Experimental Design Epidemiological

The clinical and epidemiological evidence is summarized below. The deficiencies in the studies include the lack of appropriate sampling techniques, exposure determinations, mortality standards, and other aspects of experimental design or methodology. Additionally, intermittent exposures to benzene made it difficult to assume that the average concentrations of benzene measured in a workplace actually indicated the true exposure experienced by each worker (Goldstein 1985). A cause-effect relationship between benzene and leukemia is sufficiently clear however, there are few data from which dose-response relationships can be established. 

Random allocation of animals to treatment groups is a prerequisite of good experimental design. If not carried out, it is not possible to be sure whether treatment versus control differences are due to treatment or to confounding by other relevant factors. The ability to randomize easily is a major advantage animal experiments have over epidemiology. 

Early hiunan studies on gasohne containing up to 15% MTBE were more in the nature of reports of complaints from communities, rather than well-controlled epidemiological of experimental designs. The weaknesses inherent... 

Epidemiological studies, as outlined previously, are difficult, and when bioassays are based on measuring spore survival, infection versus colonization rates, disease intensity, inoculum potential, or any other characteristic, careful experimental design is vital to generating meaningful results (Kranz Rotem 1988). 

Category IA Strongly recommended and supported by well-designed experimental, clinical, or epidemiologic studies. 

In conclusion, phytic acid forms soluble complexes with Ca2+ at intestinal pH under a variety of conditions and fails to inhibit Ca2 bioavailability to mice in our experimental system. Despite the hazard in direct extrapolation of results obtained with animals kept on a well-defined dietary regimen to humans consuming a complex diet, many elements of which affect Ca2+ bioavailability, our data demonstrate the need for a reevaluation of the putative antinutritional properties of dietary phytate. Our further contention that adequate levels of dietary phytate may actually be beneficial due to its food preserving properties and its protection against colonic cancer will warrant a prospective epidemiological human study designed to assess the longterm effects of dietary phytate on mineral bioavailability and inflammatory bowel diseases. 

Table 9 presents a comparison of basic epidemiological study designs for assessing child health outcomes by their inherent methodological strengths and limitations. While experimental study designs are included for completeness, none is appropriate for the evaluation of environmental influences on children s health when the exposure(s) cannot be randomized within acceptable research practices. 

For economic outcomes, we can use pharmacoecon-omy as the main tool. " There is a great variety of clinical indicators that we can relate to drugs efficacy and safety. These clinical indicators, obtained with designs from clinical epidemiology (observational and experimental),are excellent to measure clinical outcomes. To obtain indicators for humanistic outcomes, such as satisfaction and quality of life, we have different tools, such as surveys, and different qualitative research methods (interviews, focus groups, etc.). " ... 

In Section III, we review studies on persistent effects of exposure to cholinesterase inhibitors. The human epidemiological literature is examined for evidence that persistent behavioral effects of exposure can be measured in populations with histories of acute poisoning and/or chronic ongoing exposure. We then review behavioral data from animal models designed to characterize the behavioral changes caused by experimental treatments with cholinesterase-inhibiting pesticides and identify similarities with the literature on human.s exposed occupationally to these compounds. 

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