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PubMed1990

[Progress in biostatistics correlated with the development of computer technics].

The development of computers has positively influenced both Biostatistics and Medical Informatics. Close cooperation between Physicians, Biostatisticians and Experts of Medical Informatics is necessary. The leading role has to play the medical question, the medical problem to be solved, and not one of the cooperating disciplines. Both Biostatistics and Medical Informatics are parts of Medicine and must therefore taught as natural-scientific basic discipline of Medicine.

Biometry↗
PubMed1989

Biostatistical evaluation of evidence from continuous allele frequency distribution deoxyribonucleic acid (DNA) probes in reference to disputed paternity and identity.

We present a development and discussion of the biostatistical evaluation of deoxyribonucleic acid (DNA) probe evidence in forensic science cases of disputed paternity and identity. We restrict ourselves to single-locus codominant systems (highly analogous to more conventional systems) which have the apparently novel complication of an experimentally continuous allele frequency distribution. This complication necessitates reformulations of standard biostatistical summaries of the evidence (the paternity index (PI) and the phenotype frequency, respectively). These reformulations, rather than representing a unique case, have applicability to the evaluation of evidence obtained in standard genetic systems now in widespread use.

DNA↗
PubMed1989

[Plea for the training and continuing education of physicians in biostatistics. Results of a survey among Belgian physicians].

In order to test physicians' knowledge of statistics, a survey was conducted with a questionnaire in a sample of 250 doctors registered in the province of Brabant. The questionnaire consisted of two parts: a 9-item self-assessment test, and an opinion questionnaire about the importance of biostatistics and of its teaching. Forty-six physicians completed the two parts (18.4% of the sample); two other physicians only completed the second part of the questionnaire. For each subject, a score was computed: this score, ranging from 0 to 9, represents a simple sum of the right answers to the questionnaire. The median score is 2 (mean = 2.4; standard deviation = 1.8). No difference in the scores were found between groups defined by sex, the university of graduation, by the practice, general or specialized. The scores were not correlated to age, nor to graduation. The data from the opinion questionnaire show that the problem of biostatistics is considered important by 69% of the physicians, and that 88% of them think that this problem justifies training. With such training, physicians should be able to read the biomedical literature with discrimination, which supports the viewpoint of several authors. Although the small size of the sample and the small rate of answers might bias these results, we believe that physicians should be trained in statistics, which has become a pillar of medicine.

Attitude of Health Personnel↗
PubMed1988

Blood pressure monitoring from a biostatistical and clinical viewpoint for predicting fetal distress in preeclamptic pregnancy.

With technological progress, blood pressure monitoring has become a procedure largely applied in medical practice but not adequately systematized under a biostatistical viewpoint. This paper shows the complexity and importance of the biomathematical approach and its clinical implications in preeclamptic pregnancy. Data series were analyzed by means of noninferential and inferential procedures of biostatistics. A progressive gain of information is obtained, the inferential procedures showing an analytical resolution able to discriminate fetal distress in preeclamptic pregnancy.

Adult↗
PubMed1991

Biostatistics in otolaryngology journals.

Clinical research depends on biostatistics to form meaningful inferences from uncertain data. We performed a cross-sectional analysis of clinical research in otolaryngology journals to identify trends in statistical usage and determine the statistical aptitude expected of journal readers. Statistical content and study design were assessed for 1262 articles from 1969, 1979, and 1989. General trends toward an increasing use of inferential statistics and stronger study designs were observed. The number of analytic and experimental studies employing inferential statistics has risen from 20 (31%) in 1969 to 145 (65%) in 1989. Although familiarity with only five statistical techniques gave access to 90% of current articles, this study suggests that the level of statistical expertise demanded of both researchers and readers will continue to increase.

Bibliometrics↗
PubMed1999

The role of biostatistics in the prevention, detection and treatment of fraud in clinical trials.

