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The influence of maternal weight on HCG in the multiple marker screening test
SPO Abstracts
Volume 172, Number 1, Part 2 Am J Obstet Gynecol
478 THE PROGNOSTIC VALUE OF UNEXPLAINED ELEVATED AMNIOTIC FLUID AND MATERNAL SERUM ALPHAFETOPROTEIN. K. Wenstrom. J. Owen, R. Davis, C. Brumfield. The University of Alabama at Birmingham. OBJECTIVE: To compare the prognostic values of unexplained elevated amniotic fluid alphafstoprotein (AFAFP -> 2.0 MOM) and unexplained elevated maternal serum AFP (MSAFP > 2.5 MOM). STUDY DESIGN: A Data Base containing the results of MSAFP screening tests and genetic amniocenteses as well as complete pregnancy outcome data on all women undergoing genetic amniocentesis since October 1988 was accessed. After excluding all patients whose elevated AFP levels were associated with positive AF acetylcholinesterase, AF blood contamination, fetal malformation or aneuploidy, multiple gestation, or other identifiable cause, 5742 cases were analyzed. Indications for amniocentesis included advanced maternal age (N = 4439), abnormal MSAFP (low = 510, high = 153), increased risk for aneuploidy or neural tube detect (N = 244) or other reasons (N = 396). Relative risks for selected pregnancy complications were determined with respect to the presence of elevated AFAFP (in association with any MSAFP), elevated MSAFP (with any AFAFP) and ~ elevated AFAFP (with only normal MSAFP). RESULTS: Relative Risks [95% Confidence I.mvelsl t' MSAFP t AFAFP 'rAFAFP [any MSAFP) (0nly Normal MSAFp) IUGR 2.5 (1.4-4.4) NS NS Stillbirth 3.5 (1.4-8.3) NS NS Preeclampsia 2.8 (1.1-7.0) 4.4 (2.0-10.0) 4.6 (1.9-11.2) Preterm delivery 2.8 (2.3-3.4) 1.7 (1.3-2.4) NS CONCLUSIONS: MSAFP is a better predictor than AFAFP of later pregnancy complications. However, unexplained elevated AFAFP appears to be associated with preaclampsia. In our study, if, elevated AFAFP was found in association with normal MSAFP, it predicted a 4.6 Relative Risk to develop this complication.
479 THE INFLUENCE OF MATERNAL WEIGHT ON HCG IN THE
MULTIPLE MARKER SCREENING TEST. K D. Wenstrom, J. Owen, L. Boots, M. Ethier. The University of Alabama at Birmingham. OBJECTIVE: Human Chorionic Gonadotrophin (hCG) is the most predictive serum marker for Down Syndrome (DS) employed in the multiple marker screening test ( MSAFP, estriol, hCG, and maternal age). Although hCG levels would be expected to vary with maternal weight (reflecting volume of distribution), such levels are not currently weight corrected. We sought to 1) Determine if hCG concentration is influenced by maternal weight, and 2) Derive a weight correction formula for hCG and evaluate its effect on both the screen positive rate and detection rate of DS. STUDY DESIGN: Two Genetics Databases were used: Data Base I, containing the results of 8,297 multiple marker screening tests, performed according to current standards with only MSAFP weightcorrected, and Data Base II, containing multiple marker screening tests anti fetal karyotypes from 1,936 women (including 51 cases of DS). RESULTS: In Data Base I, the overall screen positive rate (DS risk > 190) was 7.1%; it was 7.5% in patients <180 pounds, and 5.1%~-in patients > 180 pounds (p=0.001) When analyzed by maternal age group~weight significantlyaffected the screen positive rate only in women > age 30 (p=0.048 for age 30-34, p = 0.002 for age > 35). A w e i g h ~ o r r e c t i o n formula was then derived by fitting an e=~uation to the distribution of hCG MOMS in Data Base I. Application of this formula to Data Base I eliminated any weight related differences in screen positive rate for all maternal age groups. However, when a p p l i e d t o Data Base II, weight correction for hCG had no appreciable effect on either the screen positive rate (18.3% vs 18.6%) or the DS detection rate (35/51 or 69% in both). CONCLUSION: hCG concentrations are affected by maternal weight; we derived a correction formula to eliminate weight-related differences in the screen positive rate. However, application of this formula to a Genetics Data Base did not change either the DS screen positive rate or the detection rate.
