Objective:

Randomized controlled clinical trials represent the study of choice to evaluate the safety and effectiveness of interventions against any health problems. The internal validity of these can be affected by the frequent losses of patients. The main objective of the study is to describe what are the main causes of loss of patients during clinical trials in the area of medicine in four major medical journals of high impact factor, if there are differences according to the group that they belong and if the authors performed the intention to treat analysis.

Methods:

Descriptive observational study. A convenience sample of 100 controlled clinical trials, related to the area of medicine was selected, the articles were published in the last five years (2011- 2016), of four journals of high scientific impact, in which the main causes of loss of patients were identified.

Outcomes:

A total of 100 articles of internal medicine were reviewed. We identified 15 causes of patient losses during clinical trials; the three most prevalent according to the number of patients were loss of follow-up (61.42%), discontinuation of the intervention (25.28%), and death (2.34%). The three most frequent according to the number of clinical trials were loss of follow-up (73%), retirement (34%) and death (31%). An analysis by intention to treat was used in 36% of the clinical trials analyzed.

Conclusion:

In the total of reviewed clinical trials, the most frequent cause of loss of patients was loss of follow-up. Furthermore, the intention to treat analysis was used in about one third of the articles reviewed.

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