DIAGNOSIS OF CONGENITAL TOXOPLASMA-GONDII INFECTION BY POLYMERASE-CHAIN-REACTION (PCR) ON AMNIOTIC-FLUID SAMPLES - THE NORWEGIAN EXPERIENCE

As part of a screening project for detection of Toxoplasma gondii infe ction among pregnant women in Norway, nested polymerase chain reaction (PCR) aimed at the detection of T. gondii in amniotic fluid samples w as included in the diagnostic routine. The results were compared with the routine criteria for congenital infection: i) T. gondii detected i n amniotic fluid or cord blood by mouse inoculation, ii) specific IgM or IgA in serum collected after birth, and/or iii) specific IgG persis ting beyond one year of age. The PC-R was based on the BI gene with an internal control gene amplified together with the BI gene. One hundre d and two amniotic fluid samples collected during pregnancy and/or at delivery from 67 pregnant women with serological evidence of primary T . gondii infection were available for examination by both BI-PCR and m ouse inoculation. Six samples were positive and 86 samples were negati ve by both methods (90% concordance). One sample was mouse inoculation positive and BI-PCR negative while nine samples were BI-PCR positive and mouse inoculation negative, of which five were associated with fou r infants without proven infection. 59% and 41% of samples associated with infected infants were positive by BI-PCR and mouse inoculation, r espectively. The difference was mainly due to a lower detection rate b y mouse inoculation after antiparasitic treatment. The specificity of BI-PCR was 94%. Even though BI-PCR performed on amniotic fluid samples did not detect all infected infants, it represented a valuable tool i n addition to conventional methods in the diagnosis of congenital T. g ondii infection.