Performance of the Dutch clinical prediction rule for the ambulation outcome after spinal cord injury in a middle-income country clinical setting: an external validation study in the Thai retrospective cohort

Objective
To perform external geographic and domain validation of the clinical prediction rule (CPR) of the ambulation outcome of patients with traumatic spinal cord injury (SCI) originally developed by van Middendorp, et al. (2011) in Thais with traumatic and non-traumatic SCI.

Study design
Retrospective cohort study.

Setting
A tertiary rehabilitation facility in Chiang Mai, Thailand.

Methods
A validation data set, including predictive (age and four neurological variables) and outcome (ambulation status) parameters was retrospectively collected from medical records of patients with traumatic and non-traumatic SCI admitted between December 2007 and December 2019. The performance of the original model was evaluated in both discrimination and calibration aspects, using an area under the receiver-operating characteristic curve (auROC) and calibration curves, respectively.

Results
Three hundred and thirty-three patients with SCI were included in the validation set. The prevalence of ambulators was 59% (197 of 333 participants). An auROC of 0.93 (95% CI 0.90–0.96) indicated excellent discrimination whereas the calibration curve demonstrated underestimation, especially in patients with AIS grade D. Performance of the CPR was decreased but acceptable in patients with non-traumatic SCI.

Conclusions
Our external validation study demonstrated excellent discrimination but slightly underestimated calibration of the CPR of ambulation outcome after SCI. Regardless of the geographic and etiologic background of the population, the Dutch CPR could be applied to predict the ambulation outcome in patients with SCI.