Letter to Editor

  • Oktay ÖzmanEmail author
Letter to the Editor

Dear Editor

I refer to the article entitled ‘‘Could surgical experience of adult endourologist overcome the learning curve of retrograde intrarenal surgery in children?’’, published in Urolithiasis (September 2019) [1].

We recently have sent a manuscript that has similar design to your journal(URES-D-19-00159). We compared the RIRS results of patients who underwent regular surgery (n: 13) and operated in live surgery events (n: 14) at the same period and same centers. The aim of this study, which was not previously reported in the literature, was to investigate the effect of live surgical events on the success and complication rates of the RIRS. We used the Student’s t test to compare the clinical characteristics of the groups. There was no statistically significant difference between regular and live surgeries according to success and complication rates. However, the article was rejected due to insufficient number of patients and inappropriate statistical analysis.

Then we have deepened our research for appropriate statistical analysis. We found that the absence of a statistically significant difference between the two means does not always indicate that the two means are statistically equivalent. When researchers want to argue for the absence of an effect, they should use tests for equivalence such as the two one-sided tests (TOST) [2]. There are few studies in the literature designed using equivalence test [3]. I could not find a urological study in PubMed.

Consequently, we criticize that the statistical analysis of the above-mentioned study is not appropriate. The equivalence between the groups should be analyzed by TOST test.

Sincerely yours,

Oktay Özman, MD


Compliance with ethical standards

Conflict of interest

The author declares no conflict of interest.


  1. 1.
    Sforza S, Tuccio A, Grosso AA, Crisci A, Cini C, Masieri L (2019) Could surgical experience of adult endourologist overcome the learning curve of retrograde intrarenal surgery in children? Urolithiasis. (Epub ahead of print) CrossRefPubMedGoogle Scholar
  2. 2.
    Lakens D (2017) Equivalence tests: a practical primer for t tests, correlations, and meta-analyses. Soc Psychol Pers Sci 8(4):355–362. (Epub 2017 May 5) CrossRefGoogle Scholar
  3. 3.
    Yu CC, Kadri O, Kadado A, Buraimoh M, Pawloski J, Bartol S, Graziano G (2019) Intravenous and oral tranexamic acid are equivalent at reducing blood loss in thoracolumbar spinal fusion: a prospective randomized trial. Spine (Phila Pa 1976) 44(11):755–761. CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Gaziosmanpaşa Education and Research Hospital Urology ClinicHealth Sciences UniversityIstanbulTurkey

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