Analytical epidemiological study is a more detailed and all encompassing epidemiological study than the descriptive epidemiological study. An analytical study describes the association between exposure and outcome (disease). It is meant to test the hypothesis of a descriptive epidemiology. Analytical study investigates the cause of a disease by studying how exposure of individuals relate to the disease (i.e. it studies the relationship between a disease and its determinants). Virtually all epidemiological studies (except observational studies) are analytical in nature. In analytical epidemiological study, the epidemiologists or researcher systematically investigates whether or not the risk of a disease is different for exposed and unexposed persons in relation to a particular variable. Analytical epidemiological studies deal more with the “how” of a disease/infection in a population at a given time. It looks at the cause of a disease, the process of transmission (i.e. the how), and the relationship of the different factors or variables of the disease (i.e. the why) in a population/community. This study usually involves some series of laboratory procedures in order to supplement epidemiological studies.
Analytical epidemiological study may include:
- Case-control (Retrospective) studies
- Cohort (Prospective) studies
Case reports are epidemiological studies that consist of the careful and thorough or comprehensive description of a patient’s health or disease summary which is usually given by the physician in charge of that patient. It is the most fundamental type of descriptive epidemiological study obtained from an individual in the investigation of a disease outbreak. A case report involves a single case (i.e. one subject) with respect to a patient and, it describes unusual characteristics of the case or disease at the moment. It does not measure disease frequency and risk, and this type of descriptive epidemiological study is usually inexpensive to perform, speedy to carry out, and have no follow-up period. Case reports are entirely descriptive and as such it cannot be effectively used to make conclusions about the general population of individuals (in this case patient’s) that are harbouring the disease being investigated. The sole purpose of a case report is to generate hypothesis that will further be used to address a disease outbreak properly.
Case series is an expanded case report epidemiological study. It is the qualitative study of the experience (exposure) of a small group of patient’s or individual patient to a disease and, that has a related medical diagnosis. Data from a case series epidemiological study are used to analytically investigate the underlying characteristics of a disease in any population/community of people. Case series epidemiological study describes the characteristics of a number of patient’s (more than a single case) with a given disease in a population. Such studies are quick, inexpensive, and the cause-effect relationship of a case series study (just as in case report study) cannot be interpreted. A group of patient is examined in line with factors of a given disease, and case series studies also help to generate hypothesis. Case series studies can either be case-control studies or cohort studies.
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