Integrated serum screening for Down syndrome in primary obstetric practice.
OBJECTIVE
Integrated serum screening for Down syndrome is potentially more effective than current second-trimester screening. We report results of an intervention trial of integrated serum screening that involved 229 primary prenatal care practitioners throughout Maine.


METHODS
Women provided a first-trimester serum (for PAPP-A) followed by a second-trimester serum (for AFP, uE3, hCG, and DIA). These five marker measurements were used to calculate a Down syndrome risk in the second trimester. Screen-positive women (risk > or = 1:100) were managed according to standard practice.


RESULTS
During 24 months' enrollment, 11 159 women provided a first-trimester sample (61% of women receiving screening services). Nine thousand seven hundred twenty-three women also provided a second-trimester sample; 8773 women satisfied gestational age criteria for testing in both trimesters. Integrated serum screening detected 14 of 16 Down syndrome cases (87%) and 79% after adjustment for trimester-of-ascertainment bias. The initial false-positive rate was 3.2% and was 2.7% when restricted to ultrasound-dated pregnancies. Performance was better than any combination of second-trimester markers. Implementation challenges included initial samples being collected too early and sample matching.


CONCLUSIONS
Integrated serum screening for Down syndrome was successfully implemented in primary care settings; screening performance was consistent with predictions. It provides an accessible and acceptable alternative to screening protocols that require nuchal translucency measurements.
Knight
George J
GJ
Foundation for Blood Research, Scarborough, Maine, USA. GKnight@ipmms.org
Palomaki
Glenn E
GE
Neveux
Louis M
LM
Smith
Dwight E
DE
Kloza
Edward M
EM
Pulkkinen
Andrea J
AJ
Williams
Josephine
J
Haddow
James E
JE
D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D016001:Confidence Intervals; D004314:Down Syndrome / Q000097:blood* / Q000175:diagnosis*; D004964:Estriol / Q000097:blood; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D007265:Inhibins / Q000097:blood; D008281:Maine; D008403:Mass Screening / Q000592:standards; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D011296:Prenatal Diagnosis / Q000379:methods*; D011320:Primary Health Care / Q000379:methods*; D011331:Private Practice
D018997:Chorionic Gonadotropin, beta Subunit, Human; C422362:inhibin A; D007265:Inhibins; D011266:Pregnancy-Associated Plasma Protein-A; D004964:Estriol