Prenatal screening for trisomy 21: a comparative performance and cost analysis of different screening strategies

Abstract Background Prenatal screening for chromosome aneuploidies have constantly been evolving, especially with the introduction of cell-free fetal DNA (cfDNA) screening in the most recent years. This study compares the performance, costs and timing of test results of three cfDNA screening implementation strategies: contingent, reflex and primary. Methods We modelled enhanced first trimester screening (eFTS) as the first-tier test in contingent or reflex strategies. cfDNA test was performed contingent on or reflex from eFTS results. A comparison was made between cfDNA screening using sequencing technology and Rolling Circle Amplification (RCA)/imaging solution. All model assumptions were based on results from previous publications or information from the Ontario prenatal screening population. Results At an eFTS risk cut-off of ≥1/1000, contingent and reflex cfDNA screening have the same detection rate (DR) (94%) for trisomy 21. Reflex cfDNA screening using RCA/Imaging solution provided the lowest false positive rate and cost. The number of women requiring genetic counselling and diagnostic testing was significantly reduced and women received their cfDNA screening result 9 days sooner compared with the contingent model. While primary cfDNA screening improved the trisomy 21 DR by 3–5%, it was more costly and more women required diagnostic testing. Conclusion Reflex cfDNA screening is the most cost-effective prenatal screening strategy. It can improve the efficiency of prenatal aneuploidy screening by reducing the number of patient visits and providing more timely results

The γ-Crystallins and Human Cataracts: A Puzzle Made Clearer

Despite the fact that cataracts constitute the leading cause of blindness worldwide, the mechanisms of lens opacification remain unclear. We recently mapped the aculeiform cataract to the γ-crystallin locus (CRYG) on chromosome 2q33-35, and mutational analysis of the CRYG-genes cluster identified the aculeiform-cataract mutation in exon 2 of γ-crystallin D (CRYGD). This mutation occurred in a highly conserved amino acid and could be associated with an impaired folding of CRYGD. During our study, we observed that the previously reported Coppock-like–cataract mutation, the first human cataract mutation, in the pseudogene CRYGE represented a polymorphism seen in 23% of our control population. Further analysis of the original Coppock-like–cataract family identified a missense mutation in a highly conserved segment of exon 2 of CRYGC. These mutations were not seen in a large control population. There is no direct evidence, to date, that up-regulation of a pseudogene causes cataracts. To our knowledge, these findings are the first evidence of an involvement of CRYGC and support the role of CRYGD in human cataract formation

Digenic Inheritance of Early-Onset Glaucoma: CYP1B1, a Potential Modifier Gene

“Early-onset glaucoma” refers to genetically heterogeneous conditions for which glaucoma manifests at age 5–40 years and for which only a small subset is molecularly characterized. We studied the role of MYOC, CYP1B1, and PITX2 in a population (n=60) affected with juvenile or early-onset glaucoma from the greater Toronto area. By a combination of single-strand conformation polymorphism and direct cycle sequencing, MYOC mutations were detected in 8 (13.3%) of the 60 individuals, CYP1B1 mutations were detected in 3 (5%) of the 60 individuals, and no PITX2 mutations were detected. The range of phenotypic expression associated with MYOC and CYP1B1 mutations was greater than expected. MYOC mutations included cases of juvenile glaucoma with or without pigmentary glaucoma and mixed-mechanism glaucoma. CYP1B1 mutations involved cases of juvenile open-angle glaucoma, as well as cases of congenital glaucoma. The study of a family with autosomal dominant glaucoma showed the segregation of both MYOC and CYP1B1 mutations with disease; however, in this family, the mean age at onset of carriers of the MYOC mutation alone was 51 years (range 48–64 years), whereas carriers of both the MYOC and CYP1B1 mutations had an average age at onset of 27 years (range 23–38 years) (P=.001). This work emphasizes the genetic heterogeneity of juvenile glaucoma and suggests, for the first time, that (1) congenital glaucoma and juvenile glaucoma are allelic variants and (2) the spectrum of expression of MYOC and CYP1B1 mutations is greater than expected. We also propose that CYP1B1 may act as a modifier of MYOC expression and that these two genes may interact through a common pathway

A Progressive Autosomal Recessive Cataract Locus Maps to Chromosome 9q13-q22

Cataracts are the leading cause of blindness in most countries. Although most hereditary cases appear to follow an autosomal dominant pattern of inheritance, autosomal recessive inheritance has been clearly documented and is probably underrecognized. We studied a large family—from a relatively isolated geographic region—whose members were affected by autosomal recessive adult-onset pulverulent cataracts. We mapped the disease locus to a 14-cM interval at a novel disease locus, 9q13-q22 (between markers D9S1123 and D9S257), with a LOD score of 4.7. The study of this progressive and age-related cataract phenotype may provide insight into the cause of the more common sporadic form of age-related cataracts

Modified multiple marker aneuploidy screening as a primary screening test for preeclampsia

