28/11/2022 - Last update 20/04/2023

Randomized controlled trial (RCT)

[reading time: 4 minutes]

Typically, this type of study aims to scrutinize a new preventive or therapeutic regimen and it naturally must adhere, like all other studies, to the Good Clinical Practice and obtain the approval of the Ethics Committee.

The RCT typically analyzes two types of intervention (drug and placebo) in a population randomly divided into two groups. They have a lot in common with the other quantitative studies. For example they formulate a quantitative question, recruit an even population and impose as a starting point the approval of the null hypothesis. However, they stand out for specific methodological characteristics that make them more rigorous.

  • Control group
    The presence of a control group allows the comparison of an intervention group with another homogeneous group, selected in accordance with the eligibility criteria. This allows to minimize the effects of all variables except the independent one.
  • Randomization
    It is the division of the population into two or more groups through a random procedure, which can be realized by drawing lots possibly supported by specific softwares. In this way many allocation bias are avoided.
  • Blinding
    It is the process for which certain categories of subjects involved in the study are precluded from the access to some information for the entire duration of the study.

The most frequently hidden piece of information is the allocation to the different groups. However, in order to reduce the risk of bias, the researchers may also arrange that the practitioners administering the questionnaires used to measure the outcomes are blinded to the aim of the study, or that the execution of the statistical analysis is entrusted to operators who are blinded to the requirements of the study.

The blinding can have various levels, for example, the studies are defined as “single-blinded”, or double-, triple-, quadruple-blinded depending on the number of categories kept in the dark.

    • in a single-blinded study, the participants are typically not aware if they have been allocated to the study group or to the control group;
    • in a double-blinded study, also the experimenters or the practitioners measuring the outcomes may be in the dark about the allocation of the participants;
    • in a triple-blinded study, typically the experimenters, the patients and the practitioners measuring the outcomes are all blinded;
    • In a quadruple-blinded study, besides the three categories mentioned above, the practitioners carrying out the statistical analysis can also be blinded.


  • Methodological rigor
    Amongst the useful guidelines for conducting and reporting parallel groups RCT there is the CONSORT 2010 statement.

In the osteopathic literature the RCT are often penalized by their inability to keep the practitioner in the dark of what they are doing. It is a problem shared also by other disciplines, like, for example the surgical practice, many psychological therapies and other manual therapies.

Amongst the many methodological reflections in the field of the osteopathic research please refer, for example, to an article by Licciardone and Russo1, which can help as an introductory approach on the topic of the simulated therapy in the control group of the osteopathic RCT.

As a practical example of RCT, realized according to the CONSORT guidelines, we can mention the study by Cerritelli et al.2 on preterm infants (also available in Italian in the page of the translated publications on the Come Collaboration website). This study recruited 695 infants born between the 29th and 37th gestational week, admitted in the intensive therapy unit of three public hospitals, and allocated by block randomization to two groups. One of the groups underwent OMT twice a week. Both the study group and the control group received 30-minutes treatments, the staff of the neonatal intensive therapy unit, UTIN (Unità di terapia intensiva neonatale), were blinded to the allocation of the patients. The parameter chosen in this study to evaluate the effect of OMT was the length of stay (LOS). The study found statistically significant differences in LOS (13,8 against 17,5 days for the OMT group and the control groups respectively).

For further information please refer to the Osteopedia’s page reporting the reviews of scientific studies, and to the volume edited by Francesco Cerritelli and Diego Lanaro3.


  1. Licciardone JC, Russo DP. Blinding protocols, treatment credibility, and expectancy: methodologic issues in clinical trials of osteopathic manipulative treatment. J Am Osteopath Assoc. 2006 Aug;106(8):457-63.
  2. Cerritelli F, Pizzolorusso G, Renzetti C, Cozzolino V, D’Orazio M, Lupacchini M, Marinelli B, Accorsi A, Lucci C, Lancellotti J, Ballabio S, Castelli C, Molteni D, Besana R, Tubaldi L, Perri FP, Fusilli P, D’Incecco C, Barlafante G. A multicenter, randomized, controlled trial of osteopathic manipulative treatment on preterms. PLoS One. 2015 May 14;10(5):e0127370.
  3. Cerritelli F, Lanaro D. Elementi di ricerca in osteopatia e terapie manuali. Napoli: Edises, 2018.





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