Maternal weight and ethnic adjustment within a first-trimester Down syndrome and trisomy 18 screening program

OBJECTIVE(S)

To estimate weight and ethnic group correction factors for first-trimester screening markers.

METHODS

Ethnic-specific median MoM free beta hCG and pregnancy associated plasma protein A (PAPP-A) and delta nuchal translucency values were calculated for cohorts of maternal weight (20 lb each) using data from 51,206 patients undergoing first-trimester screening. False-positive rates for Down syndrome and trisomy 18 were evaluated both prior to and after weight and ethnicity adjustment.

RESULTS

Free beta hCG and PAPP-A significantly decreased with increasing maternal weight while nuchal translucency increased by a clinically insignificant amount. For free beta hCG the regression formula indicated that after accounting for maternal weight MoM values were 16% higher for African Americans, 6% higher for Asians and 9% lower for Hispanics compared to Caucasians (p < 0.001, p = 0.001, p < 0.001, respectively) but there was no significant difference for Asian Indians. For PAPP-A, MoM values were 35% higher for African Americans (p < 0.001) but were not significantly different for the other ethnic groups compared to Caucasians. Down syndrome false-positive rates did not vary with maternal weight prior to (p = 0.291) or after weight adjustment of biochemistry (p = 0.054). Trisomy 18 false-positive rates varied significantly with weight both before (OR = 1.455 per 20-pound increase, p < 0.001) and after (OR = 1.066 per 20-pound increase, p = 0.01) weight adjustment of biochemistry; however, the odds ratio was greatly reduced after weight adjustment.

CONCLUSION(S)

The first-trimester screening markers, free beta hCG, PAPP-A and nuchal translucency vary with maternal weight and ethnicity. Adjustment of free beta hCG and PAPP-A is indicated but adjustment of nuchal translucency results may not be necessary.

Predicting the result of additional second-trimester markers from a woman's first-trimester marker profile: a new concept in Down syndrome screening

OBJECTIVE

To describe a method for deciding whether an individual's first-trimester Down syndrome screening test result justifies further testing in the second trimester.

METHODS

Statistical modelling was used to estimate the distribution of second-trimester marker profiles for a given first-trimester profile and hence the probability of a final positive result, using a 1 in 250 term cut-off. A multi-variate log Gaussian model was used with published parameters. Markers were maternal serum pregnancy-associated plasma protein-A and free beta-human chorionic gonadotrophin (hCG) at 10 weeks, nuchal translucency at 11 weeks, and second-trimester maternal serum alpha-fetoprotein, total hCG, unconjugated estriol and inhibin-A. To illustrate the method, the model was applied to a published series of 24 Down syndrome and 367 unaffected pregnancies.

RESULTS

Modelling predicts that for 63% Down syndrome and 0.4% unaffected pregnancies having first-trimester tests, there is a 50% or more probability of a final positive result. A step-wise sequential screening policy based on immediate prenatal diagnosis for those with high probability and second-trimester testing for the remainder would have a 90% detection rate and 1.7% false-positive rate. Modelling also predicts 8.0% Down syndrome and 89% unaffected pregnancies with probabilities below 3%. A contingent screening policy restricting second-trimester testing to those with 3-49% probabilities would have an 88% detection rate and 1.4% false-positive rate.

CONCLUSION

Predicting the probability of a positive final result from the first-trimester marker profile has potential utility, either as a decision aide for individual women or as a formal part of screening policy in selecting a subset of women for second-trimester testing.

Integrated serum screening for Down syndrome in primary obstetric practice

OBJECTIVES

Integrated serum screening for Down syndrome is potentially more effective than current second-trimester screening. We report results of an intervention trial of integrated serum screening that involved 229 primary prenatal care practitioners throughout Maine.

METHODS

Women provided a first-trimester serum (for PAPP-A) followed by a second-trimester serum (for AFP, uE3, hCG, and DIA). These five marker measurements were used to calculate a Down syndrome risk in the second trimester. Screen-positive women (risk > or = 1:100) were managed according to standard practice.

