Generalisability theory analyses of concept mapping assessment scores in a problem-based medical curriculum.

CONTEXT: In problem-based learning (PBL), students construct concept maps that integrate different concepts related to the PBL case and are guided by the learning needs generated in small-group tutorials. Although an instrument to measure students' concept maps in PBL programmes has been developed, the psychometric properties of this instrument have not yet been assessed. OBJECTIVES: This study evaluated the generalisability of and sources of variance in medical students' concept map assessment scores in a PBL context. METHODS: Medical students (Year 4, n = 116) were asked to construct three integrated concept maps in which the content domain of each map was to be focused on a PBL clinical case. Concept maps were independently evaluated by four raters based on five criteria: valid selection of concepts; hierarchical arrangement of concepts; degree of integration; relationship to the context of the problem, and degree of student creativity. Generalisability theory was used to compute the reliability of the concept map scores. RESULTS: The dependability coefficient, which indicates the reliability of scores across the measured facets for making absolute decisions, was 0.814. Students' concept map scores (universe scores) accounted for the largest proportion of total variance (47%) across all score comparisons. Rater differences accounted for 10% of total variance, and the student × rater interaction accounted for 25% of total variance. The variance attributable to differences in the content domain of the maps was negligible (2%). The remaining 16% of the variance reflected unexplained sources of error. Results from the D study suggested that a dependability level of 0.80 can be achieved by using three raters who each score two concept map domains, or by using five raters who each score only one concept map domain. CONCLUSIONS: This study demonstrated that concept mapping assessment scores of medical students in PBL have high reliability. Results suggested that greater improvements in dependability might be made by increasing the number of raters rather than by increasing the number of concept map domains.

Hyperhomocysteinemia in pregnant rats: effects on arterial pressure, kidneys and fetal growth.

OBJECTIVE: This study aimed to test the hypothesis that hyperhomocysteinemia plays a role in the development of pathological changes similar to human preeclampsia in pregnant rats. STUDY DESIGN: Arterial pressure and 24-h urinary excretion of proteins and electrolytes were measured during pre-pregnancy, pregnancy and postpartum periods in control (n = 12) and methionine-treated (2.0 g/kg/day, n = 11) Sprague-Dawley rats. Rats were then sacrificed at the end of this protocol and renal histological examination was performed. In another protocol, control (n = 6) and methionine-treated (n = 6) rats were anaesthetized at day 20 of gestation and pregnancy outcome was assessed. Hemodynamic and renal excretory differences between groups were analyzed using ANOVA and differences in renal histology and gestation outcome using t-test. RESULTS: Serum homocysteine in the methionine group (24.0+/-2.0 micromol/L) was significantly higher compared with controls (8.5+/-0.5 micromol/L). Systolic pressure, urinary protein excretion and renal histological changes were not significantly different between the two groups. However, fetal weights were significantly smaller and percent of dead fetuses were 15% higher in methionine-treated compared with control rats. CONCLUSION: Hyperhomocysteinemia is unlikely to cause maternal hypertension, proteinuria or renal damage in pregnant rats. However, hyperhomocysteinemia may restrict fetal growth and increase fetal mortality.

Serum leptin and insulin levels during chronic diurnal fasting.

Ramadan fasting is a unique model that is associated with restriction of the timing of food and fluid intake food from dawn to sunset and reduction in meal frequency and sleep duration. Leptin levels are thought to play a role in long-term regulation of caloric intake and fat deposition. However, the long-term changes in leptin levels during this pattern of fasting are not known. The study was conducted on lean (N=6, BMI=22.5+/-0.4) and obese (N=18, BMI=33.1+/-1.0) healthy female volunteers. Fasting serum levels of leptin, insulin and glucose were estimated at baseline (day 1), days 14 and 28 of the month of Ramadan and 2 weeks after Ramadan. Baseline serum levels of leptin were significantly higher in obese (13.5+/-1.96 microg/L,P<0.05) compared with lean subjects (9.60+/-0.80 microg/L) and correlated positively with body fat (r=0.82, P=0.0004). Serum leptin levels exhibited a significant and comparable increase by 39% and 37% throughout the month in lean and obese subjects, respectively. In addition, a significant correlation (r=0.52, P=0.003) was found between changes in serum leptin and serum insulin levels. We conclude that chronic diurnal fasting is associated with significant elevations in serum leptin. These elevations appear to be mediated by changes in serum levels of insulin. These data support the role of insulin in the long-term regulation of leptin secretion during chronic diurnal fasting followed by nocturnal eating during the month of Ramadan.