ûÈ9ÍÆusòj›¯•š®‰ubA��Qm ±±ŞGjØ¨On%÷šÊã7)nR8®v¨‰°Òss_i¡&?½c÷T¬(ÁA‚ÕuÿG^Zr||´…6�ıÔ¦Dúbà8ÑÖVKVªbÎ¸âlcÇÊ×xGŒ�cÍÛH�Şd. The false positive rate for Trisomy 13 is only 1%. Clipboard, Search History, and several other advanced features are temporarily unavailable. The overall FPR in screening for trisomies 18/13 and 21 was compared with the FPR in screening for trisomy 21 alone. Purpose: To determine the false-positive rates (FPR) associated with screening for trisomy 18/13 using first-trimester combined screening (FTCS) and an ultrasound plus cfDNA-based approach (US-cfDNA), which includes a detailed ultrasound examination, a cfDNA analysis and a FTCS reflex backup test for cases with uninformative results. The accuracy of detection for both Trisomy 18 and 21 is very similar as both have about 99% accuracy of detection. 2017 Sep;50(3):302-314. doi: 10.1002/uog.17484. | In conclusion, the addition of screening for trisomies 18 and 13 to screening for trisomy 21 does not significantly change FPR.