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Both commercial assays can be applied to tampon-collected specimens for automated detection of sexually transmitted diseases. The detection of C trachomatis was similar to the in-house PCR test for both assays (P = 0.73, 0.68). Detection of N gonorrhoeae resulted in fewer positive tampon specimens when tested by ligase chain reaction than both Roche Amplicor and in-house PCR.

Pallister-Killian syndrome (PKS) is a rare but distinctive chromosomal syndrome distinguished by severe intellectual impairment, characteristic facial features, and variable structural anomalies. The characteristic cytogenetic abnormality in PKS is a supernumerary isochromosome 12p that confers mosaic tetrasomy. We describe a female child with PKS in whom tetrasomy 12p resulted from a supernumerary ring chromosome containing two copies of chromosome 12cen --> p13, a novel cytogenetic finding. The ring chromosome exhibited tissue-limited mosaicism, being absent in blood but detected in 38% of buccal mucosa cells and 41% of skin fibroblasts. Our patient demonstrated the typical dysmorphic characteristics of PKS, but her development was relatively advanced in comparison to children with isochromosome PKS. Her milder developmental phenotype may be attributable to differences in the mosaic distribution or the genomic content of the ring chromosome compared to mosaic isochromosome 12p.

Objectives: To evaluate the performance of cell-free DNA (cfDNA) screening for common fetal aneuploidies, choice of prenatal procedure, and chromosome conditions identified during pregnancy after low-risk cfDNA screening.Method: A single-center prenatal cfDNA screening test was employed to detect trisomies 21, 18, and 13 (T21, T18, T13) and sex chromosome aneuploidies (SCAs).Test performance, choice of prenatal procedure, and cytogenetic results in pregnancies with low-risk cfDNA screening were reviewed.Results: CfDNA screening of 38,289 consecutive samples identified 720 (1.9%) pregnancies at increased risk for aneuploidy. Positive predictive values (PPVs) for high-risk singleton pregnancies were 98.5% (T21), 92.5% (T18) and 55.2% (T13).PPVs for SCAs ranged from 30.6% to 95.2%. Most women elected chorionic villus sampling for prenatal diagnosis of T21, T18 and T13; amniocentesis and/or postnatal testing were commonly chosen for SCAs. Cytogenetic tests from 616 screennegative pregnancies identified 64 cases (12.7%) with chromosome conditions not detected by cfDNA screening, including triploidy (n = 30) and pathogenic and likely pathogenic copy number variants (n = 34). A further 15 (0.04%) false-negative common aneuploidy results were identified.Conclusions: CfDNA screening was highly accurate for detecting fetal aneuploidy in this general-risk obstetric population. Fetal ultrasound and prenatal diagnostic testing were important in identifying chromosome conditions in pregnancies screened as low-risk. Key pointsWhat's already known about this topic? � Prenatal cell-free DNA (cfDNA) screening for common autosomal trisomies has high sensitivity and specificity. Fewer data are available for sex chromosome aneuploidies (SCAs), which show greater variability in screening performance.