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Objective To evaluate the efficacy of the quadruple test for potential use as a Thai national policy for Down syndrome (DS) screening and establish an accurate equation for risk estimation of Down syndrome based on gestational age, weight and the ethnic-specific reference range of our population. Methods A prospective study was conducted on singleton pregnancies at 14 to 21 weeks of gestation to evaluate the efficacy of quadruple DS screening using the automatically calculated Western European descent factor (WF) in our population and the impact of screening using a specific Thai ethnic factor as well as to establish an equation for the risk estimation of DS based on gestational age, weight and a local Thai ethnic factor to correct for the impact of ethnic factor on the screening efficacy. Results Of a total of 5,515 women, 12 cases of DS and 8 cases of other aneuploidies were found. The detection rate, false positive rate and specificity were 75.0%, 9.1% and 90.9%, respectively, by automatic calculation with the widely used WF; the screening efficacy was lower when used in Asian populations than in other studies. The best-fitted regression equation of serum quadruple screening of AFP, free β-hCG, uE3 and inhibin A was established by adjustment for gestational age (GA) in days, maternal weight and our Thai-specific ethnic reference range which was created for this study. Calculations with our Thai-specific ethnic model gave a better detection rate of 83.3%, a false positive rate of 9.6% and specificity of 90.4%. Conclusion The serum quadruple test had a lower detection rate than expected when the risk estimation was based on the WF reference range. The serum quadruple test using WF had significantly different levels when corrected with our ethnic-specific factor. Using our local ethnic specific model could increase the detection rate of DS screening in Thailand with a minimal increase in false positive rates. Our findings indicate that DS screening should be adjusted with an appropriate individual ethnic factor when used for national screening.

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Purpose: To compare the reliability of measurements of five fetal facial profile parameters by operators with different levels of experience, at 15 to 23 weeks of gestation in Thai fetuses.Methods: An observational study was conducted. The inferior facial angle, anteroposterior mandibular diameter, mandible width, maxilla width, and mandible length were measured in 123 normal fetuses, using 2D ultrasonography, by three operators with different levels of experience. Each participant was examined by two operators. Each operator performed three independent measurements for each parameter and was blinded to the results of the other. Reliability of measurement was evaluated using intraclass correlation coefficient. Bland-Altman analysis was used to evaluate agreement. Results:The ability to obtain a mandible length measurement was highest (100%) among the five parameters. Intraobserver variabilities of anteroposterior mandibular diameter, mandible width, maxilla width, and mandible length measurements were excellent for all operators (ICC 0.958-0.986), while those of inferior facial angle measurements were moderate to excellent (ICC 0.560-0.923), depending on the operators' experience. Interobserver variabilities varied between pairs of operators; only two parameters, anteroposterior mandibular diameter and mandible length, showed excellent interobserver variabilities (ICC >0.9), with good agreement. Conclusions:The mandible length measurement was the best parameter in terms of feasibility and reliability.

The UCA measurements had a higher intra- and interobserver reliabilities than the CL measurements.