THE SENSITIVITY OF ALLELE-SPECIFIC POLYMERASE CHAIN-REACTION CAN OBVIATE CONCERN OF MATERNAL CONTAMINATION WHEN FETAL SAMPLES ARE GENOTYPEDFOR IMMUNE CYTOPENIC DISORDERS

OBJECTIVE: Fetuses at risk for immune cytopenic disorders can be ident ified by molecular genotyping assays. To better understand the impact of maternal contamination on genotyping results, the levels of contami nation that are routinely encountered during prenatal testing of fetal samples and the sensitivity of allele-specific polymerase chain react ion in detecting paternal alloalleles were examined. STUDY DESIGN: Rec onstitution experiments were performed to define the sensitivity of al lele-specific polymerase chain reaction assays. The sensitivities of a llele-specific polymerase chain reactions and polymerase chain reactio n-restriction fragment length polymorphism were compared for detection of the factor V Leiden mutation. RESULTS: A quantitative analysis of variable-number tandem repeat loci revealed maternal contamination in 4 of 56 fetal samples. Contaminating deoxyribonucleic acid compromised genotyping results when it comprised between 94% and 99% of the total deoxyribonucleic acid. Allele-specific polymerase chain reaction was found to be the more sensitive technique (0.8% sensitivity vs 13% sens itivity). CONCLUSION: These results illustrate that allele-specific po lymerase chain reaction is well suited for reliable prenatal identific ation of fetuses at risk of immune cytopenic disorders.