bluuebunny/crossref_metadata_2025_split huggingface dataset:
A distribution‐free test for paired growth curve analyses with application to an animal tumour immunotherapy experiment
Authors: Koziol James A. , Maxwell Donna A. 
Published: April 2007

AbstractWe describe distribution‐free statistical methodology for assessing the equivalence of paired growth curves. This procedure may be used with incomplete observations, and in situations where parametric models for growth are inappropriate. We present data from an experiment investigating an immunotherapy regimen in a murine tumour system and which we have analysed with this technique.
Long term survival analysis: The curability of breast cancer
Authors: Pocock Stuart J. , Gore Sheila M. , Kerr Gillian R. 
Published: April 2007

AbstractMethods of survival analysis for long‐term follow‐up studies are illustrated by a study of mortality in 3878 breast cancer patients in Edinburgh followed for up to 20 years. The problems of life tables, advantages of hazard plots and difficulties in statistical modelling are demonstrated by studying the relationship between survival and both clinical stage and initial menopausal status at diagnosis.To assess the ‘curability’ of breast cancer, mortality by year of follow‐up is compared with expected mortality using Scottish age‐specific death rates. Techniques for analysing such relative survival data include age‐corrected life tables, ratio of observed to expected deaths and excess death rates. Finally, an additive hazard model is developed to incorporate covariates in the analysis of relative survival and curability.
Third variable analysis: Application to causal sequences among nutrient intake, maternal weight, birthweight, placental weight, and gestation
Authors: Susser Mervyn , Stein Zena 
Published: April 2007

AbstractWe applied a set of procedures, aimed at enhancing the strengh of inferences about the direcion of causal paths among variables measured at the same time, to foetal and maternal indices recorded at birth and collected for study of the Dutch famine of 1944/5. The analysis of three‐variable sets yielded strong inferences about the relations among caloric intake, maternal weight, birthweight, placental weight, and length of gestation. These procedures constitute not only a useful preliminary to the construction of multivariate path models, but produce useful results in their own right.
Tables of the number of patients required in clinical trials using the logrank test
Authors: Freedman L. S. 
Published: April 2007

AbstractThe logrank test is commonly used in the analysis of clinical trials in chronic diseases such as cancer. Existing tables for the number of patients required in such trials are based on the direct comparison of two proportions. This paper presents tables of numbers required in clinical trials using the logrank test and describes their use. The numbers required are considerably smaller than those in existing tables when the event‐free proportions are small, but otherwise comparable.
Use of a designed experiment for the study of muscle fibre size
Authors: Morton R. Hugh 
Published: April 2007

AbstractMalignant Hyperpyrexia (MH) is the manifestation of an underlying muscle disease. In routine clinical examination of muscle biopsy tissue it had been noted that muscle fibre sizes appeared to differ between MH‐susceptible individuals and non‐susceptible individuals. A designed experiment was required to utilize data from the muscle samples at hand and to form the basis for a more general investigative study. The experiment and ensuing analysis are described and the results and their implications are discussed.
Severity measurement in multiple trauma by use of ICDA conditions
Authors: Levy Paul S. , Goldberg Jack , Hui Siu , Rothrock Janet , Iverson Norman , Hosmer Trina 
Published: April 2007

AbstractWe report here the results of a study of grading injury severity for patients with multiple traumatic injuries from ICDA codes listed on the face sheets of hospital medical records. We developed a method of scoring the severity of individual ICDA traumatic injuries with use of data from the NCHS Hospital Discharge Survey. When tested on a set of patients having multiple trauma conditions (also from the NCHS Hospital Discharge Survey), these scores had a strong relationship with fatality. The development of an injury severity index based on ICDA codes has considerable impact on the feasibility of conducting studies involving large numbers of patients hospitalized with traumatic injuries.
Strategies for analysing ecological health data: Models of the biological risk of individuals
Authors: Manton Kenneth G. , Stallard Eric , Riggan Wilson 
Published: April 2007

AbstractFrequently, the analysis of environmental health hazards using ecological data does not involve explicit recognition of the difficulties in translating health effects expressed in the aggregate to the health risks of individuals. We discuss these difficulties and suggest the need for the appropriate conceptualization of risk mechanisms at the individual level and of the population processes that determine the form in which these risk mechanisms are expressed in aggregate data. To illustrate the implications of these concepts we develop a biologically motivated model of lung cancer risk and apply it to both national and county data. In addition, to measure the total health effects of the long term elevation or depression of lung cancer incidence rates, we calculate prevalence distributions from the time series analysis of incidence patterns in county data.
Detection of minimal epidemics
Authors: Knox E. G. , Lancashire R. 
Published: April 2007

