Review of Intention-to-Treat Analysis in Randomized Controlled Trials

무작위 대조군 실험 연구에서 치료의향분석 (Intention-to-treat analysis)에 대한 고찰

  • 김정헌 (극동대학교 작업치료학과)
  • Received : 2020.02.04
  • Accepted : 2020.03.12
  • Published : 2020.05.31


Introduction : This review aims to introduce an intention-to-treat analysis(ITT) method and demonstrate the importance of rigorous utilization of this method to researchers in Korea. Discussion : ITT analysis includes all data as results in randomized control trials (RCT). Thereby the result of RCT is high validated to adapt in the real-world so that the result should be expected at clinical practice. Therefore, many RCT quality assessment tools include the question of the utilization of ITT analysis in individual trials. However, many researchers omit to report ITT, not utilize ITT or use ITT incorrectly. Conclusion : Through this review, more Korean researchers may understand and utilize ITT which is expected to enhance the quality of RCT papers.


  1. Akl, E. A., Briel, M., You, J. J., Sun, X., Johnston, B. C., Busse, J. W., ... Vera, C. (2012). Potential impact on estimated treatment effects of information lost to follow- up in randomised controlled trials (LOST-IT): Systematic review. British Medical Journal, 344. doi:10.1136/bmj.e2809.
  2. Alshurafa, M., Briel, M., Akl, E. A., Haines, T., Moayyedi, P., Gentles, S. J., ... Lamontagne, F. (2012). Inconsistent definitions for intention-to-treat in relation to missing outcome data: Systematic review of the methods literature. PLoS One, 7(11). doi:10.1371/journal.pone.0049163.
  3. Barczynski, M. (2013). Intention to treat analysis: Are we really doing it? Reply. World Journal of Surgery, 37(5), 1183-1184. doi:10.1007/s00268-013-1984-y
  4. Batista, K. B. D. S. L., Thiruvenkatachari, B., & O'Brien, K. (2019). Intention-to-treat analysis: Are we managing dropouts and missing data properly in research on orthodontic treatment? A systematic review. American Journal of Orthodontics and Dentofacial Orthopedics, 155(1), 19-27. doi:10.1016/j.ajodo.2018.08.013
  5. Bennett, S., & Bennett, J. W. (2000). The process of evidence -based practice in occupational therapy: Informing clinical decisions. Australian Occupational Therapy Journal, 47(4), 171-180. doi:10.1046/j.1440-1630.2000.00237.x.
  6. Bondemark, L., & Abdulraheem, S. (2018). Intention to treat (ITT) analysis as reported in orthodontic randomized controlled trials-evaluations of methodology and recommendations for the accurate use of ITT analysis and handling dropouts. European Journal of Orthodontics, 40(4), 409-413. doi:10.1093/ejo/cjx084.
  7. Brighton, B., Bhandari, M., Tornetta, P., & Felson, D. T. (2003). Hierarchy of evidence: From case reports to randomized controlled trials. Clinical Orthopaedics and Related Research, 413, 19-24. doi:10.1097/01.blo.0000079323.41006.12
  8. Centre for Evidence-Based Medicine. (2009). Oxford centre for evidence-based medicine - levels of evidence (March 2009). Retrieved from dence-based-medicine-levels-evidence-march-2009/
  9. Cochrane Methods Bias. (2019). RoB 2: A revised cochrane risk-of-bias tool for randomized trials. Retrieved from
  10. Consort. (2010). The CONSORT 2010 checklist. Retrieved from
  11. Consort. (2019). Non-pharmacologic treatment; 16. Numbers analysed. Retrieved from
  12. Elkins, M. R., & Moseley, A. M. (2015). Intention-to-treat analysis. Journal of Physiotherapy, 61(3), 165-167. doi:10.1016/j.jphys.2015.05.013
  13. Elkins, M. R., Moseley, A. M., Sherrington, C., Herbert, R. D., & Maher, C. G. (2013). Growth in the Physiotherapy Evidence Database (PEDro) and use of the PEDro Scale. British Journal of Sports Medicine, 47(4), 188-189. doi:10.1136/bjsports-2012-091804
  14. Fergusson, D., Aaron, S. D., Guyatt, G., & Hebert, P. (2002). Post-randomisation exclusions: The intention to treat principle and excluding patients from analysis. British Medical Journal, 325(7365), 652-654. doi:10.1136/bmj.325.7365.652
  15. Fisher, L. l. D., Dixon, D. O., Herson, J., Frankowski, R. K., Hearon, M. S., & Peace, K. E. (1990). Intention to treat in clinical trials. Peace. K. E. (Ed.), Statistical issues in drug research and development (pp. 331-350). New York: Marcel Dekker.
  16. Gibaldi, M., & Sullivan, S. (1997). Intention-to-treat analysis in randomized trials: Who gets counted? Journal of Clinical Pharmacology, 37(8), 667-672. doi:10.1002/j.1552-4604.1997.tb04353.x
