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Biomedical subjects

C D Naylor

Publications and source records attributed to C D Naylor.

211 records · Page 12Linked to original sources
PubMedDate not supplied

Communicating the benefits of chronic preventive therapy: does the format of efficacy data determine patients' acceptance of treatment?

Patients' informed acceptance of chronic medical therapy hinges on communicating the potential benefits of drugs in quantitative terms. In a hypothetical scenario of treatment initiation, the authors assessed how three different formats of the same data affected the willingness of 100 outpatients to take what were implied to be three different lipid-lowering drugs. Side-effects were declared negligible and costs insured. Subjects make a "yes-no" decision about taking such a medication, and graded the decision on a certainty scale. Advised of a relative risk reduction--"34% reduction in heart attacks"--88% of the patients assented to therapy. All other formats elicited significantly more refusals (p < 0.0001): for absolute risk difference--"1.4% fewer patients had heart attacks"--42% assented; for inverted absolute risk--"treat 71 persons for 5 years to prevent one heart attack"--only 31% accepted treatment. When the data were extrapolated to disease-free survival--"average gain of 15 weeks"--40% consented. Similar responses were obtained for descriptions of an antihypertensive drug: 89% assented to therapy when given relative risk reduction but only 46% when given absolute risk reduction. The subjects were confident in both acceptance and refusal: 93% of the decisions were rated "somewhat certain" to "completely certain." The authors conclude that patients' views of medical therapy are shaped by the formats in which potential benefits are presented. Multiple complementary formats may be most appropriate. The results imply that many patients may decline treatment if briefed on the likelihood or extent of benefit.

Adult↗
PubMedDate not supplied

The relationship between cardiac functional capacity and patients' symptom-specific utilities for angina: some findings and methodologic lessons.

Forty-one angina patients with coronary disease were interviewed to examine the correlation between prespecified and individualized weights for disease-specific measures of the effects of angina on the patients' well-being. Modifications of the Canadian Cardiovascular Society (CCS) scale for angina and the Duke Activity Specific Index (DASI) were used to rate functional capacity with prespecified items. Disease-specific utilities based on descriptions of functional status were obtained directly, and again indirectly with different anchoring conditions to control for noncardiac comorbidity. Correlations between the functional-capacity measures and the derived utilities were not strong, ranging from -0.25 (p > 0.1) to -0.35 (p = 0.02). Correlation between the two prespecified measures was higher (r = -0.51 or -0.69, both p < 0.01, for DASI versus CCS graded from walking and stair-climbing, respectively). The direct and indirect disease-specific utility scores were similar (r = 0.92, p < 0.01). The method described provides an approach to measuring disease-specific utilities by adapting existing scales for use in a standard gamble. It confirms that prespecified functional status scores inconsistently reflect patients' valuations of functional states. Further investigation should address whether the observed null effect of comorbidity on disease-specific utilities arose from inadequate coverage of the comorbidity issues in patient interviews or from lack of power given the small size of the feasibility study.

Activities of Daily Living↗
PubMedDate not supplied

Using a trade-off technique to assess patients' treatment preferences for benign prostatic hyperplasia.

The probability-tradeoff technique may be used to assess treatment preferences in dichotomous choices. In this feasibility study, it was used to elicit benign prostatic hyperplasia (BPH) patients' attitudes towards three different treatments. Eighty-seven male outpatients used rating scales and the standard gamble to indicate the extents to which they were free of BPH symptoms. Paired descriptions of "watchful waiting" (WW), treatment with an alpha blocker (AB), and transurethral resection of the prostate (TURP) were presented, and the probability-tradeoff technique was used to obtain treatment-preference scores. The tradeoff task identified six internally consistent preference-order subgroups. The majority (n = 55; 63.2%) were in the two subgroups in which TURP was the least-preferred treatment. Compared with the other respondents, the members of these two subgroups reported significantly higher utilities for their BPH symptom status (89 vs 79; t = 2.87; p < 0.0005). Within each subgroup, preference scores for the middle- and top-ranked treatments were computed relative to the bottom-ranked treatment; for both WW and AB, significant across-subgroup differences were observed. In this preliminary study the probability-tradeoff technique was feasible, able to identify unique preference-order subgroups, and able to generate apparently meaningful preference scores in a clinical situation involving three alternative treatments. Further development of tradeoff tasks as the value-clarification component of decision aids for individual patients seems warranted.

Aged↗
PubMedDate not supplied

Predicting mortality after coronary artery bypass surgery: what do artificial neural networks learn? The Steering Committee of the Cardiac Care Network of Ontario.

