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Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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At least 1,225 records · Page 68Linked to original sources
PubMed2005

Statistical analysis of the DIAMOND MI study by the multipole method.

We present a new method to describe the dynamics of the beat-to-beat RR time series. The classification of the phase-space plots obtained from RR time series is performed by a calculation of parameters which describe the features of the two-dimensional plot. We demonstrate that every parameter has its specific consequence on the evaluation of the state of the cardiac function. By applying the method to the DIAMOND MI study we demonstrate that these parameters have more prognostic power than previously suggested risk markers. The results suggest that the RR intervals constitute a highly complex time series which necessitates the use of refined mathematical-statistical methods in order to reveal pathologies in the heart rate.

Double-Blind Method↗
PubMed2000

[Principles of evidence-based medicine; merits and pitfalls].

Historical background, main principles, methodology of evidence based medicine (EBM) and prospective randomized trials (incl. megatrials) are reviewed. EBM has a significant beneficial influence on medical activities as follows: improving efficacy of medical therapy, generation of new research trends, optimizing decision making in clinical settings of incomplete pathophysiological background, exploring new associations can be found beyond the individual clinician's scope, regular financial support of gradual, postgradual medical training, medical research and international scientific programs. Potential adverse influences related to EBM are: weakening position of individual (versus modus) patient-oriented approach in medical care, diminution of pathophysiology- (versus product-) oriented medical research, reevaluation of medical, scientific activity, interrelations between medical doctors and patients. Potential misuse of statistical methods in evaluation of megatrials is briefly discussed. A combination of benefits related to EBM and traditional elements of classical medical care, clinical research is needed to establish a more improved medical care for the individual patient.

Animals↗
PubMed1991

The effect of topical retinoids on the leukotriene-B4-induced migration of polymorphonuclear leukocytes into human skin.

Systemic retinoids are effective in a variety of inflammatory dermatoses. Disorders in which polymorphonuclear leukocytes (PMN) are involved, such as psoriasis and acne, respond particularly well to various retinoids. However, side-effects restrict the use of systemic retinoids to severe manifestations. Topical application might provide the possibility of avoiding the systemic side-effects of these compounds. In this communication we report on the modulation of transepidermal migration of PMN by topical application of all-trans-retinoic acid, 13-cis-retinoic acid, arotinoid methyl sulphone and arotinoid ethyl sulphone. Test areas of healthy volunteers were pretreated with these retinoids in a cream base and with corresponding placebo creams, and intraepidermal accumulation of PMN was quantified 24 h after epicutaneous challenge with leukotriene B4 (LTB4), using elastase as a marker enzyme. Topical treatment with 13-cis-retinoic acid resulted in a marked and statistically significant inhibition of the LTB4-induced migration of PMN. All-trans-retinoic acid, arotinoid methyl sulphone and arotinoid ethyl sulphone reduced the accumulation of PMN slightly, but not statistically significantly. Topical treatment with arotinoid methyl sulphone had no effect.

Administration, Topical↗
PubMed1991

Statistical guidelines for The British Journal of Surgery.

A set of statistical guidelines is presented which should be followed by authors preparing manuscripts for submission to The British Journal of Surgery. Simple points relating to presentation are explained in full, and more complex issues are highlighted and discussed in an accompanying review article.

Periodicals as Topic↗
PubMed1995

Events per person year--a dubious concept.

In 1982 a new measure was introduced in research into osteoporosis and is now used everywhere in the literature. The so called "fracture rate" relates the number of fractures (single in some patients, multiple in others) to the cumulative time of observation of all patients. This concept, however, has no sound basis. Counting events instead of patients usually violates basic statistical assumptions and invalidates the use of common statistical tests and estimators. Its clinical interpretation is rather dubious. The use of such a measure impedes the search for valid and clinically meaningful outcome criteria and should be abandoned.

Estrogens↗
PubMed1996

Study design, methodology and statistical analyses in the clinical development of sparfloxacin.

Many publications in the past 10 years have emphasised the difficulties of evaluating anti-infective drugs and the need for well-designed clinical trials in this therapeutic field. The clinical development of sparfloxacin in Europe, involving more than 4000 patients in ten countries, provided the opportunity to implement a methodology for evaluation and statistical analyses which would take into account actual requirements and past insufficiencies. This methodology focused on a rigorous and accurate patient classification for evaluability, subgroups of particular interest, efficacy assessment based on automation (algorithm) and individual case review by expert panel committees. In addition, the statistical analyses did not use significance testing but rather confidence intervals to determine whether sparfloxacin was therapeutically equivalent to the reference comparator antibacterial agents.

Anti-Infective Agents↗
PubMed1990

[Medicine, mathematics and statistics. Practical aspects].

