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Biochemical analysis of cultured chorionic villi for the prenatal diagnosis of peroxisomal disorders: biochemical thresholds and molecular sensitivity for maternal cell contamination detection
  1. S Steinberg1,
  2. S Katsanis2,
  3. A Moser1,
  4. G Cutting2
  1. 1Kennedy Krieger Institute and Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
  2. 2Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
  1. Correspondence to:
 Dr S J Steinberg
 Room 500H, The Kennedy Krieger Institute, 707 N Broadway, Baltimore, MD 21205;


Objectives: The prenatal diagnosis of peroxisomal disorders is most often performed by biochemical analysis of cultured chorionic villus sample (CVS) or amniocytes. We aimed to (a) highlight the risk of maternal cell contamination (MCC) in biochemical prenatal diagnosis, (b) establish the threshold of these biochemical assays to MCC, and (c) document the sensitivity of PCR based genotyping of microsatellites for the detection of MCC in prenatal diagnosis of inborn errors by biochemical analysis.

Methods: The threshold of each biochemical assay was assessed by co-cultivating fibroblasts from known affected and normal individuals. Genotypes for three polymorphic loci were determined by PCR and GeneScan analysis. The sensitivity of the molecular test was determined by DNA mixing experiments and isolation of DNA from co-cultivated fibroblasts.

Results: MCC was detected in 2.5% of at risk CVS cultures (n = 79). Co-cultivation of defective and normal fibroblasts demonstrated that the peroxisomal biochemical assays were accurate at 25% contamination. Very low level DNA or cell contamination (1–5%) was detectable by genotyping, but an allele did not yield a definitive peak based on morphology until ∼10% contamination. Furthermore, we demonstrated that other inborn errors of metabolism might be more susceptible to diagnostic error by low level MCC.

Conclusion: The sensitivity of the microsatellite analysis (⩾10%) is well within the threshold of peroxisomal biochemical assays. Although peroxisomal biochemical assays would not be predicted to introduce a false positive or negative result if MCC <10% were present but not recognised by molecular analysis, the same may not be true for other inborn errors of metabolism.

  • CVS, chorionic villus sample
  • MCC, maternal cell contamination
  • X-ALD, X linked adrenoleukodystrophy
  • PBD, peroxisomal biogenesis disorders (PBD)
  • RCDP, rhizomelic chondrodysplasia punctata
  • VLCA, very long chain fatty acid
  • Krabbe disease
  • maternal cell contamination
  • peroxisome biogenesis disorder
  • prenatal diagnosis
  • X linked adrenoleukodystrophy

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  • * A Moser has observed acquired plasmalogen biosynthetic activity in deficient amniocytes infected with fungus.

  • A Moser has documented significant MCC in amniocytes derived from fluid containing a tissue plug.

  • Competing interests: none declared