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Balkan Journal of Medical Genetics

The Journal of Macedonian Academy of Sciences and Arts


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1311-0160
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Value of the Combined Test in Prenatal Diagnostics

D Lončar1

Gynecology and Obstetrics Clinic, Clinical Center Kragujevac, Kragujevac, Serbia1

This content is open access.

Citation Information: Balkan Journal of Medical Genetics. Volume 13, Issue 2, Pages 53–59, ISSN (Print) 1311-0160, DOI: 10.2478/v10034-010-0027-3, January 2011

Publication History

Published Online:
2011-01-20

Value of the Combined Test in Prenatal Diagnostics

Congenital anomalies are the cause of 20.0-25.0% of cases of perinatal death, while 3.0% of children are born with malformations of varying size. We examined the predictive values and defined the credibility ratio of the combined test results. Of 317 examined pregnant women, 16 (5.05%) gave a pathological karyotype after amniocentesis: of these, nine (2.84%) had chromosomal number aberrations and seven (2.21%) had chromosomal structure aberrations. We determined the ultrasonographic parameters using the standards of the Fetal Medicine Foundation (location please). We measured free β-subunit of choriogronadotropin (β-HCG) and pregnancy associated plasma protein A (PAPP-A) in venous blood from pregnant women using a combined commercial assay. Sensitivity of the test is 94.0%, and specificity is 99.0%. The positive likelihood ratio [likelihood ratio test (LR+)] is 94.00, a negative likelihood ratio is [likelihood ratio test (LR-)] 0.06. The pretest probability that pregnant women carry a fetus with chromosomal abnormality is 1:250. Posttest odds after the combined test to discover this abnormality is 0.3760, and probability of the same case is 0.2732 if it happens that the test result is positive. The result of our study confirms the justification of combined test usage in routine clinical practice, since the posttest odds rate in the case of a positive screening increases several times over (almost 90 times); the probability of detecting a chromosomal abnormality was about 70 times. The combined screening test, if used methodologically correctly, has a high predictive value in detecting fetal congenital anomalies.

Keywords: Predictive value; Combined test; Ultrasonography; Biochemical markers

  • Ebrahim S, Daponte A, Guidozzi F. The impact of free antenatal care on perinatal mortality. Int J Gynaecol Obstet. 2000; 71(3): 205-207.

  • Alfirevic Z, Neilson JP. Antenatal screening for Down's syndrome. Br Med J. 2004; 329(7470): 811-812.

  • Spencer K. Age related detection and false positive rates when screening for Down's syndrome in the first trimester using fetal nuchal translucency and maternal serum βhCG and PAPP-A. Br J Obstet Gynaecol. 2001; 108: 1043-1046.

  • Wald NJ, Watt HC, Hackshaw AK. Integrated screening for Down's syndrome on the basis of tests performed during the first and second trimesters. N Engl J Med. 1999; 341(7): 461-467.

  • Wald NJ, Rodeck C, Hackshaw AK, Walters J, Chitty L, Mackinson AM. First and second trimester antenatal screening for Down's syndrome: the results of the Serum, Urine and Ultrasound Screening Study (SURUSS). J Med Screen. 2003; 10(2): 56-104. (Erratum in: J Med Screen. 2006; 13(1): 51-52.) [CrossRef]

  • Stojilkovic-Mikic T, Rodeck CH. Screening for chromosomal anomalies: first or second trimester, biochemical or ultrasound? Ann Acad Med Singapore. 2003; 32(4): 583-589.

  • Haddow JE, Palomaki GE, Knight GJ, Williams J, Miller WA, Johnson A. Screening of maternal serum for fetal Down's syndrome in the first trimester. N Engl J Med. 1998; 338(14): 955-961.

  • Wald NJ, George L, Smith D, Densem JW, Petterson K. Serum screening for Down's syndrome between 8 and 14 weeks of pregnancy. International Prenatal Screening Research Group. Br J Obstet Gynaecol. 1996; 103(5): 407-412.

  • Snijders RJM, Farrias M, Kaisenberg C, Nicolaides KH. Fetal abnormalities. In: Sniijders RJM, Nicolaides KH, Eds. Ultrasound Markers for Fetal Chromosomal Defects. New York: Parthenon, 1996: 1-63.

  • Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap L, Wenstrom KD, Eds. Prenatal diagnosis and fetal therapy. Williams Obstetrics. New York: McGraw-Hill, 2005: 313-340.

  • Wellesley D, Boyle T, Barber J, Howe DT. Retrospective audit of different antenatal screening policies for Down's syndrome in eight district general hospitals in one health region. Br Med J. 2002; 325(7354): 15-17.

  • Lončar D, Varjačić M, Novaković T, Milovanović D, Janković S. Correlation between serum biochemical markers and early amniocentesis in diagnosis of congenital fetal anomalies. Bosnian J Basic Med Sci. 2010; 10(1): 9-14.

  • Hallahan T, Krantz D, Orlandi F, Rossi C, Curcio P, Macri S, Larsen J, Buchanan P, Macri J. First trimester biochemical screening for Down syndrome: free β-hCG versus intact hCG. Prenat Diagn. 2000; 20(10): 785-789. [CrossRef] [PubMed]

  • Brigatti KW, Malone FD. First trimester screening for aneuploidy. Obstet Gynecol Clin North Am. 2004; 31(1): 1-20. [CrossRef]

  • Nicolaides KH. Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities. Am J Obstet Gynecol. 2004; 191(1): 45-67.

  • 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 β-human chorionic gonadotropin and pregnancy-associated plasma protein-A. Ultrasound Obstet Gynecol. 1999; 13(4): 231-237. [Web of Science]

  • Krantz DA, Hallahan TW, Orlandi F, Buchanan P, Larsen JW Jr, Macri JN. First-trimester Down syndrome screening using dried blood biochemistry and nuchal translucency. Obstet Gynecol. 2000; 96(2): 207-213.

  • Spencer K, Spencer CE, Power M, Moakes A, Nicolaides KH. One stop clinic for assessment of risk for fetal anomalies: a report of the first year of prospective screening for chromosomal anomalies in the first trimester. Br J Obstet Gynaecol. 2000; 107(10): 1271-1275.

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