First-trimester biochemical screening for Down syndrome

Maternal serum protein profile and immune response protein subunits as markers for non-invasive prenatal diagnosis of trisomy 21, 18, and 13

OBJECTIVES

To use proteomics to identify and characterize proteins in maternal serum from patients at high-risk for fetal trisomy 21, trisomy 18, and trisomy 13 on the basis of ultrasound and maternal serum triple tests.

METHODS

We performed a comprehensive proteomic analysis on 23 trisomy cases and 85 normal cases during the early second trimester of pregnancy. Protein profiling along with conventional sodium dodecyl sulfate polyacrylamide gel electrophoresis/Tandem mass spectrometry analysis was carried out to characterize proteins associated with each trisomy condition and later validated using Western blot.

RESULTS

Protein profiling approach using surface enhanced laser desorption/ionization time-of-flight mass (SELDI-TOF/MS) spectrometry resulted in the identification of 37 unique hydrophobic proteomic features for three trisomy conditions. Using sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by Matrix Assisted Laser Desorption Ionization - Time of Flight/Time of Flight (MALDI-TOF/TOF) and western blot, glyco proteins such as alpha-1-antitrypsin, apolipoprotein E, apolipoprotein H, and serum carrier protein transthyretin were identified as potential maternal serum markers for fetal trisomy condition. The identified proteins showed differential expression at the subunit level.

CONCLUSIONS

Maternal serum protein profiling using proteomics may allow non-invasive diagnostic testing for the most common trisomies and may complement ultrasound-based methods to more accurately determine pregnancies with fetal aneuploidies.

Proteome analysis of maternal serum samples for trisomy 21 pregnancies using ProteinChip arrays and bioinformatics

A surface-enhanced laser desorption/ionization time of flight (SELDI-TOF)-based ProteinChip System was used as a tool for rapid discovery and identification of protein patterns in serum that discriminate between trisomy 21 and unaffected pregnancies. We analyzed 24 serum samples from women carrying a trisomy 21 pregnancy and 32 with an unaffected pregnancy, ranging from 10.0 to 14.0 weeks of gestation. The resulting protein profiles were submitted to a clustering algorithm, a rule extraction, a rating, and a rule base construction step. For the generated combined rule base, the specificity and sensitivity for the prediction of a trisomy 21 pregnancy reach 97% and 91%, respectively.

Down's syndrome

The sequencing of chromosome 21 and the use of models of Down's syndrome in mice have allowed us to relate genes and sets of genes to the neuropathogenesis of this syndrome, and to better understand its phenotype. Research in prenatal screening and diagnosis aims to find methods to identify fetuses with Down's syndrome, and reduce or eliminate the need for amniocentesis. Other areas of active research and clinical interest include the association of Down's syndrome with coeliac disease and Alzheimer's disease, and improved median age of death. Medical management of the syndrome requires an organised approach of assessment, monitoring, prevention, and vigilance. Improvements in quality of life of individuals with Down's syndrome have resulted from improvements in medical care, identification and treatment of psychiatric disorders (such as depression, disruptive behaviour disorders, and autism), and early educational interventions with support in typical educational settings. Approaches and outcomes differ throughout the world.

Decreased first trimester PAPP-A is a predictor of adverse pregnancy outcome

OBJECTIVE

Low levels of maternal serum pregnancy associated plasma protein-A (PAPP-A) have been linked to chromosome anomalies such as trisomy 21, 13 and 18, triploidy and sex chromosome aneuploidy. Low levels of PAPP-A have also been implicated in spontaneous miscarriage. The purpose of this study was to evaluate whether low levels of first trimester PAPP-A are predictive of other adverse pregnancy outcomes.

STUDY DESIGN

The study included patients with singleton pregnancies who underwent combined first trimester screening using nuchal translucency (NT) and maternal serum free beta-human chorionic gonadotrophin (free beta-hCG) and PAPP-A at 10-13 weeks' gestation. Patients with chromosome aberrations or fetal anomalies were excluded. Serum marker levels were expressed as gestational age-specific multiples of the median (MoMs). The incidences of various adverse pregnancy outcomes (spontaneous preterm labor, fetal growth restriction (FGR), proteinuric and non-proteinuric pregnancy induced hypertension (PIH), intrauterine fetal demise, oligohydramnios, spontaneous miscarriage and placental abruption) were evaluated, according to maternal PAPP-A MoM levels.

RESULTS

Of the 1622 patients in the study, pregnancy complications were observed in 184 (11.3%). Patients with PAPP-A < or =0.25 MoM had significantly higher rates of FGR (RR = 3.12), proteinuric PIH (RR = 6.09), spontaneous miscarriage (RR = 8.76). No statistically significant differences were noted for other adverse outcomes evaluated Women with PAPP-A < or =0.50 MoM also had significantly higher rates of FGR (RR = 3.30) and spontaneous miscarriage (RR = 3.78).

CONCLUSIONS

We conclude that decreased levels of first trimester maternal serum PAPP-A are predictive not only of chromosome anomalies but also of adverse pregnancy outcome.