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PubMed2003

[Use of the major components methods in epidemiological studies].

When multifactorial processes are analyzed, it is most rational to use the methods of multidimensional statistical analysis, including the major components methods. This method is rather new in epidemiological surveys. Its advantage is that it may be used to get information that is difficult derived by other ways. Noteworthy is the versatility of the method, which lies in that the problems of analysis, prediction, and classification (stratification) of temporal series are solved by using actually the same techniques. How to apply the major components method are considered by using an example of investigating the general trends in the development of an epidemic tuberculous process in a specific area. Statistical data on tuberculosis morbidity in the areas of the Novosibirsk Region were employed as the initial material.

Causality↗
PubMed1990

[Molecular biologic methods for epidemiological precision characterization of disease agents using Salmonella enteritidis from poultry as an example].

The principles of molecular biological methods for epidemiological investigation of infectious bacteria are described. They were applied for differentiating S. enteritidis isolates originating from poultry. Among the methods described are the determination of the chromosomal DNA fingerprints (BRENDA), the methods of multilocus enzyme electrophoresis, plasmid profiles, and the outer membrane protein as well as lipopolysaccharide pattern. It turned out, that S. enteritidis strains isolated before 1987, in 1988 and the ones originating from Great Britain did not differ in anyone of these criteria. Consequently one has to assume, that the strains recently causing problems originate from the population of S. enteritidis which had existed in poultry before.

Animals↗
PubMed1995

Evaluation of phenotypic and genotypic methods for epidemiological typing of Staphylococcus aureus isolates from bovine mastitis in Denmark.

The value of five different typing methods (antibiogram typing, biotyping, phage typing, plasmid profiling and restriction fragment length polymorphism of the gene encoding 16S and 23S ribosomal RNA (ribotyping)), in discriminating 105 Staphylococcus aureus strains from bovine milk samples obtained from 105 different Danish dairy herds was investigated. A total of 85 strains (81%) proved susceptible to all of the 11 antibiotics tested, and the remaining 20 strains could be divided into 5 different antibiogram patterns. The predominant resistance pattern, penicillin resistance, was observed in 15 (75%) of the 20 antibiotic resistant strains. Biotyping assigned the strains to 14 different types, with the most common type accounting for 25.7% of the strains. Ninety eight (93.3%) strains could be typed by phages, assigning them to 19 different phage types. The predominant phage type accounted for 31.4% of the strains. Eight different plasmid profiles was observed among 24 (23%) strains harbouring plasmids. Ribotyping yielded 30 different types, with the most common accounting for 29.5% of the strains. The single most discriminatory typing method was ribotyping (0.863) followed by biotyping (0.842) and phage typing (0.795). Plasmid profiling (0.395) and antibiogram typing (0.327) had low discriminatory indices. Correspondence among ribotypes and the presence or absence of plasmids were observed, as was some degree of correspondence between ribotype, phage type and biotype. In general the correspondence between phage type and ribotype were stronger than between biotype and ribotype and between biotype and phage type. All combinations of two or more methods led to an improved index of discrimination compared to the individual methods indicating, that some subdivision of types had taken place. The combination of phage, bio- or ribotyping or all three methods in combination are considered to be an efficient combination of typing methods for epidemiological investigation of S. aureus mastitis.

Animals↗
PubMed1989

Epidemiologic research in fibromyalgia.

This paper reviews epidemiological methods, discusses the epidemiology of fibromyalgia and attempts to provide a blueprint for epidemiologic research in fibromyalgia by suggesting a number of studies that might be undertaken in the future.

Case-Control Studies↗
PubMed1997

How to select and interpret molecular strain typing methods for epidemiological studies of bacterial infections: a review for healthcare epidemiologists. Molecular Typing Working Group of the Society for Healthcare Epidemiology of America.

Strain typing is an integral part of epidemiological investigations of nosocomial infections. Methods for distinguishing among bacterial strains have improved dramatically over the last 5 years, due mainly to the introduction of molecular technology. Although not all molecular techniques are equally effective for typing all organisms, pulsed-field gel electrophoresis is the technique currently favored for most nosocomial pathogens. Criteria to aid epidemiologists in interpreting results have been published. Nucleic acid amplification-based typing methods also are applicable to many organisms and can be completed within a single day, but interpretive criteria still are under debate. Strain typing cannot be used to replace a sound epidemiological investigation, but serves as a useful adjunct to such investigations.

Bacterial Typing Techniques↗
PubMedDate not supplied

Estimating cumulative ambient concentrations of air pollutants: description and precision of methods used for an epidemiological study.

Methods for estimating cumulative ambient air pollution concentrations for individuals enrolled in an epidemiological cohort study are described and studied. Monthly interpolations from fixed-site monitoring stations in California to zip code centroids were used. The precision of the interpolation methods for total suspended particulates and ozone was assessed, and fixed-site monitoring stations were used in turn as receptor sites. Actual versus interpolated 2-y mean concentrations did not differ significantly and were correlated with a Pearson correlation coefficient of .78 for total suspended particulates and .87 for ozone. The impact of the change from monitoring total oxidants to ozone on oxidant/ozone cumulations was evaluated, and monthly mean concentrations for total oxidants were compared with ozone for 435 station months during which both pollutants were measured simultaneously. Average concentrations did not differ significantly and were highly correlated (r = 0.94). Exceedance frequency statistics, which averaged slightly higher for ozone than for total oxidants, were also highly correlated.

