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Biomedical subjects

P L Canner

Publications and source records attributed to P L Canner.

30 records · Page 2Linked to original sources
PubMed1983

Aspirin in coronary heart disease. Comparison of six clinical trials.

Data from six randomized, placebo-controlled clinical trials of aspirin, involving a total of 10,703 postmyocardial infarction (MI) patients, are compared and combined. After adjustment for a number of prognostically important baseline factors, the reduction in total mortality by aspirin was 10% (P = 0.044). This beneficial trend was particularly pronounced during the 1st yr of daily aspirin ingestion, but did not differ between patients who entered the trial less than 6 mo and greater than 6 mo after their last MI. Significant beneficial effects of aspirin were noted with respect to 1) diagnosis of definite nonfatal MI and 2) hospitalization for greater than 2 wk for MI. Significant adverse effects of aspirin were noted with respect to the side effects of stomach pain, heartburn and vomiting, elevation of systolic blood pressure to greater than 160 mm Hg, and elevation of serum urea nitrogen and serum uric acid levels to the abnormal range.

Aspirin↗
PubMed1982

High-density lipoprotein cholesterol and prognosis after myocardial infarction.

The Coronary Drug Project was a randomized, placebo-controlled trial of lipid-influencing drugs in men who had recovered from one or more documented myocardial infarctions. Determinations of high-density lipoprotein (HDL) cholesterol were made at baseline in a group of 354 men randomized to the placebo group. Five-year mortality was highest (33.0%) in men with baseline serum HDL cholesterol levels of less than 35 mg/dl; it was 15.9%, 17.7%, and 21.8% in men with levels of 35--39, 40--44, and greater than or equal to 45 mg/dl, respectively (for the linear inverse relationship between HDL cholesterol and 5-year mortality, p = 0.029). Adjustment for 40 baseline variables had a minimal effect on this relationship (p = 0.042).

Adult↗
PubMed1981

On the detection of outlier clinics in medical and surgical trials: I. Practical considerations.

In the conduct of multicenter clinical trials, comparisons among the clinical centers are often made with respect to such measures as incidence of diagnosis of various events, operative mortality (in the case of a surgical trial), and patient adherence of the treatment regimen. If one or two clinics seem to stand out from all the other clinics with respect to any such measures, this may indicate - among other things - differences in skill levels or possible deficiencies in understanding and following the protocol among these clinics. On the other hand, when clinics are ranked on any measure, one clinic must of necessity be first and one last; thus, it is necessary to determine whether the extreme values represent true differences from the values of the other clinics or whether they can be attributed to random variation alone. A statistical test is described for detecting clinics that are outliers - i.e., truly different from all the rest of the clinics in the trial. Critical values for this test are given for various numbers of clinics, numbers of patients enrolled per clinic, and probabilities of a patient incurring a given event under the null hypothesis of no differences among the clinics. Use of this test in detecting outlier clinics with respect to incidence of various endpoints is illustrated for the case of a large, multicenter drug trial.

Clinical Trials as Topic↗
PubMed1981

On the detection of outlier clinics in medical and surgical trials: II. Theoretical considerations.

In the conduct of multicenter clinical trials, comparisons among the clinical centers are often made with respect to such measures as incidence of diagnosis of various events, operative mortality, and patients adherence to the treatment regimen. Slippage and outlier tests for statistically identifying clinics that are outliers - that is, truly different from the rest of the clinics - with respect to such measures are described. Critical values obtained for these tests by computer simulation are given for various numbers of clinics, numbers of patients enrolled per clinic, and probabilities (p) of a patient incurring a given event under the null hypothesis of no differences among the clinics. Previously published critical values based on normally distributed response variables are applicable only for p close to 0.5. The slippage and outlier tests are compared with respect to statistical power. Alternative forms of the slippage test based on the angular transformation and on hypergeometric probabilities are considered.

Clinical Trials as Topic↗
PubMed1979

Terminating a long-term clinical trial.

Long-term trials often include more than one active treatment group. These may be discontinued independently if found ineffective or possibly harmful. Certain subgroups of patients may be discovered, in the course of a clinical trial, who do not respond satisfactorily and are, therefore, excluded during the course of a trial. Yet anouther kind of termination comes when we have a therapeutic breakthrough or when hope has to be abandoned for demonstrating beneficial effects for one, several, or all treatments included in a trial. Examples from the authors' experience are presented, as are successful and unsuccessful techniques in managing terminations of various types.

Clinical Trials as Topic↗
PubMed1977

Monitoring treatment differences in long-term clinical trials.

When the data from long-term clinical trials are reviewed continually over time for evidence of adverse or beneficial treatment effects, the classical significance tests are not appropriate. A stimulation procedure is described which provides, for different mortality rates and different patterns of patient enrollment, the correct critical regions corresponding to specified frequencies of looks at the data over the course of the study. The power of the test and the robustness of the critical regions for differences in pattern of enrollment, length of study, mortality model, and sample size are discussed. An application is made to a drug trial in coronary heart disease.

Biometry↗
PubMedDate not supplied

An overview of six clinical trials of aspirin in coronary heart disease.

Data from six randomized, placebo-controlled clinical trials of aspirin, involving a total of 10,703 post-myocardial infarction patients, have been compared and combined. An apparent heterogeneity of findings among the six trials with respect to all-cause mortality is noted (P = 0.08). The reasons for this heterogeneity are explored. Two common methods of combining the results of several trials--the logrank and the log odds ratio methods--yield two-sided P-values of 0.112 and 0.110, respectively, for the aspirin-placebo effect on all-cause mortality. Alternative statistical methods of combining the results of the six trials give two-sided P-values ranging from 0.017 to 0.487.

Aspirin↗