A systematic, concept-based method of developing the exposure measure for drug safety and effectiveness studies.

Purpose: In drug safety and effectiveness studies based on secondary data, the choice of an appropriate exposure measure for a given outcome can be challenging. Different measures of exposure can yield different estimates of treatment effect and safety. There is a knowledge gap with respect to developing and refining measures of drug exposure, to ensure that the exposure measure addresses the study question and is suitable for statistical analysis.

Constructing treatment episodes from concomitant medication logs: a prospective observational study.

Objectives: To describe an approach using concomitant medication log records for the construction of treatment episodes. Concomitant medication log records are routinely collected in clinical studies. Unlike prescription and dispensing records, concomitant medication logs collect utilisation data.

Mammographic non-dense area and breast cancer risk in postmenopausal women: a causal inference approach in a case-control study.

Purpose: The association between high mammographic density (MD) and elevated breast cancer risk is well established. However, the role of absolute non-dense area remains unclear. We estimated the effect of the mammographic non-dense area and other density parameters on the risk of breast cancer.

The effect of waiting time on pain intensity after elective surgical lumbar discectomy.

Background Context: Waitlists are commonly used in Canada to manage access to surgical procedures such as elective surgical lumbar discectomy (ESLD). The timing of enrollment onto the waitlist is important as this is a proxy measure for the concordance of preferences for surgery between a patient and surgeon. After enrollment, the waiting time to actual surgery extends the duration of preoperative symptoms, which possibly affects the outcome of ESLD.

The occurrence of adverse events in relation to time after registration for coronary artery bypass surgery: a population-based observational study.

Background: Our objective was to evaluate the effect of delays on adverse events while waiting for coronary artery bypass grafting (CABG).

Methods: An observational study that prospectively followed patients from registration on a wait list to removal for planned surgery, death while waiting, or unplanned emergency surgery. The population-based registry provided data on 12,030 patients with a record of registration on a wait list for first-time isolated CABG surgery between 1992 and 2005.

Evaluation of supply-side initiatives to improve access to coronary bypass surgery.

Background: Guided by the evidence that delaying coronary revascularization may lead to symptom worsening and poorer clinical outcomes, expansion in cardiac surgery capacity has been recommended in Canada. Provincial governments started providing one-time and recurring increases in budgets for additional open heart surgeries to reduce waiting times. We sought to determine whether the year of decision to proceed with non-emergency coronary bypass surgery had an effect on time to surgery.

An observational study to evaluate 2 target times for elective coronary bypass surgery.

Background: Guidelines for timing of elective bypass surgery were established by expert opinion; yet, there is little evidence to support the recommended target times.

Objectives: To estimate the effect of timing of the procedure on in-hospital mortality by comparing groups of patients that differ in the duration of time between decision to operate and performed procedure.

Research Design: We used a population-based registry to identify patients who underwent surgical coronary revascularization and their hospital discharge summaries to identify in-hospital death.

Medication errors associated with the use of ethanol and fomepizole as antidotes for methanol and ethylene glycol poisoning.

Introduction: Little is known about medication errors which occur with the antidotes ethanol and fomepizole, used for treatment of methanol and ethylene glycol poisoning. Study objectives were to describe and compare the frequency, type, outcome and underlying causes of medication errors associated with ethanol and fomepizole.

Methods: Patients aged ≥13 years were included if they were hospitalized in 1996-2005 for methanol or ethylene glycol poisoning and treated with ethanol or fomepizole.

Systematic review of the use of computer simulation modeling of patient flow in surgical care.

Computer simulation has been employed to evaluate proposed changes in the delivery of health care. However, little is known about the utility of simulation approaches for analysis of changes in the delivery of surgical care. We searched eight bibliographic databases for this comprehensive review of the literature published over the past five decades, and found 34 publications that reported on simulation models for the flow of surgical patients.

Evaluation of booking systems for elective surgery using simulation experiments.

Objective: This study compared two methods of booking elective surgery - booking from wait lists and pre-booking surgery dates at the time of decision to operate - in terms of cancellations of elective procedures and time to surgery.

Methods: The authors conducted simulation experiments with group randomized design, in which the unit of allocation was the hospital and the units of analysis were both the hospital and the patient.

Results: In the case of pre-booking, cancellation of high-priority elective procedures was only one-third as likely as it was in the case of booking from wait lists (odds ratio 0.

Delay in admission for elective coronary-artery bypass grafting is associated with increased in-hospital mortality.

