The reviewer must pay attention not only to the eligibility criteria and the treatment or diagnosis performed in the intervention and control groups, but also the maintenance of the patients in those groups. It is important that the reviewer checks for equal treatment and makes sure that the patients are treated as equally as possible. For example, if one group of patients receives a course of physiotherapy while the other does not, you would expect the group in physiotherapy to show a better early outcome. Without having a comparable group to measure them against, the manuscript cannot conclude that the better outcomes observed were related to the surgery or the physiotherapy sessions.
The conclusion of the study can only be confirmed if the patients who are lost to follow-up during the study are accounted for. Many may have dropped out due to treatment-related complications. A dropout rate below 5% is excellent; if the rate is 5%–20%, the results are questionable; a rate equal to or higher than 20% is considered unacceptable and poses serious threats to validity. It is important that the reviewer analyzes if the losses are equally distributed and have similar characteristics. Similarly, the crossover needs to be assessed.
Maintenance means to certify that the patients were:
1) treated equally and received identical care apart from the actual intervention
2) compliant with the study and completed all the evaluations
3) compliant with the allocation group or crossover during the treatment. The reviewer can clearly understand the trial design, conduct, analysis, and interpretation, and assess the validity of its results if the manuscript includes the Consolidated Standards of Reporting Trials (CONSORT) statement flow diagram
Questions to be answered by the reviewers are:
1) are patients treated equally and comparable apart from the intervention group
2) how many patients dropped out during the study
3) what is the dropout rate
4) are the dropouts equally distributed and do they have similar characteristics
5) how many patients completed all the evaluations
6) how many patients crossed over during the study
7) is there a flow diagram reporting the quantity of patients eligible and included in the study, the number of subjects in each treatment arm, and how the study ended, by having the number and the reasons why patients left the study at various points in time?