serum called master dilution. Add 1800 µl of normal saline + 200 µl of patient serum.

11. Serial Dilution Take 16 test tube & arrange in 4 rows. Add 250 µl Normal saline in each test tube. Add 250 µl master diluted serum in 1 st vertical row only. Do the serial dilution by transferring the 250 µl serum from 1 st to 2 nd vertical row 2 nd to 3 rd , 3 rd to 4 th & from 4 th it will discard. So, dilution in 1 st, 2 nd, 3 rd, & 4 th vertical row is 1:20, 1:40, 1:80, 1:160 respectively.

12. Final dilution Add 250 µl O, H, AH & BH Ag 1 st, 2 nd, 3 rd, & 4 th horizontal row respectively. So, final dilution in 1 st, 2 nd, 3 rd, & 4 th vertical row is 1:40, 1:80, 1:160 and 1:320 respectively. Put positive & negative control also.

13. incubation Test tube are incubated in water bath at 37ºC overnight.(16-18 Hr.) Some authors recommend initial incubation at 50-55ºC for 2 Hr.

14. RESULT O Agglutination :- Disc like clumps at bottom of tube. H Agglutination :- spherical, granular, cotton woolly clumps at the bottom of test tube. Positive ;- Indicating enteric fever. Negative :- No enteric fever.

15. Tube widal test

16. S.NO. Titre ( O/H/AH/BH) INTERPRETATION 1 <40 Negative 2 Any one 40 Kindly repeat the after one weak to see rise in titer 3 O-80 H/AH/BH-40 <40 Could be Early Typhoid/Paratyphoid Fever Kindly repeat the after one weak to see rise in titer 4 O-40/ <40 H/AH/BH-80 Could be past Typhoid/Paratyphoid Fever 5 O-80 Any one 160 Suggestive of Typhoid/Paratyphoid Fever 6 Any one 160 Suggestive of Typhoid/Paratyphoid Fever 7 O-160 Any one H-160 Significant for Typhoid/Paratyphoid Fever 8 Any one 320>320 Significant for Typhoid/Paratyphoid Fever 9 O-80/40/ <40 Multiple H-80/160 Anamnestic Response with non Samonella organisms (Malara, Dengue, Influenza etc.)

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