Question:medium
Consider the following serological tests:
1. Treponema Pallidum Immobilization Test (TPI)
2. T. Pallidum Haemagglutination Assay (TPHA)
3. Fluorescent Treponemal Antibody Absorbed Test (FTA-ABS)
4. Venereal Disease Research Laboratory Test (VDRL)
Which of these are specific for diagnosing syphilis?
Consider the following serological tests:
1. Treponema Pallidum Immobilization Test (TPI)
2. T. Pallidum Haemagglutination Assay (TPHA)
3. Fluorescent Treponemal Antibody Absorbed Test (FTA-ABS)
4. Venereal Disease Research Laboratory Test (VDRL)
Which of these are specific for diagnosing syphilis?
1. Treponema Pallidum Immobilization Test (TPI)
2. T. Pallidum Haemagglutination Assay (TPHA)
3. Fluorescent Treponemal Antibody Absorbed Test (FTA-ABS)
4. Venereal Disease Research Laboratory Test (VDRL)
Which of these are specific for diagnosing syphilis?
Show Hint
VDRL is a screening test, not a treponemal-specific one.
Updated On: Jul 7, 2026
- 1 only
- 2 and 4
- 3 and 4
- 1, 2 and 3
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question:
We are given four serology tests used around syphilis and must sort out which ones are truly specific for the organism Treponema pallidum.
Step 2: Key Formula or Approach:
Syphilis tests fall into two groups: treponemal tests, which use antigens from the organism itself and are specific, and non treponemal tests, which use a non specific lipid antigen (cardiolipin) and are mainly used for screening.
Step 3: Detailed Explanation:
The Treponema Pallidum Immobilization test uses live organisms and patient antibodies to see if the organism is immobilized, so it directly targets Treponema pallidum and is specific. The T. Pallidum Haemagglutination Assay detects antibodies against Treponema pallidum antigens on red cells coated with the organism's material, again specific. The Fluorescent Treponemal Antibody Absorbed test uses a fluorescently tagged anti-human antibody against serum that has already reacted with Treponema pallidum antigen, and is both highly sensitive and specific. The VDRL test, by contrast, measures antibodies against cardiolipin, a substance released from damaged tissue and the organism, and this is not unique to syphilis, which is why VDRL can be falsely positive in other conditions and is used as a screening tool rather than a specific confirmatory test.
Step 4: Final Answer:
TPI, TPHA and FTA-ABS are specific for syphilis, matching option (D), 1, 2 and 3.
We are given four serology tests used around syphilis and must sort out which ones are truly specific for the organism Treponema pallidum.
Step 2: Key Formula or Approach:
Syphilis tests fall into two groups: treponemal tests, which use antigens from the organism itself and are specific, and non treponemal tests, which use a non specific lipid antigen (cardiolipin) and are mainly used for screening.
Step 3: Detailed Explanation:
The Treponema Pallidum Immobilization test uses live organisms and patient antibodies to see if the organism is immobilized, so it directly targets Treponema pallidum and is specific. The T. Pallidum Haemagglutination Assay detects antibodies against Treponema pallidum antigens on red cells coated with the organism's material, again specific. The Fluorescent Treponemal Antibody Absorbed test uses a fluorescently tagged anti-human antibody against serum that has already reacted with Treponema pallidum antigen, and is both highly sensitive and specific. The VDRL test, by contrast, measures antibodies against cardiolipin, a substance released from damaged tissue and the organism, and this is not unique to syphilis, which is why VDRL can be falsely positive in other conditions and is used as a screening tool rather than a specific confirmatory test.
Step 4: Final Answer:
TPI, TPHA and FTA-ABS are specific for syphilis, matching option (D), 1, 2 and 3.
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