Question

Which test is most diagnostic for syphilis? A. Culture B. VDRL C. RPR D. FTA-ABS

Short answer

Answer: The FTA-ABS (Fluorescent Treponemal Antibody Absorption) test is considered the most diagnostic test for syphilis because it is highly sensitive and specific, detecting specific antibodies to Treponema pallidum. This means it is less likely to produce false-positive or false-negative results compared to non-treponemal tests such as VDRL and RPR.

Step-by-step solution

Option A: Culture

Culture is a method used to grow microorganisms in a controlled environment, like a laboratory. However, Treponema pallidum, the bacterium responsible for syphilis, is difficult to culture. Thus, culture is not considered a very diagnostic method for syphilis.

Option B: VDRL

VDRL (Venereal Disease Research Laboratory) is a non-treponemal serological test used to screen for syphilis. It detects antibodies produced in response to the infection, but it can produce false positives and negatives. VDRL is generally not considered the definitive diagnostic test, but it can be helpful in identifying syphilis infection cases.

Option C: RPR

RPR (Rapid Plasma Reagin) is another non-treponemal serological test that detects antibodies to syphilis. Like the VDRL test, it can produce false-positive and false-negative results, making it an imperfect diagnostic tool. RPR is usually used for screening and monitoring treatment rather than definitive diagnosis.

Option D: FTA-ABS

FTA-ABS (Fluorescent Treponemal Antibody Absorption) is a treponemal test that detects specific antibodies to Treponema pallidum. The FTA-ABS test is highly sensitive and specific, meaning it is less likely to produce false-positive or false-negative results compared to non-treponemal tests. As a result, FTA-ABS is considered more diagnostic than other tests for syphilis, even though it may not be used as a primary screening method. Based on the information above, the most diagnostic test for syphilis is:

Answer

D. FTA-ABS