Abstract Background Abnormal levels of maternal biochemical markers used in multiple marker aneuploidy screening have been associated with adverse pregnancy outcomes. This study aims to assess if a combination of maternal characteristics and biochemical markers in the first and second trimesters can be used to screen for preeclampsia (PE). The secondary aim was to assess this combination in identifying pregnancies at risk for gestational hypertension and preterm birth. Methods This case-control study used information on maternal characteristics and residual blood samples from pregnant women who have undergone multiple marker aneuploidy screening. The median multiple of the median (MoM) of first and second trimester biochemical markers in cases (women with PE, gestational hypertension and preterm birth) and controls were compared. Biochemical markers included pregnancy-associated plasma protein A (PAPP-A), placental growth factor (PlGF), human chorionic gonadotropin (hCG), alpha feto-protein (AFP), unconjugated estriol (uE3) and Inhibin A. Logistic regression analysis was used to estimate screening performance using different marker combinations. Screening performance was defined as detection rate (DR) and false positive rate (FPR). Preterm and early-onset preeclampsia PE were defined as women with PE who delivered at < 37 and < 34 weeks of gestation, respectively. Results There were 147 pregnancies with PE (81 term, 49 preterm and 17 early-onset), 295 with gestational hypertension, and 166 preterm birth. Compared to controls, PE cases had significantly lower median MoM of PAPP-A (0.77 vs 1.10, p < 0.0001), PlGF (0.76 vs 1.01, p < 0.0001) and free-β hCG (0.81 vs. 0.98, p < 0.001) in the first trimester along with PAPP-A (0.82 vs 0.99, p < 0.01) and PlGF (0.75 vs 1.02, p < 0.0001) in the second trimester. The lowest first trimester PAPP-A, PlGF and free β-hCG were seen in those with preterm and early-onset PE. At a 20% FPR, 67% of preterm and 76% of early-onset PE cases can be predicted using a combination of maternal characteristics with PAPP-A and PlGF in the first trimester. The corresponding DR was 58% for gestational hypertension and 36% for preterm birth cases. Conclusions Maternal characteristics with first trimester PAPP-A and PlGF measured for aneuploidy screening provided reasonable accuracy in identifying women at risk of developing early onset PE, allowing triage of high-risk women for further investigation and risk-reducing therapy. This combination was less accurate in predicting women who have gestational hypertension or preterm birth

Prenatal screening for preeclampsia: the roles of placental growth factor and pregnancy–associated plasma protein A in the first trimester and placental growth factor and soluble fms-like tyrosine kinase 1–placental growth factor ratio in the early second trimesterAJOG Global Reports at a Glance

BACKGROUND: Professional societies have recommended universal first trimester screening for preeclampsia and a second or third trimester soluble fms-like tyrosine kinase-1–placental growth factor ratio test to assess for preeclampsia and its severity. However, it may not be feasible to implement the most optimal screening protocol for preeclampsia in the first trimester which uses a combination of maternal characteristics, maternal biophysical and biochemical markers due to limitations in the access to uterine artery doppler ultrasound. There are inconsistent findings on how early in the second trimester the fms-like tyrosine kinase-1–placental growth factor ratio begins to provide useful information in preeclampsia prediction. OBJECTIVE: This study aimed to assess the accuracy of (1) a combination of maternal characteristics, maternal serum pregnancy-associated plasma protein A, and placental growth factor in the screening for preeclampsia in the first trimester; and (2) placental growth factor or soluble fms-like tyrosine kinase-1–placental growth factor ratio in the prediction of preeclampsia in the early second trimester. STUDY DESIGN: This retrospective case–control study used frozen residual blood samples from women who had aneuploidy screening and delivered at a tertiary center. The case group included pregnancies with gestational hypertension or preeclampsia (further classified as early-onset [birth at <34 weeks’ gestation] and preterm preeclampsia [birth at <37 weeks’ gestation]). Each case was matched with 3 control pregnancies by date of blood sample draw, gestational age at first blood sample draw, maternal age, maternal ethnicity, type of multiple-marker screening, and amount of residual sample. Mann–Whitney U tests were used to assess the associations between serum markers and the risk of preeclampsia. Logistic regressions were used to assess if the risk of preeclampsia can be predicted using a combination of maternal characteristics and serum markers. RESULTS: The case group included 146 preeclampsia and 295 gestational hypertension cases. Compared with the controls, preeclampsia cases had significantly lower first-trimester pregnancy-associated plasma protein A and placental growth factor. At a 20% false-positive rate, 71% of early-onset and 58% of preterm preeclampsia cases can be predicted using maternal characteristics, pregnancy-associated plasma protein A, and placental growth factor. Preeclampsia cases had lower second-trimester placental growth factor and a higher soluble fms-like tyrosine kinase-1–placental growth factor ratio. At a 10% false-positive rate, 80% and 53% of early-onset preeclampsia can be predicted using maternal characteristics and placental growth factor or soluble fms-like tyrosine kinase-1–placental growth factor ratio, respectively. CONCLUSION: The current first-trimester aneuploidy screening programs may be expanded to identify women at increased risk of developing preeclampsia. Early in the second trimester, placental growth factor alone provided better prediction for preeclampsia compared with the soluble fms-like tyrosine kinase-1–placental growth factor ratio