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The letter recalculates Cohen’s d from the pooled means and pooled standard deviations and shows that the reported d values (e.g., 2.19 for operative time) do not match the implied differences. Recommendations include providing a transparent extraction table, disclosing analytic workflow, and reporting raw mean differences with 95% confidence intervals to support reproducibility and improve interpretability.",{"@graph":69,"@context":123},[70,84,106],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":35,"@type":76,"position":81},"https://docshare.wps.com/document/healthcare/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/letter-to-editor-clarification-regarding-effect-size-reporting-in-biportal-endoscopic-versus-conventional-open-spine-surgery/434027/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/letter-to-editor-clarification-regarding-effect-size-reporting-in-biportal-endoscopic-versus-conventional-open-spine-surgery/434027.png","ImageObject",300,407,{"name":92,"@type":93},"Genevieve","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-02","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":105},"InteractionCounter",{"@type":104},"ViewAction",11,{"@type":107,"mainEntity":108},"FAQPage",[109,115,119],{"name":110,"@type":111,"acceptedAnswer":112},"What inconsistency does the letter highlight in the reported effect sizes?","Question",{"text":113,"@type":114},"The letter points out that the standardized effect sizes for operative time (and a fusion subgroup) are numerically inconsistent with the pooled means and standard deviations reported in the original meta-analysis.","Answer",{"name":116,"@type":111,"acceptedAnswer":117},"How does the author assess whether the effect size values are correct?",{"text":118,"@type":114},"The letter applies the conventional Cohen’s d formula using the reported pooled descriptive statistics to compute an implied effect size and compares it with the published d values.",{"name":120,"@type":111,"acceptedAnswer":121},"What actions does the letter recommend to resolve the issue?",{"text":122,"@type":114},"The authors recommend providing a transparent extraction table, disclosing the analytic workflow for reproducibility, and recalculating and reporting raw mean differences with 95% confidence intervals in consistent units.","https://schema.org",{"og:url":83,"og:type":125,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":127,"canonical":83},"index,follow",{"doc_id":129,"site_id":62},434027,1790914070,{"code":4,"msg":5,"data":132},{"doc_id":129,"user_id":133,"nickname":92,"user_avatar":134,"doc_module":4,"category_id":34,"category_name":35,"doc_title":65,"doc_description":67,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":105,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":14,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":24,"preview_page_count":4},1374391974585,"https://ap-avatar.wpscdn.com/davatar_276721f389ce27ea32af1340a28f341c","Letter to the Editor  \nASJ  \nAsian Spine J. 2025;19(6): 1101-1102 [https://doi.org/10.31616/asj.2025.0604.r1](https://doi.org/10.31616/asj.2025.0604.r1)[ ](https://doi.org/10.31616/asj.2025.0604.r1)PISSN 1976-1902 • eISSN 1976-7846  \nLetter to editor: Clarification regarding effect size reporting in “biportal endoscopic versus conventional open spine surgery: a systematic review and  \nmeta-analysis”  \nAudai H. Abudayeh1, Iakiv V. Fishchenko2  \n1Department of Traumatology and Orthopedics, Bogomolets National Medical University, Kyiv, Ukraine  \n2Department with Spinal (Neurosurgical) Center, SI Institute of Traumatology and Orthopedics ofthe National Academy of Medical Sciences of Ukraine, Kyiv, Ukraine  \nReceived Sep 21, 2025, Accepted Oct 6, 2025 Corresponding author: Audai H. Abudayeh  \nDepartment of Traumatology and Orthopedics, Bogomolets National Medical University, Kyiv, Ukraine Tel: +380-636306555, Fax: +380-442349276, E-mail: [oudayhelmi@gmail.com](oudayhelmi@gmail.com)  \nDear Editor,  \nWe read with interest the recent meta-analysis by Yu et al. [1] comparing biportal endoscopic spine surgery (BESS) with conventional open techniques. The authors are to be commended for synthesizing evidence in this rapidly evolving field. Nevertheless, we would like to highlight a significant numerical inconsistency in the reported standardized effect sizes for operative time, which, unless clarified, may compromise the reliability of the study’s primary conclusion.  \nThe manuscript reports pooled descriptive statistics of 101.34±41.91 minutes (open) and 134.57±80.75 minutes (BESS), alongside a pooled standardized effect size of d=2.19 (95% confidence interval [CI], 0.75–3.64; p=0.003) [1] . By the conventional formula for Cohen’sd (mean difference divided by pooled standard deviation) [2-4], the pooled standard deviation (SD) of these groups is: pooled SD=√((41 .91²+80 .75²)/2)≈64 .33.  \nThe observed mean difference is 134.57−101.34=33.23 minutes, yielding Cohen’s d≈0.52, not 2.19. A value of d=2.19 would correspond to an operative-time difference of approximately 141 minutes, which is incompat-  \nible with the reported group means. Similarly, in the fusion subgroup, the reported means (129.25±24.87 minutes vs. 186.69±63.83 minutes) imply an observed difference of 57.44 minutes and a pooled SD≈48.44, giving d≈1.19, rather than the stated 2.57 [1] . These discrepancies suggest an error in calculation, transcription, or labeling of the effect sizes.  \nAccurate computation of standardized mean differences is essential, as they are conceptually distinct from inferential statistics and directly influence the interpretation of pooled results [2,3,5] . Misestimation of effect sizes ofthis magnitude may overstate clinical differences and misinform subsequent evidence syntheses. Established methodological guidance emphasizes precise calculation and transparent reporting [2,4,5] .  \nIn light of these findings, we would recommend that the authors (1) provide a transparent extraction table including per-study means, standard deviations, and sample sizes used for the operative-time analysis; (2) disclose the analytic workflow (e.g. , RevMan file, R syntax, or equivalent) to ensure reproducibility; and (3) recalculate the pooled effect size, preferably reporting  \nCopyright Ⓒ 2025 by Korean Society of Spine Surgery  \nThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ([http://creativecommons.org/licenses/by-nc/4.0/](http://creativecommons.org/licenses/by-nc/4.0/)) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.  \nAsian Spine Journal • pISSN 1976-1902 eISSN 1976-7846 • [www.asianspinejournal.org](www.asianspinejournal.org)  \nthe raw mean difference in minutes with 95% CIs, as this metric is more interpretable when all studies share the same unit of measurement.  \nSuch revisions would not only en","cbCairvIigQjrT2k","https://ap.wps.com/l/cbCairvIigQjrT2k","pdf",159963,"English","# Letter to the Editor\n## Clarification of effect size inconsistencies\n## Recommendations for transparent reporting\n## Conflict of Interest and ORCID\n## References","[{\"question\":\"What inconsistency does the letter highlight in the reported effect sizes?\",\"answer\":\"The letter points out that the standardized effect sizes for operative time (and a fusion subgroup) are numerically inconsistent with the pooled means and standard deviations reported in the original meta-analysis.\"},{\"question\":\"How does the author assess whether the effect size values are correct?\",\"answer\":\"The letter applies the conventional Cohen’s d formula using the reported pooled descriptive statistics to compute an implied effect size and compares it with the published d values.\"},{\"question\":\"What actions does the letter recommend to resolve the issue?\",\"answer\":\"The authors recommend providing a transparent extraction table, disclosing the analytic workflow for reproducibility, and recalculating and reporting raw mean differences with 95% confidence intervals in consistent units.\"}]","Letter to editor - Clarification regarding effect size reporting in biportal endoscopic versus conventional open spine surgery | PDF",1790666601]