Understanding of Study Designs in Clinical Research: Major Prompting Points

Study design plays an important role in clinical epidemiology and public health. This helps in not only quantifying level of relationship between exposure and outcome accurately but also in differentiating whether a measured relationship between an exposure and outcome is an indication of merely association or suggestive of risk/ causality. It also helps in quantifying prevailing burden of disease/ disease frequency (i.e., prevalence, incidence rate, incidence density rate) in a considered region. Study designs are classified mainly based on evidence regarding involvement of comparison group; control of exposure (e.g., treatments) in the hand of the researcher (yes/no); exposure precedes outcome (e.g., cure) or not; use of randomization (yes/ no); timing of data collection (i.e., before occurrence of exposure and outcome; or otherwise); and direction of data collection between exposure and outcome. Taking into account these considerations, the focus of the present write-up is to briefly describe various study designs and related merits and demerits so that researchers can be aware and make use of them to specify study designs of their planned clinical studies accurately.