Cuckle H, Wald N, Stevenson J D, May H M, Ferguson-Smith M A, Ward A M, Barbour H M, Laurence K M, Norgaard-Pedersen B
Department of Environmental and Preventive Medicine, St Bartholomew's Medical College, London, U.K.
Prenat Diagn. 1990 Feb;10(2):71-7. doi: 10.1002/pd.1970100202.
Data on maternal serum alpha-fetoprotein (AFP) levels at 13-24 weeks' gestation in 46 twin pregnancies with open neural tube defects (22 with anencephaly, 24 with open spina bifida) and 169 unaffected twins were used to estimate the detection and false-positive rates associated with different cut-off levels. Using the conventional cut-off level of 2.5 multiples of the median (MoM) for unaffected singleton pregnancies of the same gestation and laboratory, the detection rate in twins was 99 per cent for anencephaly and 89 per cent for open spina bifida, with a false-positive rate of 30 per cent. Using a 5.0 MoM cut-off level to maintain a similar false-positive rate to that found among singleton pregnancies at 16-18 weeks' gestation (about 3 per cent), the detection rate was 83 per cent for anencephaly and 39 per cent for open spina bifida. Estimates are provided of the odds of having an affected twin pregnancy given a positive AFP result as well as the odds for individual women with a raised AFP level.
对46例怀有神经管开放性缺陷双胎妊娠（22例无脑儿、24例脊柱裂）孕妇以及169例未受影响的双胎孕妇在妊娠13 - 24周时的母血清甲胎蛋白（AFP）水平数据进行分析，以评估不同临界值水平下的检测率和假阳性率。对于相同孕周和实验室条件下未受影响的单胎妊娠，采用传统的2.5倍中位数（MoM）临界值水平，双胎妊娠中无脑儿的检测率为99%，脊柱裂的检测率为89%，假阳性率为30%。采用5.0 MoM临界值水平以维持与妊娠16 - 18周单胎妊娠相似的假阳性率（约3%），无脑儿的检测率为83%，脊柱裂的检测率为39%。报告了AFP检测结果为阳性时怀有受影响双胎妊娠的几率以及AFP水平升高的个体女性的几率。
