Taichi Isozaki

Screening for down syndrome pregnancy using β-core fragment : Prospective study

Two recent publications by Cuckle et al., and one each by Canick et al. and Kellner et al., describe the use of urine β‐core fragment measurements as a screening test for Down syndrome pregnancies. Median levels of over 5·4 MOM were reported for cases of Down syndrome, with an over 72 per cent detection rate for a 5 per cent false‐positive rate. Urine β‐core fragment was suggested as a superior screening test for Down syndrome pregnancies. These four studies were retrospectives, with samples from affected cases collected at different sites from those from normal cases. In the present study, prospective data were collected for 726 pregnancies over a 9‐month period at a single medical centre. Fresh samples were assayed continuously, without knowledge of the karyotype. Urinary β‐core fragment levels in 709 unaffected samples continually declined from 12 to 24 weeks of pregnancy. A logarithmic fit was optimal for the median curve. The log standard deviation of unaffected samples was 0·368. All 13 Down syndrome cases had levels exceeding 1·0 MOM, with a median value of 4·1 MOM. Eight of 13 Down syndrome cases (62 per cent) had levels exceeding the 95th centile. Results have not been adjusted for maternal age, which may improve the detection rate. The results reported here, while less impressive than those reported previously, confirm the usefulness of urine β‐core fragment as a screening test for Down syndrome. Because of the prospective nature of this study, the 62 per cent sensitivity suggested here might be more representative of the true performance of urinary β‐core fragment in clinical practice than the higher rates observed in previous studies. Results for this single urine test are similar to those for triple screen and other serum combination tests. Single analyte urine β‐core fragment tests, or β‐core fragment combination protocols, may eventually replace serum analytes in screening for Down syndrome pregnancies.

Midtrimester urine human chorionic gonadotropin β-subunit core fragment levels and the subsequent development of pre-eclampsia☆☆☆★

OBJECTIVE Our purpose was to determine whether midtrimester maternal urine human chorionic gonadotropin beta-subunit core fragment predicts later pre-eclampsia. STUDY DESIGN Urine beta-core fragment levels standardized to spot creatinine concentration and expressed as multiples of the median were prospectively determined in 347 midtrimester singleton pregnancies undergoing genetic amniocentesis. All women considered in the analysis were white and nonsmokers. Obstetric chart review was undertaken after delivery to identify cases in which pre-eclampsia developed. The risk of pre-eclampsia at different threshold levels of beta-core fragment of human chorionic gonadotropin was determined. RESULTS The median maternal age was 36.0 years, with a median gestational age at urine collection of 16.0 weeks. The median level of the beta-core fragment of human chorionic gonadotropin was 1385.5 ng/mg of creatinine in those with pre-eclampsia, whereas that in those without pre-eclampsia was 1061.2 ng/mg. The difference was significant (Mann-Whitney U test, P = .03). A significant linear association was found between the beta-core fragment concentration and the risk of pre-eclampsia (Mantel-Haenszel test of linear association, P = .03). The relative risk and 95% confidence interval of subsequent pre-eclampsia increased from 2.07 (1.06 to 4.05) at beta-core fragment levels of human chorionic gonadotropin > or = 2.0 multiples of the median to 5.17 (1.95 to 13.7) at > or = 4.0 multiples of the median. CONCLUSION Clinically normal patients with elevated midtrimester levels of urine beta-core fragment of human chorionic gonadotropin are at increased risk for the subsequent development of pre-eclampsia. The clinical value of this urine analyte as a marker for pre-eclampsia needs to be further investigated.

Elevated serum nicked and urinary beta-core fragment hCG in preeclamptic pregnancies

Objective To determine whether different molecular forms of hCG in serum and urine are elevated in preeclamptic pregnancies Methods Forty-three pregnant women were studied: 25 preeclamptic women and 18 normotensive women. Immediately after blood and urine samples were collected, the protease inhibitors leupeptin (0.35mM) and phenanthroline (22 mM were added. Various molecular forms of hCG in serum (complete hCG, nonnicked hCG, complete free beta hCG) and in urine (complete hCG, beta-core fragment hCG) were measured by matched immunoassays with a common enzyme-labeled tracer antibody. The nicked hCG assay used a coating of beta-subunit monoclonal antibody with the addition of scavenger antibody to remove nonnicked hCG. Mann-Whitney U test and X2 test were used for statistical analyses. Results Preeclamptic women had significantly higher median (range) levels of serum complete and nicked hCG than did normotensive women (3620 [850–12,0001 versus 2420 [310–4850] ng/mL, P = .024; and 102 [45–275] versus 71 [11–143] ng/mL, P = .010, respectively). Both median (range) urinary complete hCG-creatinine and beta-core fragmentcreatinine ratios were significantly higher in preeclamptic women that in normotensive women (37.6 [0.5–185] versus 11.3 [1.9–54], P = .013; and 11.8 [2–67] versus 5.3 [0.3–29], P = .009, respectively). Conclusion Various molecular forms of hCG in serum and urine were significantly higher in preeclamptic than in normotensive pregnancies.

