Plan and Conduct of Research: Observational and Interventional Study Designs

  • Vikram Kate
  • Sathasivam Sureshkumar
  • Mohsina Subair


  • 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.


  1. 1.
    Jolles BM, Martin E. Study designs in orthopaedic clinical research. Clin Orthop Relat Res. 2011;469:909–13.CrossRefGoogle Scholar
  2. 2.
    Altman D. Introduction to study design. 2014.
  3. 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
  4. 4.
    Sut N. Study designs in medicine. Balkan Med J. 2014;31:273–7.CrossRefGoogle Scholar
  5. 5.
    Dawson B, Trapp RG. Basic and clinical biostatistics. New York: Lange Medical Books/McGraw-Hill; 2004.Google Scholar
  6. 6.
    Silva DS. Overview of study designs. In: Silva DS, editor. Cancer epidemiology: principles and methods. France: IARC Publications.
  7. 7.
    Lewallen S, Courtright P. Epidemiology in practice: case-control studies. Commun Eye Health. 1998;11(28):57–8.Google Scholar
  8. 8.
    Szumilas M. Explaining odds ratios. J Can Acad Child Adolesc Psychiatry. 2010;19(3):227–9.CrossRefGoogle Scholar
  9. 9.
    Song JW, Chung KC. Observational studies: cohort and case-control studies. Plast Reconstr Surg. 2010;126(6):2234–42.CrossRefGoogle Scholar
  10. 10.
    Andrade C. Understanding relative risk, odds ratio, and related terms: as simple as it can get. J Clin Psychiatry. 2015;76(7):e857–61.CrossRefGoogle Scholar
  11. 11.
    National Ethical Guidelines for Biomedical and Health Research Involving Human Participants. 2017. Accessed 22 Nov 2017.
  12. 12.
    Šimundić A-M. Measures of diagnostic accuracy: basic definitions. EJIFCC. 2009;19(4):203–11.PubMedPubMedCentralGoogle Scholar
  13. 13.
    Cook C, Cleland J, Huijbregts P. Creation and critique of studies of diagnostic accuracy: use of the STARD and QUADAS methodological quality assessment tools. J Man Manip Ther. 2007;15(2):93–102.CrossRefGoogle Scholar
  14. 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
  15. 15.
    Hopewell S, Dutton S, Yu LM, Chan AW, Altman DG. The quality of reports of randomised trials in 2000 and 2006: comparative study of articles indexed in Pub Med. BMJ. 2010;340:c723.CrossRefGoogle Scholar
  16. 16.
    Iaggio G, Elbourne DR, Altman DG, Pocock SJ, Evans SJ, CONSORT Group. Reporting of non-inferiority and equivalence randomized trials: an extension of the CONSORT statement. JAMA. 2006;295(10):1152–60.CrossRefGoogle Scholar
  17. 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. [Epub ahead of print]CrossRefPubMedGoogle Scholar
  18. 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. Scholar
  19. 19.
    Concato J, Shah N, Horwitz RI. Randomized, controlled trials, observational studies, and the hierarchy of research designs. N Engl J Med. 2000;342(25):1887–92.CrossRefGoogle Scholar
  20. 20.
    Efird J. Blocked randomization with randomly selected block sizes. Int J Environ Res Public Health. 2011;8(1):15–20. Scholar
  21. 21.
    Zhao W. A better alternative to stratified permuted block design for subject randomization in clinical trials. Stat Med. 2014;33(30):5239–48. Scholar
  22. 22.
    Doig GS, Simpson F. Randomization and allocation concealment: a practical guide for researchers. J Crit Care. 2005;20(2):187–91.CrossRefGoogle Scholar
  23. 23.
    Hollis S, Campbell F. What is meant by intention to treat analysis? Survey of published randomised controlled trials. Br Med J. 1999;319(7211):670–4.CrossRefGoogle Scholar
  24. 24.
    Suresh K. An overview of randomization techniques: an unbiased assessment of outcome in clinical research. J Hum Reprod Sci. 2011;4(1):8–11. Scholar
  25. 25.
    Philip S. What is a non-randomised controlled trial? BMJ. 2014;348:g4115.CrossRefGoogle Scholar
  26. 26.
    Haidich AB. Meta-analysis in medical research. Hippokratia. 2010;14(Suppl 1):29–37.PubMedPubMedCentralGoogle Scholar
  27. 27.
    Moher D, Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DF. Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement. Quality of reporting of meta-analyses. Lancet. 1999;354(9193):1896–900.CrossRefGoogle Scholar
  28. 28.
    Checkoway H, Pearce N, Kriebel D. Selecting appropriate study designs to address specific research questions in occupational epidemiology. Occup Environ Med. 2007;64(9):633–8.CrossRefGoogle Scholar

Copyright information

© Springer Nature Singapore Pte Ltd. 2018

Authors and Affiliations

  • Vikram Kate
    • 1
  • Sathasivam Sureshkumar
    • 2
  • Mohsina Subair
    • 3
  1. 1.Department of Surgery and Senior Consultant General and Gastrointestinal SurgeonJawaharlal Institute of Postgraduate Medical Education and ResearchPondicherryIndia
  2. 2.Department of SurgeryJawaharlal Institute of Postgraduate Medical Education and ResearchPondicherryIndia
  3. 3.Department of Plastic and Reconstructive SurgeryPostgraduate Institute Medical Education and ResearchChandigarhIndia

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