Plan and Conduct of Research: Observational and Interventional Study Designs
The study design is the overall strategy chosen to logically assimilate the different study components so as to effectively address the research question and is determined by the research question and not vice-versa.
Study designs in medical research can be broadly classified as basic, observational and interventional studies. Observational studies can be further divided into descriptive and analytic studies.
Case-control study proceeds from outcome to exposure, whereas cohort study proceeds from exposure to outcome.
RCTs can be divided as parallel arm, cross-over and factorial studies based on design and as superiority and non-inferiority based on hypothesis.
The keystones in the decision making process for suitable study design is “reducing bias” and “increasing efficiency”.
Although RCTs and controlled cohort studies provide higher level of evidence, the best study design is the one that answers the research question most explicitly.
- 2.Altman D. Introduction to study design. 2014. http://www.equator-network.org.
- 3.Rohrig B, du Prel JB, Wachtlin D, Blettner M. Types of study in medical research: part 3 of a series on evaluation of scientific publications. DtschArzteblatt Int. 2009;106:262–8.Google Scholar
- 5.Dawson B, Trapp RG. Basic and clinical biostatistics. New York: Lange Medical Books/McGraw-Hill; 2004.Google Scholar
- 6.Silva DS. Overview of study designs. In: Silva DS, editor. Cancer epidemiology: principles and methods. France: IARC Publications. http://www.iarc.fr/en/publications/pdfs-online/epi/cancerepi/.
- 7.Lewallen S, Courtright P. Epidemiology in practice: case-control studies. Commun Eye Health. 1998;11(28):57–8.Google Scholar
- 11.National Ethical Guidelines for Biomedical and Health Research Involving Human Participants. 2017. http://www.icmr.nic.in/guidelines/ICMR_Ethical_Guidelines_2017.pdf. Accessed 22 Nov 2017.
- 14.Kabisch M, Ruckes C, Seibert-Grafe M, Blettner M. Randomized controlled trials: part 17 of a series on evaluation of scientific publications. Deutsches Ärzteblatt Int. 2011;108(39):663–8.Google Scholar
- 17.Mohsina S, Shanmugam D, Sureshkumar S, Kundra P, Mahalakshmy T, Kate V. Adapted ERAS pathway vs. standard care in patients with perforated duodenal ulcer-a randomized controlled trial. J Gastrointest Surg. 2018;22(1):107–16. https://doi.org/10.1007/s11605-017-3474-2. [Epub ahead of print]CrossRefPubMedGoogle Scholar
- 18.Das R, Sureshkumar S, Sreenath GS, Kate V. Sequential versus concomitant therapy for eradication of Helicobacter Pylori in patients with perforated duodenal ulcer: a randomized trial. Saudi J Gastroenterol. 2016;22(4):309–15. https://doi.org/10.4103/1319-3767.187605.CrossRefPubMedPubMedCentralGoogle Scholar