Outlier robust model-assisted small area estimation.

Small area estimation with M-quantile models was proposed by Chambers and Tzavidis (). The key target of this approach to small area estimation is to obtain reliable and outlier robust estimates avoiding at the same time the need for strong parametric assumptions. This approach, however, does not allow for the use of unit level survey weights, making questionable the design consistency of the estimators unless the sampling design is self-weighting within small areas. In this paper, we adopt a model-assisted approach and construct design consistent small area estimators that are based on the M-quantile small area model. Analytic and bootstrap estimators of the design-based variance are discussed. The proposed estimators are empirically evaluated in the presence of complex sampling designs.

Lack of concordance between the 75-g and 100-g glucose load tests for the diagnosis of gestational diabetes mellitus.

BACKGROUND: Gestational diabetes mellitus (GDM) is common and can have a substantial impact on fetal growth, birth weight, and morbidity. The American Diabetes Association recommends GDM testing with either a 3-h, 100-g glucose load (100 g) (criteria according to Am J Obstet Gynecol 1982;144:768-73) or a 2-h, 75-g glucose load (75g). We investigated the comparability of the 75 g and the 100g tests in the diagnosis of GDM. METHODS: From January 1997 to December 1999, in 1061 consecutive Caucasian nonobese and nondiabetic pregnant women who attended the Maternal-Fetal Medicine Unit, we performed GDM testing with a 75-g load during 2 periods of pregnancy: early (16-20 weeks) and late (26-30 weeks). Because we assumed there would be few GBM cases in women with a 1-h plasma glucose <1300 mg/L in the 75 g test, we did not retest these women. We retested the remaining women with possible or diagnosed GDM with a 100-g load within a week. RESULTS: GDM was diagnosed in 41 of 227 women with the 100-g load and 15 of 227 with the 75-g load (11 concordant); the kappa index was 0.21. At 26-31 weeks of pregnancy, 484 of 976 women (49.9%) underwent both tests. GDM was diagnosed in 60 of 484 woman with the 100-g load and in 26 of 484 with the 75-g load (13 concordant); the kappa index was 0.18. CONCLUSIONS: Among women with possible GDM in both early and late periods of pregnancy, there was only weak diagnostic agreement between results determined with 75-g and 100-g glucose loads.

The 75-gram glucose load in pregnancy: relation between glucose levels and anthropometric characteristics of infants born to women with normal glucose metabolism.

OBJECTIVE: To investigate, in pregnant women without gestational diabetes mellitus (GDM), the relation among obstetric/demographic characteristics; fasting, 1-h, and 2-h plasma glucose values resulting from a 75-g glucose load; and the risk of abnormal neonatal anthropometric features and then to verify the presence of a threshold glucose value for a 75-g glucose load above which there is an increased risk for abnormal neonatal anthropometric characteristics. RESEARCH DESIGN AND METHODS: The study group consisted of 829 Caucasian pregnant women with singleton pregnancy who had no history of pregestational diabetes or GDM, who were tested for GDM with a 75-g, 2-h glucose load, used as a glucose challenge test, in two periods of pregnancy (early, 16-20 weeks; late, 26-30 weeks), and who did not meet the criteria for a GDM diagnosis. In the newborns, the following abnormal anthropometric characteristics were considered as outcome measures: cranial/thoracic circumference (CC/TC) ratio /=90th percentile for GA, and macrosomia (birth weight >/=90th percentile for GA), on the basis of growth standard development for our population. For the first part of the objective, logistic regression models were used to identify 75-g glucose load values as well as obstetric and demographic variables as markers for abnormal neonatal anthropometric characteristics. For the second part, the receiver operating characteristic (ROC) curve was performed for the 75-g glucose load values to determine the plasma glucose threshold value that yielded the highest combined sensitivity and specificity for the prediction of abnormal neonatal anthropometric characteristics. RESULTS: In both early and late periods, maternal age >35 years was a predictor of neonatal CC/TC ratio 35 years being an independent predictor for macrosomia. The 2-h, 75-g glucose load values were significantly associated in both periods with neonatal CC/TC ratio /=90th percentile, whereas maternal age >35 years was an independent predictor of both neonatal CC/TC ratio