Predicting Outdoor Walking 1 Year After Spinal Cord Injury: A Retrospective, Multisite External Validation Study

Abstract

Background and Purpose: Predicting future outdoor walking ability after spinal cord injury (SCI) is important, as this is associated with community engagement and social participation. A clinical prediction rule (CPR) was derived for predicting outdoor walking 1 year after SCI. While promising, this CPR has not been validated, which is necessary to establish its clinical value. The objective of this study was to externally validate the CPR using a multisite dataset. Methods: This was a retrospective analysis of US SCI Model Systems data from 12 centers. L3 motor score, L5 motor score, and S1 sensory score were used as predictor variables. The dataset was split into testing and training datasets. The testing dataset was used as a holdout dataset to provide an unbiased estimate of prediction performance. The training dataset was used to determine the optimal CPR threshold through a “leave-one-site-out” cross-validation framework. The primary outcome was self-reported outdoor walking ability 1 year after SCI. Results: A total of 3721 participants' data were included. Using the optimal CPR threshold (CPR ≥ 33 threshold value), we were able to predict outdoor walking 1 year with high cross-validated accuracy and prediction performance. For the entire dataset, area under receiver operator characteristic curve was 0.900 (95% confidence interval: 0.890-0.910; P < 0.0001). Discussion and Conclusions: The outdoor walking CPR has been externally validated. Future research should conduct a clinical outcomes and cost-benefit impact analysis for implementing this CPR. Our results support that clinicians may use this 3-variable CPR for prediction of future outdoor walking ability. Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A411).

Commentary on: “Predicting Outdoor Walking 1 Year After Spinal Cord Injury: A Retrospective, Multisite External Validation Study”

“…We agree with Draganich et al's statement that “any degree of improved walking function (i.e. indoor surfaces and household) may be a top priority...”6 Even incremental improvements may have important daily utility for those with SCI. Walking into a bathroom where a wheelchair does not fit, for example, may drastically improve one's safety and independence, while decreasing caregiver burden, all of which can facilitate an improved quality of life.…”

“…In addition to validating the accuracy, sensitivity, and specificity of the original CPR, this study determined an optimal CPR score threshold that predicted outdoor walkers versus nonwalkers. A cutoff score of greater than or equal to 33 was found predictive of outdoor walking 6. Having this access to an established cut score serves to reduce therapist burden and ambiguity in determining the significance of a score between 0 and 120, and is therefore of great value in the clinic.…”

“…This exceeds the Draganich cutoff score of 33, which is favorable for outdoor walking 1 year post-injury. 6 While gait may not be an intuitive goal for someone lacking lower extremity function, this work by Draganich et al suggests that it is appropriate to focus on recovery-based interventions, and to consider future walking ability when making equipment recommendations. This could help therapists and patients make more appropriate, fiscally responsible decisions regarding mobility devices serving both short-and long-term needs.…”

“…. " 6 Even incremental improvements may have important daily utility for those with SCI. Walking into a bathroom where a wheelchair does not fit, for example, may drastically improve one's safety and independence, while decreasing caregiver burden, all of which can facilitate an improved quality of life.…”

“…A cutoff score of greater than or equal to 33 was found predictive of outdoor walking. 6 Having this access to an established cut score serves to reduce therapist burden and ambiguity in determining the significance of a score between 0 and 120, and is therefore of great value in the clinic.…”