AbstractEpidemiologists seeking epidemics of events in time, and attempting to distinguish real epidemics from random clusters, need to calculate the random probability ofnor more events occurring within a time window of durationw, and for any position of the window as it scans continuously across the period of observation. Exact algebraic solutions have been proposed by other workers, but, over a wide range of important values, systematic arithmetic evaluation is beyond the capacity of existing computers. This paper proposes an approximate test which is quick and simple and which achieves the same purpose. An example of its application is given.
Reliability of basic cancer patient data
Authors: Feigl Polly , Polissar Lincoln , Lane Warren W. , Guinee Vincent 
Published: April 2007

AbstractPooling patient data from multi‐institutional medical chart review occurs commonly in the study of cancer and other diseases. To determine the consistency of reporting among institutions, we presented a test set of 25 standardized medical charts to coders at 18 Comprehensive Cancer Centers and compared their resulting codes. This study measures the reproducibility of coding by different persons, but does not assess the accuracy of the underlying medical record. Among 34 data items, we found high disagreement rates in coding stage of disease (14 per cent) and date of diagnosis (8 per cent). Primary site, histologic type and other key items had good reproducibility (disagreement rates < 5 per cent). A number of minor disagreements indicated that detailed distinctions could not be reliably coded from medical charts.
Neonatal mortality in San Serriffe: A game for teaching survey methods
Authors: Macfarlane S. B. J. , Moody J. B. 
Published: April 2007

AbstractThe San Serriffe Game is a simulated epidemiological research exercise for demonstrating survey methods to medical postgraduates. A computer model has been developed to simulate medical and socio‐economic data relating to births and neonatal deaths on the imaginary island of Lower Caisse, San Serriffe. Participants, working in teams, are asked to investigate the extent and causes of neonatal mortality in Lower Caisse and to make recommendations which will bring about a reduction in the mortality rate. Participants are expected to implement some of the ideas learnt in parallel lecture sessions on the planning, design and analysis of survey work.
Magnitude and likelihood of loss resulting from non‐stratified randomization
Authors: Palta Mari , Amini Saeid B. 
Published: April 2007

AbstractWe investigate the power of detecting treatment differences by the stratified logrank test for balanced samples as compared to samples with unequal allocation to treatments within strata. Given non‐stratified randomization to treatments, we relate power losses to their probability of occurrence. In addition, we evaluate the likelihood of zero cells. For power calculations, we employ an asymptotic formula and complement by Monte Carlo simulations to verify results in small samples. In the cases investigated, our results show that large power losses due to imbalance are relatively unlikely with 2 strata. Small strata, however, involve a non‐negligible probability of wasting all observations because of zero cells or censoring.
The effect of unbalanced randomization on the progressively censored savage test
Authors: Lesser Martin L. 
Published: April 2007

AbstractEqual allocation of patients to treatment in a randomized clinical trial may have disadvantages ethically if the new treatment is believed to be at least as beneficial as the standard treatment. Others have considered, in a non‐sequential setting, unbalanced randomized designs which allocate fewer patients to the potentially inferior standard treatment. This paper examines unbalanced randomized designs in a sequential comparison of two exponential survival distributions using the progressively censored Savage test. The results reveal no substantial sacrifice in asymptotic power or early stopping properties.
BCG and vole bacillus vaccination in adolescence and mortality from leukaemia
Authors: Sutherland Ian 
Published: April 2007

AbstractIn total, 28 deaths from leukaemia are known to have occurred among the 54,239 participants in the Medical Research Council tuberculosis vaccines trial (initially aged about 14 years), from its beginning in 1950 to the end of 1979. There is evidence that this total is likely to be very nearly complete. During the entire period (average 27.1 years) the leukaemia mortality per million person‐years was 25 in the BCG vaccinated group, 20 in the vole‐bacillus vaccinated group, and 21 in the randomly‐allocated unvaccinated (control) group.Although there was neither a benefit nor a disadvantage from vaccination over the whole period, detailed figures suggested that there may have been a beneficial effect against leukaemia during the first 15 years after entry (that is between age 15 and 30 years) and a deleterious effect after longer intervals (or above the age of 30 years). Alternatively this swing may simply represent an unusual chance fluctuation.There has been no sign in recent years of any substantial decrease in leukaemia mortality in England and Wales at ages 15–29 years, although the proportion of children given BCG vaccine at about age 13 years has risen from less than 1 per cent (for the cohort aged 15–19 years in 1951–1955) to more than 70 per cent 25 years later. It has therefore been provisionally concluded that chance is the explanation for the apparent swing from prevention to enhancement, and that BCG vaccination at age 13–14 years in Great Britain does not affect subsequent mortality from leukaemia.
Epidemiology of prenatal infections: An extension of the congenital rubella model
Authors: Knox E. G. 
Published: April 2007

