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J Van Nueten

Publications and source records attributed to J Van Nueten.

9 recordsLinked to original sources
PubMed2006

Weight correction of MoM values: which method?

BACKGROUND: Adjusting maternal serum markers for maternal weight is considered to be a standard practice when screening for pregnancies associated with Down's syndrome. The choice of model for taking maternal weight into account is, however, rarely explicitly evaluated. METHOD: The relationship between the maternal serum markers alphafetoprotein (AFP), human chorionic gonadotropin (HCG) and unconjugated oestriol (uE3), determined with the Beckman Coulter access reagents and maternal weight was investigated in a cohort of 752 Belgian women being screened for pregnancy associated with Down's syndrome. Two different models (the log-linear equation and the linear-reciprocal equation) were used to determine the relationship between the serum markers and maternal weight. RESULTS: A significant relationship between log(10) multiples of median (MoM) values and weight (kg) was obtained for all markers, and the log-linear model had higher coefficients of determination (r(2)) when compared with the linear-reciprocal model. Weight correction with either method achieved the optimum effect that the correction factor for a woman with a population median weight of 65.5 kg was not significantly different from 1. Simulated weight-corrected MoM values with the two approaches were compared and variation was estimated. The mean difference between the weight-corrected MoM values calculated by the two methods was 7.8% (SD 4.3%) for AFP, 14.0% (4.4%) for HCG and 5.9% (3.2%) for uE3. This resulted in a difference in risk estimate of 1.66-5.34% for Down's syndrome owing to weight correction algorithm differences in women of median weight. CONCLUSION: The log-linear weight correction approach was shown to be marginally more effective by a goodness-of-fit analysis. Differences in weight-corrected MoM values estimated with the two approaches are highly significant (p<0.0001, Wilcoxon's paired sample test), but the effect on risk calculation was not significant. It was observed that the changes in risk became significant the more the MoM correction factors deviated from 1.

Biomarkers↗
PubMed2006

Medians for second-trimester maternal serum markers: geographical differences and variation caused by median multiples-of-median equations.

OBJECTIVES: To establish gestational age-specific mid-trimester normal medians for the prenatal serum markers alpha fetoprotein (AFP), human chorionic gonadotropin (HCG) and unconjugated oestriol (uE3) for a Belgian population by using the Beckman Coulter Access chemiluminiscent immunoassays; to compare these data with data obtained from other geographical regions; to propose regression coefficients for regressed medians and analyse variation induced by different regression equations; to evaluate the effect of formulas used for gestation correction on estimating risk in Down's syndrome. DESIGN: Data derived from 862 fresh serum samples from women being screened for Down's syndrome pregnancy, composed of selected pregnancies deemed to be normal, were examined in a retrospective study. Regressed medians were calculated by using a first-degree logarithmic-linear fit of the raw data. Multiples-of-median (MoM) values estimated by using a simple logarithmic-linear equation were compared with those calculated with higher-degree polynomials chosen with a goodness-of-fit analysis. Model-specific variation was estimated and the effect on risk for Down's syndrome was evaluated. RESULTS: Regressed medians (Y) for Access serum markers AFP (IU/ml), HCG (IU/ml) and uE3 (nmol/l) for a Belgian population can be estimated with the equation Y = 10((A+BX)) with X = decimal weeks. The best fit was obtained with a third-degree and a second-degree polynomial for AFP and uE3, respectively. Differences between the medians and among the slopes of the geographical populations were found to be significant (analysis of covariance, p<0.001). CONCLUSIONS: Belgian marker medians versus gestational time are found to show a pattern that is similar to that in the literature. The log-linear equation is observed to give a good fit and can be suggested as a tool for calculating median MoM values for Belgian laboratories that use Access biochemical prenatal markers.

Belgium↗
PubMed1995

Cryptorchidism and extragonadal germ cell tumor.

A patient with an extragonadal germ cell tumor and a history of bilateral cryptorchidism is reported. The rarity of this concurrence in a single patient is discussed. The necessity for thorough investigation of the cryptorchid testes in patients with metastatic germ cell cancer remains essential.

Adult↗
PubMed1992

Role of penile nocturnal tumescence and rigidity measurement in the diagnosis of erectile impotence.

Reviewing a group of 100 patients undergoing nocturnal penile tumescence and rigidity measurement (NPTR), we tried to define normal values and compared these results with those of other authors. We also tried to answer two important questions: Is an abnormal NPTR registration always a proof of biogenic impotence? Is a normal NPTR always a proof of psychogenic impotence?

Erectile Dysfunction↗
PubMed1988

Clinical aspects in the surgical treatment of varicocele in subfertile men. I. Comparison of observed and expected pregnancy rates.

Ninety-six couples, consulting for primary (n = 73) or secondary (n = 23) infertility, and thought to be infertile due to a varicocele in the husband associated with sperm abnormalities, were subjected to a follow-up study. Of these, 57 were surgically corrected and 39 were not, depending only on the patient's choice. All women were intensively treated where necessary. From our data we conclude that (1) fertility prognosis is significantly better in couples with secondary subfertility than in couples with primary subfertility, (2) surgical correction of varicocele in cases of secondary subfertility does not increase subsequent pregnancy rates, and (3) surgical correction of varicocele in cases of primary subfertility significantly increases subsequent pregnancy rates, since cumulative observed pregnancy rates are more than double the cumulative theoretically expected treatment-independent pregnancy rates.

Female↗
PubMed1988

Clinical aspects in the surgical treatment of varicocele in subfertile men. II. The role of the epididymal factor.

Ninety-six couples, consulting for primary (n = 73) or secondary (n = 23) infertility, and thought to be infertile due to a varicocele in the husband associated with sperm abnormalities, were subjected to a follow-up study. Of these, 57 were surgically corrected and 39 were not, depending only on the patient's choice. All women were intensively treated where necessary. All patients who were corrected were subjected to scrotal exploration in a search for epididymal anomalies. From our data we conclude that (1) on a statistical basis, comparing observed with expected pregnancy rates, varicocelectomy is useful in primary infertility and unnecessary in secondary infertility and (2) on an individual basis, patients with primary infertility and 'pure' varicoceles have a better prognosis than patients with concomitant epididymal dysfunction.

Epididymis↗