Article
Details
Citation
Kunzmann K, Wernisch L, Richardson S, Steyerberg EW, Lingsma H, Ercole A, Maas AIR, Menon D & Wilson L (2021) Imputation of ordinal outcomes: a comparison of approaches in traumatic brain injury. Journal of Neurotrauma, 38 (4), pp. 455-463. https://doi.org/10.1089/neu.2019.6858
Abstract
Loss to follow-up and missing outcomes data are important issues for longitudinal observational studies and clinical trials in traumatic brain injury. One popular solution to missing 6-month outcomes has been to use the last observation carried forward (LOCF). The purpose of the current study was to compare the performance of model-based single-imputation methods with that of the LOCF approach. We hypothesized that model-based methods would perform better as they potentially make better use of available outcome data. The Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI) study (n = 4509) included longitudinal outcome collection at 2 weeks, 3 months, 6 months, and 12 months post-injury; a total of 8185 Glasgow Outcome Scale extended (GOSe) observations were included in the database. We compared single imputation of 6-month outcomes using LOCF, a multiple imputation (MI) panel imputation, a mixed-effect model, a Gaussian process regression, and a multi-state model. Model performance was assessed via cross-validation on the subset of individuals with a valid GOSe value within 180 ± 14 days post-injury (n = 1083). All models were fit on the entire available data after removing the 180 ± 14 days post-injury observations from the respective test fold. The LOCF method showed lower accuracy (i.e., poorer agreement between imputed and observed values) than model-based methods of imputation, and showed a strong negative bias (i.e., it imputed lower than observed outcomes). Accuracy and bias for the model-based approaches were similar to one another, with the multi-state model having the best overall performance. All methods of imputation showed variation across different outcome categories, with better performance for more frequent outcomes. We conclude that model-based methods of single imputation have substantial performance advantages over LOCF, in addition to providing more complete outcome data.
Keywords
GOSe; imputation; missing data; traumatic brain injury
Journal
Journal of Neurotrauma: Volume 38, Issue 4
Status | Published |
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Funders | European Commission (Horizon 2020) |
Publication date | 15/02/2021 |
Publication date online | 13/11/2020 |
Date accepted by journal | 27/10/2020 |
URL | http://hdl.handle.net/1893/31967 |
ISSN | 0897-7151 |
eISSN | 1557-9042 |
People (1)
Emeritus Professor, Psychology