Molecular diagnosis of Down syndrome using quantitative APEX-2 microarrays.

OBJECTIVE: To develop a new rapid and high-throughput microarray-based prenatal diagnostic test for the detection of trisomy 21 (T21). METHODS: The T21 arrayed primer extension-2 (APEX-2) assay discriminates between trisomy and euploid DNA samples by comparing the signal intensities of allelic fractions of heterozygous single nucleotide polymorphisms (SNPs) after APEX reaction. After preliminary validation using DNA samples from Down syndrome patients, we analyzed DNA samples from cultured and uncultured amniocytes and chorionic villus for 90 SNPs with high heterozygosity from the 21(q21.1q22.2) region. Differences in allelic ratios of heterozygous SNPs in normal and T21 individuals were verified by t-test. RESULTS: Analysis of the T21 APEX-2 assay results revealed that 90 SNPs were sufficient for reliable discrimination between T21 and euploid DNA samples (P≤0.05 for one or both strands). Using 134 clinical samples from cultured or uncultured fetal cells, both the sensitivity and the specificity of the assay were 100%. CONCLUSION: Our study provides a proof of principle demonstration of the use of the modified APEX-2 assay as a new, fast and reliable method for prenatal diagnosis of fetal T21.

Out-of-hospital resuscitation in Estonia: a bystander-witnessed sudden cardiac arrest.

OBJECTIVE: To evaluate the results of the first epidemiological study on out-of-hospital resuscitation in Estonia. METHODS: A prospective cohort study of 2108 consecutive standardized reports on out-of-hospital resuscitation attempts from 1 January 1999 to 31 December 2002 was conducted according to the Utstein style. RESULTS: In all, 67.3% (1419/2108) of the cardiac arrests were of presumed cardiac aetiology and 60.2% (854/1419) of them were bystander-witnessed. Of these, the 28% bystander cardiopulmonary resuscitation was initiated, and the first rhythm was recorded as ventricular fibrillation or pulseless ventricular tachycardia in 40% of the cases. In the subgroup of patients with bystander-witnessed cardiac arrest of cardiac origin, 10.7% (91/854) were discharged alive in good cerebral performance categories and 7.7% were alive at the 1-year follow-up. The chances of survival increased if the median response time interval was <6 min, cardiac arrest occurred in a public place, patients received bystander cardiopulmonary resuscitation and had an initial rhythm of ventricular fibrillation or pulseless ventricular tachycardia. The discharge rate was 24% (82/343) in the subgroup of patients who had bystander-witnessed cardiac arrest of cardiac origin and an initial rhythm of ventricular fibrillation or pulseless ventricular tachycardia. In this subgroup, the survival rate was 42.6% (40/94) in Tartu urban area, 16.9% (22/130) in Tallinn urban area and 16.8% (20/119) in other regions of Estonia (mostly urban and suburban areas). CONCLUSION: The results demonstrate that despite the progress in the management of out-of-hospital cardiac arrest in Estonia, only one centre (Tartu) achieves a better survival rate. Further improvements are needed to raise the quality of the Estonian emergency medical services system, especially in rural areas.