Contemporary CT can rapidly produce images that reliably depict major cerebral artery occlusion. The STOPStroke study demonstrates that CTA acquisition does not hinder stroke patient management, and that additional information provided by CTA may enhance patient care. Combining the imaging-based BASIS classification instrument with the NIHSS substantially enhances outcome prediction, and may help in identifying subsets of patients that are more or less likely to benefit from therapy.
Among vessel imaging methods, CTA is more reliable than MRA because it is less susceptible to motion, pulsation, flow, and other artifacts, and more reliable than ultrasound because the latter is often limited in coverage due to calcification/tortuous or deep vessels/overlying bone. There were no relevant side effects of the iodinated intravenous CT contrast in this patient cohort, as reported in a publication obtained in the same patient cohort. 
That there is a clinical need for refinement of the existing classification instruments used in the evaluation and therapeutic management of acute stroke patients - most notably the NIH stroke scale and ASPECT scores - is supported by the current DIAS III and IV study designs, which use CTA as a critical component of patient selection. 
NIHSS has been shown to predict length of stay, hospital cost, clinical outcomes, and hospital discharge disposition. 
However, the NIHSS and similar instruments do not identify the occluded artery, the initiating event that leads to neurological symptoms. As noted by Caplan, the lack of information on arterial occlusion has likely limited progress in the treatment of ischemic stroke. 
Neuroimaging overcomes this limitation. Several stroke classification systems that employ imaging have been described. 
However, BASIS 
is the only instrument that incorporates angiographic data, is independent of whether CT or MRI is used, and classifies patients with either anterior or posterior circulation strokes. The use of CTA has previously been shown to predict outcomes, 
and BASIS was built upon that foundation.
The majority of patients in this study had mild neurological symptoms (54.6% had NIHSS 0–5), and good outcomes (61%). Patients classified with severe strokes by all 3 instruments were found to have a higher prevalence of atrial fibrillation, higher use of thrombolytic therapy, and a much higher proportion of poor outcomes. BASIS and NIHSS were more sensitive than ASPECTS for prediction of poor outcomes, probably due to the poor sensitivity of NCCT for identifying early ischemia. While BASIS+ and NIHSS>10 have similar power in predicting poor outcomes, they are not equivalent, and they are independent predictors of poor outcomes. Some have suggested that NIHSS>10 is predictive major artery occlusion. This was not found to be the case in the present study in which 185 patients had NIHSS>10, but only122 of these had a major artery occlusion.
Combined NIHSS/BASIS classification is substantially more powerful in predicting outcomes than any single classification instrument. Close to 80% of all patients were dual-classified as either NIHSS≤10/BASIS− or NIHSS>10/BASIS+, with nearly 80% of NIHSS≤10/BASIS− patients having a good outcomes and a similar percentage of NIHSS>10/BASIS+ patients having poor outcomes, regardless of treatment. The potential prognostic clinical utility of this classification is substantial as indicated by the odds ratio of a poor outcome of over 12 in NIHSS>10/BASIS+ patients when compared to those classified as NIHSS≤10/BASIS−.
The predictive efficacy of combining NIHSS and BASIS into a single classification instrument is reasonable given our current understanding of ischemic stroke. BASIS is a measure of the early physiological abnormalities underlying the ischemic stroke process while the NIHSS reflects the functional significance of the same process. It is the amalgamation of this complementary information that makes the combined classification scheme potent in predicting the functional status of the patient several months after the event. For example, a NIHSS>10/BASIS+ classification indicates that the pathophysiology of a major stroke is present (either occlusion of a major cerebral artery, substantial parenchymal injury or both), and that this abnormal physiology is functionally severe. In the absence of therapy, the expected outcome would be a major cerebral infarction producing a severe functional disability.
The improvement of predictive power in ischemic stroke through the combination of imaging information with clinical assessments to has been previously demonstrated in transient ischemic attacks by 2 groups. 
Both groups have shown that the presence of a DWI abnormality greatly improves the prediction of the early risk of stroke after TIA. The similarity to the work presented here is that imaging provides physiological information that is complementary to the clinical evaluation.
The STOPstroke study has demonstrated that CT angiography can be performed while maintaining a high percentage of patients that receive thrombolytic therapy, and the imaging data can be used for classification that can predict outcomes independent of neurological evaluation. Classifications by NIHSS and BASIS are superior to ASPECTS, and the combination of NIHSS and BASIS instruments is substantially more powerful than any single instrument. These observations may be explained by the early identification by neuroimaging of stroke pathophysiology that produces functionally severe symptoms, a hypothesis that merits further investigation. The use of combined NIHSS/BASIS classification may permit the design of efficient prospective trials of stroke treatment.