RESULTS

During 24 months' enrollment, 11 159 women provided a first-trimester sample (61% of women receiving screening services). Nine thousand seven hundred twenty-three women also provided a second-trimester sample; 8773 women satisfied gestational age criteria for testing in both trimesters. Integrated serum screening detected 14 of 16 Down syndrome cases (87%) and 79% after adjustment for trimester-of-ascertainment bias. The initial false-positive rate was 3.2% and was 2.7% when restricted to ultrasound-dated pregnancies. Performance was better than any combination of second-trimester markers. Implementation challenges included initial samples being collected too early and sample matching.

CONCLUSIONS

Integrated serum screening for Down syndrome was successfully implemented in primary care settings; screening performance was consistent with predictions. It provides an accessible and acceptable alternative to screening protocols that require nuchal translucency measurements.

Repeated measures screening for Down's Syndrome

OBJECTIVE

To demonstrate the potential value of screening for Down's Syndrome using highly correlated repeated measures of serum markers taken in the first and second trimesters of pregnancy.

DESIGN

A Monte Carlo simulation study.

POPULATION

Detection rates and false positive rates relating to the maternal age distribution of England and Wales for the period 1996 to 1998 were obtained using marker distributions from the SURUSS study.

RESULTS

Screening using first trimester nuchal translucency and repeated measures of uE3 and PAPP-A in the first and second trimester has an estimated false positive rate of 0.3% for an 85% detection rate. This should be compared with the integrated test with an estimated false positive rate of 1.2% for the same detection rate.

CONCLUSIONS

The performance of repeated measures screening tests, and their acceptability to women, should be assessed in further prospective studies.

[First trimester diagnosis of chromosomal defects]

Fetal nuchal translucency thickness at the 11(+0) - 13(+6) weeks scan has been combined with maternal age to provide an effective method of screening for trisomy 21; for an invasive testing rate of 5%, about 75% of trisomic pregnancies can be identified. When maternal serum free B-human chorionic gonadotropin and pregnancy-associated plasma protein-A at 11(+0) - 13(+6) weeks are also taken into account, the detection rate of chromosomal defects is about 85-90%. In 60-70% of fetuses with trisomy 21 the nasal bone is not visible at the 11(+0) - 13(+6) weeks scan and examination of the nasal bone can increase the detection rate of screening by the first trimester scan and serum biochemistry to more than 95%.

Weight adjustment of serum markers in early first-trimester prenatal screening for Down syndrome

OBJECTIVE

To assess whether existing weight correction formulas for PAPP-A and free-beta-hCG developed for weeks 11 to 14 can be applied to pregnancies in weeks 8 to 10.

METHODS

Development of formulas based on limited data sets of 8- to 10-week pregnancies and comparison with existing formulas. Calculation of median MoMs adjusted with different formulas for weight correction.

RESULTS

Weight correction formulas for the gestational age of 11 to 14 weeks were not appropriate in the 8- to 10-week gestational age interval for PAPP-A, whereas existing weight correction formulas could be applied to free-beta-hCG, independent of gestational age interval.

CONCLUSION

If PAPP-A is used in different gestational age intervals, weight corrections should be developed for the interval.

Practical strategies in contingent sequential screening for Down syndrome

OBJECTIVE

To design and assess the performance of protocols for contingent sequential Down syndrome screening that can be implemented in practice.

METHODS

Protocols were designed in which all women received first-trimester measurement of nuchal translucency (NT) together with maternal serum pregnancy-associated plasma protein-A (PAPP-A) and either free beta- or total human chorionic gonadotrophin (hCG). Those women with borderline Down syndrome risks received follow-up second-trimester maternal serum involving double, triple, or quadruple serum screening markers: alpha-fetoprotein, free beta-hCG or total hCG, unconjugated estriol and inhibin-A. Specific ranges of risks were used to define the borderline group. Separate protocols were developed for the United Kingdom and the United States to reflect differences in commonly used tests, cut-offs, and the gestational age at testing. Detection rates and false-positive rates were estimated by multivariate Gaussian modelling with Monte Carlo simulation.

