The authors have to describe how the confounding factors were controlled (exclusion criteria).

For example, some of the variables controlled could be: demographic characteristics (age and sex), habits (smoker, drinker), use of medications (steroids), comorbidities (diabetes mellitus, morbid obesity, neoplasm), general conditions of quality of life (unemployed), pregnancy, previous surgeries, degree of severity of the disease, and early or late presentation. The adequate description of eligibility criteria allows the reproducibility of the study.

The questions that need to be answered by the reviewers are the following:

1) are the eligibility criteria for inclusion and exclusion broad and clearly stated

2) is the condition used in the selection clear, such as tests, scores, signs, and symptoms

3) is the group homogeneous

4) are the characteristics of the patients representative of those of the clinical question

5) are the baseline characteristics reported

6) were patients similar at baseline in terms of demographics and comorbidity?