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Biomedical subjects

A L Gould

Publications and source records attributed to A L Gould.

14 recordsLinked to original sources

Interim analyses for monitoring clinical trials that do not materially affect the type I error rate.

Monitoring clinical trials often requires examining the interim findings to see if the sample size originally specified in the protocol will provide the required power against the null hypothesis when the alternative hypothesis is true, and to increase the sample size if necessary. This paper presents a new method, based on the overall response rate, for carrying out interim power evaluations when the observations have binomial distributions, without unblinding the treatment assignments or materially affecting the type I error rate. Simulation study results confirm the performance of the method.

Bias

Expanded clinical evaluation of lovastatin (EXCEL) study results. II. Assessment of the human lens after 48 weeks of treatment with lovastatin.

The crystalline lenses of hypercholesterolemic patients were assessed before and after 48 weeks of treatment with lovastatin or placebo to determine the effect of lovastatin on the human lens. Patients were given a biomicroscopic (slit-lamp) examination of the lens, and a previously validated, standardized classification system was used to describe the findings. A total of 8,245 patients were randomly assigned in equal numbers to treatment with placebo or lovastatin 20 or 40 mg once or twice daily in this double-blind, parallel-group study. Statistical analyses of the distribution of cortical, nuclear and subcapsular opacities at 48 weeks, adjusted for age and presence of an opacity at baseline, showed no significant differences (p less than 0.01) between the placebo and lovastatin-treated groups. Visual acuity assessments at week 48 were also not found to have significantly different distributions among treatment groups. Moreover, no significant differences were found among the groups in the frequencies of greater than or equal to 2-line worsening in visual acuity with concurrent progression in lenticular opacity, cataract extraction, or any spontaneously reported adverse ophthalmologic experience. No evidence was found for an effect of lovastatin on the human lens after 48 weeks of treatment.

Adolescent

Expanded Clinical Evaluation of Lovastatin (EXCEL) study results. I. Efficacy in modifying plasma lipoproteins and adverse event profile in 8245 patients with moderate hypercholesterolemia.

In the Expanded Clinical Evaluation of Lovastatin (EXCEL) Study, a multicenter, double-blind, diet- and placebo-controlled trial, we evaluated the efficacy and safety of lovastatin in 8245 patients with moderate hypercholesterolemia. Patients were randomly assigned to receive placebo or lovastatin at a dosage of 20 mg once daily, 40 mg once daily, 20 mg twice daily, or 40 mg twice daily for 48 weeks. Lovastatin produced sustained, dose-related (P less than .001) changes as follows (for dosages of 20 to 80 mg/d): decreased low-density lipoprotein-cholesterol level (24% to 40%), increased high-density lipoprotein-cholesterol level (6.6% to 9.5%), decreased total cholesterol level (17% to 29%), and decreased triglyceride level (10% to 19%). The National Cholesterol Education Program's low-density lipoprotein-cholesterol level goal of less than 4.14 mmol/L (160 mg/dL) was achieved by 80% to 96% of patients, while the less than 3.36 mmol/L (130 mg/dL) goal was achieved by 38% to 83% of patients. The difference between lovastatin and placebo in the incidence of clinical adverse experiences requiring discontinuation was small, ranging from 1.2% at 20 mg twice daily to 1.9% at 80 mg/d. Successive transaminase level elevations greater than three times the upper limit of normal were observed in 0.1% of patients receiving placebo and 20 mg/d of lovastatin, increasing to 0.9% in those receiving 40 mg/d and 1.5% in those receiving 80 mg/d of lovastatin (P less than .001 for trend). Myopathy, defined as muscle symptoms with a creatine kinase elevation greater than 10 times the upper limit of normal, was found in only one patient (0.1%) receiving 40 mg once daily and four patients (0.2%) receiving 80 mg/d of lovastatin. Thus, lovastatin, when added after an adequate trial of a prudent diet, is a highly effective and generally well-tolerated treatment for patients with moderate hypercholesterolemia.

Adult

Another view of active-controlled trials.

Placebo-controlled efficacy trials may become more difficult to carry out with the increasing availability of effective therapies, especially for serious illnesses where denial of effective therapy may be objectionable ethically. Active-controlled trials aimed at establishing efficacy by demonstration of "equivalence" to "standard" therapy have potentially serious interpretational problems, and do not necessarily encourage good experimental practice. This article describes an alternative approach to the analysis of data from active-controlled trials using the information that makes an active-controlled trial necessary or desirable, namely a large, valid body of information about the consequence of using placebo. The approach uses information about placebo responses and also active agent responses from prior placebo-controlled trials to determine the likelihood of a significant active-placebo difference in an active-controlled trial, or in a trial with a vestigial placebo group. The sensitivity of the treatment comparisons depends directly on the quality of the design and execution of the active-controlled trial. The method is illustrated with data from trials of an H2-receptor antagonist in the treatment of acute duodenal ulcer.

Bayes Theorem

Applying survival methodology to adverse experience occurrences in controlled clinical trials.