480 SERUM SCREENING: DISPARITY IN PRACTICE PATTERNS
391
BETWEEN OBSTETRICIANS (OBs) AND FAMILY PHYSICIANS (FPs). D. Howserx, J. Yankowitz. J.W. Elyx. Depts. OB/GYN and Family Practice, Univ. of Iowa, Iowa City, IA. OBJECTIVE: We compared the use of the Iowa Expanded Serum Screening Program (F,SS) by OBs and FPs. ESS is maternal serum (MS) screening using alphafetopmtein (AFP), unconjugated esaiol, and haman chorionic gonadotropin. STUDY DESIGN: A state registry was used to identify all OBs (160) and FPs (413) who practice obstea'ics in Iowa. A questinnnaite exploring attitudes, practice patterns, and knowledge related to MS screening was mailed to these physicians. RESULTS: The response rate was 74.2% overall (OBs=76.9%, and FPs = 73.1%, p=0.36). OBs were significantly more likely to offer ESS to their obstetrical patients than were FPs (98.3 % vs 77.7%, p<0.001). An additional 19.6% of FPs offered MSAFP alone. Among physicians who offer ESS several differences emerged: (1) OBs were more likely than FPs to offer ESS to all obstetrical patients (99.2% vs 92.9%, p<0.02), whereas FPs were more likely to offer testing to patients with perceived risks for neural tube defects (NTDs) or chromosomal abnormalities, as well as those patients who requested it, (2) OBs were more likely to recommend ESS than F'Ps (36.4% vs 26.I%, p<0.05), who were more likely to remain neutral or discourage testing. Offering MS testing without either recommending or discouraging it was the most common practice for beth groups (OBs=61.9%, and FPs--68.6%, 1~--0.21), (3) FPs more than OBs felt that ESS was not necessary if the patient would not terminate the pregnancy for NTDs (38.5% vs 19.5%, p
481 aBCOND TRIMEBTKR 8CRIHmIIM FOR DOWN BTNDR4~glL WITH KPP AND FREE DrEA:
RBaULT8 OF aTUDZKS
WITH
&DVANCKDMATKRNKLAGB P&TIKNTS. R. Kasturi "I, P. Buchanan 2, J. Larsen 3, D. Krantz l, J. Macrit° tNTD Laboratories, Inc,, Huntington Station, MY, 2GoneCare Medical Genetics Center, Chapel Bill, NC, 3George Washington University Medical Center, Washington, DC. OBJECTIVE: To determine if maternal serum Down syndrome tDS l screening with free Beta (hOG l and AIpha-fetoprotein (AFP l should be offered to advanced maternal age patients (>-35 at EDC) who decline auniocentesis. STUDY DZSIGM: We analyzed 128 cases of DS and 7,677 control patients gathered from both prospective and retrospective studies of women aged 35 and over at BDC. DS risks were calculated based on the patient's age and analyte levels of free Beta (hOG l and AFP. A cut-off risk of 1 in 365 was used for patients in New York and 1 in 380 for all others. RESITLTB: In 114 (89%) DS cases and 1,889 (25%) unaffected cases, the patient's risk was greater than the cut-off risk. CONCLUSION: The American Co]logo of Medical Geneticn and the American college of Obstetricians and Gynecologists do not recoumend replacing CVS or amniocentesis by multiple marker screening in women 35 years or older. If advanced maternal age patients decline CVS and/or amniocentesis, DS screening using free Beta (hOG) and AFP can detect 89% of DS cases and reduce the amniocentesis rate to twenty-five percent. However, chromosomal abnormalities, other than DS may not be detected by such a screening protocol.
