Rare autosomal trisomies are not rare and often associated with poor obstetric outcomes. They should be discussed with the clinician to guide management. Pregnancy outcomes varied by chromosome being generally favourable for some (eg, trisomy 7) and poor for others (eg, trisomy 22). In the presence of a RAT, pregnancy-associated plasma protein-A is predictive of placental dysfunction and fetal growth restriction.

A combination of maternal age, NT and maternal serum biochemistry gives a high detection rate for both trisomy 21 and other chromosomal abnormalities. Down syndrome screening using either maternal age alone or age in combination with first trimester biochemistry conferred screen positive rates significantly higher than when combined with NT.

Purpose Anti-Müllerian hormone (AMH) is used as a marker for ovarian reserve. Since 2011, the standard test for AMH has been the Beckman Coulter Generation (Gen) II assay. However, in July 2013, the protocol was revised due to falsely low readings. The aim of this study was to compare AMH levels measured with the original and revised Gen II assay and to establish a fertile female reference range for the revised protocol. Methods Serum AMH levels were measured for 492 natural conception first trimester pregnant women using the original and revised Gen II assay. Results The original protocol significantly underestimated AMH levels compared with the revised protocol (p<0.001), the median being 8.4 and 14.2 pmol/L, respectively. In all samples with detectable AMH levels, the revised protocol yielded a higher concentration compared with the original protocol, the magnitude shift ranging from 3.4 to 283.3 % (median 68.0 %). AMH levels measured with the revised protocol were collated to generate an age-specific reference range, with median levels peaking at 27 years then declining with advancing age. The median AMH concentration for ages 20-24 was 17.3 pmol/L, ages 25-29 was 20.5 pmol/L, ages 30-34 was 17.8 pmol/L, ages 35-39 was 10.8 pmol/L, and ages 40-44 was 6.1 pmol/L. Conclusions Our study demonstrated that the original Gen II assay significantly underestimated AMH levels, suggesting caution is required when interpreting literature and testing results achieved with this assay. We also established the revised Gen II assay reference range for AMH in women with unassisted proven fertility.

False-negative cell-free DNA (cfDNA) screening results involving Down syndrome are rare, but have high clinical impact on patients and their healthcare providers. Understanding the biology behind these results may allow for improved diagnostic follow-up and counseling. In 5 different centers offering cfDNA prenatal screening, 9 false-negative results were documented in 646 confirmed cases of trisomy 21; a false-negative rate of 1.4% (95% CI, 0.7-2.6). False-negative results included 4 cases of classical trisomy 21 and 5 cases with a de novo 21q;21q rearrangement. Two out of five rearrangements had molecular studies and were confirmed as isochromosomes. When combined with reports from the cfDNA screening literature, 8 out of 29 (28%) Down syndrome cases with a false-negative "non-invasive prenatal test" (NIPT) were associated with a 21q;21q rearrangement, compared with 2% reported in live born children with Down syndrome. In our laboratory series, evidence for placental or fetal mosaicism was present in 3 out of 3 true-positive cases involving a 21q;21q rearrangement and was confirmed in one false-negative case where placental material was available for study. Isochromosome 21q rearrangements are thus overrepresented among false-negative cfDNA screening results involving Down syndrome. Postzygotic isochromosome formation leading to placental mosaicism provides a biological cause for the increased prevalence of these rearrangements among false-negative cases. For clinical practice, a low trisomic fraction (z-score or equivalent measure) relative to the fetal fraction suggests placental mosaicism. Care should be taken as these cases may not reflect confined placental mosaicism, but rather full trisomy in the presence of a placenta containing normal cells.

BackgroundThe manual Generation II (Gen II) ELISA method used to measure Anti-Müllerian Hormone (AMH) from Beckman Coulter has recently been superseded by a fully automated AMH immunoassay. The aim of this study was to evaluate the performance of the Access AMH assay and directly compare it to the modified Gen II ELISA method. A secondary aim was to verify that the fertile age-related AMH range previously established using the Gen II ELISA could be used to interpret results from the new automated Access assay.MethodsThe precision, stability, linearity, measurement range and detection limits were determined using recombinant AMH and patient serum samples. Different diluents and their effects on AMH concentration were compared. A correlation study was performed on patient samples to compare the Access AMH assay to the ELISA method on the Access2 and DxI800 analysers. The fertile AMH range was verified by comparing the 10th, 50th and 90th percentile values from both methods obtained from 489 natural conception pregnant women.ResultsThe Access AMH assay showed good performance across the measuring range for both intra-assay (CV 1.41–3.30 %) and inter-assay (CV 3.04–5.76 %) precision and acceptable sample stability. Dilution of the high concentration samples with the recommended diluent resulted in a small but significant downward shift in values. The assay was linear over the range of values recommended by the manufacturer, allowing for accurate reporting within the reported range. The two assay types were highly correlated (R2 = 0.9822 and 0.9832 for Access2 and DxI800, respectively), and the differences observed between the Access2 and DxI800 analysers were within clinically acceptable ranges, indicating that the methods are interchangeable. Furthermore, we demonstrated that results from the published reference range for the Gen II ELISA correlate with those from the automated Access AMH assay.ConclusionHere, we verified the published performance of the Access AMH assay and showed excellent correlation with the Gen II ELISA method. Moreover, we validated this correlation by confirming that the results from a fertile AMH reference range established using the preceding Gen II ELISA are interchangeable with the new automated Access AMH assay.Electronic supplementary materialThe online version of this article (doi:10.1186/s12958-016-0143-3) contains supplementary material, which is available to authorized users.