Strengths and limitations
Since IP is a relatively rare disease, research in this field with a big cohort is a big challenge. Nevertheless, our cohort appears to be relatively large compared to the other clinical IP studies. For more support of evidence of our results, more studies (with greater numbers) should be performed. Furthermore, the retrospective nature of the intervention analyses does not provide conclusive evidence for the future. Lastly, to date there is no minimal clinically important difference (MCID) known of the EES-Q.