Did experimental and control group begin the study with a similar prognosis?
The importance of patient randomization can be seen in many drug trials that disprove initial promising results shown in observational studies. For instance, a randomized control trial (RCT) that evaluated the usage of a heart failure medication oral milrinone, showed an increase in morbidity and mortality of patients with this treatment despite beneficial results shown in prior non-randomized trials. [4] In addition, other heart failure medication such as iboapmine and epoprostenol both showed positive results in observational studies, but when evaluated in the context of RCT trials, the results were contradictory, thus invalidating the prior non-randomized studies. [5],[6] Such contradictions are common between observational and RCT study designs. A safe heuristic is to trust RCTs over observational studies. They have been shown to be more reliable and less biased than observational studies. [7],[8],[9],[10] Hence, RCTs are considered to be higher in the hierarchy of research designs
