Five myths about variable selection

Heinze, Georg; Dunkler, Daniela

doi:10.1111/tri.12895

Cited by 394 publications

(284 citation statements)

References 25 publications

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“…However, in this single‐centre experience our graft allocation policy and even donor selection remained basically the same throughout the entire observation period, except for a more aggressive acceptance of multiple donor comorbidities in DP group. Moreover, the rigorous variable selection procedure applied in this study may have missed to identify some important risk factors and may have overestimated the real effect sizes and underestimated the P ‐values of the selected risk factors . Several other variables may have a relevant weight in promoting or reducing the risk of ITBL, such as surgical technique, mode of graft revascularisation, and intra‐operative use of vasopressors.…”

Section: Discussionmentioning

confidence: 99%

Dual aortic and portal perfusion at procurement prevents ischaemic-type biliary lesions in liver transplantation when using octogenarian donors: a retrospective cohort study

et al. 2018

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Several risk factors for ischaemic-type biliary lesions (ITBL) after liver transplantation (LT) have been identified, but the role of portal vein perfusion at graft procurement is still unclear. This was a prospective study on double aortic and portal perfusion (DP) of liver grafts stratified by donor's decade (<60 yo; 60-69 yo; 70-79 yo and ≥80 yo) versus similar historical cohorts of primary, adult grafts procured with single aortic perfusion (SP) only. The primary study aim was to assess the role of DP on the incidence of ITBL. There was no difference in the incidence of overall biliary complications according to procurement technique for recipients of grafts <80 years. A higher incidence of ITBL was observed for patients receiving grafts ≥80 years and perfused through the aorta only (1.9 vs. 13.4%; P = 0.008). When analysing octogenarian grafts, donor male gender (HR = 6.4; P = 0.001), haemodynamic instability (HR = 4.9; P = 0.008), and type-2 diabetes mellitus (DM2) (HR = 3.0; P = 0.03) were all independent risk factors for ITBL, while double perfusion at procurement (HR = 0.1; P = 0.04) and longer donor intensive care unit (ICU) stay (HR = 0.7; P = 0.04) were protective factors. Dual aortic and portal perfusion has the potential to reduce post-transplant ITBL incidence for recipients of octogenarian donor grafts. Larger series are needed to confirm this preliminary experience.

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Section: Discussionmentioning

confidence: 99%

Dual aortic and portal perfusion at procurement prevents ischaemic-type biliary lesions in liver transplantation when using octogenarian donors: a retrospective cohort study

et al. 2018

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“…Continuous variables were dichotomized according to known cut‐off values defining, for example, elderly (age > 75) or obese (BMI ≥ 30) patients, or clear resection margins (CRM > 2 mm) . In the initial regression model, all variables with a P value < 0.2 in the univariate analysis were included . Then, a simplified model was generated with predictor selection guided by statistical significance and clinical relevance.…”

Section: Methodsmentioning

confidence: 99%

Assessing surgical difficulty in locally advanced mid–low rectal cancer: the accuracy of two MRI‐based predictive scores

et al. 2018

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Aim Predicting surgical difficulty is a critical factor in the management of locally advanced rectal cancer (LARC). This study evaluates the accuracy and external validity of a recently published morphometric score to predict surgical difficulty and additionally proposes a new score to identify preoperatively LARC patients with a high risk of having a difficult surgery. Methods This is a retrospective study based on the European MRI and Rectal Cancer Surgery (EuMaRCS) database, including patients with mid/low LARC who were treated with neoadjuvant chemoradiation therapy and laparoscopic total mesorectal excision (L‐TME) with primary anastomosis. For all patients, pretreatment and restaging MRI were available. Surgical difficulty was graded as high and low based upon a composite outcome, including operative (e.g. duration of surgery) and postoperative variables (e.g. hospital stay). Score accuracy was assessed by estimating sensitivity, specificity and area under the receiver operating characteristic curve (AROC). Results In a total of 136 LARC patients, 17 (12.5%) were graded as high surgical difficulty. The previously published score (calculated on body mass index, intertuberous distance, mesorectal fat area, type of anastomosis) showed low predictive value (sensitivity 11.8%; specificity 92.4%; AROC 0.612). The new EuMaRCS score was developed using the following significant predictors of surgical difficulty: body mass index > 30, interspinous distance < 96.4 mm, ymrT stage ≥ T3b and male sex. It demonstrated high accuracy (AROC 0.802). Conclusion The EuMaRCS score was found to be more sensitive and specific than the previous score in predicting surgical difficulty in LARC patients who are candidates for L‐TME. However, this score has yet to be externally validated.

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“…For example, the FDArecommended CKD273 signature for diagnosis of early kidney disease is based on univariate protein filtering followed by a machine-learning algorithm applied to the filtered features (Good et al, 2010;Dakna et al, 2010;Nkuipou-Kenfack, Zürbig and Mischak, 2017). Among non-statisticians, it is still even believed that univariate significance is a prerequisite for including a variable in a multivariable model (Heinze and Dunkler, 2017). In contrast, it is generally accepted among statisticians that the difference between unadjusted and adjusted effects of a variable can go in either direction, therefore that univariable selection may be misleading (Sun, Shook and Kay, 1996).…”

Section: Traditional Variable Selection Strategiesmentioning

confidence: 99%

State of the art in selection of variables and functional forms in multivariable analysis—outstanding issues

et al. 2020

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How to select variables and identify functional forms for continuous variables is a key concern when creating a multivariable model. Ad hoc 'traditional' approaches to variable selection have been in use for at least 50 years. Similarly, methods for determining functional forms for continuous variables were first suggested many years ago. More recently, many alternative approaches to address these two challenges have been proposed, but knowledge of their properties and meaningful comparisons between them are scarce. To define a state-of-the-art and to provide evidence-supported guidance to researchers who have only a basic level of statistical knowledge many outstanding issues in multivariable modelling remain. Our main aims are to identify and illustrate such gaps in the literature and present them at a moderate technical level to the wide community of practitioners, researchers and students of statistics.We briefly discuss general issues in building descriptive regression models, strategies for variable selection, different ways of choosing functional forms for continuous variables, and methods for combining the selection of variables and functions. We discuss two examples, taken from the medical literature, to illustrate problems in the practice of modelling.Our overview revealed that there is not yet enough evidence on which to base recommendations for the selection of variables and functional forms in multivariable analysis. Such evidence may come from comparisons between alternative methods. In particular, we highlight seven important topics that require further investigation and make suggestions for the direction of further research.

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Five myths about variable selection

Cited by 394 publications

References 25 publications

Dual aortic and portal perfusion at procurement prevents ischaemic-type biliary lesions in liver transplantation when using octogenarian donors: a retrospective cohort study

Dual aortic and portal perfusion at procurement prevents ischaemic-type biliary lesions in liver transplantation when using octogenarian donors: a retrospective cohort study

Assessing surgical difficulty in locally advanced mid–low rectal cancer: the accuracy of two MRI‐based predictive scores

State of the art in selection of variables and functional forms in multivariable analysis—outstanding issues

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