AbstractThe properties of prenatal infections are studied through the development of a theoretical model. The responses of such epidemic systems to natural changes in transmission rates, age at maternity, social stratification, geographical heterogeneity, epidemic instability and the introduction of vaccination, are examined. The effects of age‐at‐vaccination, efficacy of vaccination, wild virus interaction, and vaccine‐immunity decay rates, are also examined in some detail. Several powerful putative influences upon the evolution of prenatally determined infective diseases are identified. They provide scientific tools for detecting processes of this kind.
An analysis of repeated biopsies following cardiac transplantation
Authors: Spiegelhalter D. J. , Stovin P. G. I. 
Published: April 2007

AbstractBiopsy specimens are taken from the heart at regular intervals during the weeks following cardiac transplantation. Three specimens at most have been taken at each session, and classified by the pathologist on a histological four‐point scale of rejection. Since the rejection reaction in the myocardium is uniform neither in intensity nor distribution, there is often disagreement between the findings from a single session; even after three negative specimens there is some doubt as to whether rejection has taken place. In an attempt to quantify this residual uncertainty, we have adapted a procedure of Dawid and Skene1 for ‘estimating error rates’ when the true state is not known. The model is shown to provide a good explanation of the observed data, and provides guidance on the number of negative specimens required to give a defined level of certainty that rejection is not taking place.
Unbiased assessment of treatment effects on disease recurrence and survival in clinical trials
Authors: Kay Richard , Schumacher Martin 
Published: April 2007

AbstractRecently there has been considerable discussion concerning the analysis of data and presentation of results from clinical trials in breast cancer. A problem stems from there being several events of interest, notably disease recurrence and death. Current methods based on ‘so‐called’ disease‐free survival are criticized on the grounds that they confuse events, such as disease recurrence and death, in the treatment comparison and consequently could be very misleading. Alternative methods of analysis, based on separate measures of treatment effect are presented and illustrated.
Log‐linear model selection in a rural dental health study
Authors: Oler Jacqueline , Bentley J. Marvin 
Published: April 2007

AbstractThis field study sought to measure the effects of dental delivery and school‐based, dental health education on use of dental health care by children in grades K‐6. We attempted to control for two potential confounding factors by an approximate randomization of children into treatment groups with stratification on grade and initial oral disease levels. A backward elimination log‐linear model selection procedure for the 5‐factor classification permitted tests for higher‐order interaction, namely effect‐modification, confounding and collapsibility. We found that the effect of dental health education on use of dental care depended on the mode of dental delivery.
Between medicine and law
Authors: Finney D. J. 
Published: April 2007

AbstractA recent experience as an expert witness in a legal action intended to prevent the fluoridation of water supplies has emphasized to me some of the problems of explaining statistical reasoning to persons unfamiliar with the mode of thought. The procedures of cross‐examination are not ideal for clarifying scientific truth, and regrettably the language of statistics offers much scope for misunderstanding when words used technically are read with more colloquial meaning. I illustrate this by discussing the meaning of significance tests and by examples relating to the combination of independent test results, the misunderstanding of independence, covariance analysis, the use of interpolation, the relation between source of data and interpretation, and spurious correlation.
The importance of internal quality control data in national external quality assessment schemes. Plasma progesterone assays
Authors: Kay C. , Kemp K. W. , Nix A. B. J. , Rowlands R. J. , Groom G. V. , Wilson D. W. , Griffiths K. 
Published: April 2007

AbstractCo‐ordinators of external quality assessment schemes in the U.K. despatch samples of quality control material to participant laboratories at frequent intervals to assess laboratory performance. We show, via a controlled experiment on the plasma progesterone assay, that the current analysis performed by the external assessors is inadequate and often leads to erroneous conclusions about a laboratory's performance. It is concluded that for a proper assessment of a laboratory's performance, the external assessor should prepare large pools of plasma and distribute them to all participants in the scheme to use as internal quality control material.
Are definitive (reference) methods and Shewhart's principle the best approach towards accuracy?
Authors: Leijnse B. 
Published: April 2007

AbstractThe current state of quality control in clinical chemistry cannot be characterized as good; the appropriate description is acceptable. This statement is illustrated by results from quality control programmes. The influence of the matrix in which the analyte is embedded points to serious analytical deficiences in the methods used in clinical chemistry. The abundant application of statistics is criticized and it is argued that such application can be avoided by improving the accuracy and precision of the analytical methods. Difficulty in defining a definitive method results from accuracy and ‘true value’ not being determinate. The approved IFCC definition of the reference method and the connection between this definition and the basis of quality control in clinical chemistry is discussed. The pioneering work of Shewhart on quality control in industry in the 1930s is revealed. It is pointed out that the main principle of this method, a continuous process of tracing and eliminating assignable sources of variation, should be the aim of quality control in clinical chemistry.
Application of cusum techniques to the routine monitoring of analytical performance in clinical laboratories
Authors: Rowlands R. J. , Griffiths K. , Kemp K. W. , Nix A. B. J. , Richards G. , Wilson D. W. 
Published: April 2007

