ASK: Types of Studies
Different types of published studies may be more or less rigorous and subject to more or less inherent bias or systematic error. The chart below explains how different types of studies are conducted and how they are best used.
In addition, other types of research can be used when consider a clinical question:
- Cross-sectional studies describe the relationship between diseases and other factors at one point in time in a defined population. Cross sectional studies lack any information on timing of exposure and outcome relationships and include only prevalent cases. They are often used for comparing diagnostic tests. Studies that show the efficacy of a diagnostic test are also called prospective, blind comparison to a gold standard study. This is a controlled trial that looks at patients with varying degrees of an illness and administers both diagnostic tests — the test under investigation and the “gold standard” test — to all of the patients in the study group. The sensitivity and specificity of the new test are compared to that of the gold standard to determine potential usefulness.
- Qualitative Research answers a wide variety of questions related to human responses to actual or potential health problems. The purpose of qualitative research is to describe, explore, and explain the health-related phenomena being studied.
- Retrospective Cohort (or Historical Cohort) Studies follow the same direction of inquiry as a cohort study. Subjects begin with the presence or absence of an exposure or risk factor and are followed until the outcome of interest is observed. However, this study design uses information that has been collected in the past and kept in files or databases. Patients are identified for exposure or non-exposures and the data is followed forward to an effect or outcome of interest.