Epidemiologic Study Methods

Breast BRCA 1, BRCA2 Tumor suonressor eenes APC. AXIN2. TP53 (n53i. STKll. PTEN, BMPRIA, and SMAD4 (DPC4) 

Colon Renair/Stabilitv eenes hMLH1. hMSH2. hMSH6. PMS2. MYH (MutYH), and BLM Oncogenes KIT and PDGFRA 

Endometrium Hereditary nonpolyposis colon cancer (HNPCC) 

Lymphoma Eamily history of lymphoma and certain common genetic variations in immune response genes 

Multiple endocrine neoplasia type 2 RET proto-oncogene 

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EPIDEMIOLOGIC STUDY METHODS 403 TABLE 15.4. Inherited Genetic Mutations Associated with Increased Risk for Selected Cancers (ACS 2008 NCI 2008c-e) ... 

Agarwal et al. 1978), the quantification of these specific enzymes may indicate that exposure to endosulfan has occurred. Blood tests, such as decay curves for aminopyrine in plasma, which are semiquantitative indices of liver enzyme induction, have been used successfully in the past to demonstrate enzyme induction in pesticide-exposed workers. Because numerous chemicals found at hazardous waste sites also induce these hepatic enzymes, these measurements are not specific for endosulfan exposure. However, measurements of enzyme activity, together with the detection of the parent compound or its metabolites in tissue or excreta, can be useful indicators of exposure. All of these potential biomarkers require further verification in epidemiological studies. Further studies with focus on the development of methods to separate and measure the estrogenicity of endosulfan in in vitro assays would be valuable since these assays are more sensitive and discriminative than other conventional biomarkers. Preliminary results have been presented by Sonnenschein et al. (1995). 

In most studies, phytoestrogen intake has been estimated by direct methods that evaluate food intake either by recall (food-frequency questionnaires -FFQs) or by record (food diary), and subsequently by composition databases based on information of this kind. Food-frequency questionnaires are widely administered to subjects involved in epidemiological studies. Their validity and reproducibility is considered sufficient when statistically correlated to data obtained from dietary records (a properly-completed and comprehensive food diary) and from analysis of blood and urine samples (Kirk et ah, 1999 Huang et al, 2000 Yamamoto et al, 2001 Verkasalo et al, 2001). FFQs can be repeated several times a year and may be administered to large populations. Such an approach provides an easy and low-cost method of assessing the... 

We would, of course, prefer not to see anything but negative results from epidemiology studies. In an ideal world information on toxic properties would be collected before human exposure is allowed to take place, and that information would be used to place limits on the amount of human exposure that is permissible. If mechanisms existed to enforce those limits, then excess chemical risk would not occur and, it obviously follows, would not be detectable by the epidemiologist (unless, of course, the data or methods for setting limits were in error). 

We still lack an adequate dose-response relationship for humans exposed to ozone, particularly at concentrations less than about 0.2 ppm. The data base for the development of such a relationship for both short-and long-term exposures is inadequate. Although some data from controlled studies are available for concentrations above 0.3 ppm, methods for extrapolating to lower concentrations are needed. Moreover, it is not clear how to weight the results of pulmonary function tests on humans, animal studies, and epidemiologic studies in a general dose-response relationship. 

One can readily see that the conclusions of the authors are based on numerous assumptions rather than on factual data. Unfortunately, this is the nature of retrospective epidemiological studies. One cannot really fault the authors for their sequence of theories leading them to a possible source of the infections. Such efforts are necessary for sorting out the potential source of infections and. through follow-up studies and designed experiments, we can determine sources of infections and methods for prevention. They evidently did omit some observations on the meat samples they did check and observations on the adjacent dairy herd and. they did not take samples from the cattle s environment on the beef farm. If the beef farm was thought to be the source, there should have been more effort to find the organism on that farm. 

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). 

Epidemiological studies have different strengths and weaknesses associated with their design (Table 4) shows some of the strengths and weaknesses of the two main methods of prospective cohort studies and retrospective case-control studies. 

The autonomic regulation of cardiac activity can be monitored through entirely noninvasive techniques. These methods are ideal for large-scale epidemiological studies as well as developmentally based research. Autonomic... 

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