RESULTS

Proposed protocols based on first-trimester NT, PAPP-A and free beta-hCG or total hCG, followed by selective use of second-trimester quadruple markers can result in a 91% detection rate and 2.1% false-positive rate for the United Kingdom and a detection rate of 89% and false-positive rate of 3.1% for the United States. For both countries, over 60% of affected pregnancies would be detected in the first trimester and less than 20% of women would require a second-trimester Down syndrome risk assessment. Use of alternative cut-offs to define those with borderline risks or different combinations of second-trimester markers also yielded high detection rates and low false-positive rates.

CONCLUSION

With appropriate patient counselling, it should be possible to provide highly effective Down syndrome screening using contingent sequential protocols.

Expectation and knowledge of women undergoing first-trimester combined screening for Down syndrome in a Chinese population

OBJECTIVES

To study the preference of pregnant women regarding the time taken to report the results of first-trimester combined screening for Down syndrome and their knowledge about it.

METHODS

A questionnaire survey was conducted on a cohort of 325 pregnant participants who attended our first-trimester combined nuchal translucency and biochemical screening programme for fetal Down syndrome. This service was operated in a one-stop setting and the result of the screening test was available within 1 to 2 h after the collection of blood sample.

RESULTS

The majority of participants: (1) could recall the quoted detection rate correctly (96.6%); (2) understood that a negative test does not exclude Down syndrome (91.1%); (3) understood that a positive test does not equate to an affected fetus (91.0%), and (4) could decide on the need for further invasive tests on the basis of the screening test results (98.1%). Twenty-nine percent of participants considered that a one-stop setting was very important because any delay in releasing the results made a significant difference to them, while 48.9% considered it acceptable if the results were available on the same day. The percentage dropped dramatically to 6.3% (within 2 days), 6.7% (within 3 days), 5.7% (within 1 week), and 3.1% (more than 1 week).

CONCLUSION

The majority of the pregnant women in our test considered same day reporting of screening test results to be no different from a one-stop clinic. This would have important implications for the organisation and structuring of our service provision, since the operation of a one-stop clinic imposes significant stresses on the clinical staff involved.

CDC/AHA Workshop on Markers of Inflammation and Cardiovascular Disease

Inflammation is a recognized key component of acute coronary syndromes. Such pathogenetic achievement has led to the use of inflammatory cells and proteins as prognostic markers in these syndromes. A number of markers have been proposed, including proinflammatory cytokines such as interleukin-6, interleukin-1RA, and tumor necrosis factor-α, adhesion molecules such as intracellular adhesion molecule-1 and vascular adhesion molecule-1 and markers of cell activation. Although all are of scientific interest, the clinical use of these markers is limited by their high cost, low availability, and unfavorable biological profile. Conversely, common markers of inflammation such as C-reactive protein (CRP), the prototypic acute phase protein, and to a lesser extent fibrinogen, have been proven to be reliable and important markers of risk in ischemic heart disease. CRP, in particular, has been found to be associated with short- and long-term prognosis in acute coronary syndromes, including ST-elevation myocardial infarction, and in stable angina, and to predict the risk of restenosis and major events, including death, after revascularization procedures. CRP has been consistently found to be independent from other risk factors and to have an incremental value beyond the common risk factors and biochemical markers of risk, including troponin. Whether CRP also should be used as a guide to therapy is still a matter of discussion that deserves further, properly designed studies.

Factors affecting women's preference for type of prenatal screening test for chromosomal anomalies

OBJECTIVE

To ascertain, by means of a questionnaire, women's preferences for four different approaches to prenatal screening for Down syndrome.