OBJECTIVE: To compare the abilities of artificial neural network and logistic regression models to predict the risk of in-hospital mortality after coronary artery bypass graft (CABG) surgery. METHODS: Neural network and logistic regression models were developed using a training set of 4,782 patients undergoing CABG surgery in Ontario, Canada, in 1991, and they were validated in two test sets of 5,309 and 5,517 patients having CABG surgery in 1992 and 1993, respectively. RESULTS: The probabilities predicted from a fully trained neural network were similar to those of a "saturated" regression model, with both models detecting all possible interactions in the training set and validating poorly in the two test sets. A second neural network was developed by cross-validating a network against a new set of data and terminating network training early to create a more generalizable model. A simple "main effects" regression model without any interaction terms was also developed. Both of these models validated well, with areas under the receiver operating characteristic curves of 0.78 and 0.77 (p > 0.10) in the 1993 test set. The predictions from the two models were very highly correlated (r=0.95). CONCLUSIONS: Artificial neural networks and logistic regression models learn similar relationships between patient characteristics and mortality after CABG surgery.

Aged↗
PubMedDate not supplied

Health care in Canada: incrementalism under fiscal duress.

Driven by fiscal pressures in the 1990s, Canada's provincial Medicare systems cut inpatient care, expanded community services, and consolidated hospitals under regional authorities in nine of ten provinces. Public confidence has been badly shaken by the transition. No province has successfully integrated services across the continuum of care. Home care and prescription drug coverage vary from province to province. Efforts to reform physician payment have stalled, and capacity to measure and manage the quality of care is generally underdeveloped. Thus, for the next few years, policymakers must stabilize the acute care sector, while cautiously pursuing an agenda of piece-meal reforms.

Canada↗
PubMedDate not supplied

Does treatment with essential amino acids and hypertonic glucose improve survival in acute renal failure?: A meta-analysis.

We performed a meta-analysis of four randomized trials (RCTs) and one concurrent control study which addressed the following question: Does treatment with amino acid solutions and hypertonic glucose improve survival of seriously ill patients with acute renal failure who are unable to take oral or enteral feedings? Three RCTs compared outcomes with essential amino acid solutions (EAA) and hypertonic glucose against hypertonic glucose alone, and their results were pooled. Use of EAA was associated with an absolute increase in initial survival of 0.24 as compared to glucose (confidence interval: +.015 to +.446). Without weighting the data to reflect the quality of the RCTs, this effect was significant (p = .017). Patients needing dialysis showed a significant treatment effect (p = .015), while those not requiring dialysis did not (p = .11). However, survival to hospital discharge was not significantly improved for the patient population as a whole (p = .10). Using a standardized quality assessment protocol, the four RCTs received scores ranging from .188 to .357 out of a possible 1.00. Any statistically significant treatment effects were abolished by factoring the quality scores of the studies into the data-pooling process. Sensitivity analysis was performed to determine the effect of including the nonrandomized study. Although it had more patients than the other studies combined, the nonrandomized study was of low quality (score: .032) and its inclusion did not change the outcome of data pooling once quality weighting was applied. We conclude that the efficacy of these parenteral nutritional regimens remains uncertain in this clinical setting.

Acute Kidney Injury↗
PubMedDate not supplied

Potential cost effectiveness of intravenous tissue plasminogen activator versus streptokinase for acute myocardial infarction.

OBJECTIVE: An economic evaluation of the potential incremental benefits of intravenous tissue plasminogen activator (tPA) versus streptokinase (SK) for treatment of acute myocardial infarction. DESIGN: Cost effectiveness analysis from a third-party payer perspective (Ontario Ministry of Health). ECONOMIC INPUTS: Fully allocated costs for cardiovascular procedures and hospitalization for myocardial infarction were obtained anonymously for four Ontario teaching hospitals and converted to 1988 Canadian dollars. Professional charges were taken from the provincial health insurance fee schedule and drug costs obtained from the manufacturers. CLINICAL INPUTS: The baseline analysis was for nonelderly patients with uncomplicated myocardial infarctions; sensitivity analyses allowed extrapolation to higher risk subgroups. Short and longer term mortality and short term invasive procedure rates were estimated using data from clinical trials. MAIN RESULTS: If tPA achieves a 1% short term mortality advantage over SK with no advantages for other survivors, cost per life-year gained can be comparable to other cardiovascular interventions at $58,600. In the absence of immediate survival advantages, but assuming greater left ventricular preservation, the constant annual hazard rate advantage must be about 0.5% per year for competitive cost effectiveness ratios. CONCLUSIONS: A full range of projections is presented to help guide the policy decisions that will arise in the wake of the Global Utilization of SK and tPA for Occluded Coronary Arteries (GUSTO) trial. The analysis also illustrates the general importance of considering longer term effects of in-hospital therapies for acute myocardial infarction.