Volume 172, Number 1, Part 2 Am J Obstet Gynecol
478 THE PROGNOSTIC VALUE OF UNEXPLAINED ELEVATED AMNIOTIC FLUID AND MATERNAL SERUM ALPHAFETOPROTEIN. K. Wenstrom. J. Owen, R. Davis, C. Brumfield. The University of Alabama at Birmingham. OBJECTIVE: To compare the prognostic values of unexplained elevated amniotic fluid alphafstoprotein (AFAFP -> 2.0 MOM) and unexplained elevated maternal serum AFP (MSAFP > 2.5 MOM). STUDY DESIGN: A Data Base containing the results of MSAFP screening tests and genetic amniocenteses as well as complete pregnancy outcome data on all women undergoing genetic amniocentesis since October 1988 was accessed. After excluding all patients whose elevated AFP levels were associated with positive AF acetylcholinesterase, AF blood contamination, fetal malformation or aneuploidy, multiple gestation, or other identifiable cause, 5742 cases were analyzed. Indications for amniocentesis included advanced maternal age (N = 4439), abnormal MSAFP (low = 510, high = 153), increased risk for aneuploidy or neural tube detect (N = 244) or other reasons (N = 396). Relative risks for selected pregnancy complications were determined with respect to the presence of elevated AFAFP (in association with any MSAFP), elevated MSAFP (with any AFAFP) and ~ elevated AFAFP (with only normal MSAFP). RESULTS: Relative Risks [95% Confidence I.mvelsl t' MSAFP t AFAFP 'rAFAFP [any MSAFP) (0nly Normal MSAFp) IUGR 2.5 (1.4-4.4) NS NS Stillbirth 3.5 (1.4-8.3) NS NS Preeclampsia 2.8 (1.1-7.0) 4.4 (2.0-10.0) 4.6 (1.9-11.2) Preterm delivery 2.8 (2.3-3.4) 1.7 (1.3-2.4) NS CONCLUSIONS: MSAFP is a better predictor than AFAFP of later pregnancy complications. However, unexplained elevated AFAFP appears to be associated with preaclampsia. In our study, if, elevated AFAFP was found in association with normal MSAFP, it predicted a 4.6 Relative Risk to develop this complication.
479 THE INFLUENCE OF MATERNAL WEIGHT ON HCG IN THE
MULTIPLE MARKER SCREENING TEST. K D. Wenstrom, J. Owen, L. Boots, M. Ethier. The University of Alabama at Birmingham. OBJECTIVE: Human Chorionic Gonadotrophin (hCG) is the most predictive serum marker for Down Syndrome (DS) employed in the multiple marker screening test ( MSAFP, estriol, hCG, and maternal age). Although hCG levels would be expected to vary with maternal weight (reflecting volume of distribution), such levels are not currently weight corrected. We sought to 1) Determine if hCG concentration is influenced by maternal weight, and 2) Derive a weight correction formula for hCG and evaluate its effect on both the screen positive rate and detection rate of DS. STUDY DESIGN: Two Genetics Databases were used: Data Base I, containing the results of 8,297 multiple marker screening tests, performed according to current standards with only MSAFP weightcorrected, and Data Base II, containing multiple marker screening tests anti fetal karyotypes from 1,936 women (including 51 cases of DS). RESULTS: In Data Base I, the overall screen positive rate (DS risk > 190) was 7.1%; it was 7.5% in patients <180 pounds, and 5.1%~-in patients > 180 pounds (p=0.001) When analyzed by maternal age group~weight significantlyaffected the screen positive rate only in women > age 30 (p=0.048 for age 30-34, p = 0.002 for age > 35). A w e i g h ~ o r r e c t i o n formula was then derived by fitting an e=~uation to the distribution of hCG MOMS in Data Base I. Application of this formula to Data Base I eliminated any weight related differences in screen positive rate for all maternal age groups. However, when a p p l i e d t o Data Base II, weight correction for hCG had no appreciable effect on either the screen positive rate (18.3% vs 18.6%) or the DS detection rate (35/51 or 69% in both). CONCLUSION: hCG concentrations are affected by maternal weight; we derived a correction formula to eliminate weight-related differences in the screen positive rate. However, application of this formula to a Genetics Data Base did not change either the DS screen positive rate or the detection rate.
