Salazar LR, Ibarra GAL, Iduma MM, Leyva BR

Language: Spanish
References: 10
Page: 576-581
PDF size: 229.44 Kb.

ABSTRACT

Background: One of main targets of prenatal diagnosis is Down’s syndrome. Biochemical and sonographic markers together are efficient. The use of a single marker has not shown the same efficiency, although it has not been sufficient evaluated.
Objective: To shown results of PAPP-A as a single marker in first pregnancy trimester.
Materials and methods: Prospective, cross-sectional and random study, which evaluated 400 women with biochemical marker PAPP-A in the first pregnancy trimester.
Results: PAPP-A detected a true positive case (0.3%), 28 false positive cases (7.0%) and 371 true negative cases (92.8%), there were no false negative cases. Between 9 to 11 weeks, rate of false positives fluctuated between 5.5 and 6.7%, in 12th week it was 1.2% and in 13th week 18.2%. PAPP-A has 95.1% of specificity (weeks 9 to 12) and 82.2% of maternal age.
Discussion: A 5% of false positive rate is acceptable for prenatal diagnosis markers. It has been reported that PAPP-A is less discriminatory at 10 weeks of gestation. In this study the rate fluctuated between 6 and 7% (weeks 9 to 11), which increased at 13th week. Markers with low false positive rate stimulate the use of prenatal screening.
Conclusions: The use of combined markers: biochemical (free fraction of β-hGC, PAPP-A) and sonographic, are most recommendable in the first trimester of the pregnancy because of them low rate of false positives. PAPP-A can be used as a single marker between 9 to 11 weeks; false positive cases must be studied with combined markers.

REFERENCES

1. Parga M, Martínez M, Idoeta M, Sánchez-Pastor M. Diagnóstico prenatal y cribado de cromosomopatías. Med Fam Ginecol Obstet 2001;11:590-8.

2. Snijders R, Sebire N, Cuckle H, Nicolaides KH. Maternal age and gestational-age specific risks for chromosomal defects. Fetal Diagn Ther 1995;10:356-67.

3. ACOG Committee on Practice Bulletins. ACOG Practice Bulletin No. 77: screening for fetal chromosomal abnormalities. Obstet Gyncol 2007;109:217-27.

4. Andrade E, Guzmán M. Diagnóstico prenatal en el primer trimestre, ¿a quién y cómo? Ginecol Obstet Méx 2002;70(12):607-12.

5. Wald NJ, Rodeck C, Hackshaw AK, Walters J, et al. First and second trimester antenatal screening for Down’s syndrome: the results of the serum, urine and ultrasound screening study (SURUSS). Health Technol Assess 2003;7:1-77.

6. Spencer K, Souter V, Tul N, Snijders R, Nicolaides KH. A screening program for trisomy 21 at 10-14 weeks using fetal nuchal translucency, maternal serum free beta-human chorionic gonadrotropin and pregnancy-associated plasma protein-A. Ultrasound Obstet Gynecol 1999;13:231-7.

7. Krantz DA, Larsen JW, Buchanan D, Macri JN. First-trimester Down syndrome screening: free beta-human chorionic gonadotropin and pregnancy-associated plasma protein A. Am J Obstet Gynecol 1996;174:612-6.

8. Wenstrom KD. Aneuploidy screening: the changing scene. Obstet Ginecol 2003;101:840-2.

9. Salinas P, Valdés R, Carmona G. Screening genético antenatal para la detección de aneuploidías. Rev Chil Obstet Ginecol 2003;68:529-35.

10. Drugan A. Advanced maternal age and prenatal diagnosis: It’s time for individual assessment of genetic risk. Isr Med Assoc J 2005;7:99-102.