To identify the statistical methods more frequently used in the medical literature, we reviewed 4,218 papers equivalent to 26 years/periodical. 26% of the papers did not have any statistical method. In the remaining 74% only descriptive (24.5%) or inferential (75.5%) methods were used. Overall there were 3,882 inferential test done. Based on a probability analysis we propose a framework to rationalize the teaching of statistics to improve the decision making process in medicine.

Education, Medical↗
PubMed2005

Methodological aspects of outcomes research.

A critical evaluation of existing scientific evidence of treatment efficacy can be an important part of communicating risk and benefits of treatment options to patients during the course of clinical practice. A checklist of key methodological issues to examine when reading a research study is presented and discussed. Steps in reading a paper include: identifying the research question; identifying the manner in which subjects get enrolled in the study; identifying the treatments and outcomes used; identifying the study design and the comparisons being made; evaluating the study methods for the possibility of bias and uncontrolled confounding; assessing whether the statistical analysis used is appropriate for the study design; assessing whether the study has sufficient statistical power to demonstrate hypotheses being tested. Finally, procedures for grading and evaluating evidence, as used by systematic review groups and international best evidence synthesis consensus groups is briefly described.

Back Pain↗
PubMed1980

Significance, importance and equality--three basic concepts in the analysis of a difference.

By means of data from fictitious cross over trials, it is first demonstrated that a statistically significant difference is not necessarily of a practically important order of magnitude. This fact is of special interest when the number of observations is large. Second, a statistically non significant difference does not prove the hypothesis about equality between, say, treatment effects. This fact is of special interest when the number of observations is small. For investigating whether equality is plausible, confidence intervals are more useful than non significant results from tests of significance.

Clinical Trials as Topic↗
PubMed1989

Use of restricted significance tests in clinical trials: beyond the one- versus two-tailed controversy.

Whether to use "one-tailed" or "two-tailed" tests for clinical trials is examined in the more general context of restricted tests, developed by J. Neyman. This is complimented by a discussion of theoretical work of Savage and Bahadur. It is concluded that all tests of statistical significance have to be "restricted" in some sense and that failure to recognize the restrictions implied by "standard" methods of analysis can have a negative effect on the ability to detect treatment effects of new drugs in phase II and early phase III clinical trials.

Analysis of Variance↗
PubMed2004

Large trials or meta-analysis? That is not the question.

Selection and evaluation of evidence to identify the most effective treatment modalities is a difficult process. Randomized controlled trials are well accepted as the least biased means of evaluating medical, surgical, screening or preventive manoeuvres. The most commonly used statistical strategy to pool results from trials identified during a systematic review is the meta-analysis. Heterogeneity of trial results should be evaluated, interactions and specific populations identified for the planning of the new large trial.

Decision Making↗
PubMed1998

Trials which randomize practices I: how should they be analysed?

BACKGROUND: In some general practice intervention trials, patients must be randomized in practices rather than individually, and this must be taken into account in the analysis. OBJECTIVES: In this article we aim to show how failure to do this may lead to spurious statistical significance and CIs which are narrower than they should be, and to describe the use of summary measures for each practice as a simple method of analysis. METHOD: The statistical issues are demonstrated by an example of a trial in general practice. DISCUSSION: The choice of unit of analysis will be most important where there are large numbers of patients recruited from each practice or a high degree of variability between practices.

Family Practice↗
PubMed1990

Intrauterine insemination does and clomiphene citrate does not improve fecundity in couples with infertility due to male or idiopathic factors: a prospective, randomized, controlled study.

In the present prospective study we compared, in terms of pregnancy rates, the differences between intrauterine insemination (IUI) of in vitro capacitated husband's semen and timed natural intercourse in spontaneous or clomiphene citrate (CC) stimulated cycles. A rapid urinary luteinizing hormone peak detection test was used for timing of ovulation. Forty patients suffering from longstanding infertility of male (n = 17), cervical (n = 2), and idiopathic (n = 21) origin were randomly assigned into four distinct treatment modalities during 4 consecutive cycles. A total of 132 cycles were analyzed. In 35 cycles treated with CC plus IUI, five conceptions were achieved, whereas three pregnancies occurred in 32 inseminated spontaneous cycles. Only 1 patient conceived after timed intercourse in 31 CC stimulated cycles, and no pregnancy resulted from 34 spontaneous cycles combined with timed intercourse. There was a statistically significant higher conception rate in cycles in which IUI was performed, whereas the use of CC does not seem to improve the pregnancy rate. Analysis of results for other modifying factors did not substantially affect the relative risk (odds ratio) of pregnancy.

Adult↗
PubMed2005

Misuse of statistical tests in Archives of Clinical Neuropsychology publications.