Urine β-Core Fragment, a Potential Screening Test for Ectopic Pregnancy and Spontaneous Abortion

The incidence of ectopic pregnancy in the United States has risen 6-fold in the last three decades. It now accounts for about 2% of reported pregnancies. Tests are now needed to identify ectopic pregnancy before it is clinically evident. We evaluated human chorionic gonadotropin β-core fragment as a test to predict ectopic pregnancy and spontaneous abortion. Urine samples were collected from women with in vitro fertilized pregnancies, 2½–5 weeks after embryo transfer. Fifty samples were collected from those later shown to have normal intrauterine pregnancies, samples from 13 women subsequently found (at 5–9.3 weeks) to have ectopic gestations, and 15 from those with impending spontaneous abortion. β-Core fragment levels were determined by immunoassay, and results normalized to creatinine concentration. Median β-core fragment levels at 2½–3, 3–4, and 4–5 weeks after embryo transfer, were 6.7,91 and 737 μg/g for unaffected pregnancies, 1.0, 5.9 and 0.6 μg/g for impending ectopic pregnancies (0.15, 0.065 and 0.0008, multiples of the unaffected pregnancy median, MoM), and 0.75, 6.8 and 12 μg/g for impending spontaneous abortions (0.11, 0.07 and 0.016 MoM). A gestation-linked curve was modeled to discriminate unaffected pregnancy from impending ectopic gestation or spontaneous abortion. Plotted β-core fragment levels were below this curve in 12 of 13 (92%) women with impending ectopic pregnancy, in 10 of 15 (67%) with spontaneous abortion outcome, and in 2 of 50 (4%) with intrauterine pregnancy and term outcome. Measurement of urine β-core fragment at 2½–5 weeks after embryo transfer (4½–7 weeks after last menstrual period) might be useful for identifying failing pregnancies. Over three quarters (predictive value positive 76%) of those with low β-core fragment levels have ectopic pregnancy or spontaneous abortion. On the contrary, 95% (predictive value negative) of those with normal range test values may be predicted to have a nonfailing term pregnancy. Diagnosis of ectopic pregnancy could be confirmed by transvaginal ultrasound, and ectopic pregnancy terminated early by nonsurgical methods, with minimal mortality or fertility loss. Major fetal defects that cause spontaneous abort pregnancies may also be recognized by transvaginal ultrasound. In such cases, chorionic villous sampling or possibly termination may be considered.

Comparison of 12 assays for detecting hCG and related molecules in urine samples from Down syndrome pregnancies

Urine is a new medium for Down syndrome testing. In an effort to determine the best type of human chorionic gonadotropin (hCG)‐related immunoassay for urine testing, we examined 14 Down syndrome and 91 unaffected pregnancy urine samples with 12 established assays. The assays included (a) those that detect hCG β‐core fragment only; (b) those that detect β‐core fragment with less than 18 per cent free β‐subunit cross‐reactivity; (c) that which equally detects free β‐subunit and β‐core fragment; and (d) those that detect hCG, free β‐subunit, or combinations thereof. The seven type a and b assays had the highest sensitivity for Down syndrome. The median MOM for Down syndrome was 5·93 (range 4·73–7·53). At a 10 per cent false‐positive rate, the median observed detection rate was 93 per cent (range 79–100 per cent) and the median predicted detection rate was 85 per cent (range 69–96 per cent). The assays that did not mainly detect β‐core fragment (types c and d) had poorer screening performance. The median MOM for Down syndrome was 2·70 (range 2·16–3·63 MOM). At a 10 per cent false‐positive rate, the median observed detection rate was 50 per cent (range 36–64 per cent) and the median predicted detection rate was 37 per cent (range 21–62 per cent). We infer that the assays that only detect β‐core fragment, or β‐core fragment with minor free β‐subunit cross‐reactivity (types a and b), are the better urine‐based tests for Down syndrome screening.

Screening for Down syndrome using urine hCG free β-subunit in the second trimester of pregnancy

Human chorionic gonadotropin (hCG) free β‐subunit levels were determined in 709 control and 13 Down syndrome urine samples from the second trimester of pregnancy. Results were normalized to urine creatinine concentration and converted to multiples of the unaffected pregnancy medium (MOM). The concentration of free β‐subunit in Down syndrome cases was 3·9 MOM. Seven of 13 Down syndrome pregnancies (54 per cent) had free β‐subunit levels at or above the 95th centile of unaffected pregnancies. Urine free β‐subunit may potentially be useful as a screening test for Down syndrome.