  17. Gillings, D., & Koch, G. (1991). The application of the principle of intention-to-treat to the analysis of clinical trials. Drug Information Journal, 25(3), 411-424.
  18. Greenhalgh, T. (1997). How to read a paper: Getting your bearings (deciding what the paper is about). British Medical Journal, 315(7102), 243-246. doi:10.1136/bmj.315.7102.243
  19. Gupta, S. K. (2011). Intention-to-treat concept: A review. Perspectives in Clinical Research, 2(3), 109-112. doi:10.4103/2229-3485.83221
  20. Hewitt, C. E., Kumaravel, B., Dumville, J. C., Torgerson, D. J., & Group, T. A. S. (2010). Assessing the impact of attrition in randomized controlled trials. Journal of Clinical Epidemiology, 63(11), 1264-1270. doi:10.1016/j.jclinepi.2010.01.010
  21. Isaacs, D., & Fitzgerald, D. (1999). Seven alternatives to evidence based medicine. British Medical Journal, 319(7225), 1618. doi:10.1136/bmj.319.7225.1618.
  22. Joseph, R., Sim, J., Ogollah, R., & Lewis, M. (2015). A systematic review finds variable use of the intention-to-treat principle in musculoskeletal randomized controlled trials with missing data. Journal of Clinical Epidemiology, 68(1), 15-24. doi:10.1016/j.jclinepi.2014.09.002
  23. Lewis, J. A., & Machin, D. (1993). Intention to treat-who should use ITT? British Journal of Cancer, 68(4), 647-650. doi:10.1038/bjc.1993.402
  24. McCoy, C. E. (2017). Understanding the intention-to-treat principle in randomized controlled trials. The Western Journal of Emergency Medicine, 18(6), 1075-1078. doi:10.5811/westjem.2017.8.35985
  25. Moseley, A. M., Herbert, R. D., Maher, C. G., Sherrington, C., & Elkins, M. R. (2011). Reported quality of randomized controlled trials of physiotherapy interventions has improved over time. Journal of Clinical Epidemiology, 64(6), 594-601. doi:10.1016/j.jclinepi.2010.08.009.
  26. Pandis, N., Tu, Y. K., Fleming, P. S., & Polychronopoulou, A. (2014). Randomized and nonrandomized studies: Complementary or competing? American Journal of Orthodontics and Dentofacial Orthopedics, 146(5), 633-640. doi:10.1016/j.ajodo.2014.08.002.
  27. Polit, D. F., & Gillespie, B. M. (2009). The use of the intention-to-treat principle in nursing clinical trials. Nursing Research, 58(6), 391-399. doi:10.1097/NNR.0b013e3181bf1505.
  28. Ruiz-Canela, M., Martinez-Gonzalez, M. A., & Irala, J. (2000). Intention to treat analysis is related to methodological quality. British Medical Journal, 320(8), 1007-1008.
  29. Sackett, D. L., Rosenberg, W. M., Gray, J. M., Haynes, R. B., & Richardson, W. S. (1996). Evidence based medicine: What it is and what it isn't. British Medical Journal, 312(7023), 71-72. doi:10.1136/bmj.312.7023.71
  30. Schulz, K. F., Altman, D. G., & Moher, D. (2010). CONSORT 2010 statement: Updated guidelines for reporting parallel group randomised trials. Bio Med Central Medicine, 8(1), 18. doi:00.1136/bmj.c332
  31. Shiwa, S. R., Costa, L. O. P., Costa, L. d. C. M., Moseley, A., Hespanhol Junior, L. C., Venancio, R., ... Lopes, A. D. (2011). Reproducibility of the portuguese version of the PEDro Scale. Cadernos de Saude Publica, 27(10), 2063-2068. doi:10.1590/S0102-311X2011001000019
  32. Shrier, I., Verhagen, E., & Stovitz, S. D. (2017). The intention-to-treat analysis is not always the conservative approach. The American Journal of Medicine, 130(7), 867-871. doi:10.1016/j.amjmed.2017.03.023
  33. Tierney, J. F., & Stewart, L. A. (2005). Investigating patient exclusion bias in meta-analysis. International Journal of Epidemiology, 34(1), 79-87. doi:10.1093/ije/dyh300
  34. Tooth, L., BOccThy, S. B., McCluskey, A., Hoffmann, T., McKenna, K., & Lovarini, M. (2005). Appraising the quality of randomized controlled trials: Inter-rater reliability for the OTseeker evidence database. Journal of Evaluation in Clinical Practice, 11(6), 547-555. doi:10.1111/j.1365-2753.2005.00574.x
  35. Whittaker, K., Sutton, C., & Burton, C. (2006). Pragmatic randomised controlled trials in parenting research: The issue of intention to treat. Journal of Epidemiology & Community Health, 60(10), 858-864. doi:10.1136/jech.2005.044214
  36. Yamato, T. P., Maher, C., Koes, B., & Moseley, A. (2017). The PEDro Scale had acceptably high convergent validity, construct validity, and interrater reliability in evaluating methodological quality of pharmaceutical trials. Journal of Clinical Epidemiology, 86, 176-181. doi:10.1016/j.jclinepi.2017.03.002