Clinical Predictive Value of Real-Time PCR Quantification of Human Cytomegalovirus DNA in Amniotic Fluid Samples

Abstract

The aim of this study was to evaluate the diagnostic reliability and prognostic significance of the quantification of cytomegalovirus (CMV) DNA in amniotic fluid (AF). We retrospectively reviewed the results for 282 amniotic fluid samples that had been tested for CMV by a quantitative real-time PCR. We observed three cases in which no CMV genomes were detected in the AF but in which the children were nevertheless congenitally infected. Hence, we conclude that a negative result by PCR for CMV in AF cannot rule out the possibility of congenital infection. No false-positive PCR results were observed. A correlation between the CMV viral load in AF and the fetal and neonatal outcomes could not be demonstrated in our study. Instead, a correlation was found between the CMV viral load and the gestational age at the time of amniocentesis.Human cytomegalovirus (CMV) is the leading cause of congenital viral infection in developed countries, with the reported incidence varying between 0.2 and 2.2% of all live births (15,35). The transmission rate following primary infection of the mother is about 40%. Only 10 to 15% of the CMV-infected children are symptomatic at birth, and the symptoms range from mild to life-threatening disease. The remaining 85 to 90% of the children are asymptomatic at birth, but 10% of them will develop complications later on, mainly neurodevelopmental defects and sensorineural hearing loss. Among pregnant women with recurrent infection, the rate of transmission to the infant is about 1%. Despite a preexisting immunity in the mother, epidemiological data suggest that the frequency and the severity of symptoms might be in the same range as those for a primary CMV infection (11,12).The issue of whether pregnant women should be screened for CMV during pregnancy has been debated for many years, but no consensus has been agreed upon (6). None of the current international guidelines recommend routine serologic screening of pregnant women (1,7,16,23,26). Indeed, there is no prognostic marker in the mother to predict whether the virus will be transmitted to the fetus (32). To obtain more information, invasive prenatal diagnostic techniques, such as amniocentesis or cordocentesis, have been used. Moreover, CMV infection of the fetus can lead to a great variety of clinical and biological conditions, but there is no reliable marker that can be used to predict which infected fetuses will have serious sequelae (32, 33). Finally, no vaccine or prophylactic therapy is available at present (24, 32). Nigro et al. examined whether CMV-specific hyperimmune globulin therapy could be useful for the prevention and treatment of congenital CMV infection, yet the results of the study did not allow any conclusions to be drawn (28). Despite the drawbacks of the diagnosis and treatment of a congenital CMV infection, gynecologists do screen their patients for CMV (18). Supporters of routine prenatal screening argue that the use of precautionary hygienic measures can be suggested to CMV-seronegative pregnant women. Otherwise, the k...

The “Silent” Global Burden of Congenital Cytomegalovirus

“…Several studies suggest that low AF virus loads can provide reassurance for lower risks of both symptomatic infection and longterm sequelae (42,140,143,155,156). Although an association between high AF virus loads and symptomatic infection at birth has been documented in some studies (42,140,155), other studies have failed to show such an association (146,157,158). Virus load was also found to correlate with gestational age (146,157).…”

“…Although an association between high AF virus loads and symptomatic infection at birth has been documented in some studies (42,140,155), other studies have failed to show such an association (146,157,158). Virus load was also found to correlate with gestational age (146,157). It is important to bear in mind that in the absence of international PCR quantification standard, the different assays deployed in these studies would have suffered from substantial inter-and intralaboratory variations, making the use of predictive cutoff values less generalizable.…”

“…On the other hand, when both tests are negative, fetal infection can be ruled out with a high degree of certainty (negative predictive value, Ͼ94%) (42). Falsenegative culture and PCR results have occasionally been reported and may be a result of delayed transmission of CMV to the fetus (69,146,147). Invasive prenatal testing may also be justified in nonprimary infections when sonographic findings suggest in utero CMV abnormalities (77).…”

Management of Pregnancies with Confirmed Cytomegalovirus Fetal Infection

“…At least four studies [13,92,93,94] have compared viral load levels in AF between groups of symptomatic and asymptomatic fetuses. The median viral loads in these studies were higher in the AF of symptomatic fetuses than in the AF of asymptomatic fetuses; however, this difference reached statistical significance in only one study [92].…”

CMV Infection and Pregnancy

“…A large amount of virus as measured by PCR in the amniotic fluid is most likely related to gestational age and should not be used as an independent predictor of a poor fetal outcome [20]. If both CMV culture and PCR are negative, then fetal infection can be ruled out with a high degree of certainty.…”