On the basis of calculated cumulative hazard rates for initial occurrence of adverse experiences of patients following treatment for rheumatoid arthritis and osteoarthritis, a simple function is evolved that fits such cumulative hazard rate data very well. From this simple function, we obtain the estimated hazard rate in terms of two physically meaningful parameters. These two parameters can be used to describe the rate of occurrence of adverse experiences, and to convey the concept of risk of adverse experience associated with duration of exposure to a drug. The parameters are rho 1, which represents the risk of adverse experience at baseline, and rho 2, which defines the rate of occurrence of adverse experience immediately following drug administration. A method of estimating rho 1 and rho 2 is the maximum likelihood approach, and the estimated parameters are given for series of data referring to patients treated for arthritis.

Clinical Trials as Topic

The analysis of titration studies in phase III clinical trials.

Clinical trials commonly employ the titration design for certain drugs such as antihypertensives. In a Phase III trial the design has purposes distinct from those of a Phase I or II trial, as well as from those of a trial with a parallel design. In this paper we compare the titration design with the usual parallel design in their respective purposes for Phase III trials, explore the relevant questions addressed, and examine typical data from such trials. We also discuss work which focuses primarily on the Phase I or II titration trials. We formulate the problem in the framework of one-way contingency table augmented with incomplete data and obtain the maximum likelihood estimates of the parameters and their estimated variances/covariances via the EM algorithm. An example of a Phase III study of an antihypertensive agent illustrates the proposed procedure.

Analysis of Variance

Dexamethasone and severe head injury. A prospective double-blind study.

A prospective double-blind study of the effects of dexamethasone administration on the outcome of patients with severe head injuries was performed. Patients were stratified for severity of neurological injury and were treated with placebo, low-dose dexamethasone (16 mg/day), or high-dose dexamethasone (96 mg/day) for a period of 6 days. Outcome was evaluated at 6 months following injury. Of the 76 patients available for analysis, a good outcome was achieved in 37% of placebo-treated patients, 44% of low-dose-treated patients, and 29% of high-dose-treated patients. These differences are not statistically significant. Similarly dexamethasone administration had no statistically significant effect on intracranial pressure patterns or serial neurological examinations during hospitalization. Gastrointestinal bleeding occurred in only one patient. Good outcome was associated with age under 10 years, lighter depth of coma on admission, and the preservation of brain-stem reflexes upon admission. A recalculation of data in previous clinical series purporting to show an improvement in outcome as a result of corticosteroid therapy shows no significant difference in outcome when steroid- and placebo-treated patients are compared. In our series, 90% of all deaths were caused by recurrent intracranial hematomas, medical complications, or diffuse brain injuries with parenchymal hemorrhage and tissue disruption -- causes of death which cannot be affected by corticosteroid therapy. The study suggests that dexamethasone in either high or low dosages has no significant effect on morbidity and mortality following severe head injury.

Adolescent

Intraocular pressure decrease in normal volunteers following timolol ophthalmic solution.

Timolol ophthalmic solutions 0.5 per cent, 1.0 per cent, and 1.5 per cent lowered intraocular pressures significantly in normal human volunteers. Maximum lowering of the intraocular pressures was reached at two hours with the 0.5 per cent solution of timolol and at one hour with the 1.0 per cent and 1.5 per cent timolol ophthalmic solutions. The effect lasted the full seven hours of observations. No objective or subjective evidence of ocular irritation could be attributed to the drug. A single dose of timolol applied topically to the eyes of normal human volunteers had no effect on pupillary size, visual acuity, blood pressure, or pulse rate.

Adrenergic beta-Antagonists

Safety of cefoxitin: an approach to the analysis of laboratory data.

The safety of cefoxitin, in terms of values obtained in laboratory tests during and after therapy, was estimated by three methods for analysis of data derived from controlled clinical comparisons of cephalothin and cefoxitin. Both antibiotics were found to be safe with respect to hematologic, renal, and hepatic function and did not differ significantly from each other. Laboratory data confirmed by tests performed serially and by paired related tests were analyzed by a novel method of comparison.

Cefoxitin

Effect of cancer chemotherapy on the immune response to influenza virus vaccine: review of published studies.

Controversy exists regarding the ability of cancer chemotherapy to prevent the development of an adequate immune response to influenza virus vaccine. Of 12 studies addressing this issue, eight demonstrated a significant lessening of the immune response among patients receiving cancer chemotherapy. The other four studies failed to find a significant difference between the immune responses of patients receiving cancer chemotherapy and persons not receiving chemotherapy; for these studies the Type 2 error rate (i.e., the probability of wrongly concluding that no difference exists) was calculated. Since the response rates in the four inconclusive studies were consistent with those in the other eight studies but the sample sizes were much smaller, the failure of the former studies to find significant differences in immune responses probably was due to insensitivity rather than to the absence of such differences. The preponderance of evidence suggests that the serum antibody response to influenza virus vaccine is significantly weaker in patients receiving cancer chemotherapy than in persons not receiving chemotherapy.

Adolescent