MEDICAL POLICY FIRST-TRIMESTER PRENATAL SCREENING FOR GENETIC DEFECTS MP POLICY TITLE POLICY NUMBER

Transcription

1 Original Issue Date (Created): February 23, 2004 Most Recent Review Date (Revised): Effective Date: May 15, 2007 January 31, RETIRED I. DESCRIPTION/BACKGROUND Over the years many types of biologic markers have been investigated for utility in detecting Down syndrome fetuses. Fetal nuchal translucency refers to the ultrasound detection of subcutaneous edema in the fetal neck, and is measured as the maximal thickness of the sonolucent zone between the inner aspect of the fetal skin and the outer aspect of the soft tissue overlying the cervical spine or the occipital bone. In the early 1990s, screening studies of pregnant women reported an association between increased nuchal translucency in the first trimester of pregnancy (10-13 weeks of gestation) and chromosomal defects, most commonly Down syndrome, but also trisomy 18 and 13. In addition, increased nuchal translucency has been associated with other genetic syndromes, abnormalities of the heart and great arteries, and a wide range of skeletal dysplasias. Two studies have been published that evaluate the use of nuchal translucency in combination with other maternal serum markers to detect Down syndrome. The methodology and analytic methods of the studies reflect an important maturation, in that nuchal translucency interpretation is standardized and incorporated into appropriate statistical models in combination with other maternal serum markers that are also known to be associated with Down syndrome in the first trimester. First-trimester screening, if accurate, can provide important information to the mother several weeks before it would be available with traditional second-trimester screening. To understand the potential role of this technique, the following discussion reviews established screening methods. Definitive diagnosis of Down syndrome and other chromosomal abnormalities requires amniocentesis or chorionic villus sampling (CVS), both of which are invasive procedures that carry a risk of miscarriage estimated at 1/300 and 1%, respectively. Because of this risk, before biochemical screening existed, diagnosis was generally only offered to women 35 years or older, for whom the risk of the procedure approximated the risk of Down syndrome. However, the majority of Down syndrome babies are born from mothers younger than 35 years, even though the mothers are at lower individual risk. This situation created interest in developing less-invasive screening programs based on assessment of serum markers that have shown associations with Down syndrome. In the late 1980s, biochemical screening at 16 weeks' gestation was developed Page 1

2 and began to be offered to all pregnant women. Biochemical screening consists of maternal serum measurements of alpha-fetoprotein, free-beta human chorionic gonadotropin (βhcg), and unconjugated estriol (i.e., triple screen); using this screening method, approximately 60% of Down syndrome pregnancies can be identified at a 5% false-positive rate. This false-positive rate refers to the proportion of all tests administered that are falsely positive at the cutoff that produces that particular value of sensitivity. Among women who test positive, only about 2% actually have a Down syndrome fetus. A fourth biochemical marker, inhibin-a has also been included in biochemical screening (i.e., quadruple screen) that may boost detection to 75% at a false-positive rate of 5%. At the present time, the American College of Obstetricians and Gynecologists (ACOG) states that first trimester biochemical marker testing be offered to all pregnant women, regardless of maternal age. Those with results indicating an increased risk of Down s syndrome or trisomy 18 are offered amniocentesis or chorionic villous sampling for definitive diagnosis. Pregnant women over the age of 35 may initially be offered genetic amniocentesis, given the baseline-elevated risk of aneuploidy associated with advanced maternal age in these patients. II. DEFINITIONS ANEUPLOIDY is a condition of having an abnormal number of chromosomes for the species indicated. BIOCHEMICAL MARKER refers to any biochemical compound such as an antigen, antibody, abnormal enzyme, or hormone that is sufficiently altered in a disease to serve as an aid in diagnosing or in predicting susceptibility to the disease. CHORIONIC VILLUS is the vascular (blood-vessel like) projections from the chorion, which form the fetal portion of the placenta. DOWN SYNDROME refers to the clinical consequences of having three copies of chromosome 21. The condition is marked by mild to moderate mental retardation and physical characteristics that include a sloping forehead, low-set ears with small canals, and short, broad hands, with a single palmar crease. Cardiac valvular disease and a tendency to develop Alzheimer-like changes in the brain are common consequences of this syndrome. NUCHAL refers to the nape (back) of the neck. TRISOMY 13 is a severe developmental disorder in which a third copy of chromosome thirteen (13) is present in the cell nucleus. It is often lethal in-utero. Children who survive fetal development may have severe facial, scalp, and cranial deformities and a predisposition to leukemia. Page 2

