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PubMed1989

Diagnostic methods and epidemiologic surveillance of Taenia solium infection.

Taeniasis and cysticercosis caused by Taenia solium, the pork tapeworm, are widespread infections of Latin America, Africa, and Asia. The disease in humans (neurocysticercosis), caused by the cystic larval stages which develop in the central nervous system, is often disabling and sometimes fatal. T. solium infections are endemic in rural and urban areas in some countries that have limited resources to introduce and sustain control programs. To give T. solium control high national priority, the effect of the diseases on health and social care budgets must be accurately measured. Surveys are needed to establish prevalence and geographical distribution of the diseases, to obtain basic epidemiologic data, to learn about transmission, to provide baseline data for the establishment of control measures, and to monitor control measures. Continuing surveys can provide information on changes in prevalence brought about by specific control measures or by changes in the standard of living, education, animal husbandry, and meat processing. Data are not yet available for any endemic-cysticercosis area, and this has hindered efforts to control the disease. There are technical limitations of currently-available methods for diagnosing both taeniasis and cysticercosis in humans in and lower animal hosts. This paper reviews the status and limitations of diagnostic methods and emphasizes the need for further research.

Animals↗
PubMed1997

Average age at first occurrence as an alternative occurrence parameter in epidemiology.

BACKGROUND: Current epidemiological methods focus mostly on incidence rates and their ratios as measures of occurrence and effect. Incidence rates and rate ratios can be hard to interpret when the outcome disease is common. METHODS: The possibilities of using an alternative measure, average age at first occurrence of the disease, are discussed. RESULTS: Methods for the analysis of average age at first occurrence are illustrated in a study of occupation and disability pension. We estimate that the average age at pension among crane drivers is only about 0.8 that of maintenance workers, regardless of the method, although the confidence intervals depend on the method. CONCLUSIONS: Average age at first occurrence is easier to interpret than the incidence rate for a very common disease. Because estimates are not readily available in software packages, we encourage further development of packaged software for this measure.

Adolescent↗
PubMedDate not supplied

Interaction effects of epidemiologic factors in the feline urological syndrome.

Disease-associated factors are most often evaluated individually, while as disease determinants they act in mutual combinations. Applying simple epidemiologic methods, the present study evaluates the effect on occurrence of the Feline Urological Syndrome (FUS) of combining categories within sex, diet and activity. Some factor interactions could be described as additive, while certain combinations acted in a synergistic fashion. The apparent overall effect which might be explained by the excess-risk categories within these three factors was found to account for approximately 90% of the total occurrence of FUS in the population at risk. As a further result of the epidemiologic methods applied, a possible pathogenesis is outlined. It involves relative impairment of kidney function affected through two pathways: increased kidney working load and decreased kidney capability, both associated in various ways with castration, high levels of dry cat foods, and indoor confinement.

Animal Feed↗
PubMed1994

[Psychiatric and clinico-psychologic epidemiology: critique of methods and systematization approach].

The development of typical epidemiological questions is discussed. Possible definitions und fields of applications for simple status-diagnostics as well as for epidemiological longitudinal research are presented. Examples for the application of complex mathematical models like LOGIT- or LISREL-analysis are presented. Insufficient methodological systematisation and problems in comparing studies of different origin (i.e. for metaanalysis) are identified as problems for the future development of epidemiology. A classification system of epidemiological methods is presented that includes content aspects as well as methodological aspects on four levels. These are: the demand of the study (descriptive vs. inferential), the time dimension (status diagnostics vs. longitudinal research), the content level of operationalisation (micro- vs. macrolevel) and the level of explanation (correlative vs. causal). Examples show that this system can be used for classification of existing studies as well as for the conceptualisation and optimization of planned studies.

Cross-Sectional Studies↗
PubMed1992

Two critical confounding factors in periodontal epidemiology.

