PAPPA and Down syndrome: Therefore, quantitative measurement of hCG-sLHCGR together with PAPP-A and free hCGbeta increased the overall detection rate in the combined data sets from 58.13% to 72.1% (9/43 T21; 20.9% were additionally detected) with a false positive rate of 4.99%; suggesting that hCG-sLHCGR could be an effective marker for primary biochemical screening of Down’s syndrome in both low and high risk populations.