George A. Wells

A Comparison of Confidence Interval Methods for the Intraclass Correlation Coefficient

Different methods of obtaining confidence intervals for the intraclass correlation coefficient rho in the unbalanced one-way random-effects model are investigated, focusing on applications to family studies. Methods based on simple modifications of formulas for the case of equal group sizes are found to provide adequate coverage at small to moderate values of rho. A method based on the large-sample standard error of the sample intraclass correlation, as derived by Smith (1956, Annals of Human Genetics 21, 363-373), is shown to provide consistently good coverage at all values of rho. A method proposed by Thomas and Hultquist (1978, Annals of Statistics 6, 582-587) also provides consistently good coverage, but generates mean interval widths substantially greater than those generated by Smiths method at values of rho likely to arise in practice.

Biventricular Function in the Adult Respiratory Distress Syndrome: Hemodynamic and Radionuclide Assessment, with Special Emphasis on Right Ventricular Function

We examined biventricular function in patients with the adult respiratory distress syndrome (ARDS) by a combmation of invasively determined pressures and flows and concomitant radionuclide angiography. Right (RVEF) and left (LVEF) ventricular ejection fractions were measured; right and left ventricular end-diastolic (EDVI) and end-systolic (ESVI) volume indices were calculated from the respective ejection fraction and measured ther. modilution stroke volume. With an increase in the outflow pressure load on the right ventricle,measured as the mean pulmonary artery pressure (PAP), the RVEF fell (Y66.25-l.O1X; r2.42; p <.001) and both the RVEDVI (y13.39+3.66X; r�.33; p <.001)and RVESVI (Y = 23.9 + 3.57X; r’ .41; p <.001) increased. Progressive Acute microvascular lung injury, a complication of

Canadian C-Spine Rule study for alert and stable trauma patients: I. Background and rationale

This paper is Part I of a 2-part series to describe the background and methodology for the Canadian C-Spine Rule study to develop a clinical decision rule for rational imaging in alert and stable trauma patients. Current use of radiography is inefficient and variable, in part because there has been a lack of evidence-based guidelines to assist emergency physicians. Clinical decision rules are research-based decision-making tools that incorporate 3 or more variables from the history, physical examination or simple tests. The Canadian CT Head and C-Spine (CCC) Study is a large collaborative effort to develop clinical decision rules for the use of CT head in minor head injury and for the use of cervical spine radiography in alert and stable trauma victims. Part I details the background and rationale for the development of the Canadian C-Spine Rule. Part II will describe in detail the objectives and methods of the Canadian C-Spine Rule study.

Validity of a Two-variable Nutritional Index for Use in Selecting Candidates for Nutritional Support

The relationship of baseline nutritional test values to clinical outcome was prospectively studied in 55 consecutive surgical and critically ill patients referred for nutritional support. Eight nutritional tests were evaluated with respect to their ability to discriminate between patients who had major septic complications (MSC) and/or died, and patients who survived (without MSC). Our results show that a value of serum albumin (SA) less than 3.0 grams per deciliter had the best predictive accuracy for outcome (PPA) of the single tests (PPA = 76%, s = 0.86, f = 0.82), correctly separating 84% of the patients into the outcome groups. The combination of SA less than 3.0 grams per dl and serum transferrin (ST) less than 175 milligrams per deciliter had excellent ability to predict risk in patients deficient in both proteins (PPA = 77%, s = 1.0, f = 0.88, % correctly classified = 91%). The delayed cutaneous hypersensitivity (DCH) test was not useful for identifying high-risk patients (s = 0.44, f = 0.88). The...

Adverse events among patients registered in high-acuity areas of the emergency department: a prospective cohort study.

OBJECTIVE To enhance patient safety, it is important to understand the frequency and causes of adverse events (defined as unintended injuries related to health care management). We performed this study to describe the types and risk of adverse events in high-acuity areas of the emergency department (ED). METHODS This prospective cohort study examined the outcomes of consecutive patients who received treatment at 2 tertiary care EDs. For discharged patients, we conducted a structured telephone interview 14 days after their initial visit; for admitted patients, we reviewed the inpatient charts. Three emergency physicians independently adjudicated flagged outcomes (e.g., death, return visits to the ED) to determine whether an adverse event had occurred. RESULTS We enrolled 503 patients; one-half (n = 254) were female and the median age was 57 (range 18-98) years. The majority of patients (n = 369, 73.3%) were discharged home. The most common presenting complaints were chest pain, generalized weakness and abdominal pain. Of the 107 patients with flagged outcomes, 43 (8.5%, 95% confidence interval 8.1%-8.9%) were considered to have had an adverse event through our peer review process, and over half of these (24, 55.8%) were considered preventable. The most common types of adverse events were as follows: management issues (n = 18, 41.9%), procedural complications (n = 13, 30.2%) and diagnostic issues (n = 10, 23.3%). The clinical consequences of these adverse events ranged from minor (urinary tract infection) to serious (delayed diagnosis of aortic dissection). CONCLUSION We detected a higher proportion of preventable adverse events compared with previous inpatient studies and suggest confirmation of these results is warranted among a wider selection of EDs.

Vocational adaptation of patients on home dialysis: Its relationship to personality, activities and support received☆

This analysis identifies, in terms of relative contribution, seven independent variables which appear to be associated with the vocational adaptation of home dialysis patients. The tentative model created by the analysis can be used as a guide for assessing a patients potential vocational adaptation. It has also identified some conditions associated with adaptation which are amenable to treatment by dialysis staff. Validation of the model, however, requires further testing with other patient groups.

Factors influencing the intentions of nurses and respiratory therapists to use automated external defibrillators during in-hospital cardiac arrest: a qualitative interview study.

OBJECTIVES Nurses and respiratory therapists are seldom allowed to use automated external defibrillators (AED) during in-hospital cardiac arrest. This can result in significant time delays before defibrillation occurs and lower survival for cardiac arrest victims. We sought to identify barriers and facilitators to AED use by nurses and respiratory therapists. METHODS We conducted semi-structured qualitative interviews with a purposeful sample of nurses and respiratory therapists. We developed the interview guide based on the constructs of the theory of planned behaviour, which elicits salient attitudes, social influences, and control beliefs potentially influencing the intent to use an AED. Interviews were recorded, transcribed verbatim, and analysed until achieving data saturation. Two independent reviewers performed inductive analyses to identify emerging categories and themes, and ranked them by frequency of the number of participants stating the topic. RESULTS Demographics for the 24 interviewees include mean age 40.5, 79.2% female, 87.5% performed cardiopulmonary resuscitation (CPR), 29.2% defibrillated a patient. Identified attitudes pertained to the timeliness of defibrillation, patient survival, simplicity of AED use, accuracy of rhythm recognition, and harm to self or others. Social influences consisted of physician and hospital administration support of AED use. Control beliefs included training on AED use, policy allowing AED use, familiarity with AED, and task burden during resuscitation. CONCLUSIONS Most nurses and respiratory therapists intended to use an AED if permitted to do so by a medical directive. Successful implementation would require educational initiatives focusing on safety and efficacy of AEDs, support from physicians and hospital administrators, and additional training on AED use.

Development of Formulas for the Bias and Mean Square Error of the Logit Estimator

Formulas for calculating the bias and mean square error of the logit estimator are developed. These formulations involve asymptotic series which should provide adequate approximations provided the parameters n and P of the binomial model are such that nP is not small. Although the asymptotic expansions are algebraically complicated, they have been mathematically expressed in such a way that general coefficients can be isolated and calculated.