Background: Many health care systems now use priority wait lists for scheduling elective coronary artery bypass grafting (CABG) surgery, but there have not yet been any direct estimates of reductions in in-hospital mortality rate afforded by ensuring that the operation is performed within recommended time periods.

Methods: We used a population-based registry to identify patients with established coronary artery disease who underwent isolated CABG in British Columbia, Canada. We studied whether postoperative survival during hospital admission for CABG differed significantly among patients who waited for surgery longer than the recommended time, 6 weeks for patients needing semi-urgent surgery and 12 weeks for those needing non-urgent surgery.

Adverse drug events associated with the antidotes for methanol and ethylene glycol poisoning: a comparison of ethanol and fomepizole.

Study Objective: We investigate adverse drug events associated with antidotes ethanol and fomepizole in methanol or ethylene glycol poisonings. An "adverse drug event" is harm associated with normal or incorrect drug use. We describe type, frequency, severity, seriousness, and onset time of adverse drug events and test the hypothesis that fomepizole results in fewer adverse drug events than ethanol.

Survival benefit of coronary-artery bypass grafting accounted for deaths in those who remained untreated.

Background: Currently there are no direct estimates of mortality reduction afforded by coronary-artery bypass grafting (CABG) that take into account the deaths among patients for whom coronary revascularization was indicated but who did not undergo the treatment. The objective of this analysis was to compare survival after the treatment decision between patients who underwent CABG and those who remained untreated.

Methods: We used a population-based registry to identify patients with established coronary artery disease who were to undergo first-time isolated CABG.

On reporting results from randomized controlled trials with recurrent events.

Background: Evidence-based medicine has been advanced by the use of standards for reporting the design and methodology of randomized controlled trials (RCT). Indeed, without this information it is difficult to assess the quality of evidence from an RCT. Although a variety of statistical methods are available for the analysis of recurrent events, reporting the effect of an intervention on outcomes that recur is an area that remains poorly understood in clinical research.

Do women spend longer on wait lists for coronary bypass surgery? Analysis of a population-based registry in British Columbia, Canada.

Background: Studies have shown patients who are delayed for surgical cardiac revascularization are faced with increased risks of symptom deterioration and death. This could explain the observation that operative mortality among persons undergoing coronary artery bypass surgery (CABG) is higher among women than men. However, in jurisdictions that employ priority wait lists to manage access to elective cardiac surgery, there is little information on whether women wait longer than men for CABG.

Cumulative incidence for wait-list death in relation to length of queue for coronary-artery bypass grafting: a cohort study.

Background: In deciding where to undergo coronary-artery bypass grafting, the length of surgical wait lists is often the only information available to cardiologists and their patients. Our objective was to compare the cumulative incidence for death on the wait list according to the length of wait lists at the time of registration for the operation.

Methods: The study cohort included 8966 patients who registered to undergo isolated coronary-artery bypass grafting (82.

The risk of death associated with delayed coronary artery bypass surgery.

Background: The detrimental effect of delaying surgical revascularization has been estimated in randomized trials and observational studies. It has been argued that the Kaplan-Meier method used in quantifying the hazard of delayed treatment is not appropriate for summarizing the probability of competing outcomes. Therefore, we sought to improve the estimates of the risk of death associated with delayed surgical treatment of coronary artery disease.

Do longer delays for coronary artery bypass surgery contribute to preoperative mortality in less urgent patients?

Background: Priority wait lists are common for managing access to cardiac surgery in publicly funded health systems. We evaluated whether longer delays contribute to the probability of death before surgery among patients prioritized into the less urgent category.

Methods: We studied records of 9233 patients registered for isolated coronary artery bypass graft (CABG) in British Columbia, Canada.

Chances of late surgery in relation to length of wait lists.

Background: The proportion of patients who undergo surgery within a clinically safe time is an important performance indicator in health systems that use wait lists to manage access to care. However, little is known about chances of on-time surgery according to variations in existing demand. We sought to determine what proportion of patients have had late coronary bypass surgery after registration on wait lists of different size in a network of hospitals with uniform standards for timing of surgery.

Time on wait lists for coronary bypass surgery in British Columbia, Canada, 1991-2000.

Background: In British Columbia, Canada, all necessary medical services are funded publicly. Concerned with growing wait lists in the mid-1990s, the provincial government started providing extra funding for coronary artery bypass grafting (CABG) operations annually. Although aimed at improving access, it is not known whether supplementary funding changed the time that patients spent on wait lists for CABG.