480 SERUM SCREENING: DISPARITY IN PRACTICE PATTERNS
391
BETWEEN OBSTETRICIANS (OBs) AND FAMILY PHYSICIANS (FPs). D. Howserx, J. Yankowitz. J.W. Elyx. Depts. OB/GYN and Family Practice, Univ. of Iowa, Iowa City, IA. OBJECTIVE: We compared the use of the Iowa Expanded Serum Screening Program (F,SS) by OBs and FPs. ESS is maternal serum (MS) screening using alphafetopmtein (AFP), unconjugated esaiol, and haman chorionic gonadotropin. STUDY DESIGN: A state registry was used to identify all OBs (160) and FPs (413) who practice obstea'ics in Iowa. A questinnnaite exploring attitudes, practice patterns, and knowledge related to MS screening was mailed to these physicians. RESULTS: The response rate was 74.2% overall (OBs=76.9%, and FPs = 73.1%, p=0.36). OBs were significantly more likely to offer ESS to their obstetrical patients than were FPs (98.3 % vs 77.7%, p<0.001). An additional 19.6% of FPs offered MSAFP alone. Among physicians who offer ESS several differences emerged: (1) OBs were more likely than FPs to offer ESS to all obstetrical patients (99.2% vs 92.9%, p<0.02), whereas FPs were more likely to offer testing to patients with perceived risks for neural tube defects (NTDs) or chromosomal abnormalities, as well as those patients who requested it, (2) OBs were more likely to recommend ESS than F'Ps (36.4% vs 26.I%, p<0.05), who were more likely to remain neutral or discourage testing. Offering MS testing without either recommending or discouraging it was the most common practice for beth groups (OBs=61.9%, and FPs--68.6%, 1~--0.21), (3) FPs more than OBs felt that ESS was not necessary if the patient would not terminate the pregnancy for NTDs (38.5% vs 19.5%, p
481 aBCOND TRIMEBTKR 8CRIHmIIM FOR DOWN BTNDR4~glL WITH KPP AND FREE DrEA:
RBaULT8 OF aTUDZKS
WITH
&DVANCKDMATKRNKLAGB P&TIKNTS. R. Kasturi "I, P. Buchanan 2, J. Larsen 3, D. Krantz l, J. Macrit° tNTD Laboratories, Inc,, Huntington Station, MY, 2GoneCare Medical Genetics Center, Chapel Bill, NC, 3George Washington University Medical Center, Washington, DC. OBJECTIVE: To determine if maternal serum Down syndrome tDS l screening with free Beta (hOG l and AIpha-fetoprotein (AFP l should be offered to advanced maternal age patients (>-35 at EDC) who decline auniocentesis. STUDY DZSIGM: We analyzed 128 cases of DS and 7,677 control patients gathered from both prospective and retrospective studies of women aged 35 and over at BDC. DS risks were calculated based on the patient's age and analyte levels of free Beta (hOG l and AFP. A cut-off risk of 1 in 365 was used for patients in New York and 1 in 380 for all others. RESITLTB: In 114 (89%) DS cases and 1,889 (25%) unaffected cases, the patient's risk was greater than the cut-off risk. CONCLUSION: The American Co]logo of Medical Geneticn and the American college of Obstetricians and Gynecologists do not recoumend replacing CVS or amniocentesis by multiple marker screening in women 35 years or older. If advanced maternal age patients decline CVS and/or amniocentesis, DS screening using free Beta (hOG) and AFP can detect 89% of DS cases and reduce the amniocentesis rate to twenty-five percent. However, chromosomal abnormalities, other than DS may not be detected by such a screening protocol.