False negative NIPT results: Risk figures for chromosomes 13,18 and 21 based on chorionic villi results in 5967 cases and literature review

Non-invasive prenatal testing (NIPT) demonstrated a small chance for a false negative result. Since the "fetal" DNA in maternal blood originates from the cytotrophoblast of chorionic villi (CV), some false negative results will have a biological origin. Based on our experience with cytogenetic studies of CV, we tried to estimate this risk. 5967 CV samples of pregnancies at high risk for common aneuplodies were cytogenetically investigated in our centre between January 2000 and December 2011. All cases of fetal trisomy 13,18 and 21 were retrospectively studied for the presence of a normal karyotype or mosaicism < 30% in short-term cultured (STC-) villi. 404 cases of trisomies 13,18 and 21 were found amongst 5967 samples (6,8%). Of these 404 cases, 14 (3,7%) had a normal or low mosaic karyotype in STC-villi and therefore would potentially be missed with NIPT. It involved 2% (5/242) of all trisomy 21 cases and 7.3% (9/123) of all trisomy 18 cases. In 1:426 (14/5967) NIPT samples of patients at high risk for common aneuploidies, a trisomy 18 or 21 will potentially be missed due to the biological phenomenon of absence of the chromosome aberration in the cytotrophoblast

The posterior parahippocampal gyrus is preferentially affected in age-related memory decline.

Atrophy in the medial temporal lobe is generally considered to be highly associated with age-related memory decline. Volume loss in the hippocampus and entorhinal cortex has extensively been investigated, but the posterior parts of the parahippocampal gyrus have received little attention. The present MRI study investigated whether volume differences in medial temporal lobe areas are differentially related to age-related memory decline. Thirty-nine subjects from a longitudinal study on cognitive aging (the Maastricht Aging Study) have been examined: 20 participants (mean age = 67 years, range 52-80) with memory decline over a period of 12 years were matched to 19 participants without memory decline. Manual tracing was performed on 3. T MR images to measure the volumes of the anterior, middle and posterior parts of the hippocampus and parahippocampal gyrus. A robust group difference and a significant association with memory decline were observed only in the posterior part of the parahippocampal gyrus. Our results may suggest that the posterior parahippocampal gyrus plays a key role in age-related memory decline. © 2009 Elsevier Inc