DIAGNOSIS OF CONGENITAL CMV INFECTION BY DETECTION OF VIRAL DNA BY PCR IN DRIED NEWBORN BLOOD SPOTS

Early laboratory diagnosis of congenital CMV infection is useful as it limits the applica¬tion of diagnostic procedures when neurologic or other types of sequelae will appear and allows adequate measures of identifying and correcting impairements to be adopt¬ed. The presence of the virus in the blood of infected babies can be demonstrated by PCR. In this study the CMV genome was sought in dried blood spots (Guthrie cards) collected in the first week of life from 15 babies, 7 symptomatic and 8 asymptomatic at birth, from which CMV was isolated in the first 2 weeks of life. A group of 30 uninfect¬ed babies (no virus isolated at birth) and a further 15 infants with a perinatal CMV in¬fection were taken as controls. The DNA was extracted from the cards by incubation in sterile distilled water, heating at 55 °C for 60 min. and at 100 °C for 7 min. and centri¬fugation at 10.000 rpm for 5 min. (Shibata et al, '94). The supernatant was subjected to nested PCR for the amplification of two regions in the 1E1 and gp58 genes, the amplifi¬ed products were electrophoresed in agarose gel (Barbi et al, 1994). Each sample was tested at least twice in different analytical sessions. Strict control measures were adopt¬ed to avoid carry-overs and contaminations. Thirteen of 15 congenitally infected babies turned positive while all the CMV negative control babies were negative. One of the 15 infants referred as perinatally infected was diagnosed as congenitally infected on the basis of a positive PCR. 100% of positive cases were identified by gp58 PCR and 61% by 1E1 PCR. These results are encouraging in view of the use of this technique in the rou¬tine screening of newborns for congenital CMV infection. Great care must be paid to the correct blood loading of the cards since the negative results obtained in two CMV infected babies might be due to a poor quality of the specimens.