This article reviews the (mis)use of statistical tests in neuropsychology research studies published in the Archives of Clinical Neuropsychology in the years 1990-1992 and 1996-2000, and 2001-2004, prior to, commensurate with the internet-based and paper-based release, and following the release of the American Psychological Association's Task Force on Statistical Inference. The authors focused on four statistical errors: inappropriate use of null hypothesis tests, inappropriate use of P-values, neglect of effect size, and inflation of Type I error rates. Despite the recommendations of the Task Force on Statistical Inference published in 1999, the present study recorded instances of these statistical errors both pre- and post-APA's report, with only the reporting of effect size increasing after the release of the report. Neuropsychologists involved in empirical research should be better aware of the limitations and boundaries of hypothesis testing as well as the theoretical aspects of research methodology.

Bibliometrics↗
PubMedDate not supplied

Problems with publishing results of interim analyses of randomized clinical trials.

PURPOSE: This purpose of this study was to illustrate how publication of interim analyses of randomized clinical trials (RCTs) can cause problems in the interpretation of final results. METHOD: The effect of publishing interim analyses on the results of a typical HIV RCT comparing regimens of registered antiretroviral drugs was illustrated using a simulation study. Simulations modeled an RCT comparing the effect of two treatment combinations on changes in log HIV viral load from baseline. Publication of interim results at 6 months was assumed to lead to 50% of patients switching from the poorer treatment if interim results were statistically significant (p <.05), 20% of patients switching from the poorer treatment if interim results were marginally significant (.05 < p <.20), and 10% of all patients switching treatment if interim results were not statistically significant. Three scenarios were simulated: a large treatment difference (0.4 log HIV viral load), a moderate difference (0.2 log), and no treatment difference (0.0 log). RESULTS: The simulation study showed that if the true treatment difference was large (0.4 log) the power of the trial was reduced from over 80% at 6 months to under 37% at 12 months. Furthermore, given the statistical significance of the interim analysis results at 6 months, the simulations illustrated that the trial results would appear similar at 12 months, regardless of the true underlying treatment difference. CONCLUSION: The simulations reinforce the fact that publication of interim analyses of RCTs can affect the future conduct of a trial and make interpretation of final results difficult.

Anti-HIV Agents↗
PubMed1994

Statistical methods for clinical trials.

The object of this paper is to describe the essential features for the design and conduct of clinical trials. We include aspects of patient eligibility, random allocation to treatment including the principle of uncertainty, assessment of endpoints including those observed at different time points for each patient and trial size. Indications of appropriate methods of analysis are given, and the intention to treat principle is discussed. Some pointers to difficulties associated with data collection and management are included.

Clinical Trials as Topic↗
PubMed2001

Should Dukes' B patients receive adjuvant therapy? A statistical perspective.

The benefit of adjuvant therapy, such as 5-fluorouracil (5-FU) combined with leucovorin, is a matter of debate for patients with Dukes' B colon cancer. Several approaches have been taken to address this issue. Initially, studies were conducted to assess treatment benefits in both Dukes' B and Dukes' C patients. These studies identified an overall benefit of adjuvant treatment and enrolled enough Dukes' C patients to determine a treatment benefit for adjuvant 5-FU/leucovorin in this subpopulation. However, the individual studies were insufficiently powered to detect a treatment benefit in Dukes' B patients. An analysis of four separate studies (National Surgical Adjuvant Breast and Bowel project) compared the benefit of adjuvant treatment in Dukes' B patients with that in Dukes' C patients and showed similar relative reductions in mortality and disease-free survival in Dukes' B and in Dukes' C patients. The Liver Infusion Meta-Analysis Group also reported similar relative benefits from a portal vein infusion of 5-FU-based chemotherapy in Dukes' B and Dukes' C patients. The International Multicenter Pooled Analysis of Colon Cancer Trials B2 study, which combined data from patients with Dukes' B colon cancer in five separate trials, failed to show a statistically significant benefit of adjuvant 5-FU/leucovorin compared with surgery alone. We review the advantages and limitations of different approaches to detect treatment benefits in patients with Dukes' B colon cancer, and we argue that there is a need for a meta-analysis of all adjuvant trials to reliably address this question.

Antimetabolites, Antineoplastic↗
PubMed2003

A method for comparing two normal means using combined samples of correlated and uncorrelated data.

A method is proposed for comparing two normal means when the data consist of some observations that are correlated and others that are uncorrelated. Typically, such data will consist of one subsample in which the observations for treatment 1 and treatment 2 are independent of each other, and another subsample which consists of paired observations taken under both treatments. The proposed method is developed using asymptotic results and is evaluated using simulation. The simulation results indicate that the proposed method can provide substantial improvement in type I error rate and power when compared with standard methods of analysis.

Antihypertensive Agents↗