Descriptive Studies PDF - Biomedical Research & Biostatistics

Descriptive Studies Prof. Dr. Zeinab Kasemy Biomedical Research and Biostatistics (CMS 181) 2024-2025 Prof. Dr. Adel Al-Wehedy Prof. Dr. Mohamed El-Helaly, Descriptive studies  DESCRIPTIVE STUDIES First phase in the epidemiological investigation. Describes the disease distrib...

Descriptive Studies Prof. Dr. Zeinab Kasemy Biomedical Research and Biostatistics (CMS 181) 2024-2025 Prof. Dr. Adel Al-Wehedy Prof. Dr. Mohamed El-Helaly, Descriptive studies  DESCRIPTIVE STUDIES First phase in the epidemiological investigation. Describes the disease distribution in the population. Give data about: When the disease occurs (Time). Where the disease occurs (Place). Who is getting the disease (Person).  1) Case reports Types of descriptive 2) Case series studies: 3) Correlation (Ecological) Study 4) Cross-sectional studies  1-Case Reports: Detailed presentation of a single case with a new or unique finding. Example: In 1961, pulmonary embolism has been described in a 40- years pre-menopausal female after 5 years of using oral contraceptive pills.  2-Case Series Case series describe characteristics of a few patients with a given disease. 3- Correlation (Ecological) Study It uses data from entire populations to compare disease frequencies in relation to supposed harmful (or beneficial) exposures during the same period or at different points in time. It uses available data like vital statistics, censuses and national health surveys Cross-Sectional Studies 4- Cross-Sectional Studies (Prevalence studies) An “observational” design that surveys exposures and disease status at a single point of time (a cross- section of the population). For this reason, you cannot determine if really exposure preceded disease or not. It measures the prevalence of health outcomes or determinants of health, or both, in a population at a point in time. The outcome of cross-sectional study: Prevalence rate N N T D Examples of cross-sectional studies: Assess the prevalence of coronary heart disease in relation to physical exercises. Assess the prevalence of obesity in relation to diabetes mellitus. Assess the prevalence of thrombo-phlebitis in relation to the use of oral contraceptive pills. Uses of Cross-Sectional Studies Used to study conditions that are Not suitable for studying Rare relatively frequent with long disease, with short duration of duration of expression (non-fatal, expression and Highly fatal acute chronic conditions) conditions)  Advantages & disadvantages of cross-sectional study Advantages Disadvantages Used to study Chronis diseases Cannot study acute diseases, fatal diseases or rare diseases Can estimate prevalence of disease Cannot estimate the incidence of disease Generates hypothesis about the association Cannot provide solid evidence about causation Can estimate exposure proportions Does not allow to determine which came first (disease or exposure) Relatively easy, quick and inexpensive Gives very little information about the natural history of the disease Thanks