Accuracy of CMV-DNA detection by PCR in amniotic fluid samples according to gestational age

Objectives: To evaluate the efficacy of the polymerase chain reactionin amniotic fluid for the detection of fetal cytomegalovirus and assesswhether it was influenced by the gestational age at the time of theamniocentesis. Methods: The clinical charts of 65 patients referredto a fetal medicine reference center in the city of São Paulo overan 8-year period (1997 to 2004) were analyzed by identificationof maternal serum IgM positive for cytomegalovirus or by fetalultrasound signs suggestive of the infection. Amniocentesis wascarried out to determine the PCR specific for viral DNA detection.Results of this test and of ultrasound monitoring were confrontedwith the immediate perinatal result, and viral cultures in newbornurine were performed using human fibroblasts, the gold standard fordiagnosis of congenital infection. Results: With no restriction as togestational age at the time of amniocentesis, results showed 30.8%sensitivity, 100.0% sensitivity, 100.0% positive predictive value, and68.4% negative predictive value. There was a statistically significantdifference between the negative result (median of 16 weeks) versuspositive result (median of 18 weeks) groups, p value = 0.016.Considering the tests carried out as of the 21st week of gestation,the test shows the following performance: 87.5% sensitivity, 100.0%specificity, 100.0% positive predictive value, 75% negative predictivevalue. Conclusion: The efficacy of amniotic fluid PCR is influencedby the gestational age at the time of the amniocentesis, and shouldbe performed only after 21 weeks of gestation