Recent cases of fraud in clinical trials have attracted considerable media attention, but relatively little reaction from the biostatistical community. In this paper we argue that biostatisticians should be involved in preventing fraud (as well as unintentional errors), detecting it, and quantifying its impact on the outcome of clinical trials. We use the term 'fraud' specifically to refer to data fabrication (making up data values) and falsification (changing data values). Reported cases of such fraud involve cheating on inclusion criteria so that ineligible patients can enter the trial, and fabricating data so that no requested data are missing. Such types of fraud are partially preventable through a simplification of the eligibility criteria and through a reduction in the amount of data requested. These two measures are feasible and desirable in a surprisingly large number of clinical trials, and neither of them in any way jeopardizes the validity of the trial results. With regards to detection of fraud, a brute force approach has traditionally been used, whereby the participating centres undergo extensive monitoring involving up to 100 per cent verification of their case records. The cost-effectiveness of this approach seems highly debatable, since one could implement quality control through random sampling schemes, as is done in fields other than clinical medicine. Moreover, there are statistical techniques available (but insufficiently used) to detect 'strange' patterns in the data including, but no limited to, techniques for studying outliers, inliers, overdispersion, underdispersion and correlations or lack thereof. These techniques all rest upon the premise that it is quite difficult to invent plausible data, particularly highly dimensional multivariate data. The multicentric nature of clinical trials also offers an opportunity to check the plausibility of the data submitted by one centre by comparing them with the data from all other centres. Finally, with fraud detected, it is essential to quantify its likely impact upon the outcome of the clinical trial. Many instances of fraud in clinical trials, although morally reprehensible, have a negligible impact on the trial's scientific conclusions.

Biometry↗
PubMed2006

FDA's critical path initiative: a perspective on contributions of biostatistics.

This article describes the motivation for, description of, and the objectives and plans for the FDA's initiative that was introduced in March of 2004 by way of a report titled 'Innovation or Stagnation?--Challenge and Opportunity on the Critical Path to New Medical Products'. The FDA initiative is very much an outreach effort and a wake-up call to many constituencies to contribute and partner to improve the product development process and thereby to contribute to the success rate of new products that will benefit the public. We discuss in general terms where some of the opportunities and challenges exist for the discipline of biostatistics to make contributions to this effort over the next few years. In particular, guidance development in five areas is considered as is the need to devote new energy and efforts to quantitative risk assessment and safety evaluation, an area that has lagged the attention received in the efficacy evaluation area.

Biometry↗
PubMed2005

Tutorial in biostatistics: spline smoothing with linear mixed models.

The semi-parametric regression achieved via penalized spline smoothing can be expressed in a linear mixed models framework. This allows such models to be fitted using standard mixed models software routines with which many biostatisticians are familiar. Moreover, the analysis of complex correlated data structures that are a hallmark of biostatistics, and which are typically analysed using mixed models, can now incorporate directly smoothing of the relationship between an outcome and covariates. In this paper we provide an introduction to both linear mixed models and penalized spline smoothing, and describe the connection between the two. This is illustrated with three examples, the first using birth data from the U.K., the second relating mammographic density to age in a study of female twin-pairs and the third modelling the relationship between age and bronchial hyperresponsiveness in families. The models are fitted in R (a clone of S-plus) and using Markov chain Monte Carlo (MCMC) implemented in the package WinBUGS.

Adolescent↗
PubMed1995

Biostatistical concepts and methods in the legal setting.

Biostatistical concepts and methods apply to various problems arising in actual U.S. legal cases. These involve: measures of association, assessing the potential effect of omitted variables and the Peters-Belson approach to regression. In particular, we present the inapplicability of Fisher's exact test in the case where the process determining the marginal sample sizes is not independent of the hypothesis under study by the 2 x 2 table. We adapt Cornfield's procedure to assess whether the omission of another factor could have contributed to a non-significant finding of the effect of the major factor under investigation. Finally, we demonstrate the relevance and utility of the Peters-Belson regression methodology to equal pay and promotion cases.

Biometry↗
PubMed1992

Biostatistical evaluation of blood group, HLA and DNA findings in Jeffreys' immigrant test-case using special kinship and DNA algorithms.

In the immigration case cited by Jeffreys et al. (1985), the biostatistical evaluation of blood group findings in 16 systems and of HLA-A,B findings for the mother and child, using a special kinship algorithm developed by Ihm and Hummel (1975), produced a probability of maternity of the Ghanaian-born putative mother of W = 6%; the probability of maternity for her sister was W = 94%. Using the DNA multilocus probes 33.15 and 33.6 and the bandsharing technique, the authors analysed band patterns from the putative mother and child as well as another 3 children of the same woman. It was concluded that the putative mother was the mother of all 4 children. An evaluation of the band patterns using the multi-di-allelism model and the kinship algorithm in accordance with the Essen-Möller principle produced: W = 99.99999999999999991%, or, if the "-----" constellations were not considered, W = 99.99998%.