Air Pollutants↗
PubMed2000

Childhood injuries in the European Union: can epidemiology contribute to their control?

UNLABELLED: An average of 6000 children (0-14-y-old) died every year from injuries in the European Union during the last decade. Although the trends are overall favorable, injuries continue to represent the leading cause of death in this age group. The aim of this paper is to present childhood-injury-related public health issues and consider possible remedies of contemporary epidemiologic methods as applied to injury epidemiology and prevention. It has been estimated that half of the lives lost to childhood injuries could have been saved if all European Union countries matched the accomplishments of the country with the lowest mortality rate in each injury category. There is no specific pattern of association between Gross Domestic Product and incidence of motor-vehicle accidents by category of road user, whereas fatality from motor-vehicle accidents seems to be inversely, strongly and significantly related to Gross Domestic Product. CONCLUSION: The ongoing development of large injury databases in the European Union is a prerequisite for understanding the complex interactions that lead to a childhood injury. Moreover, possible remedies for overcoming the genuine problems associated with the application of traditional epidemiologic methods to the investigation of the frequently transient in nature causes of injuries should be considered.

Accident Prevention↗
PubMed1998

Statistical methods in epidemiology. II: A commonsense approach to sample size estimation.

PURPOSE: It has been argued, by many, that mathematical formulae for estimating sample size are unnecessarily complex, so much so that researchers may be reluctant to seek statistical advice. METHOD: This paper reviews methods of sample size estimation arguing that two formulae (one based on comparison of proportion of 'successes', the other based on comparison of means of normally distributed data) suffice for many situations. This paper argues the case by taking examples drawn mainly from clinical trials research. However, the methods outlined can also be used in epidemiology specifically in both case-control and cohort studies with no loss of information. RESULTS: For the situations outlined, worked examples are provided. CONCLUSIONS: Sample size estimation need not necessarily be a complex process. Simple techniques exist which enable the clinician and the statistician to work together. Continued dialogue between both parties is required so that good ideas do not go to waste.

Data Interpretation, Statistical↗
PubMed1998

Statistical methods in epidemiology: I. Statistical errors in hypothesis testing.

PURPOSE: Although scientific journal editors are making use of statisticians in the review process, the quality of statistical reporting in many journals remains poor. In many cases the problem for the scientist would appear to be a lack of understanding of basic statistics. The focus of the scientist is on showing 'p < 0.05', when what is actually required is a statement about effect size and interval estimation. The aim of this paper is to show the inadequacy of reporting of results using p-values alone. This paper is the first in a series detailing common statistical methods, with a view to aiding potential authors in their statistical presentation of data. METHOD: A review of the basic hypothesis test, using examples from the author's own teaching experiences. RESULTS: Type I and type II errors are defined; the problem of multiple comparisons is highlighted; interval estimation is introduced. CONCLUSIONS: The case for considering the p-value as an error probability is made which suggests ways of improving statistical presentation and thus expediting the statistical review process.

Confidence Intervals↗
PubMed2000

[Psychiatric cases identification by multi-step epidemiological studies: methods, problems and applicability].

OBJECTIVE: To discuss methodological aspects of the two stages in the identification of psychiatric cases in epidemiological studies. METHODS: Analyze the methodology used in the Multicentric Psychiatric Morbidity Study, which was conducted in three Brazilian cities (São Paulo, Brasília and Porto Alegre). In the first stage of that study, a random sample (6,740 individuals) of the population was drawn and all the participants were screened with the Questionnaire of Psychiatric Morbidity of the Adult (QMPA). In the second stage, a sample (775 individuals) of this population was drawn and these individuals were submitted to the Inventory of Symptoms of DSM-III, carried out by psychiatrists and trained psychologists. RESULTS: The study procedure for estimating the prevalence is described in details, showing that though the screening scales are a weak tool, they don't interfere with the methodology. CONCLUSION: The advantage of this methodology is to correct any distortions caused by the current tools used in the identification of psychiatric cases.

Adolescent↗
PubMed2001

Statistical methods in epidemiology. VII. An overview of the chi2 test for 2 x 2 contingency table analysis.

PURPOSE: The odds ratio is an appropriate method of analysis for data in 2 x 2 contingency tables. However, other methods of analysis exist. One such method is based on the chi2 test of goodness-of-fit. Key players in the development of statistical theory include Pearson, Fisher and Yates. METHOD: Data are presented in the form of 2 x 2 contingency tables and a method of analysis based on the chi2 test is introduced. There are many variations of the basic test statistic, one of which is the chi2 test with Yates' continuity correction. The usefulness (or not) of Yates' continuity correction is discussed. Problems of interpretation when the method is applied to k x m tables are highlighted. RESULTS: Some properties of the chi2 the test are illustrated by taking examples from the author's teaching experiences. CONCLUSION: Journal editors should be encouraged to give both observed and expected cell frequencies so that better information comes out of the chi2 test statistic.

Breast Neoplasms↗