Cost-Benefit Analysis↗
PubMedDate not supplied

Coronary angiography and revascularization: defining procedural indications through formal group processes. The Canadian Revascularization Panel, the Canadian Coronary Angiography Panel.

OBJECTIVES: To summarize the process and extent of interphysician agreement within two panels convened to derive indications for the appropriate use of coronary angiography and for coronary revascularization procedures. PARTICIPANTS: Two panels, each with nine practitioners. METHODS: Panelists rated the appropriateness of intervention for a comprehensive set of indications for each procedure. Indications were brief profiles created by combining and permuting clinical characteristics pertinent to case selection for intervention. Ratings were first made at home, with a second round at the panel meeting following open discussion. Final rankings of indications as 'appropriate', 'uncertain' or 'inappropriate' were based on the pattern of panelists' responses on a nine-point scale, including the median rating and extent of agreement among panelists. Agreement was defined as at least seven panelists' ratings within the three-point region containing the median rating. Panelists were later mailed a much-reduced list of indications for which there was agreement on appropriateness. These were re-rated on a necessity scale. A procedure was rated 'necessary' only if a physician was ethically obligated to recommend it as the preferred treatment option. RESULTS: For appropriateness of angiography, agreement occurred in 38.2% of indications in round 1 and 64.4% in round 2 (P < 0.0001). For coronary artery bypass graft (CABG) versus medical therapy, the corresponding increase was from 43.5 to 54.0% (P < 0.0001). Agreement on necessity of angiography occurred for 44.3% of scenarios. For indications where CABG alone was appropriate, agreement on necessity was 56%. However, for indications where percutaneous transluminal coronary angioplasty (PTCA) could be regarded as the first-line intervention, agreement on necessity was only 5%. CONCLUSIONS: A two-step panel process permitted considerable convergence of panelists' ratings, highlighting the importance of formal panel methods in setting utilization management criteria. However, the extent of continuing disagreement on ratings underscores the need to avoid a forced consensus; instead, divergent opinions should be taken as indicative of uncertainty about the appropriateness of intervention. Interpanelist agreement on necessity ratings was modest, but may help in setting benchmarks to assess possible underprovision of invasive cardiac services in Canada.

Angioplasty, Balloon, Coronary↗
PubMedDate not supplied

Coronary angiography and bypass surgery in Manitoba and the United States: a first comparison.

OBJECTIVE: To compare the appropriateness of use of coronary angiography (CA) and bypass surgery (CABS) in the early 1980s in one Canadian hospital and several American hospitals using explicit case-based criteria. Procedure rates were much lower in Canada during this period. SUBJECTS: Canadian subjects, 502 Manitoba residents undergoing CA at one hospital in 1981-82 were tracked forward to determine whether and when they underwent CABS. CA comparisons were made with 351 Canadian patients aged 55 years or older; 1677 American CA patients aged 65 years or older and were drawn in 1981 from three hospitals. Two hundred and forty-five patients undergoing CABS within 12 months of CA made up the Canadian sample. American CABS patients were sampled from three hospitals during 1979-82. Manitoba patients assigned to medical treatment after CA were also appraised. METHODS: Criteria were derived by an American panel of clinicians following a Delphi process; indications were rated appropriate, equivocal and inappropriate. A trained abstractor reviewed charts and assigned ratings. Results of exercise electrocardiograms were not available in the Manitoba data set, hence sensitivity analyses were performed to determine how differing proportions of positive exercise electrocardiograms might affect the Manitoba results. RESULTS: Even assuming only 50% of treadmill tests were positive in the Manitoba sample, the proportion of inappropriate CA was lower in Manitoba than for the American hospitals: 9% versus 15 to 18%. For CABS, only one of the three comparison American hospitals approached the Manitoba hospital level of appropriateness. CONCLUSIONS: In the early 1980s, there was more appropriate use of CA and CABS in a Manitoba hospital compared with several American hospitals. Many Canadian patients undergoing CA and treated medically met American indications for appropriate use of CABS. Whether this represents underprovision of necessary care remains uncertain.

Aged↗