Adult↗
PubMed1975

[Praxis of the blood group opinion of parentage: systems with low exclusions potency; evidence of serological exclusion; biostatistical problems. Comments to a paper of H. Ritter in FamRZ 1973, 121 (author's transl)].

Blood group systems with a rare second allel are in praxis ineffective and therefore uneconomical because of their low exclusion potency as well as their low serostatistical value. The evidence of exclusion in particular blood group systems is fixed by the German "Richtlinien". With the new German law, however, one has to differentiate between the requirements in respect of the "offenbar unmöglich" ("fatherhood evidently impossible") in cases of extramatriomonial children, and those in respect of "schwerwiegende Zweifel" ("serious doubts in fatherhood") in cases of illegitimate children. The serostatistical results can give an indication on non-fatherhood, but in no case a real exclusion of paternity. Further evidence, as an anthropological or an HL-A expert opinion, is necessary to decide if the negative hint is reliable or not. To evaluate blood group (and HL-A) findings biostatistically, one uses the BAYES' Theorem with ESSEN-MOLLER's frequencies X and Y (in two-hypothesis cases). As prior plausibility one sets ESSEN-MOLLER's normative 0.5 or a realistic value, calculated from a concrete material of forensic cases. Statistical values on the basis of the exclusion chance as A, WA, Z, P and x do not give the whole information, because the phenotype of the man is not (or not fully) regarded. Therefore these values are of no use in serostatistical evaluation. With appropriate frequencies it is possible to calculate the probability of paternity also in cases in which foreign people is involved. If foreign frequencies are not available, the German "Richtlinien" allow to use european frequencies, if the involved people shares the caucasoid (europid) race.

Alleles↗
PubMed1998

[A critical analysis of studies of varicocele therapy from the biostatistics viewpoint].

Since approximately 45 years subfertile patients with varicocele are treated with different techniques of a varicocelectomy if there are no (other) causes of infertility. In the meantime, a varicocelectomy is being applied prophylactically in adolescents, too. In this article, there should be investigated whether the conducted clinical trials provide evidence of the efficacy of a varicocelectomy. Due to the fact that there are only a few valuable trials concerning the therapy of varicocele, the meta-analysis is mainly a critical analysis of the considered biostatistical methods. It comes to the conclusion that there is no clinical evidence for efficacy as well as against, and this conclusion is valid for the treatment as well as for the prophylaxis of male factor infertility. To achieve evidence, intensification of cooperation in multicenter study groups is necessary and methodical quality of the clinical trials on varicocelectomy should be improved.

Adolescent↗
PubMed1997

[Value of blue-on-yellow VEP for early diagnosis in suspected glaucoma. Biostatistical considerations and results].

BACKGROUND: In the Erlangen glaucoma study, the blue-on-yellow VEP was shown to be able to discriminate between controls and manifest glaucoma patients. SCIENTIFIC QUESTIONS AND AIMS: In our investigation, we assessed the validity of the blue-on-yellow VEP for early diagnosis of glaucoma. With this aim, we compared different subgroups of glaucoma suspects. The main issue of the investigation was the biostatistical aspects of early diagnosis of glaucoma. MATERIAL, METHODS AND RESULTS: Within a group of patients who were suspected of having ocular hypertensive glaucoma without visual field loss we compared 109 patients with optic disc damage [preperimetric (PPM) 47 +/- 11 years] and 91 patients without optic disc damage [ocular hypertension (OHT) 45 +/- 10 years]. We evaluated the N 1-amplitude and the peak latency of the blue-on-yellow VEP. The peak latency was significantly longer in the PPM group (first examination: OHT 118 +/- 9.5 ms, PPM 122.0 +/- 10.5 ms; second examination: 119.1 +/- 7.4/121.9 +/- 11.0 ms; third examination: 118.5 +/- 9.1/122.4 +/- 10.9 ms). The amplitude was reduced in the PPM group (P = 0.08). The differences between the two groups only allowed limited individual separation: (sensitivity of 42% for advanced optic disc damage with 80% specificity among OHT patients). CONCLUSIONS: The reduced sensitivity of a diagnostic procedure within a group of glaucoma suspect patients compared with patients with manifest glaucoma might be explained by: (1) possible misclassifications of patients and (2) a smaller degree of loss of visual function in the early stages of the disease.

