Biochemical screening of fetal aneuploidies and neural tube defects by "double-test" in Croatia: a 10 years' experience.

The aim of the study is to investigate the efficiency of the second-trimester biochemical screening, with maternal serum alpha-fetoprotein (MS-AFP) and free beta-subunit of human chorionic gonadotropin (free beta-hCG), during the ten-year period. The study included 11,292 of pregnant women between the 15th and 18th gestational week, who underwent screening from November 1996 to December 2006. The risk for trisomy 21 and trisomy 18 were calculated by computer software, based on a model which generated the final risk for fetal aneuploidies from the pregnant woman's a priori age risk and the likelihood ratio of the distribution of the biochemical markers, according to the second-trimester gestation. With the cut-off value of the final risk > or = 1:250, the detection rate for trisomy 21 was 75% (21/28). In women less than or equal to 35, the detection was 57.1% (8/14) and 92.9% (13/14) in those over 35 years, respectively. The detection rate of trisomy 18 was 50% (2/4). The results confirmed that the implementation of double-test, as non-invasive screening for fetal aneuploidies, should be accepted as a complementary method of antenatal care.

Pallister Killian syndrome: unusual significant postnatal overgrowth in a girl with otherwise typical presentation.

Pallister Killian syndrome (PKS) is a rare genetic disorder caused by tetrasomy of the short arm of chromosome 12, revealed usually in mosaic distribution of an extra i (12) (p10) chromosome in fibroblasts. The syndrome presents with a recognizable pattern of findings including pigmentary skin changes, coarse face, high forehead, sparse anterior scalp hair, hypertelorism, seizures and progressive psychomotor developmental delay. It was first described independently by Pallister in 1977 and by Killian and Teschler-Nikola in 1981. We report a case of 21 month old girl with PKS and significant overgrowth. Cytogenetic analysis was performed using the GTG banding technique. The karyotype of cultured lymphocytes was normal. The karyotype from skin fibroblasts was established as mosaic tetrasomy of 12p 47,XX,+i (12) (p10)/46,XX. The origin of the extra marker chromosome was determinated by fluorescence in situ hybridization with chromosome 12 specific DNA probes confirming that supernumerary marker is chromosome i (12p) in 68% of cells. Despite the excessive postnatal growth we found low serum growth hormone levels and reduced response to pharmacological stimulation test. This is also the first report of a postnatal patient in our country.

Rapid prenatal diagnosis of numerical aberrations of chromosome 21 and 18 by PCR-STR method.

In this study we reported the results for the first time of applying Polymerase Chain Reaction-Short Tandem Repeats (PCR-STR) method in the field of detection of aneuploidies for chromosomes 21 and 18 in Croatians. The aims of the study were: (I) validation of the diagnostic informativeness of 6 STR loci (D18S51, D18S858, D18S535, D21S1435, D21S1411, and D21S1414) in sample of 205 unrelated healthy individuals; (II) evaluation of diagnostic power of the PCR-STR method for those 6 microsatellites; (III) establishment protocol for use STRs as routine method for rapid prenatal detection of trisomy 21 and 18. DNA samples were amplified by fluorescence-based PCR reaction, subjected to electrophoresis in automated laser fluorescence DNA sequencer (ALFexpress). Results of our study were: (I) all 6 tested loci are informative (68-85% of heterozygous individuals); (II) comparison between PCR-STR method and conventional cytogenetics did not revealed any false positive or false negative results; (III) in prenatal screening of 105 samples of uncultured amniotic fluid 6 (5.7%) samples with chromosomal abnormalities were identified.

[Screening for Down syndrome using triple marker testing in the second trimester of pregnancy]. / Probir Downova sindroma trostrukim testom u drugom tromjesecju trudnoce.

The aim of this study was to check the validity of the biochemical screening of pregnancies with Down's syndrome during the second trimester of pregnancy, in order to reduce the incidence of invasive diagnostic procedures. We used the optimal balance between sensitivity and specificity to determine the "cut off" values to estimate the results of the biochemical screening. Between January 1995 and December 2000, 2000 pregnancies were checked by double (determining hCG and AFP serum levels) and triple test, (determining hCG, AFP and uE3 serum levels). Competitive radioimmunochemical procedures (2nd trimester Amerlax-M, Ortho Clinical Diagnostics, USA) were used. The risk of Down's syndrome was calculated by Prenata program (Ortho Clinical Diagnostics, USA). The "cut off" median MoM values in pregnancies with Down's syndrome were 0.73 (AFP); 2.02 (hCG) and 0.74 (nE3). The calculated risk was compared with possibility 1:300 to estimate the results of biochemical screening. Our results were checked in the cytogenetic laboratory where samples of amniotic fluid, that we also took, were sent. We observed lower AFP levels (0.96 +/- 0.09 MoM), uE3 levels (0.65 +/- 0.1 MoM) and higher levels of hCG (1.57 +/- 0.27 MoM) in pregnancies with Down's syndrome, in comparison with euploid pregnancies of the corresponding gestational age. With 1:200 risk, the sensitivity of triple test is 80%, with acceptable number of false-positive results. This cut-off value showed to be acceptable for separating positive from negative results. Invasive procedures should be performed in pregnancies with positive screening result, with the aim of getting the tissue sample of the fetus for further cytogenetic analysis.