The prevalence and severity of periodontitis is considerably lower than was previously estimated. The available epidemiological methods are based on the premise that loss of periodontal attachment is a unique sign of periodontitis. However, additional factors resulting in loss of periodontal attachment confound data obtained from modern studies. The physiological process of continuous tooth eruption results in loss of periodontal attachment over a lifetime, at an approximate rate of 0.1 mm/year. Anthropological and clinical evidence for continuous tooth eruption is reviewed. The position of the alveolar crest appears to be stable; loss of periodontal attachment occurs as the teeth erupt and less of the root is embedded in bone. Retrograde periodontitis caused by pulpal disease is a known cause of severe, localised destruction of periodontal tissues. Its signs and symptoms include periodontal pocket formation, purulent inflammatory exudates, angular bone loss, swelling and bleeding of the gingival tissues and increased tooth mobility. Anthropological, experimental and clinical evidence for retrograde periodontitis is discussed. Misdiagnosis of angular (hemiseptal), furcal and other forms of localised periodontal damage as periodontitis has probably resulted because of the inability to determine the quality of pulpal health and the assumption of a gingivitis-periodontitis continuum. New epidemiological methods need to be developed in which physiological and all pathological conditions which affect the periodontal attachment are recognised and appropriately categorised.

Confounding Factors, Epidemiologic↗
PubMed2003

Comparison of three methods for epidemiological typing of Campylobacter jejuni and C. coli.

A total of 168 Campylobacter strains (154 C. jejuni and 14 C. coli) isolated from human clinical samples and chicken meat were typed using Penner serotyping, randomly amplified polymorphic DNA (RAPD), and pulsed-field gel electrophoresis (PFGE) with four restriction enzymes (Sac II, Sal I, Sma I, Kpn I). The 168 strains were found to represent 13 different Penner-types and 72 different RAPD-types. However, the discriminatory potential of PFGE was dependent on the restriction enzymes used. The 168 strains were divided into 74 (Sac II), 73 (Sal I), 72 (Sma I) and 69 (Kpn I) types. The DNA of some strains was not digested by Sal I, Sma I and Kpn I. Although three RAPD-types were further subdivided by PFGE, RAPD showed good discriminatory power and a high level of agreement with PFGE patterns in terms of strain differentiation. To compare the similarities of PFGE patterns (Sac II) among the strains, a dendrogram was constructed based on the unweighted pair group method with averages (UPGMA). In most cases, DNA types of C. coli were different from those of C. jejuni. The similarities between human and meat isolates were less than 0.42 except for one outbreak in which the isolates from both patients and chicken meat showed the same DNA types.

Animals↗
PubMed1986

[Evaluation of preventive measures against occupational health hazards].

The epidemiological methods which can be used to assess preventive measures against occupational health hazards are those used in the evaluation of public health interventions in general, with specific constraints. These constraints are mainly linked to the ethical aspects of intervention concerning occupational health hazards, to the long latency period of occupation related diseases, and to the complexity of the preventive actions. They probably explain in part why evaluative studies of preventive actions against occupational health hazards remain rare, and the methods used often inappropriate. Nonetheless, assessment of the efficacy of preventive measures at the workplace is necessary, and adequate methods do exist.

Epidemiologic Methods↗
PubMed2004

Molecular epidemiologic surveillance of salmonellosis in Arkansas.

OBJECTIVES: Salmonella serotype Newport and Salmonella serotype Typhimurium are the most commonly identified serotypes of Salmonella causing human disease in the state of Arkansas. The purpose of our study was to compare the results of standard and molecular epidemiologic methods of investigating human salmonellosis cases due to Salmonella serotype Newport and Salmonella serotype Typhimurium. METHODS: All isolates of Salmonella serotype Newport and Salmonella serotype Typhimurium collected and submitted to the Arkansas Department of Health between July 1, 1997 and June 30, 1998 were gathered and underwent pulsed-field gel electrophoresis (PFGE). Patients from whom the isolates were collected were contacted and completed a questionnaire. RESULTS: There were 84 patients from whom Salmonella serotype Newport was isolated and 83 from whom Salmonella serotype Typhimurium was isolated during the study period. In the 124 patients (74%) who completed the questionnaire, Salmonella serotype Newport was more likely to be the infecting agent in younger, white, and pet-owning patients (P < 0.05). The use of PFGE confirmed that approximately 20% of the organisms had genetic fingerprint patterns identical to those of at least one other individual in the state. One third of the patients from whom these isolates were obtained were linked by standard epidemiologic methods. CONCLUSIONS: The use of PFGE on our state's most common isolates provides additional confirmation that despite being linked by time of onset and location of residence, the majority of the human salmonellosis cases in our region are still sporadic. Low-level, intermittent transmission of these organisms through environmental contamination and contact with asymptomatically infected individuals would be likely vehicles of transmission in our state. Molecular techniques are important in surveillance systems that investigate human salmonellosis. Eighty-one percent of the Salmonella serotype Newport and 92% of the Salmonella serotype Typhimurium cases that appeared to be outbreak-related based upon time of onset and location were actually found not to be outbreak-related by PFGE. Using techniques such as PFGE will allow for more focused evaluations of potential outbreaks and will save the already limited financial and human resources that would otherwise be spent on investigations that are not warranted.