METHODS

Women attending antenatal clinics at six UK maternity units were asked to put in order of preference four different approaches to screening for Down syndrome all of which had the same false positive rate of 5%. The options were: (1) first-trimester testing, 90% detection of Down syndrome with results available in 1 h at one-stop clinics for the assessment of risk (OSCAR); (2) first-trimester testing, 90% detection and results available within 2-3 days (combined screening); (3) first-trimester testing plus second-trimester testing, 93% detection and results available within 2-3 days of second test (integrated testing); (4) second-trimester testing, 75% detection and results available within 2-3 days.

RESULTS

Over 1100 women attending antenatal clinics at six maternity units across the UK returned the questionnaire. A total of 75% of women selected a first-trimester test (option 1 or option 2) as their first choice with 68.2% expressing a preference for the OSCAR approach and a further 6.8% for combined screening. Twenty-four percent of women opted for integrated testing as their first choice with only 1% expressing a preference for second-trimester screening.

CONCLUSIONS

A first-trimester test is preferred by the majority of women over a test with marginally higher detection rate that delivers results later in pregnancy. Timing and rapid reporting of results appear to influence women's choice of test.

Biochemical screening for congenital defects

This article discusses biochemical screening for congenital defects. Biochemical screening remains the standard for estimating the risk of aneuploidy in pregnancy. The combination of first and second trimester markers promises to further improve diagnostic accuracy for anomaly detection.

Pregnancy outcomes in unselected singleton pregnant women with an increased risk of first-trimester Down's syndrome

BACKGROUND

The purpose of this study was to assess outcomes in pregnancies with a positive screen of first-trimester combined test (nuchal translucency, pregnancy-associated plasma protein-A and free beta-human chorionic gonadotropin).

METHODS

Using a cut-off level of 1 in 270, 216 (7.1%) women had a positive screen. Among them, 187 delivered their babies in our hospital and the adverse outcomes, such as spontaneous abortion, intrauterine fetal demize, preterm prelabor rupture of the membranes, preterm labor, intrauterine growth restriction, gestational hypertensive disorders, placenta previa, chromosomal abnormalities and fetal structural anomalies, were identified and compared with the 2097 women who screened negative for Down's syndrome.

RESULTS

Pregnancies with a positive screen had a significantly higher risk of adverse outcomes than those with negative screens (30.5% versus 15.3%; odds ratio 2.4; p < 0.001), especially for those complicated by spontaneous abortion (odds ratio 11.4; p < 0.05) and placenta previa (odds ratio 4.3; p < 0.05).

CONCLUSIONS

Besides fetal chromosomal abnormalities and structural abnormalities, pregnancies with a positive screen for Down's syndrome in the first-trimester had a significantly higher incidence of subsequent adverse obstetric outcomes.

Elevated pregnancy-associated plasma protein-a in sera from type 2 diabetic patients with hypercholesterolemia: associations with carotid atherosclerosis and toe-brachial index

Pregnancy-associated plasma protein (PAPP)-A, a superfamily of metalloproteinase, has been implicated in acute coronary syndrome. We compared PAPP-A concentrations in sera from patients with type 2 diabetes with those in sera from age-matched control subjects and also investigated whether serum PAPP-A was associated with carotid intima-media wall thickness (IMT), an early marker of atherosclerosis, and indices of peripheral vascular disease in the diabetic patients. Serum PAPP-A was measured by an ELISA in 103 type 2 diabetic patients and 32 age-matched control subjects. All subjects were not pregnant. IMT was evaluated ultrasonographically in both common carotid arteries. As measures of peripheral vascular disease, we also determined the ankle-brachial index and toe-brachial index (TBI) for systolic blood pressure. Hypercholesterolemia was defined as a serum low-density lipoprotein-cholesterol concentration exceeding 3.6 mmol/liter or alternatively as a treatment with hydroxymethylglutaryl coenzyme A reductase inhibitor. Serum PAPP-A was significantly higher in diabetic patients than control subjects (P < 0.0001). In diabetic patients, serum PAPP-A correlated positively with serum total cholesterol (r = 0.289, P = 0.0041) and IMT (r = 0.315, P = 0.0017) and negatively with TBI (r = -0.294, P = 0.0039) but not ankle-brachial index. Diabetic patients with hypercholesterolemia had higher PAPP-A concentrations than those without hypercholesterolemia [median (interquartile ranges): 8.37 (6.93, 11.6) vs. 7.29 (5.65, 9.21) mIU/liter; P = 0.0209]. Multivariate analysis identified only serum total cholesterol as an independent determinant of serum PAPP-A in patients with type 2 diabetes (partial coefficient 0.454, P = 0.020). In conclusion, serum PAPP-A concentrations were significantly elevated in diabetic patients with hypercholesterolemia and were associated positively with carotid atherosclerosis and negatively with TBI in type 2 diabetes.

