According to a recent study published in Annals of Neurology, computed tomography (CT)-based quantification of water uptake in the ischemic tissue can identify patients with stroke onset within 4.5 hours, guiding the decision to use thrombolysis.

“The optimal cut-off value of water uptake distinguishing stroke onset within and beyond 4.5 hours was calculated in patients with proximal middle cerebral artery occlusion (derivation cohort) with known time of symptom onset. The so derived cut-off value was validated in a prospective cohort from other stroke centers,” the authors wrote.

Of 178 patients of the derivation cohort, 147 had CT within 4.5 hours. Percent water uptake in patients with stroke onset within 4.5 hours was significantly lower than those patients with stroke onset beyond 4.5 hours.  The optimal cut-off value was at 11.5 percent and when this cut-off was applied to the validation cohort of the 240 patients tested, sensitivity was 98.6 percent, specificity 90.5 percent, positive predictive value 99.1 percent, and negative predictive value 86.4 percent.

“Quantification of brain water uptake identifies stroke patients with symptom onset within 4.5 hours with high accuracy and may guide the decision to use thrombolysis in patients with unknown time of stroke onset,” wrote the authors.