Abstract
ObjectiveTo establish normative weight-adjusted models for the median levels of first trimester serum biomarkers for trisomy 21 screening in southern Thai women, and to compare these reference levels with Caucasian-specific and northern Thai models.MethodsA cross-sectional study was conducted in 1,150 normal singleton pregnancy women to determine serum pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin (β-hCG) concentrations in women from southern Thailand. The predicted median values were compared with published equations for Caucasians and northern Thai women.ResultsThe best-fitting regression equations for the expected median serum levels of PAPP-A (mIU/L) and free β- hCG (ng/mL) according to maternal weight (Wt in kg) and gestational age (GA in days) were: and Both equations were selected with a statistically significant contribution (p< 0.05). Compared with the Caucasian model, the median values of PAPP-A were higher and the median values of free β-hCG were lower in the southern Thai women. And compared with the northern Thai models, the median values of both biomarkers were lower in southern Thai women.ConclusionThe study has successfully developed maternal-weight- and gestational-age-adjusted median normative models to convert the PAPP-A and free β-hCG levels into their Multiple of Median equivalents in southern Thai women. These models confirmed ethnic differences.
Highlights
The first trimester combined screening test has been proven to be an effective prenatal screening method for trisomy 21, with a high detection rate of 85–95% and a false positive rate of only 5% [1,2,3]
Compared with the Caucasian model, the median values of plasma protein-A (PAPP-A) were higher and the median values of free β-human chorionic gonadotropin (β-hCG) were lower in the southern Thai women
First trimester screening for trisomy 21 in specific ethnicity
Summary
The first trimester combined screening test has been proven to be an effective prenatal screening method for trisomy 21, with a high detection rate of 85–95% and a false positive rate of only 5% [1,2,3]. The method combines maternal age, measurement of fetal nuchal translucency thickness (NT) and serum biochemical markers, which include pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin (β-hCG). The interpretation of these biochemical markers is routinely based on the Caucasian-specific model; several studies observed that the median values of these markers are higher among Asian populations relative to other ethnicities [4, 5]. This study aimed to establish reference ranges for median levels of first trimester serum PAPP-A and free β-hCG in southern Thai women adjusted by maternal weight, and to compare these reference levels with Caucasian- specific and northern Thai models To ensure that screening is effective, population-specific models for median levels of PAPP-A, and free β-hCG should be developed to provide more accurate risk calculations [6, 7].
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