Study Design Features Associated with Patient Attrition in Studies of Traumatic Brain Injury: A Systematic Review.

Sophie Richter,Tom Newman,Susan Stevenson,Virginia F.J Newcombe,Lindsay Wilson,Hester Lingsma,Ewout W Steyerberg,Andrew I.R Maas,Daan Nieboer

doi:10.1089/neu.2020.7000

Abstract

Loss to follow-up or patient attrition is common in longitudinal studies of traumatic brain injury (TBI). Lack of understanding exists between the relation of study design and patient attrition. This review aimed to identify features of study design that are associated with attrition. We extended the analysis of a previous systematic review on missing data in 195 TBI studies using the Glasgow Outcome Scale Extended (GOSE) as an outcome measure. Studies that did not report attrition or had heterogeneous methodology were excluded, leaving 148 studies. Logistic regression found seven of the 14 design features studied to be associated with patient attrition. Four features were associated with an increase in attrition: greater follow-up frequency (odds ratio [OR]: 1.2, 95% confidence interval [CI]: 1.0-1.3), single rather than multi-center design (OR: 1.6, 95% CI: 1.2-2.2), enrollment of exclusively mild TBI patients (OR: 2.8, 95% CI: 1.6-4.9), and collection of the GOS by post or telephone without face-to-face contact (OR: 1.6, 95% CI:1.1-2.4). Conversely, two features were associated with a reduction in attrition: recruitment in an acute care setting defined as the ward or intensive care unit (OR: 0.58, 95% CI: 0.47-0.72) and a greater duration of time between injury and follow-up (OR: 0.93, 95% CI: 0.88-0.99). This review highlights design features that are associated with attrition and could be considered when planning for patient retention. Further work is needed to establish the mechanisms between the observed associations and potential remedies.

Highlights

Longitudinal studies commonly experience patient attrition, defined as the loss of patients to follow-up and the absence of outcome data
Four factors significantly increased the odds of attrition: a greater follow-up frequency, a single-center as opposed to multi-center design, studying exclusively mild Traumatic brain injury (TBI) patients compared with all severities, and collecting Glasgow Outcome Score Extended (GOSE) data by mail or telephone but not in person, compared with methods that included a face-to-face assessment
Two factors significantly decreased the odds of attrition: a greater study duration between injury and final follow-up time point and recruiting among hospital inpatients rather than in the pre-hospital setting or emergency department

Summary

Introduction

Longitudinal studies commonly experience patient attrition, defined as the loss of patients to follow-up and the absence of outcome data. Missing outcome data can arise because of multiple reasons, such as the patient lacking motivation to participate in follow-up or being unable to complete questionnaires because of a language barrier. Most commonly missing outcome data occur because of patient loss to follow-up whereby it is impossible to contact the patient and determine his or her outcome. Despite the best efforts of researchers, a proportion of patients are almost always lost to follow-up.[6,7,8,9] Various techniques are available to mitigate the effects of missing outcome data. We previously published guidance on their use in longitudinal studies of TBI.[8] Prevention of missing data, will always remain superior to compensatory statistical techniques

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