Pregnancy-associated plasma protein A during hemodialysis with polyamide and diacetate cellulosic membranes

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic factor of acute coronary syndrome in the general population. It is elevated in hemodialysis (HD) patients and at baseline, it was shown to be related to inflammation and oxidative stress. The aim of the study was to examine the relationship of PAPP-A and oxidative stress and inflammatory markers to HD treatment. Studied parameters were determined in 10 chronic HD patients treated with low flux polyamide (1st session) and diacetate cellulosic membranes (2nd session) at the beginning, after 15 minutes and at the end of the dialysis session. TRACE method (Time Resolved Amplified Cryptate Emission) was used for PAPP-A assessment. Results were evaluated with ANOVA. PAPP-A levels did not depend on the type of HD membrane but changed significantly with the time of the HD session. They increased significantly from the beginning of HD to 15 min and then decreased to the end of the HD session - p<0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for polyamide membrane and p=0.05 15 min of HD vs start, p<0.01 end vs start, p<0.0001 end vs 15 min of HD for diacetate cellulosic membrane. Changes in other parameters and differences between membranes were only minimal. We can conclude that PAPP-A as a marker of cardiovascular damage shows significant changes during the HD session. Its initial increase might be ascribed to its release from complexes or storage. During dialysis, it might be destroyed or cleaved and removed as free fragments. Its levels both before and after the HD session are higher than in healthy subjects.

Markers to define ischemia: are they ready for prime time use in patients with acute coronary syndromes?

Optimal treatment of patients who present with chest pain is predicated on accurate identification of those patients with a cardiac etiology of their discomfort. Serial troponins and electrocardiograms are very sensitive for the detection of myocardial infarction but they are insensitive for the detection of ischemia. There are many analytes that are being actively evaluated for routine use to facilitate the identification of patients with myocardial ischemia. At present, only one assay is US Food and Drug Administration-approved for the exclusion of ischemia; many other analytes are under clinical evaluation and are briefly reviewed. At present, none of these analytes are yet appropriate for routine clinical use.

Association of extreme first-trimester free human chorionic gonadotropin-beta, pregnancy-associated plasma protein A, and nuchal translucency with intrauterine growth restriction and other adverse pregnancy outcomes

OBJECTIVE

The purpose of this study was to determine the association between first-trimester trisomy 21 screening markers (free human chorionic gonadotropin-beta [hCG], pregnancy-associated plasma protein A [PAPP-A], and nuchal translucency) and adverse pregnancy outcome.

STUDY DESIGN

This was a cohort study of 8012 patients enrolled in a National Institute of Child Health and Human Development-sponsored study of first-trimester trisomy 21 and 18 screening. Trisomy 21 and 18 risk results and individual marker levels in unaffected pregnancies and pregnancies with adverse outcomes were evaluated.

RESULTS

PAPP-A <1st percentile (OR 5.4, 95% CI 2.8-10.3) and PAPP-A <5th percentile (OR 2.7, 95% CI 1.9-3.9) and free beta-hCG <1st percentile (OR 2.7, 95% CI 1.3-5.9) were associated with increased risk of intrauterine growth restriction (IUGR) with positive predictive values of 24.1%, 14.1%, and 14.3%, respectively. PAPP-A <5th percentile (OR 2.3 95% CI 1.1-4.7) and nuchal translucency >99th percentile (OR 3.5, 95% CI 1.1-11.3) were associated with increased risk of preterm delivery before 34 weeks. Increased risk at screening for trisomy 21 and 18 identified 16 of the 29 other chromosomal abnormalities (55%). Low free beta-hCG, low PAPP-A, and increased nuchal translucency were all associated with an increased rate of fetal abnormality.

