This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Congenital syphilis can be best diagnosed by ? 
Select and explain. 
A. IgM FTA- ABS, B. IgG FTA-ABS, C. VDRL, D. TPI
A: IgM FTA- ABS
Answer: A: IgM FTA- ABS 
Explanation: Ans. is 'a' i.e., IgM FTA-ABS Lab diagnosis of congenital syphils . As Ig M does not cross placenta, its presence in neonatal serum confirms congenital syphilis and helps differentiating it from seropositivity due to passively tranfered maternal antibodies. The tests to detect IgM are: . FTA-ABS (19S IgM FTA-ABS) . Syphilis Capita M test "For measurment of Ig M in neonate in whom congenital syphilis is suspected, the syphilis capita M test and the 19S IgM FTA-ABS test are available". - Note - lr/e Harrison says, "No commercially available IgM test is recommeded for evaluation of infant with suspected congenital syphillis". - 1043