CrossOver: an algorithm for the construction of efficient cross-over designs.

A cross-over experiment involves the application of sequences of treatments to several subjects over a number of time periods. It is thought that the observation made on each subject at the end of a time period may depend on the direct effect of the treatment applied in the current period, and the carry-over effects of the treatments applied in one or more previous periods. Various models have been proposed to explain the nature of the carry-over effects. An experimental design that is optimal under one model may not be optimal if a different model is the appropriate one. In this paper an algorithm is described to construct efficient cross-over designs for a range of models that involve the direct effects of the treatments and various functions of their carry-over effects. The effectiveness and flexibility of the algorithm are demonstrated by assessing its performance against numerous designs and models given in the literature.

Gestational diabetes: is a higher cesarean section rate inevitable?

OBJECTIVE: To determine the rate of and indication for cesarean section for women with gestational diabetes mellitus (GDM) compared with glucose-tolerant women. RESEARCH DESIGN AND METHODS: From a consecutive series of women with GDM seen over a 9-year period for medical management, women who had had a cesarean section were identified and the reason for the section determined from a review of the medical record. A control group of women who had had a section were obtained from an existing database of glucose-tolerant women. RESULTS: The section rate for women with GDM was higher at 19.8% than the 15.6% for glucose-tolerant women. However, after adjustment for age and parity, no significant differences were found. There were also no differences found for the primary indication for section. CONCLUSIONS: In our health area of New South Wales, Australia, women with GDM do not have a higher section rate compared with glucose-tolerant women. Concerns about the diagnosis of GDM leading to an increased rate of obstetric intervention should not be generalized.

The 75-g glucose tolerance test in pregnancy: a reference range determined on a low-risk population and related to selected pregnancy outcomes.

OBJECTIVE: To determine a reference range for the 75-g glucose tolerance test (GTT) in pregnancy using a group of women at low risk for gestational diabetes mellitus (GDM) and to determine the validity of this reference range by examining selected pregnancy outcomes for glucose-tolerant women with a 2-h result on the GTT up to 1.0 mmol/l below the diagnostic level for GDM compared with treated women with GDM. RESEARCH DESIGN AND METHODS: The reference range for the GTT was determined in 573 Caucasian women with an age <25 years and a BMI of <25 kg/m2. Selected pregnancy outcomes were compared between 272 treated women with GDM (diagnosed on the basis of a 2-h glucose level > or =8.0 mmol/l) and 308 women with a 2-h glucose level of 7.0-7.9 mmol/l. RESULTS: There was 95% confidence that at least 95% of all the fasting glucose levels are < or =5.1 mmol/l(92 mg/dl) and 95% confidence that at least 95% of all the 2-h glucose levels were < or =7.8 mmol/l (140 mg/dl). Treated women with GDM had a significantly reduced rate of large-for-gestational-age infants compared with glucose-tolerant women, without any increase in the rate of small-for-gestational-age infants or obstetric interventions. CONCLUSIONS: The reference range for the GTT in pregnancy should be determined on a low-risk population rather than on a total population. Consideration should be given to lowering the fasting glucose level to 5.0 mmol/l (90 mg/dl) and the 2-h level to 7.8 mmol/ (140 mg/dl). Glucose-tolerant women below this relatively low reference range have an increased rate of large-for-gestational-age infants and may benefit from treatment.

Paving the way: stepping stones to evidence-based nursing.

Evidence-based practice is an emerging paradigm in health care. This paper outlines the main features of this paradigm and its potential value to nursing. Evidence-based practice is based on a conceptual framework that examines the extent of evidence available in support of particular clinical practices. The Quality of Evidence Ratings adapted by the National Health and Medical Research Council (NHMRC) from the United States Preventive Services Task Force are discussed, and the strengths and weaknesses of different categories of evidence are highlighted. Potential barriers to implementation of research into practice are identified. The authors suggest that legal, ethical, economic and humane imperatives oblige nursing to develop evidence-based practice as one of several viable contributions to nursing knowledge. Suggestions for analysing current research and for the planning of the direction of future nursing research are made.

Examining athletes' attitudes toward using anabolic steroids and their knowledge of the possible effects.

One goal of contemporary sports leaders is to eradicate the use of banned drugs in competitive sport. A common approach to achieving this outcome is to provide athletes with adequate education about the effects of drug use. Ostensibly, educational programs about the deleterious effects of using anabolic steroids are thought to discourage their intake. Thus, the purpose of this study was to examine the relationships between the athletes' knowledge about the long-term effects of anabolic steroids and their attitudes toward this type of drug. Multiple regression analyses indicated relatively low R2's and correlations between the various components of subjects' knowledge and their attitude toward steroid ingestion. This suggests that educational programs for athletes about taking anabolic steroids may have limited value in terms of creating appropriate, responsible attitudes toward this illegal, unethical, and medically questionable practice.

Effect of aerobic and strength training on pain tolerance, pain appraisal and mood of unfit males as a function of pain location.

The purpose of this study was to examine the effect of aerobic and strength conditioning on pain tolerance, pain appraisal and mood as a function of upper and lower limb pain location. Unfit males (n = 48) were randomly assigned to one of four groups: aerobic training, strength training, combined aerobic and strength training, and a 'no training' (control) group. The fitness regimens consisted of exercising at least three times per week for 12 weeks. Pain tolerance and appraisal and mood were ascertained before the treatment (baseline), and after 6 and 12 weeks. Statistical analyses using MANOVA indicated that the presence of aerobic training increased upper limb pain tolerance but was also linked to a more severe pain appraisal compared with the absence of aerobic training. Aerobic work also improved vigour while decreasing fatigue, tension and depression. Strength training had no influence on pain tolerance and positive mood states, but increased depression. Lower limb pain tolerance was unaffected by the treatments.