Adolescent↗
PubMed1997

Natural sex steroids and their xenobiotic analogs in animal production: growth, carcass quality, pharmacokinetics, metabolism, mode of action, residues, methods, and epidemiology.

Natural and xenobiotic compounds having sex-related actions have long been used for growth promotion and various changes in carcass quality in meat animals. The first compounds used were synthetic estrogens; however, later on a whole battery of compounds having androgenic, and progestogenic actions have also been involved. In surveying the effects of these compounds in meat-producing animals, it became clear that these drugs increase the growth rate of the treated animals and bring about changes in the carcass that are generally characterized by lower fat content and more lean mass. Extensive studies undertaken in various countries, including the European Economic Community (EEC), have shown that if used according to good husbandry practices, the meat from treated animals does not have excessive amounts of residues compared with the endogenous amount of steroid production in the animals in question and also in human beings. The banning of these compounds in the European community brought a new phenomenon of illegal or black market cocktails. These mixtures of anabolic steroids are injected into the body of the animals rather than implanted in the ears, which is the normal practice in countries where they have not yet been banned. Several screening and confirmatory methods are now available for monitoring programs. However, these programs need excessive resources in terms of manpower, funds, and proper legislation, which in underdeveloped countries is questionable, particularly in the absence of strong scientific evidence for the exercise.

Anabolic Agents↗
PubMed2005

Parity among interpretation methods of MLEE patterns and disparity among clustering methods in epidemiological typing of Candida albicans.

The typing of C. albicans by MLEE (multilocus enzyme electrophoresis) is dependent on the interpretation of enzyme electrophoretic patterns, and the study of the epidemiological relationships of these yeasts can be conducted by cluster analysis. Therefore, the aims of the present study were to first determine the discriminatory power of genetic interpretation (deduction of the allelic composition of diploid organisms) and numerical interpretation (mere determination of the presence and absence of bands) of MLEE patterns, and then to determine the concordance (Pearson product-moment correlation coefficient) and similarity (Jaccard similarity coefficient) of the groups of strains generated by three cluster analysis models, and the discriminatory power of such models as well [model A: genetic interpretation, genetic distance matrix of Nei (d(ij)) and UPGMA dendrogram; model B: genetic interpretation, Dice similarity matrix (S(D1)) and UPGMA dendrogram; model C: numerical interpretation, Dice similarity matrix (S(D2)) and UPGMA dendrogram]. MLEE was found to be a powerful and reliable tool for the typing of C. albicans due to its high discriminatory power (>0.9). Discriminatory power indicated that numerical interpretation is a method capable of discriminating a greater number of strains (47 versus 43 subtypes), but also pointed to model B as a method capable of providing a greater number of groups, suggesting its use for the typing of C. albicans by MLEE and cluster analysis. Very good agreement was only observed between the elements of the matrices S(D1) and S(D2), but a large majority of the groups generated in the three UPGMA dendrograms showed similarity S(J) between 4.8% and 75%, suggesting disparities in the conclusions obtained by the cluster assays.

Alleles↗
PubMed2000

Sexual activity and cardiac risk: overview of epidemiologic research methods.

The goal of clinical research is to differentiate among the different possible types of associations between the factors under study: no association, artifactual association, indirect association, and causal association. This article is intended as a brief overview of the research methods used in clinical research to differentiate these types of associations. It begins with an overview of the scientific method and the types of errors that can be made (i.e., random error, confounding, and bias). It then discusses the criteria supporting the causal nature of an association (i.e., how can one tell when an association is causal?). The criteria reviewed are (1) coherence with existing information; (2) time sequence; (3) specificity; (4) consistency; and (5) strength. Included within the last are quantitative strength, dose-response relation, and study design. Finally, the article provides a very brief outline of the available research designs, i.e. , experimental studies, cohort studies, case-control studies, analyses of secular trends, case series, and case reports, and the advantages and disadvantages associated with each.