3 TRISOMY 18 is a severe, usually lethal developmental disorder in which a third copy of chromosome eighteen (18) is present in the cell nucleus. Children with trisomy 18 usually do not survive beyond the first year of life. TRISOMY 21 refers to Down syndrome. III. POLICY First-trimester screening for detection of Down syndrome incorporating maternal serum markers and measurement of fetal nuchal translucency may be considered medically necessary for women who are adequately counseled and desire information on the risk of having a child with Down syndrome. Cross-references MP Ultrasound in Maternity Care MP Pregnancy Related Testing for Genetic Chromosomal Abnormalities MP Percutaneous Umbilical Blood Sampling IV. EXCLUSIONS First-trimester screening for detection of Down syndrome using measurement of nuchal translucency alone is considered investigational. There is insufficient evidence to support a conclusion concerning the health outcomes or benefits associated with this procedure. V. BENEFIT VARIATIONS The existence of this medical policy does not mean that this service is a covered benefit under the member's contract. Benefit determinations should be based in all cases on the applicable contract language. Medical policies do not constitute a description of benefits. A member s individual or group customer benefits govern which services are covered, which are excluded, and which are subject to benefit limits and which require preauthorization. Members and providers should consult the member s benefit information or contact Capital for benefit information. VI. DISCLAIMER Capital s medical policies are developed to assist in administering a member s benefits, do not constitute medical advice and are subject to change. Treating providers are solely responsible for medical advice and treatment of members. Members should discuss any medical policy related to their coverage or condition with their provider and consult their benefit information to determine if the service is covered. If there is a discrepancy between this medical policy and a member s benefit information, the benefit information will govern. Capital considers the information contained in this medical policy to be proprietary and it may only be disseminated as permitted by law. Page 3

4 VII. REFERENCES ACOG News Release. New Recommendations for Down Syndrome Call for Screening of All Pregnant Women. January 2, [Website]: Accessed March 13, American College of Obstetrician and Gynecologists. Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin number 77. Obstet Gynecol 2007; 109 (10: Caughey AB, Musci TJ, Belluomini J et al. Nuchal translucency screening: how do women actually utilize the results? Prenat Diagn 2006; Dec 7 (Epub). Comstock CH, Malone FD, Ball Rh et al. Is there a nuchal translucency millimeter measurement above which there is no added benefit from first trimester serum screening? AM J Obstet Gynecol 2006; 195 (3): Malone FD, Canik JA, Ball RH, Nyberg DA, Comstock CH, et al. First-trimester or second-trimester screening, or both, for Down s syndrome. NEJM 2005; 353 (19) Malone FD, Canick JA, Ball Rh et al. First-trimester or second trimester screening, or both, for Down s syndrome. N Engl J Med 2005; 353(19): Platt LD, Greene N, Johnson A et al. Sequential pathways of testing after first-trimester screening for trisomy 21. Obstet Gynecol 2004; 104(4): Senat MV, Bussieres L, Couderc S et al. Long-term outcome of children born after a firsttrimester measurement of nuchal translucency at the 99 th percentile or greater with normal karyotype: a prospective study. Am J Obstet Gynecol 2007; 196 (1): 53.e1-6. Simpson JL. Choosing the best prenatal screening protocol. NEJM 2005; 353 (19): Taber s Cyclopedic Medical Dictionary, 19 th edition. Wald NJ, Rodeck C, Hacksaw AK et al. First and second trimester antenatal screening for Down s syndrome: the results of the serum, urine and ultrasound (SURUSS). J Med Screen 2003; 10(2): Wald NJ, Rodeck C, Hackshwa AK et al. SURUSS in perspective. Semin Perniatol 2005; 29 (4): Wapner R, Thom E, Simpson JL et al. First-trimester screening for trisomies 21 and 18. N Engl J Med 2003; 349(15): Wapner RJ. First trimester screening: the Bun study. Semin Perinatol 2005; 29 (4): Page 4

5 VIII. PRODUCT VARIATIONS [N] = No product variation, policy applies as stated [Y] = Standard product coverage varies from application of this policy, see below [N] CHIP POS [N] PPO [N] HMO [N] CHIP HMO [N] SeniorBlue [N] SeniorBlue PPO [N] Indemnity [N] SpecialCare [N] POS [N] FEP HMO [N] FEP PPO IX. POLICY HISTORY MP CAC 9/30/03 CAC 1/27/04 CAC 12/14/04 CAC 2/28/06 CAC 4/24/07 Policy approved for retired effective 1/31/2008. Info goes into policy First Trimester detection of Down Syndrome using Fetal US Markers Health care benefit programs issued or administered by Capital BlueCross and/or its subsidiaries, Capital Advantage Insurance Company and Keystone Health Plan Central. Independent licensees of the Blue Cross and Blue Shield Association. Communications issued by Capital BlueCross in its capacity as administrator of programs and provider relations for all companies. Page 5