文档介绍：case- control study Hui Jin Department of Epidemiology and Health Statistics School of Public Health, Southeast University 2 Overview Design of case-control studies ? Basic concept ? OR=RR? ? Exclusive (traditional) ? Inclusive (case-cohort) ? Concurrent (density) ? Case-to-case ? Case-crossover Why case-control study? ? In a cohort study , you need a large number of the subjects to obtain a sufficient number of case, especially if you are interested in a rare disease. – Gastric cancer incidence in Japanese male: / 100,000 person year ? A case-control study is more efficient in terms of study operation, time, and cost. Case-control study - Sequence of determining exposure and e status ? Step1: Determine and select cases of your research interest ? Step2: Selection of appropriate controls ? Step3: Determine exposure status in both cases and controls Case ascertainment ? What is the definition of the case? – Cancer (clinically? Pathologically?) – Virus carriers (Asymptomatic patients) → You need to screen the antibody – Including deceased cases? ? You have to describe the following points, – the definition – when, where & how to select Case definition ? Conceptual definition – Obesity defined as body fat percentage > 33% ? Operational definition – Body Mass Index > 30 Case definition: Issues ? Case definition should avoid misclassification – For example: Sinha et al (2008) ? Anemia was defined as Hemoglobin < 110 gm/L as measured by WHO Colour Scale ? WHO Colour Scale over-estimates the hemoglobin ? Misclassified cases with mild anemia ? Also, studying mild forms of cases, gives larger case group; but misclassifies cases as non-cases OR non- cases as cases as early diagnosis is generally imprecise Case definition: Issues ? A severe case definition may exclude people who have been cured or who died of disease before the condition was severe enough to be labelled as case ? Standard/consensus definitions if available, must be us