CONCLUSION

Extreme values of first-trimester free beta-hCG, PAPP-A, and nuchal translucency are all associated with adverse outcomes. The especially high predictive value for IUGR of PAPP-A levels below the 1st percentile suggests that patients within this group may benefit from increased surveillance for this condition.

Evaluation of pregnancy-associated plasma protein A as a prognostic indicator in acute coronary syndrome patients

BACKGROUND

Higher circulating concentrations of pregnancy-associated plasma protein A (PAPP-A), a potential proatherosclerotic metalloproteinase, have been associated with increased risk for acute coronary syndrome (ACS). Our goal was to determine the ability of circulating concentrations of PAPP-A to predict adverse events in patients presenting to the Emergency Department (ED) with symptoms of ACS.

METHODS

A total of 346 patients with symptoms of ACS were included in the study. Serum samples obtained immediately after enrollment were analyzed for PAPP-A and cardiac troponin T (cTnT). The occurrence of adverse events during a 30-day follow-up period was recorded, and receiver-operating characteristic (ROC) curve analysis was performed to evaluate the prognostic characteristics of PAPP-A and cTnT.

RESULTS

A total of 33 (9.5 %) patients developed adverse events during the follow up period. At a cut-off concentration of 0.22 mIU/l, PAPP-A was a predictor of adverse events with a sensitivity and specificity (95% C.I.) of 66.7% (48.2-82.0) and 51.1% (45.4-56.8), respectively. The sensitivity and specificity of cTnT were 51.5% (33.6-69.2) and 82.1% (77.4-86.2), respectively, using a 0.01-ng/ml cut-off value, which was obtained using ROC analysis.

CONCLUSIONS

PAPP-A appears to be a modest predictor of adverse events in patients presenting to the ED with ACS symptoms, being inferior to cTnT in predicting adverse events in an ED setting. PAPP-A appears to be as sensitive as cTnT, but it is less specific.

First-trimester maternal serum PAPP-A and free-beta subunit human chorionic gonadotropin concentrations and nuchal translucency are associated with obstetric complications: a population-based screening study (the FASTER Trial)

OBJECTIVE

The purpose of this study was to determine whether maternal serum levels of pregnancy-associated plasma protein A, free-beta subunit human chorionic gonadotropin, or nuchal translucency size are associated with obstetric complications.

STUDY DESIGN

Data were obtained from the First and Second Trimester Evaluation of Risk trial. Pregnancy-associated plasma protein A and free-beta subunit human chorionic gonadotropin levels were analyzed, and nuchal translucency was measured between 10 weeks 3 days and 13 weeks 6 days of gestation in 34,271 pregnancies.

RESULTS

Women with pregnancy-associated plasma protein A of < or =5th percentile were significantly more likely to experience spontaneous fetal loss at < or =24 weeks of gestation, low birth weight, preeclampsia, gestational hypertension, preterm birth ( P < .001) and stillbirth, preterm premature rupture of membranes, and placental abruption ( P < .02). Nuchal translucency at > or =99th percentile and free-beta subunit human chorionic gonadotropin at < or =1st percentile were associated with an increased risk of spontaneous loss at < or =24 weeks of gestation (adjusted odds ratios, 3.90, 3.62, respectively; P < .001).

CONCLUSION

Low pregnancy-associated plasma protein A levels in the first trimester were associated strongly with a number of adverse pregnancy outcomes. Low free-beta subunit human chorionic gonadotropin levels and large nuchal translucency were both associated with early fetal loss.

