Complex Latent Variable Modeling in Educational Assessment

Bayesian item response theory models have been widely used in different research fields. They support measuring constructs and modeling relationships between constructs, while accounting for complex test situations (e.g., complex sampling designs, missing data, heterogenous population). Advantages of this flexible modeling framework together with powerful simulation-based estimation techniques are discussed. Furthermore, it is shown how the Bayes factor can be used to test relevant hypotheses in assessment using the College Basic Academic Subjects Examination (CBASE) data

Effect of discontinuation of growth hormone treatment on risk factors for cardiovascular disease in adolescents born small for gestational age

Hyperlipidemia, diabetes mellitus type 2, and coronary heart disease have been associated with being born small for gestational age (SGA). It has been reported that GH treatment induced higher insulin levels, which has led to concern regarding the long-term effect of GH treatment in predisposed individuals such as children born SGA. In this study, we assessed the effect of discontinuation of long-term GH treatment in 47 adolescents born SGA on oral glucose tolerance tests, blood pressure (BP), and serum lipid levels for two GH dosage groups (3 vs. 6 IU/m2 x d). At 6 months after discontinuation of GH treatment mean (SD) age was 16.0 (2.1) yr. Mean duration of GH treatment had been 6.9 (1.5) yr. Fasting glucose levels and 120-min area under the curve for glucose 6 months after discontinuation of GH treatment showed no difference from pretreatment levels for both GH dosage groups. After discontinuation of GH treatment, fasting insulin levels returned to pretreatment levels (8.4 mU/liter), whereas the 120-min area under the curve for insulin decreased, compared with 6-yr levels (P < 0.01), regardless of GH dosage group. No significant difference was found when levels were compared with a control group. In addition, for both GH dosage groups, no significant changes in systolic and diastolic BP SD score, total cholesterol, and atherogenic index (total cholesterol/high-density lipoprotein cholesterol) were seen from 6 yr of GH until 6 months after discontinuation of GH treatment. In conclusion, in children born SGA, the GH-induced insulin insensitivity disappeared after discontinuation of GH, even after long-term GH treatment. Furthermore, the beneficial effect of GH on BP was not changed after discontinuation of GH, and most children had normal lipid levels

Adult height after long-term, continuous growth hormone (GH) treatment in short children born small for gestational age: results of a randomized, double-blind, dose-response GH trial

The GH dose-response effect of long-term continuous GH treatment on adult height (AH) was evaluated in 54 short children born small for gestational age (SGA) who were participating in a randomized, double-blind, dose-response trial. Patients were randomly and blindly assigned to treatment with either 3 IU (group A) or 6 IU (group B) GH/m(2).d ( approximately 0.033 or 0.067 mg/kg.d, respectively). The mean (+/-SD) birth length was -3.6 (1.4), the age at the start of the study was 8.1 (1.9) yr, and the height SD score (SDS) at the start of the study -3.0 (0.7). Seventeen of the 54 children were partially GH deficient (stimulated GH peak, 10-20 mU/liter). Fifteen non-GH-treated, non-GH-deficient, short children born SGA, with similar inclusion criteria, served as controls [mean (+/-SD) birth length, -3.3 (1.2); age at start, 7.8 (1.7) yr; height SDS at start, -2.6 (0.5)]. GH treatment resulted in an AH above -2 SDS in 85% of the children after a mean (+/-SD) GH treatment period of 7.8 (1.7) yr. The mean (SD) AH SDS was -1.1 (0.7) for group A and -0.9 (0.8) for group B, resulting from a mean (+/-SD) gain in height SDS of 1.8 (0.7) for group A and 2.1 (0.8) for group B. No significant differences between groups A and B were found for AH SDS (mean difference, 0.3 SDS; 95% confidence interval, -0.2, 0.6; P > 0.2) and gain in height SDS (mean difference, 0.3 SDS; 95% confidence interval, -0.1, 0.7; P > 0.1). When corrected for target height, the mean corrected AH SDS was -0.2 (0.8) for group A and -0.4 (0.9) for group B. The mean (+/-SD) AH SDS of the control group [-2.3 (0.7)] was significantly lower than that of the GH-treated group (P < 0.001). Multiple regression analysis indicated the following predictive variables for AH SDS: target height SDS, height SDS, and chronological age minus bone age (years) at the start of the study. GH dose had no significant effect. In conclusion, long-term continuous GH treatment in short children born SGA without signs of persistent catch-up growth leads to a normalization of AH, even with a GH dose of 3 IU/m(2).d ( approximately 0.033 mg/kg.d)

Bioenergetic Impairment in Congenital Muscular Dystrophy Type 1A and Leigh Syndrome Muscle Cells

Skeletal muscle has high energy requirement and alterations in metabolism are associated with pathological conditions causing muscle wasting and impaired regeneration. Congenital muscular dystrophy type 1A (MDC1A) is a severe muscle disorder caused by mutations in the LAMA2 gene. Leigh syndrome (LS) is a neurometabolic disease caused by mutations in genes related to mitochondrial function. Skeletal muscle is severely affected in both diseases and a common feature is muscle weakness that leads to hypotonia and respiratory problems. Here, we have investigated the bioenergetic profile in myogenic cells from MDC1A and LS patients. We found dysregulated expression of genes related to energy production, apoptosis and proteasome in myoblasts and myotubes. Moreover, impaired mitochondrial function and a compensatory upregulation of glycolysis were observed when monitored in real-time. Also, alterations in cell cycle populations in myoblasts and enhanced caspase-3 activity in myotubes were observed. Thus, we have for the first time demonstrated an impairment of the bioenergetic status in human MDC1A and LS muscle cells, which could contribute to cell cycle disturbance and increased apoptosis. Our findings suggest that skeletal muscle metabolism might be a promising pharmacological target in order to improve muscle function, energy efficiency and tissue maintenance of MDC1A and LS patients

Growth hormone treatment in children with short stature born small for gestational age: 5-year results of a randomized, double-blind, dose-response trial

The growth-promoting effect of continuous GH treatment was evaluated over 5 yr in 79 children with short stature (height SD score, less than -1.88) born small for gestational age (SGA; birth length SD score, less than -1.88). Patients were randomly and blindly assigned to 1 of 2 GH dosage groups (3 vs. 6 IU/m2 body surface-day). GH deficiency was not an exclusion criterium. After 5 yr of GH treatment almost every child had reached a height well within the normal range for healthy Dutch children and in the range of their target height SD score. Only in children who remained prepubertal during the study period was the 5-yr increase in height SD score (HSDS) for chronological age significantly higher in the study group receiving 6 compared to 3 IU GH/m2 x day. Remarkably, the 5-yr increment in HSDS for chronological age was not related to spontaneous GH secretion, maximum GH levels after provocation, or baseline insulin-like growth factor I levels. GH treatment was associated with an acceleration of bone maturation regardless of the GH dose given. The HSDS for bone age and predicted adult height increased significantly. GH treatment was well tolerated. In conclusion, our 5-yr data show that long term continuous GH treatment at a dose of 3 or 6 IU/m2 x day in short children born SGA results in a normalization of height during childhood followed by growth along the target height percentile