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  • Writer's pictureMayta

VDRL titer cut off

Updated: Jan 23

ไม่มีโว้ย บวกคือบวก ยิ่งเลขมากแสดงละลายจางก็ยังบวก 1:16 false คือมี เชื้อน้อยละ เลยเปลี่ยนจาก +ve เป็น -ve

Several steps can be taken to test the VDRL titer cut-off value.

  1. Obtain a sample of serum or plasma from the patient.

  2. Dilute the sample with saline to create a series of dilutions ranging from 1:1 to 1:64. In high titer, if it is positive, it has a lot of bacteria.

  3. Perform the VDRL test on each dilution according to the manufacturer's instructions.

  4. Read the results and record the highest dilution that gives a positive reaction.

  5. Calculate the VDRL titer by multiplying the highest dilution, giving a positive reaction by the reciprocal of the dilution factor (e.g., if the highest dilution giving a positive reaction is 1:16, the VDRL titer is 16).

  6. Compare the VDRL titer to the cut-off value of 1. If the titer is greater than 1, the result is considered positive for syphilis.

  7. Repeat the test to confirm the results.

It is important to note that the VDRL test is not specific for syphilis and can produce false positive results in certain conditions such as pregnancy, autoimmune diseases, and some infections. Therefore, positive results should be confirmed with a more specific test such as the Treponemal test.

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