A serum proteomics approach to the diagnosis of ectopic pregnancy

An ectopic pregnancy (EP) occurs when implantation of the embryo occurs outside of the uterus. If left untreated, the developing fetus will continue to grow, leading to life-threatening consequences for the mother. A major difficulty with the diagnosis of ectopic pregnancy is that methods of detection are limited, and some, such as ultrasound, are not very reliable in the earliest days of gestation. Currently, no effective serum test exists to distinguish an ectopic pregnancy from a normal intrauterine pregnancy. The incidence of ectopic pregnancy is increasing and has doubled in the last 20 years. It is now the second most common cause of maternal death in the first trimester of pregnancy. To address this issue, we initiated a project to identify serum markers of ectopic pregnancy. The subjects for these studies presented at the Hospital of the University of Pennsylvania. We obtained over 140 serum samples from women with suspected ectopic pregnancy: women presenting with pain and/or bleeding in the first trimester of pregnancy. The approximate racial breakdown of the subjects is as follows: African American, 36%; Caucasian, 3%; Asian, 2%; Hispanic, 1%; unknown, 58%. Serum samples from 139 women (62 with ectopic pregnancy and 77 with a normal intrauterine pregnancy) were applied to WCX2 (weak ion exchange) protein chip surfaces and analyzed for serum markers using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Several proteins in the 7500-18,000 Da mass range were identified that may discriminate an ectopic pregnancy from an intrauterine pregnancy. The most promising markers were analyzed using classification and regression tree analysis (CART) with and without clinical variables (serum hCG value, length of amenorrhea). Two different algorithms were developed that classify the patients on the basis of sensitivity (number of EPs who screen positive/# of EPs) or specificity (# of healthy patients who screen negative/# of healthy). Our current approach is to refine these two "rule sets" to segregate patients into three groups: those who need immediate intervention for a probable ectopic pregnancy, those who appear to have a normal pregnancy, and those who need further monitoring for diagnosis.

New developments in prenatal screening for Down syndrome

Since the introduction of the triple screen, the emergence of additional analytes found to be associated with trisomy 21 pregnancies has challenged the clinical pathology and obstetric communities to determine which combination provides the best performance characteristics as a screening test. The cost, practicality, and psychosocial and ethical dimensions of different screening regimens further complicate the issue. This review attempts to give an overview of the various markers, current methods of screening, and most promising recent developments in antenatal screening for Down syndrome, with an emphasis on performance in prospective studies that have emerged during the last few years, rather than on estimates from statistical modeling.

Increased Levels of Pregnancy-Associated Plasma Protein A Are Associated with Mortality in Hemodialysis Patients: Preliminary Results

Pregnancy-associated plasma protein A (PAPP-A) is a new prognostic indicator of acute coronary syndrome. This protein is elevated in hemodialysis (HD) patients and is closely related to inflammation and oxidative stress. The aim of our pilot study was to find out whether PAPP-A is related to mortality in HD patients. 40 HD patients in a stable clinical state (20 men and 20 women, mean age 69 +/- 12 years) were enrolled in the study and followed up for 20 months. PAPP-A was assessed immunochemically (TRACE method) in serum samples (before the HD session) at the beginning of the observation period. During the follow-up, 22 patients died, 15 of them due to cardiovascular events. PAPP-A levels were significantly higher in the patients who died, compared to living HD patients: 26.8 (21.6-36.8) vs. 20 (14.9-26.6) mU/l, p = 0.034. PAPP-A could also be a new prognostic marker in hemodialysis patients, probably due to its close association with cardiovascular risk. More extensive studies are required to confirm this hypothesis.

Pregnancy-Associated Plasma Protein A, Free β-hCG, Nuchal Translucency, and Risk of Pregnancy Loss

OBJECTIVE

To estimate the likelihood of clinical early and late pregnancy loss as a function of first-trimester maternal serum analytes and fetal nuchal translucency measurements.

