Reagents for the determination of biochemical markers in serum, pregnancy-associated plasma protein-A (PAPP-A) and the free β-human chorionic gonadotropin (free β-hCG) must bear the CE mark of approval for testing for Down’s syndrome or trisomy 21 (T21), have proven experience and have calculated median values according to gestational age. The gene discussed is PAPPA; the disease is Down syndrome.