Retrospective diagnostics of congenital cytomegalovirus infection performed by polymerase chain reaction in blood stored on filter paper.

Capillary blood samples from 63 infants collected 3-7 days after birth, and thereafter stored on filter papers for 12-18 y, were tested for the presence of CMV DNA by the polymerase chain reaction (PCR) method. Of 16 infants with proven congenital CMV infection (positive virus isolation test in urine sampled within 1 week of age), 13 (81%) had a positive CMV PCR test and 3 (19%) a negative PCR test. All blood samples from 16 control infants without congenital CMV infection (negative virus isolation test in urine sampled within 1 week of age) were CMV PCR-negative. When 31 samples on filter papers stored above or below the samples of the infected infants were tested, 6 (19%) had a weak reactivity. This suggests that CMV DNA can be transferred from one filter paper to another during storage. We conclude that PCR performed on dried blood stored on filter paper is a useful method in the retrospective diagnostics of congenital CMV infection. Consideration must be given, however, to the possibility of transfer of CMV DNA from blood samples stored nearby.