cfDNA PPV Calculator

This Cell Free Fetal DNA PPV Calculator estimates positive predictive value (PPV) and negative predictive value (NPV) for prenatal cell-free DNA (cfDNA) screening using Bayesian probability. Conditions supported: • Trisomy 21 • Trisomy 18 • Trisomy 13 • Monosomy X (45,X) • 47,XXY • 47,XYY • 47,XXX For autosomal trisomies, pretest probability may be derived from maternal-age population risk tables (midtrimester risk by age at term). For sex chromosome aneuploidies, pretest probability can be entered as population prevalence (1 in N). Sensitivity and specificity are user-editable to reflect lab-specific performance. This app is for screening support and educational use. It does not provide a diagnosis. Positive screening results should be confirmed with diagnostic testing and clinical correlation.