Urine tests for Down's syndrome screening

Area of Science:

• Genetics and Prenatal Diagnostics
• Biochemical Markers in Pregnancy
• Maternal Serum Screening

Background:

• Down's syndrome, caused by trisomy 21, is the most common cause of congenital intellectual disability, associated with various health issues.
• Pregnancy risk for Down's syndrome increases with maternal age; non-invasive screening aids in decision-making for definitive testing.
• Informed consent is crucial, requiring parents to understand screening risks, benefits, and implications of false positives/negatives.

Purpose of the Study:

• To assess and compare the diagnostic accuracy of first and second-trimester maternal urine markers for Down's syndrome detection.
• To evaluate the effectiveness of various marker combinations and the influence of maternal age on screening performance.

Main Methods:

• A comprehensive literature search identified 19 studies (18,013 pregnancies) evaluating maternal urine tests up to 24 weeks gestation.
• Meta-analysis using hierarchical summary ROC curves assessed test performance, including sensitivity and false positive rates.
• Quality assessment (QUADAS criteria) and subgroup analyses (maternal age impact) were performed.

Main Results:

• Nineteen studies evaluated 24 test combinations using markers like alpha-fetoprotein, hCG, estriol, and beta-core fragment, with or without maternal age.
• The double marker test (second-trimester beta-core fragment and estriol with maternal age) showed significantly better diagnostic accuracy than single marker tests.
• Specifically, at a 5% false positive rate, this double marker test achieved 73% sensitivity, compared to 56% for beta-core fragment and maternal age alone.

Conclusions:

• Second-trimester urine marker tests combining beta-core fragment and estriol with maternal age demonstrate improved sensitivity for Down's syndrome detection.
• However, the evidence base is limited, with few studies directly comparing these combinations.
• Further research is needed to support the routine clinical use of urine testing for Down's syndrome screening, especially when alternative methods are available.