CT angiography ousted digital subtraction angiography as the most cost-effective modality for diagnosing certain bleeding strokes in an analysis that took into account the prowess of modern scanners.  

In a study published online Oct. 21 in Stroke, researchers devised a decision-tree model to address the question of which imaging approach offers the best value for assessing patients with perimesencephalic subarachnoid hemorrhages in contemporary practice. Patients are at high risk of death if the aneurysms remain undetected and untreated.

Vivek B. Kalra, MD, of the diagnostic radiology department at Yale School of Medicine in New Haven, Conn., and colleagues focused on CT and digital subtraction angiography because both are used in this patient population. Previous studies used data based on older technology and risk assessments.

Digital subtraction reigns as the gold standard, but the researchers considered it flawed because it is operator dependent and can have a false negative rate as high as 7.1 percent. CT angiography with modern 16 and 64 row scanners, on the other hand, has a sensitivity and specificity rate of 99.2 percent per patient and a sensitivity rate of 94 percent per aneurysm in aneurysms of less than 4 mm.

The decision-tree model started with a noncontrast CT scan and 12 options, using a strict definition for perimesencephalic subarachnoid hemorrhage. CT angiography was assigned a sensitivity and specificity of 99.2 percent, which was lowered if the model called for a follow-up scan. Digital subtraction angiography, as the reference standard, had sensitivity and specificity of 100 percent.

CT angiography with no follow-up scan emerged as the most cost effective approach at a willingness-to-pay threshold of $50,000 per quality-adjusted life year. It held that spot in a one-way analysis and Monte Carlo simulations. When the cost of an untreated aneurysm exceeded $1.2 million, CT angiography with a repeat CT angiography was more cost effective.

They wrote that digital subtraction angiography cost 10 times as much as CT angiography in the study. “DSA [digital subtraction angiography], whether at initial diagnosis or as part of follow-up imaging, is never the optimal strategy in our model.”