Cardiovasc Intervent Radiol (2017) 40:1478 DOI 10.1007/s00270-017-1728-8 LETTER TO THE EDITOR Re: Intraprocedural Distal Embolization After Femoropopliteal Angioplasty: Is There a Role for Below-the-knee Stents? A Statistical Analysis Point of View 1,2 Yousef Shahin Received: 27 April 2017 / Accepted: 19 June 2017 / Published online: 26 June 2017 Springer Science+Business Media, LLC and the Cardiovascular and Interventional Radiological Society of Europe (CIRSE) 2017 To the editor: Evaluation of sparse data bias can be achieved by simple Sir, We read the article by Krokidis et al.  with great tabulation of the outcome or events over a group of the interest. However, their statistical analysis is inaccurate. variables. If the potential of bias is high, Firth’s penalised The authors retrospectively reviewed 1485 femoral angio- likelihood approach to address the small sample size in a plasties of which 12 cases where distal embolization logistic regression model is useful. occurred were analysed. In the statistical analysis, Krokidis Compliance with Ethical Standards et al. used multivariable logistic regression analysis of the factors that were associated with stent deployment. The Conﬂict of interest The corresponding author states that there is no regression model included three variables: critical limb conﬂict of interest. ischaemia, target vessel occlusion and single-vessel run- off. The total number of events for the outcome of interest References (stent deployment) was six which resulted in sparse data bias (too many variables for few outcomes). For the mul- 1. Krokidis M, Ali T, Hilliard N, Shaida N, Winterbottom A, Koo B, tivariable logistic regression model to be valid, at least 10 See TC. Intraprocedural distal embolization after femoropopliteal events of the outcome of interest or more are needed per angioplasty: is there a role for below-the-knee stents? Cardiovasc variable . Therefore, for the regression model to be Intervent Radiol. 2017. doi:10.1007/s00270-017-1621-5. 2. Peduzzi P, Concato J, Kemper E, Holford TR, Feinstein AR. A correct, 30 events or more were needed. Otherwise, there is simulation study of the number of events per variable in logistic potential for sparse data bias in addition to negative or regression analysis. J Clin Epidemiol. 1996;49(12):1373–9. positive regression coefﬁcient bias within the regression model. & Yousef Shahin firstname.lastname@example.org NIHR Academic Clinical Fellow and Specialist Registrar in Clinical Radiology, Academic Unit of Radiology, University of Shefﬁeld, Glossop Road, Shefﬁeld S10 2JF, UK Northern General Hospital, Herries Road, Shefﬁeld S5 7AU, UK
CardioVascular and Interventional Radiology – Springer Journals
Published: Jun 26, 2017
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