Which of the following does not establish a diagnosis of congenital CMV infection in a neonate?

Active CMV infection is best confirmed by virus isolation from urine, saliva, bronchoalveolar washings, breast milk,cervical secretions,buffy coat,and tissues obtained by biopsy. Rapid identification is possible with PCR.A primary infection is confirmed by seroconversion or simultaneous detection of IgM & IgG antibodies.IgG antibodies persist for life. Reference: Nelson textbook of pediatrics 21st edition Page 1116