MR angiography as a screening tool for intracranial aneurysms: Feasibility, test characteristics, and interobserver agreement

OBJECTIVE. MR angiography may be an appropriate tool to screen for unruptur ed intracranial aneurysms. Feasibility, test characteristics, and interobse rver agreement in evaluation of MR angiograms were assessed by members of t he MARS (Magnetic resonance Angiography in Relatives of patients with Subar achnoid hemorrhage) Study Group. SUBJECTS AND METHODS. We screened 626 first-degree relatives of a consecuti ve series of 193 patients with subarachnoid hemorrhage examined at two inst itutions. We used MR imaging and MR angiography (three-dimensional time-of- flight imaging at both institutions and additional three-dimensional phase- contrast imaging at one institution). Three observers independently assesse d the MR angiograms. Conventional angiography was performed in relatives wi th possible or definite aneurysms on MR angiography and was considered the standard of reference. RESULTS, Thirty-three aneurysms were found in 25 (4%; 95% confidence interv al [CI], 3-6%) of 626 relatives. Thirteen (8%) of 169 relatives who refused screening had MR-related reasons; an additional six persons could not be s creened because of contraindications for MR imaging (pregnancy, n = 1; clau strophobia, n = 5). The positive predictive value of MR angiography was 100 % (95% CI, 79-100%) for "definite" aneurysms and 58% (95% CI, 28-85%) for " possible" aneurysms. Sensitivity of MR angiography was estimated at 83% (95 % CI, 65-94%) and specificity at 97% (95% CI, 94-98%). Interobserver agreem ent in the evaluation of MR angiograms was poor (kappa < .30), probably bec ause different diagnostic strategies used by individual observers resulted in different use of the assessment category "possible aneurysm." CONCLUSION. MR angiography is a feasible screening tool for detection of in tracranial aneurysms. Positive predictive value, sensitivity, and specifici ty are acceptable when at least two neuroradiologists independently assess MR angiograms.