Combined test + inhibin A at week 13 in contingent sequential testing: an interesting alternative for first-trimester prenatal screening for Down Syndrome

New contingent sequential screening model for Down syndrome based on the combined test associated with modified genetic sonography

OBJECTIVE

The aim of this study is to evaluate the possibility of implementing a contingent sequential screening test for Down syndrome (DS) based on the combined test (CT) associated with modified genetic sonography (MGS). We evaluate sensitivity (Sen), false positive rate (FPR), and economic costs.

METHOD

We compiled data from the results of a prospective screening programme for DS during a 5-year study period (July 2005-December 2011). Pregnancies were offered the CT as the first step in the contingent sequential test. We identified an intermediate risk group (1/101-1/1000) using CT results, and offered these individuals a MGS (major malformation and nuchal fold).

RESULTS

A total of 19 440 pregnancies (103 chromosome abnormalities and 66 cases of DS) were administered the CT. We performed a MGS on 99.6% of individuals in the intermediate risk group (2188/2197); in this group, we observed 22 chromosome abnormalities (17 DS). The CT provided a Sen for DS of 80.30% (95%CI: 68.68-89.07) (53/66), and a Sen for all chromosome abnormalities of 76.70% (95%CI: 67.34-84.46) (79/103), with a FPR of 3.79% (95%CI: 3.52-4.05) (732/19 374). The contingent sequential strategy produced a Sen for DS of 81.82% (95%CI: 70.39-90.24) (54/66) and a Sen for all chromosome abnormalities of 79.61% (95%CI: 70.54-86.91) (82/103), with a FPR of 1.16% (95%CI: 1.02-1.33) (224/19 457). The economic costs of the CT and the contingent sequential model were 9 70 275 Euros and 9 41 716 Euros, respectively.

CONCLUSIONS

We present a new sequential contingent strategy for DS screening and demonstrate its usefulness for reducing FPR while maintaining a high level of Sen for DS, without requiring an increase in economic costs.

Inhibins and activins in blood: predictors of female reproductive health?

Inhibins A and B are gonadal factors which are important in fertility. Their use as predictors of female reproductive health has centred on their application to ovarian cancer, Anorexia Nervosa, Down Syndrome and preeclampsia. Inhibin B also provides an index of the endocrine feedback relationship between the ovary and pituitary particularly when the ovarian follicle reserve is low. These applications are relevant in monitoring the onset of the menopause transition, ovarian recovery following chemotherapy and disturbances in pubertal development. Currently, these applications have only found widespread use in Down Syndrome and ovarian cancer. Activins, on the other hand, appear to have a limited application.

Role of fetal echocardiography in stepwise sequential screening for chromosomal disorders (combined test associated with modified genetic sonography)

OBJECTIVES

To evaluate the contribution made by fetal echocardiography in identifying Down's syndrome (DS) and other chromosomal disorders in a stepwise sequential screening method (first step: combined test (CT), second step: modified genetic sonography (MGS) (major malformation and nuchal fold)), for DS in the general population of pregnant women.

METHODS

Prospective study. During a 5-year study period (July 2005-June 2010) 17,911 pregnant women underwent CTs with MGS (with fetal cardiac morphological evaluation performed by obstetricians in a tertiary hospital) as a screening method for DS. We evaluated the sensitivity and false positive rate (FPR) (95% confidence interval (CI)) of three screening methods for DS and all chromosomal disorders: CT, CT + MGS, and CT + fetal echocardiography.

RESULTS

A total of 17,911 cases were analyzed with 67 chromosome disorders and 45 DS cases being found. For DS, the CT sensitivity was 80% (95% CI; 68.3-91.7) (36/45) and 79.1% (95% CI; 69.4-88.8) (53/67) for all chromosome disorders, with a FPR of 4.2% (95% CI; 3.9-4.5) (752/17,866) and 4.1% (95% CI; 3.8-4.4) (735/17,844), respectively. For CT + MSG and CT + fetal echocardiography, the sensitivity for DS was 93.3% (95% CI; 85.9-0.99) (42/45) and 95.5% (95% CI; 90.5-0.99) (64/67) for all chromosome disorders. The FPR for CT + MSG was 4.8% (95% CI; 4.5-5.1) (860/17,866) and 4.6% (95% CI; 4.3-4.9) (836/17,844), respectively. The FPR of CT + fetal echocardiography was 4.4% (95% CI; 4.1-4.7) (792/17,866) for DS screening and 4.3% (95% CI; 4-4.6) (770/17,844) for chromosome abnormality screening.

CONCLUSIONS

Fetal echocardiography is highly capable of identifying DS and other chromosomal disorders as a part of genetic sonography in stepwise sequential screening.

Contribution of "modified genetic sonography" to the combined test as a screening method for chromosomal abnormalities

OBJECTIVES

We propose to assess the contribution of "modified genetic sonography" (MGS) to the combined test (CT) as a method of stepwise sequential screening (1st step: CT, 2nd step: MGS) for chromosome abnormalities in the general population of pregnant women.

METHODS

Prospective study. During a 4 year study period (July 2005-June 2009) 16,548 pregnancies underwent a CT combined with MGS (major malformation and nuchal fold) as a screening method for chromosome abnormalities. We assessed sensitivity and false positive rate (FPR) (95% CI).

RESULTS

We offered a chromosome abnormalities screening test to 96.6% of pregnancies (15,995 cases). 14,160 cases are analyzed (1st step: CT, 2nd step: MGS) including 49 chromosome abnormalities and 35 Down's syndrome (DS). The sensitivity of CT for DS was 77.1% [95% CI, 63.2-91] (27/35) and 77.5% for all chromosome abnormalities [95% CI, 65.8-89.2] (38/49) with a FPR of 4.4% [95% CI, 4.1-4.7]. If MGS was combined with CT, the sensitivity for DS was 91.4% [95% CI, 82.1-99] (32/35) and 93.8% for all chromosome abnormalities [95% CI, 87-99] (46/49) for a FPR of 5.1% [95% CI, 4.7-5.5].

CONCLUSIONS

The addition of an MGS to combined first-trimester screening test for aneuploidy improved sensitivity by 14.3% while only increasing the FPR by 0.7%.