An asymptomatic infant born at term is suspected to have congenital cytomegalovirus infection when a newborn hearing screen shows unilateral sensorineural loss. Which test result confirms CONGENITAL rather than postnatally acquired CMV infection?
- A CMV IgM positivity at 4 months of age
- B CMV IgG positivity at 3 months of age
- C Detection of CMV by PCR in saliva or urine before 3 weeks of age ✓
- D Rising CMV IgG titers between birth and 6 months
Correct answer: C. Detection of CMV by PCR in saliva or urine before 3 weeks of age
Explanation
Congenital CMV is confirmed by detecting viral DNA by PCR in urine or saliva within the first 3 weeks of life, since after this age positive samples cannot distinguish intrauterine acquisition from acquisition through breast milk or birth canal. CMV IgM is insensitive and unreliable for confirmation. IgG positivity and rising titers merely reflect passively transferred or developing maternal antibody and cannot separate congenital from postnatal infection.
Reference: Red Book: Report of the Committee on Infectious Diseases, American Academy of Pediatrics, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.