AbstractQuality control data from a radioimmunoassay of progesterone are analysed. The measurements are found to have a lognormal distribution. A likelihood analysis of the change‐point is described. Some rival continuous inspection schemes are compared and it is pointed out that more efficient schemes than Shewhart's can be implemented in clinical laboratories with the aid of a computer.
A method of analysis of laboratory data in an epidemiological study where time trends are present
Authors: Thompson S. G. 
Published: April 2007

AbstractWhere data are collected over an extended period, in either cross‐sectional or prospective studies, time trends in laboratory measurements can have misleading effects on observed associations, especially where it has not been possible to randomize the order of entry of participants to the study. In an ongoing prospective study of ischaemic heart disease, a modified cusum technique is used to examine the data for time trends. The paper considers a method for estimating where changes may have occurred, a method for adjusting for such changes in investigating the associations between variables and the appropriateness of making such adjustments.
Deficiencies in clinical reports for registration of drugs
Authors: De Jonge H. 
Published: April 2007

AbstractA considerable number of the clinical reports which are presented to the Dutch Board for the Evaluation of Drugs, have deficiencies and/or shortcomings. A number of these, including loose description of the target population and sampling method, methodological flaws, incorrect treatment of withdrawals, confounding of patients and observations per patient, incomplete or incorrect description of the data and incorrect or inappropriate use of statistical tests, are discussed.
Stopping rules for clinical trials
Authors: Freedman L. S. , Lowe D. , Macaskill P. 
Published: April 2007

AbstractWe describe a new method of formulating stopping rules for clinical trials, one that incorporates opinion on what difference is clinically important. We compare the method with conventional group sequential designs and illustrate it by application to a study of Pancuronium Bromide for prevention of haemorrhage in pre‐term infants.
Critical reflections on clinical trials
Authors: Rümke Chr. L. 
Published: April 2007

AbstractThere is often concern about the large number of patients needed for a particular clinical trial. However, one could be equally concerned that a trial is designed with a number of patients that is too small to obtain a precise enough estimate of the difference between the success rates of the treatments. The design of the trial should ensure that statistical significance is only reached if the treatment difference exceeds a specified value of clinical importance. Designs with this property generally require more than the usual number of patients. It is hoped that discussion on the ethical acceptability of this consequence will be stimulated by this paper.
The performance of logistic discrimination on myocardial infarction data, in comparison with some other discriminant analysis methods
Authors: Schmitz P. I. M. , Habbema J. D. F. , Hermans J. 
Published: April 2007

AbstractThe Imminent Myocardial Infarction study Rotterdam (IMIR), concerns patients who visit their general practitioners and have complaints suspected to be of cardiac origin. The study aims to develop a protocol for diagnosing myocardial infarction without laboratory assistance. We use the IMIR data, consisting of continuous and binary variables, to compare the diagnostic performance of logistic discrimination with some other discriminant analysis techniques. We discuss which characterizations of mixed data sets may give indications for an appropriate choice from among the alternative methods for discrimination.
Evaluation of clinical decision‐aids, with an application to a system for dyspepsia
Authors: Spiegelhalter D. J. 
Published: April 2007

AbstractThe evaluation of clinical decision‐aids is discussed both in general and in the particular case of a microcomputer‐based system designed to help general practitioners in deciding whether to refer patients with dyspepsia for specialist care. Parallels are drawn with the established framework for evaluating a new therapy, including a description of four phases of evaluation and the contrast between pragmatic and explanatory trials. Past studies are reviewed, emphasizing the difficulties of establishing a credible control group, and including some relevant examples from the areas of evaluating new diagnostic technology, medical information systems and audit procedures.
Assessing tumour markers
Authors: Tate Helen 
Published: April 2007

AbstractThis paper explores the factors involved in assessing the value of a medical test in a given clinical situation. It examines the problems involved in designing studies to investigate the role for a tumour marker in differential diagnosis and patient monitoring. An overview is given, including a critical evaluation of the preliminary research, the laboratory assay technique and potential clinical problems. Some examples are given. Specific approaches to the analysis of monitoring data are outlined, including the application of a sequential Bayesian model. This is illustrated using data from patients in the Medical Research Council's series of studies on the tumour marker Carcinoembryonic antigen.
The leicestershire perinatal mortality study: A case study of multi‐group discriminant analysis with complex sampling
Authors: Clayton David G. 
Published: April 2007

AbstractCase‐control studies are usually analysed by two‐group discriminant analysis or by a related method. However, in case‐control studies of perinatal mortality the cases (perinatal deaths) are far from homogeneous, and it is likely that some risk factors are relevant only to certain subgroups of cases. This paper proposes a seven‐category classification of perinatal deaths and reports an analysis using multi‐group discriminant analysis. The problem is further complicated by non‐random sampling of controls.