Analytical epidemiology studies

Spector TD, Hochberg MC. The protective effect of the oral contraceptive pill on rheumatoid arthritis an overview of the analytic epidemiological studies using meta-analysis. J Clin Epidemiol 1990 43(ll) 1221-30. 

As explained in the detailed report (6), the above conclusions and recommendations were based on evidence from a data base consisting of descriptive as well as analytical epidemiological studies, and a vast number and variety of animal experiments and in-vitro tests. 

Amino acids Building blocks of protein by cells there are about 20 amino acids Ames test A method of an experiment performed using bacteria as a test system to determine the mutagenic potential of a substance or chemical Anaerobic Requiring the absence of oxygen Analyte Any chemical substance measured in the laboratory Analytic epidemiologic study A study that evaluates the association between exposure to hazardous chemical substances and disease by testing scientific hypotheses... 

Gatsonis CA, Needleman HL. 1992. Recent epidemiologic studies of low-level lead exposure and the IQ of children A meta-analytic review. In Needleman HL, ed. Human lead exposure. Boca Raton, FL CRC Press, 243-255. 

There are two basic kinds of epidemiological studies, descriptive and analytical. The goal of the first is to describe the occurrence of disease in populations. Analytical studies identify and explain the cause of the disease. For instance, descriptive epidemiology may identify a new disease such as AIDS. Interpretation of descriptive results leads to analytical studies that examine the disease in more detail. Since epidemiology is the study of disease in populations, the proportion of affected individuals in a population is of basic importance. However, the epidemic pattern has varied from country to country. In the United States and the United Kingdom, 65% and 85%, respectively, of AIDS cases have... 

Different methods are used in epidemiology. Epidemiological studies are often divided into descriptive studies and analytic studies. 

In a 12-week epidemiological study conducted in a small town in Ohio, the ranges of concentrations of chlorine dioxide, chlorite ion, and chlorate ion in drinking water were 0.3-1.1, 3.2-7.0, and 0.3-1.1 mg/L, respectively (Lykins et al. 1990 Michael et al. 1981). In one study using a sensitive analytical method, the average concentration of chlorine dioxide in tap water from the city of Brest, France was 1.8x10 mol/L (0.012 mg/L) (Quentel et al. 1994). 

Laboratory analysis of human samples for trace contaminants or their metabolites inevitably produces results that deviate quantitatively from the actual concentrations. Such deviations can, for example, complicate exposure classifications in epidemiologic studies, detection of time trends in exposure, and comparison of studies that use data produced with different analytic methods. Individual laboratories can use standard QA-QC methods to minimize and define the magnitude of the variations. However, federal agencies and statutes, such as CDC, the National Institute of Standards and Technology, and statutes such as CLIA, could play important roles in improving the overall quality of biomonitoring laboratory data and their utility in health-related applications. 

Epidemiological studies can be categorized into three major types (1) descriptive or studies based on routine data, (2) analytical observational studies in which the researcher observes the occurrence of disease in two groups already segregated by disease or exposure, and (3) experimental studies in which the researcher randomly assigns individuals to the exposure in question. 

Table 9-2 also presents data from occupational and epidemiologic studies that indicate that the respiratory system is the primary target for sulfur dioxide. There was variability in the study findings that probably resulted from a lack of adequate analytical measurements (use of area sampling rather than personnel monitoring) the multiplicity of confounding, concurrent exposures to other chemicals and participates and the study indices investigated. However, some reasonable correlations between effects reported and exposure bounds can be determined. 

The analytical plan of epidemiological studies should use descrip tive and analytical techniques in describing the sample and results. Descriptive statistics, such as frequency distributions, cross-tabulations, measures of central tendency, and variation, can help explain underlying distributions of variables and direct the assessment of appropriateness of more advanced statistical techniques. Careful weighing of study findings with respect to the design and methods helps to ensure the validity of results. 

Causality can be considered in analytical or experimental epidemiological studies. That involves assessing the statistical association, the temporal relationship between exposure and outcome, and the elimina... 

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