Adult↗
PubMed1990

Biostatistical modeling of the effect of intravenous histamine-infusion on the rat gastric acid secretion.

In this study, a variety of linear and nonlinear biostatistical models of regression were tested to evaluate the histamine-induced gastric acid secretion using the lumen-perfusion model in the rat. Among the linear, parabolic, and polynomial models tested, 3rd- and 4th-order polynomial models of regression exerted best correlations between the time and histamine-induced gastric acid secretion. In order to avoid undulatory behaviors in the regression curves, we conducted the polynomial regression analysis up to 5th order.

Animals↗
PubMed1984

Biostatistical parameters of paternity and calculation by a computer programme.

Biostatistical Parameters such as the paternal markers in the child (PM), individual exclusion change (IEC) probability of incidental involvement (Z), probability of paternity (POP), plausibility of paternity according to Essen-M oller ( PLEM ) and paternity index (PI) are defined and discussed in respect to their application in cases of disputed paternity. In order to calculate these parameters for up to 24 marker systems, including HLA under strict observation of the linkage disequilibrium, a computer programme in BASIC has been developed.

Blood Group Antigens↗
PubMed1990

Introduction to biostatistics: Part 6, Correlation and regression.

Correlation and regression analysis are applied to data to define and quantify the relationship between two variables. Correlation analysis is used to estimate the strength of a relationship between two variables. The correlation coefficient r is a dimensionless number ranging from -1 to +1. A value of -1 signifies a perfect negative, or indirect (inverse) relationship. A value of +1 signifies a perfect positive, or direct relationship. The r can be calculated as the Pearson-product r, using normally distributed interval or ratio data, or as the Spearman rank r, using non-normally distributed data that are not interval or ratio in nature. Linear regression analysis results in the formation of an equation of a line (Y = mX + b), which mathematically describes the line of best fit for a data relationship between X and Y variables. This equation can then be used to predict additional dependent variable values (Y), based on the value or the independent variable X, the slope m, and the Y-intercept b. Interpretation of the correlation coefficient r involves use of r2, which implies the degree of variability of Y due to X. Tests of significance for linear regression are similar conceptually to significance testing using analysis of variance. Multiple correlation and regression, more complex analytical methods that define relationships between three or more variables, are not covered in this article. Closing comments for this final installment of this introduction to biostatistics series are presented.

Biometry↗
PubMedDate not supplied

An introduction to epidemiology and biostatistics and issues in interpretation of studies.

Epidemiology is the basic medical science that focuses on the distribution and determinants of disease frequency in human populations. An understanding of the tools of epidemiology is helpful in defining the limitations of medical research and evaluating the conclusions of studies. This is the first in a series of three articles whose objective will be to present the basic concepts of epidemiology and biostatistics. Examples of each of the tools and limitations discussed from studies of patients with end-stage renal disease (ESRD) will be presented to provide the reader with a practical application of the concepts. This series of articles will help the reader to weigh methods and study designs to understand the appropriate conclusions that may be drawn from any data.

Biometry↗
PubMedDate not supplied

Key concepts in biostatistics: using statistics to answer the question "is there a difference?".

Biostatistics seeks to answer the question "Is there a difference?" in the rate of a disease or characteristic among subgroups of patients. The goal of this article is to introduce and define measures used in epidemiology and discuss different types of analyses in clinical research with an emphasis on the concepts and implications of the analyses rather than the mathematics. The implications of the use of measures such as incidence and prevalence, as well as odds, risk, and hazards ratios may affect study conclusions. An understanding of the distinction between these summary measures is essential. The concepts of univariate and multivariate analyses, a discussion of what it means to control for potential confounders, and a description of statistical power and significance are also presented. These concepts are integral to the design and analysis of clinical studies. An understanding of their advantages and applications will enhance the reader's ability to understand and evaluate the literature.

Analysis of Variance↗