METHODS

Study subjects were recruited for a National Institute of Child Health and Human Development-sponsored multicenter cohort study initially designed to study the detection of Down syndrome during the first trimester of pregnancy. The cohort consisted of women who had a live fetus between 10 and 14 weeks of gestation and had no significant vaginal bleeding. Women with prior fetal trisomy (T21/18) and those with structural or chromosomal abnormalities in the index pregnancy were excluded. First-trimester screening consisted of pregnancy-associated plasma protein A (PAPP-A), free beta-hCG, and nuchal translucency. Pregnancy loss rates in women with various levels of PAPP-A, free beta-hCG, or nuchal translucency (less than 1st, less than 5th, more than 95th, and more than 99th percentile) were compared with losses in women with normal values (5th to 95th percentile).

RESULTS

The mean gestational age at screening of 7,932 women meeting study criteria was 12.1 weeks. Loss rates were only 0.36% at less than 20 weeks after normal free beta-hCG, PAPP-A, and nuchal translucency. Conversely, low levels of PAPP-A and free beta-hCG as well as increased nuchal translucency were individually associated with increased early loss. These associations persisted after controlling for maternal age and race using logistic regression analysis.

CONCLUSION

Normal values of PAPP-A, free beta-hCG, and nuchal translucency are associated with a very low risk of pregnancy loss at less than 20 weeks.

Nuchal translucency and other first-trimester sonographic markers of chromosomal abnormalities

There is extensive evidence that effective screening for major chromosomal abnormalities can be provided in the first trimester of pregnancy. Prospective studies in a total of 200,868 pregnancies, including 871 fetuses with trisomy 21, have demonstrated that increased nuchal translucency can identify 76.8% of fetuses with trisomy 21, which represents a false-positive rate of 4.2%. When fetal nuchal translucency was combined with maternal serum free-beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A in prospective studies in a total of 44,613 pregnancies, including 215 fetuses with trisomy 21, the detection rate was 87.0% for a false-positive rate of 5.0%. Studies from specialist centers with 15,822 pregnancies, which included 397 fetuses with trisomy 21, have demonstrated that the absence of the nasal bone can identify 69.0% of trisomy 21 fetuses, which represents a false-positive rate of 1.4%. It has been estimated that first-trimester screening by a combination of sonography and maternal serum testing can identify 97% of trisomy 21 fetuses, which represents a false-positive rate of 5%, or that the detection rate can be 91%, which represents a false-positive rate of 0.5%. In addition to increased nuchal translucency, important sonographic markers for chromosomal abnormalities, include fetal growth restriction, tachycardia, abnormal flow in the ductus venosus, megacystis, exomphalos and single umbilical artery. Most pregnant women prefer screening in the first, rather than in the second, trimester. As with all aspects of good clinical practice, those care givers who perform first-trimester screening should be trained appropriately, and their results should be subjected to external quality assurance.

First-trimester nuchal translucency and maternal serum freeβ-hCG and PAPP-A can detect triploidy and determine the parental origin

OBJECTIVE

To evaluate the levels of first-trimester screening markers in triploid pregnancies and to determine the parental origin of triploidy.

STUDY DESIGN

During the five-year study period, 12322 patients with singleton pregnancies underwent combined first-trimester screening using nuchal translucency (NT) and maternal serum free beta-human chorionic gonadotrophin (free beta-hCG) and pregnancy associated plasma protein-A (PAPP-A) at 10 to 14 weeks' gestation. Maternal serum markers and NT were evaluated in cases of triploidy. Molecular analysis was performed using polymorphic markers to establish the parental source of triploidy.

RESULTS

Eight cases of triploidy were detected at a rate of at least 1 in 1540. All cases were electively terminated early in gestation or resulted in spontaneous miscarriage. Two patterns of first-trimester markers emerged: type I, characterized by extremely high levels of free beta-hCG and elevated NT; and type II, characterized by very low levels of PAPP-A and free beta-hCG with normal NT. Molecular analysis demonstrated that type I triploidy is of paternal origin (diandric) and type II is of maternal origin (digynic).

CONCLUSIONS

On the basis of these results, it may be possible to detect triploid pregnancies in the first trimester and determine their origin using combined first-trimester screening.