An analysis for menstrual data with time-varying covariates

This paper concerns the analysis of menstrual data; in particular, methodology to identify variables that contribute to the variability of menstrual cycles both within and between women. The basis for the proposed methodology is a parameterization of the mean length of a menstrual cycle conditional upon the past cycles and covariates. This approach accommodates the length-bias and censoring commonly found in menstrual data. Data from a longitudinal study of menstrual patterns and other variables among Lese women of the Ituri Forest, Zaire, illustrate the methodology. A small simulation illustrates the bias caused by incorrectly deleting the censored cycles.     

Cerebral vascular effects of angiotensin II: new insights from genetic models.

Very little is known regarding the mechanisms of action of angiotensin II (Ang II) or the consequences of Ang II-dependent hypertension in the cerebral circulation. We tested the hypothesis that Ang II produces constriction of cerebral arteries that is mediated by activation of AT1A receptors and Rho-kinase. Basilar arteries (baseline diameter approximately 130 microm) from mice were isolated, cannulated and pressurized to measure the vessel diameter. Angiotensin II was a potent constrictor in arteries from male, but not female, mice. Vasoconstriction in response to Ang II was prevented by an inhibitor of Rho-kinase (Y-27632) in control mice, and was reduced by approximately 85% in mice deficient in expression of AT1A receptors. We also examined the chronic effects of Ang II using a model of Ang II-dependent hypertension, mice which overexpress human renin (R+) and angiotensinogen (A+). Responses to the endothelium-dependent agonist acetylcholine were markedly impaired in R+A+ mice (P<0.01) compared with controls, but were restored to normal by a superoxide scavenger (PEG-SOD). A-23187 (another endothelium-dependent agonist) produced vasodilation in control mice, but no response or vasoconstriction in R+A+ mice. In contrast, dilation of the basilar artery in response to a NO donor (NONOate) was similar in R+A+ mice and controls. Thus, Ang II produces potent constriction of cerebral arteries via activation of AT1A receptors and Rho-kinase. There are marked gender differences in cerebral vascular responses to Ang II. Endothelial function is greatly impaired in a genetic model of Ang II-dependent hypertension via a mechanism that involves superoxide.     

Caregiver negative affect is a primary determinant of caregiver report of pediatric asthma quality of life.

BACKGROUND: Quality of life has increased in popularity as an outcome measure in health research. However, the measurement of quality of life has been questioned on methodologic grounds, as it often shows little association with objective measures of disease status. OBJECTIVE: For this report we studied the determinants of pediatric asthma caregiver report of quality of life and its relationship to disease burden. METHOD: Ninety-eight children who were admitted to a Pediatric Day Program for an asthma evaluation were enrolled in an outcome study. A complete set of medical records for the 2-year period before and after the admission was collected and systematically coded for health care utilization. Using the Pediatric Asthma Caregiver's Quality of Life Questionnaire, data were collected at baseline, discharge, and year after the admission. Caregiver negative affect (anxiety and depression), measured with the Brief Symptom Inventory, was also collected at baseline and discharge. RESULTS: Caregiver report of quality of life was unrelated to health care utilization at baseline but instead was significantly related to baseline caregiver negative affect. A significant relationship between health care utilization and quality of life was present at followup. The Emotional Function scale from the quality of life measure can account for most of the relationship between quality of life and negative affect. CONCLUSIONS: Caregiver affect may have a considerable influence on report of quality of life. Understanding the individual characteristics of the respondent is important when using a quality of life instrument as an outcome measure.     

Use of ultrasound to assess healing of a mandibular distraction wound.

PURPOSE: A standardized, noninvasive technique to assess healing of the mandibular distraction wound is not available. Current methods include clinical examination, plain radiography, and computed tomography. These imaging techniques are expensive and obligate the patient to serial radiation exposure. In addition, anatomic overlap and metal artifacts may obscure the distraction gap. In contrast, ultrasound has been shown to be a noninvasive, efficient, and inexpensive way to evaluate bone healing. The purpose of this study was to test the feasibility of ultrasound to evaluate an experimental mandibular distraction osteogenesis wound. MATERIALS AND METHODS: Distraction devices were placed via a submandibular incision into 24 minipigs. The protocol consisted of 0-day latency and distraction rates of 1, 2, or 4 mm/d for a 12-mm gap. The wounds were assessed in vivo after 0, 8, 16, and 24 days of neutral fixation. Ex vivo radiographs were used to estimate bone fill using a semiquantitative score. A semiquantitative ultrasound score was assigned, and the beam penetration depth was measured in millimeters. RESULTS: In all groups, clinical stability of the distraction wound increased with the duration of fixation. Plain radiographs, taken during neutral fixation, showed that the desired distraction gap was achieved and maintained. The ultrasound score increased with fixation time, whereas beam penetration depth decreased as expected. Ex vivo radiographs showed increasing bone fill score with time and paralleled the ultrasound score. CONCLUSIONS: The results of this feasibility study indicate that ultrasound is potentially useful for the assessment of bone formation in distraction osteogenesis wounds.     

Problems with a ‘target’ approach to access in primary care: a qualitative study

We report an analysis of the qualitative phase of a study of patients' and carers' views of primary care services, focusing on their experiences of access to face-to-face general practitioner (GP) consultations during the period when new access policies were being implemented. Practices interpreted the new policy in various ways; restricted interpretations, including restriction of access to telephone booking, could cause distress to patients. Patients and carers welcomed flexible interpretations of the policy that offered choice, such as a choice of GP, or of booking in advance.     

Tissue collection for correlative studies in childhood cancer clinical trials: ethical considerations and special imperatives.

Federal regulations prescribe distinct protections for children participating in research studies. Procedures for collecting tissue specimens from children solely for research purposes must pose no more than a minor increase over minimum risk, thereby limiting the approvable correlative biologic studies to evaluate molecularly targeted agents in children with cancer. Ethical issues arise when approvable correlative studies are a mandatory component of an early-phase pediatric clinical trial of new anticancer agents. The National Cancer Institute Cancer Therapy Evaluation Program sponsored a workshop in 2002 to discuss tissue collection for correlative biologic studies in early-phase childhood cancer clinical studies of molecularly targeted agents. Workshop participants recommended the following: (1) tissue specimens for correlative studies should provide vital clinical and scientific results to qualify for early-phase pediatric study consideration; (2) parents should receive a realistic appraisal of the risks, requirements, and potential for benefit of phase I protocol participation; (3) investigators should clearly distinguish clinically necessary procedures from research procedures of no benefit to the child to improve correlative study informed consent; and (4) participation in correlative research studies included in clinical trials generally should be voluntary. The need to acquire important biologic data regarding new molecular agents will challenge the ingenuity of pediatric cancer researchers, necessitating the application of highly sensitive laboratory assay methods, new imaging procedures, and preclinical models of childhood cancer. Such innovative methods can allow necessary scientific information to be obtained while simultaneously respecting the protections appropriately afforded to children participating in research studies and minimizing the burden of research participation for children with cancer and their families.