Downloaded 111 times
More Related Content
Widal Test
- 1.
- 2. HISTORY It wasdeveloped 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 isan agglutination test where H and O antibodies against S.typhi and S. Paratyphi A and B are detected.
- 4. ANTIGEN USED Fourantigen are used. 1. O antigen of S.Typhi (TO) 2. H antigen of S.Typhi (TH) 3. H antigen of S. Paratyphi A (AH) 4. H antigen of S. Paratyphi B (BH)
- 5. METHODS OF WIDALTEST Two types as follows:- 1. Slide widal test (Rapid, Screening & Qualitative) 2. 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 slidewidal 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:- i. Master dilution ii. Serial Dilution iii. Final dilution iv. Incubation
- 10. Master dilution Takeone tube & prepare 1:10 dilution of serum called master dilution. Add 1800 µl of normal saline + 200 µl of patient serum.
- 11. Serial Dilution Take16 test tube & arrange in 4 rows. Add 250 µl Normal saline in each test tube. Add 250 µl master diluted serum in 1st vertical row only. Do the serial dilution by transferring the 250 µl serum from 1st to 2nd vertical row 2nd to 3rd , 3rd to 4th & from 4th it will discard. So, dilution in 1st, 2nd, 3rd, & 4th vertical row is 1:20, 1:40, 1:80, 1:160 respectively.
- 12. Final dilution Add250 µl O, H, AH & BH Ag 1st, 2nd, 3rd, & 4th horizontal row respectively. So, final dilution in 1st, 2nd, 3rd, & 4th vertical row is 1:40, 1:80, 1:160 and 1:320 respectively. Put positive & negative control also.
- 13. incubation Test tubeare 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.
- 17. S.N O. Titre (O/H/AH/BH) INTERPRETATION 1 <40 Negative 2Any 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.)
- 18.
Editor's Notes
- #2 ANKUR VASHISHTHA