Study: Stroke score helps determine need for add-on strategies
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Daniel Strbian, MD, PhD, of Helsinki University Central Hospital in Finland, and colleagues designed the DRAGON score as a clinical tool for physicians, patients and their families for making informed decisions quickly about treatment options for ischemic stroke patients given intravenous thrombolysis. They pointed out that about half of acute ischemic stroke patients achieve good outcomes with intravenous alteplase (Activase, Genentech), which provides benefits if administered within 4.5 hours.
Four other factors, all of which are available before or shortly after alteplase administration, can influence final functional outcome, they noted: baseline NIH Stroke Scale (NIHSS) score; patient age; blood glucose level at admission; and the presence of hyperdense cerebral artery signs or early infarct signs on admission CT head scans. Consequently, Strbian and colleagues developed their scoring system based on those four baseline parameters.
To develop the scoring system, the researchers identified 1,529 consecutive acute ischemic stroke patients who received alteplase treatment between 1995 and 2010 at Helsinki University Central Hospital. They excluded patients who had basilar artery occlusion because of differences in natural history and treatment protocol as well as patients whose records had missing data. That left a cohort of 1,319 patients.
Each variable for patients was assigned points. For instance, an NIHSS score of 0 to 4 equaled zero points; 5 to 9, one point; 10 to 15, two points; and greater than 15, three points. An age less than 65 years equaled zero points; 65 to 75 years equaled one point; and age equal or greater than 80 was two points. Points for each patient were added for a final score. The higher the score, the higher likelihood of a miserable outcome (defined as a three-month modified Rankin Scale score of 5 to 6).
They used logistic regression coefficients for the score derivation and assessed accuracy of the derivation model with 1,000 bootstrap replicates. Accuracy was determined to be 86 percent, and area under the receiver operating characteristic curve (AUC-ROC) was 0.84.
To externally validate the model, they applied the DRAGON scoring system in a cohort of 333 acute ischemic stroke patients treated between 2005 and January 2011 with the same dose of alteplase at the University Hospital Basel in Switzerland. They found no statistical difference in the AUC-ROC between the derivation and validation patient groups.
The DRAGON score took less than a minute to obtain at the Helsinki facility, Strbian and colleagues wrote, and quickly provided an estimation of the patient’s outcome to support clinical decision making for patients when alteplase treatment alone may not be sufficient.
Patients with low scores in 0 to 3 range were likely to have a good recovery after IV alteplase, with a specificity of almost 100 percent or 90 percent, they wrote. Scores in the 7 to 10 range had a very low chance of recovery.
“In fact, patients with scores of 8 and 9 to 10 never achieved good outcome, whereas the proportion of miserable outcome was 70 percent and 100 percent, respectively, and specificity for this prognosis was 99 percent to 100 percent,” the wrote. “Therefore, these patients may be suitable for 1) add-on rescue approaches, e.g., endovascular procedures with persistent major cerebral artery occlusion, 2) enrollment in future randomized trials testing rescue strategies (not only endovascular) or 3) enrollment in trials testing new experimental treatment modalities.”
They cautioned that their study could be biased by unmeasured confounders and was not applicable to ischemic stroke patients with basilar artery occlusion. Because the external validation study involved a small number of patients, they recommended external evaluations be conducted in large centers to further validate the DRAGON score model.