In the results of your MEDLINE searches you found 2 common types of medical report, or 'study design': 'Randomized controlled trials' and 'systematic reviews'. Here are 2 Wiki links to help you understand these 2 types of clinical research paper. Both types of research paper want to answer a very simple question: what is better, A or B?  For example, is 'chitosan' better than 'no chitosan'? Click on the study designs below to get more information.

Randomized Controlled Trial

Systematic reviews