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By trying different approaches (and transparent reporting)! Response to: How to approach baseline imbalance in cross-randomised studies?

  • Julian Koenig
    Correspondence
    Corresponding author.
    Affiliations
    University of Cologne, Faculty of Medicine and University Hospital Cologne, Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, Cologne, Germany
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  • Michael Kaess
    Affiliations
    University of Bern, University Hospital of Child and Adolescent Psychiatry and Psychotherapy, Bern, Switzerland

    University Hospital Heidelberg, Center for Psychosocial Medicine, Department of Child and Adolescent Psychiatry, Heidelberg, Germany
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Published:December 05, 2022DOI:https://doi.org/10.1016/j.autneu.2022.103055
      Gholamrezaei and Jafari raised an issue in their Letter to the Editor (
      • Gholamrezaei A.
      • Jafari H.
      How to approach baseline imbalance in cross-randomised studies?.
      ) and simultaneously on Twitter ( ), addressing the statistical analyses of our paper (
      • Höper S.
      • Kaess M.
      • Koenig J.
      Prefrontal cortex oxygenation and autonomic nervous system activity under transcutaneous auricular vagus nerve stimulation in adolescents.
      ), recently published in Autonomic Neuroscience: Basic and Clinical. The authors are concerned that our results carry potential bias in the intervention effect estimate due to baseline imbalance in measurements of heart rate (HR) and heart rate variability (HRV). Referring to Fig. 4 of our paper (
      • Höper S.
      • Kaess M.
      • Koenig J.
      Prefrontal cortex oxygenation and autonomic nervous system activity under transcutaneous auricular vagus nerve stimulation in adolescents.
      ), the authors state “there was already a significant difference in the period-dependent baseline measures of HR and HRV”. We have to clarify, that neither the difference in baseline HR nor baseline HRV between tVNS and sham is statistically significant (neither using parametric nor nonparametric tests). A better depiction of the individual raw data is now provided in Fig. 1. The authors state, that “[t]he size of this difference was almost the same as the size of the difference between the two conditions at follow-ups during 5 min of stimulation”. Precisely, the mean difference in HR between tVNS and sham at baseline is 3.17 beats per minute (BPM) [95%CI: −2.38; 8.72] and at 5 min of stimulation is 3.62 BPM [95%CI: −1.43; 8.66]. The mean difference in HRV at baseline is −8.78 milliseconds (ms) [−18.93; 1.37] and at 5 min of stimulation is −9.06 ms [−19.83; 1.70]. We agree, that these differences are almost the same (but slightly larger at 5 min of stimulation).
      Fig. 1
      Fig. 1Individual subject data by stimulation condition (sham versus tVNS) and time (baseline, 5 min, 10 min, and 15 min of stimulation); p-values refer to differences between baseline segments between conditions based on pairwise t-tests as implemented in the raincloud shiny app.
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