Advertisement
American Journal of Infection Control
Advanced searchSave search
Letters to the Editor| Volume 46, ISSUE 4, P477, April 2018

Comments on decreased mortality in patients prescribed vancomycin after implementation of an antimicrobial stewardship program

  • Saeid Safiri
    Affiliations
    Managerial Epidemiology Research Center, Department of Public Health, School of Nursing and Midwifery, Maragheh University of Medical Sciences, Maragheh, Iran
    Search for articles by this author
  • Erfan Ayubi
    Correspondence
    Address correspondence to Erfan Ayubi, PhD, MSc, Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Velenjak St., Shahid Chamran Highway, Tehran, Iran. (E. Ayubi)
    Affiliations
    Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
    Department of Epidemiology & Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
    Search for articles by this author
Published:January 09, 2018DOI:https://doi.org/10.1016/j.ajic.2017.11.022
Comments on decreased mortality in patients prescribed vancomycin after implementation of an antimicrobial stewardship program
Previous ArticleComparison of keyboard colonization before and after use in an inpatient setting and the effect of keyboard covers
Next ArticleDecreased mortality in patients prescribed vancomycin after implementation of an antimicrobial stewardship program
      To the Editor:
      We read the article by Conway et al
      • Conway E.L.
      • Sellick J.A.
      • Horey A.
      • Fodero K.
      • Ott M.C.
      • Krajewski M.P.
      • et al.
      Decreased mortality in patients prescribed vancomycin after implementation of antimicrobial stewardship program.
      Am J Infect Control. 2017; 45: 1194-1197
      with great interest; however, we think some methodologic and statistical issues should be taken into account to avoid misinterpretation.
      The authors
      • Conway E.L.
      • Sellick J.A.
      • Horey A.
      • Fodero K.
      • Ott M.C.
      • Krajewski M.P.
      • et al.
      Decreased mortality in patients prescribed vancomycin after implementation of antimicrobial stewardship program.
      Am J Infect Control. 2017; 45: 1194-1197
      stated that predictors with P values < .05 in univariate analysis were considered further for multivariable analysis. It is important to emphasize that such a univariate criterion can increase the risk of Testimation bias in the resulting effect estimates.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      , 
      • Pakzad R.
      • Safiri S.
      Incidence and risk factors for surgical site infection posthysterectomy in a tertiary care center: Methodologic issues.
      Am J Infect Control. 2017; 45: 580-581
      Testimation bias will occur when a conservative univariate P value is considered in multivariable analysis.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      The authors studied the effect of several baseline and clinical patient characteristics on death in univariate analysis.
      • Conway E.L.
      • Sellick J.A.
      • Horey A.
      • Fodero K.
      • Ott M.C.
      • Krajewski M.P.
      • et al.
      Decreased mortality in patients prescribed vancomycin after implementation of antimicrobial stewardship program.
      Am J Infect Control. 2017; 45: 1194-1197
      Some of them had a relatively large effect; for example, those with P < .05 and some others had a relatively small effect (eg, body mass index with P = .06 in univariate analysis).
      • Conway E.L.
      • Sellick J.A.
      • Horey A.
      • Fodero K.
      • Ott M.C.
      • Krajewski M.P.
      • et al.
      Decreased mortality in patients prescribed vancomycin after implementation of antimicrobial stewardship program.
      Am J Infect Control. 2017; 45: 1194-1197
      When predictors with relatively large effect only are included in multivariable analysis, the effect of such predictors will be overestimated.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      Such overestimation of effects of strong predictors is known as Testimation bias.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      To reduce this bias several strategies have been suggested. For example, a liberal univariate P value < .10 or < .20 can be considered in multivariable analysis or predictors can be selected based on both statistical test and clinical relevancy.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      Moreover, the authors1 point out that external validity of the results may be low. We think internal validity of the results is still questionable. Cross-validation and bootstrapping are efficient strategies for checking internal validity of results.
      • Steyerberg E.
      Clinical prediction models: a practical approach to development, validation, and updating.
      Springer Science & Business Media, 2008
      A take-home message for readers is that the estimated odds ratios for the predictors of death in patients treated with intravenous vancomycin therapy should be considered along with the degree of Testimation bias.

      References

        • Conway E.L.
        • Sellick J.A.
        • Horey A.
        • Fodero K.
        • Ott M.C.
        • Krajewski M.P.
        • et al.
        Decreased mortality in patients prescribed vancomycin after implementation of antimicrobial stewardship program.
        Am J Infect Control. 2017; 45: 1194-1197
        View in Article
        • Steyerberg E.
        Clinical prediction models: a practical approach to development, validation, and updating.
        Springer Science & Business Media, 2008
        View in Article
        • Pakzad R.
        • Safiri S.
        Incidence and risk factors for surgical site infection posthysterectomy in a tertiary care center: Methodologic issues.
        Am J Infect Control. 2017; 45: 580-581
        View in Article

      Article info

      Publication history

      Published online: January 09, 2018

      Footnotes

      Conflicts of interest: None to report.

      Identification

      DOI: https://doi.org/10.1016/j.ajic.2017.11.022

      Copyright

      © 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

      ScienceDirect

      Access this article on ScienceDirect

      Linked Article

      We use cookies to help provide and enhance our service and tailor content. To update your cookie settings, please visit the for this site.
      Copyright © 2023 Elsevier Inc. except certain content provided by third parties. The content on this site is intended for healthcare professionals.


      RELX