*4.5. Limitations of the Included Studies*

According to the hierarchy of evidence, the cross-section and observational study design ranked low as compared to the randomized control trials [42]. All five studies included in this review are of the cross-section study design that typically lacks the adequate methodology rigour that minimizes the effect of bias. However, applying a rigid design hierarchy to this research is potentially less significant than evaluating the precision of the study methodology [47]. Of the five systematic review studies, one used a sample of fewer than fifty subjects. However, no studies justified the sample size. The small sample size may result in the probability of non-significant results [48]. Out of five studies, only one was reported using random sampling techniques. This further limits the further the ability to find the wider population. Of the rest of the studies, one used convenience sampling, and four did not state the sampling procedure. The ability to extrapolate the survey to the other MIPs is difficult due to the limited number of studies. Variable types of items in the questionnaire were used in the surveys. In the current review, three out of five studies used similar questions, of which only one study reported specific to the MIPs.
