Fiducial test

Summary

Guiyang College of Traditional Chinese Medicine Basic Medicine Experimental Teaching Center Website

Operation method

Fiducial test

Principle

The known S. typhi "O" antigen, "H" antigen and S. paratyphi type A and B "H" antigen are mixed with the patient's serum for the test tube quantitative agglutination test to detect the corresponding antibodies in the patient's serum, which is clinically used as a reference basis for the diagnosis of typhoid and paratyphoid fever. It is used as a reference for diagnosing typhoid fever and paratyphoid fever.

Materials and Instruments

Sera to be examined Diagnostic bacterial fluids Distilled water Test tubes Test tube holders Micropipettes Straws Water baths

Move

1. Place small, uniformly sized test tubes in a test tube rack in 4 rows of 8 tubes each, labeled.

2. Add 0.5 ml of saline to all 32 test tubes.

3. Take another test tube, add 1.8 ml of saline and 0.2 ml of the patient's serum, mix thoroughly to obtain 1:10 diluted serum. Add 0.5 ml of this 1:10 diluted serum into the 1st tube of each row and mix thoroughly to obtain 1:20 diluted serum.

4. Double dilution of the patient's serum: respectively, from each row of the first tube to take 0.5 ml of serum added to the row of the second tube, mixing, and then from the second tube to take 0.5 ml of serum added to the third tube, mixing. And so on until 0.5 ml of diluted serum was added to tube 7 of each row, mixed well and then 0.5 ml of serum was aspirated from tube 7 of each row and discarded. Thus, 1:20, 1:40, 1:80, 1:160, 1:320, 1:640, 1:1280 para-dilution of serum was obtained from tubes 1 to 7 of each row. Tube 8 was left without serum and only saline was added as a negative control.

5. Addition of bacterial solution: each row starts from the 8th tube and adds 0.5ml of diagnostic bacterial solution to each tube from back to front.

In the first row, add S. typhi "H" bacterial solution to each tube.

Add S. typhi "O" to each tube in the second row.

The third row of tubes is filled with S. Typhimurium A "H" bacterial solution.

The fourth row of tubes is filled with S. paratyphi type B "H" bacterial solution.

At this time, the serum dilution of each serum tube was increased by a factor of 1, 1:40, 1:80, 1:160, 1:320, 1:640, 1:1,280, 1:2,560, and the total amount of each tube was 1 ml.

Common Problems

Result Determination and Writing

Depending on the strength of the agglutination reaction, the results are indicated by "＋＋＋＋", "+ + + +", "+ + +", "+" and "-", respectively.

1. ＋＋＋＋: complete agglutination, the upper layer of liquid is clear and bright, bacteria completely agglutinate and precipitate at the bottom of the tube.

2. + + + +: most of the agglutination, the upper layer of liquid is basically transparent, most (75%) of the bacteria agglutinate and settle at the bottom of the tube.

3. + + +: moderate agglutination, the upper layer of liquid translucent, the bottom of the tube has obvious agglutination precipitates.

4. +: weak agglutination, the upper layer of liquid is turbid, only a small amount of agglutination sediment at the bottom of the tube.

5. -: non-agglutination, the liquid is milky, the bottom of the tube has obvious agglutination precipitates.

Judgment of serum agglutination potency: first look at the rows of control tubes, in the control tubes do not occur agglutination, watch the test tubes in turn, to the emergence of obvious agglutination phenomenon (+ +) of the highest dilution of the serum as the serum's agglutination potency (antibody potency)

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