Animals↗
PubMed1992

The Li-Fraumeni syndrome: from clinical epidemiology to molecular genetics.

The goal of this review is to demonstrate the effective interaction of epidemiologic methods and molecular genetics in the identification of familial cancer predisposition. The example involves a hospital-based population of childhood soft tissue sarcoma patients who were less than age 16 years at diagnosis at the University of Texas M. D. Anderson Cancer Center, Houston, Texas, in 1944 through 1976, had survived at least 3 years from diagnosis, and were diagnosed at least 5 years before the start of our study. Familial data were collected on the patients' offspring, full siblings, parents, aunts, uncles, and grandparents. The initial analysis revealed a small but significant cancer excess in first-degree relatives. Genetic analysis demonstrated that the cancer distribution in families could best be explained by a rare autosomal dominant gene with penetrance such that the risk of cancer by age 35 years was nearly 50%. Most of the evidence for a dominant gene came from nine kindreds. Laboratory investigation of fibroblasts from those kindreds provided an in vitro model of cellular immortalization and carcinogenesis. Germline mutations in the tumor suppressor gene p53 were found in two of the families, and studies are ongoing in the other kindreds. This review demonstrates the power of genetic epidemiologic methods to characterize statistically a cancer-predisposing gene and the application of molecular genetics to define the genetic defect.

Adolescent↗
PubMed1996

Studies of cancer in migrants: rationale and methodology.

Migrant populations comprise substantial numbers of individuals who have undergone a change in their environment, sociocultural and physical. The corresponding changes in risk for different cancers have, therefore, been widely used to infer the relative importance of environmental factors versus inherited predisposition in cancer aetiology. The uncontrolled experiment of migration also provides an indication of the possible effects of certain preventive interventions at the population level--especially with respect to diet. In the past, there has been a surprising lack of attention to analytical methods for migrant data, and we review the epidemiological methods available to best bring out the relevant differences in risk. The major sources of bias which confuse interpretation are also described. Migrant studies are classified into four groups, in a hierarchy corresponding to the amount of information which they can provide, and examples of each type are provided.

Age Factors↗
PubMed2002

Statistical methods in epidemiology: Karl Pearson, Ronald Ross, Major Greenwood and Austin Bradford Hill, 1900-1945.

The tradition of epidemiological study through observation and the use of vital statistics dates back to the 18th century in Britain. At the close of the 19th century, however, a new and more sophisticated statistical approach emerged, from a base in the discipline of mathematics, which was eventually to transform the practice of epidemiology. This paper traces the evolution of that new analytical approach within English epidemiology through the work of four key contributors to its inception and establishment within the wider discipline.

Epidemiology↗
PubMed1989

Analysis of Listeria monocytogenes by multilocus enzyme electrophoresis and application of the method to epidemiologic investigations.

We examined 310 strains of Listeria monocytogenes by multilocus enzyme electrophoresis. Fifty-six electrophoretic types (ETs) of the organism were defined: 10 for serovar 4b strains, 11 for serovar 1/2b strains, and 30 for serovar 1/2a strains. Strains of serovars 1/2c, 3a, and 3b, and a non-typable strain were distributed among the remaining five ETs. The mean genetic diversity of the species was 0.41. Principal coordinate analysis revealed a sharp division among ETs which divided the species into two major clusters. ETs containing serovar 1/2a strains were in one cluster while all ETs containing serovar 4b, 1/2b, and 3b strains were in the second cluster. Except for two ETs that contained strains from both serovar 1/2b and serovar 3b, no ET contained strains from more than one serovar. Multilocus enzyme electrophoresis facilitated the analysis of epidemiologic data. In three separate epidemiologic investigations electrophoretic typing confirmed a common source as a cause of an outbreak; in a fourth investigation a single common source as a cause of an outbreak was effectively ruled out. Electrophoretic typing was also useful in documenting potential links between Listeria contaminated foods and persons with listeriosis who consumed those foods.

Animals↗