Background and purpose: The ABC/2 formula is a reliable estimation technique of intracerebral hematoma volume. However, oral anticoagulant therapy (OAT)-related intracerebral hemorrhage (ICH) compared with primary ICH is based on a different pathophysiological mechanism, and various shapes of hematomas are more likely to occur. Our objective was to validate the ABC/2 technique based on analyses of the hematoma shapes in OAT-related ICH.
Methods: We reviewed the computed tomography scans of 83 patients with OAT-associated intraparenchymal ICH. Location was divided into deep, lobar, cerebellar, and brain stem hemorrhage. Shape of the ICH was divided into (A) round-to-ellipsoid, (B) irregular with frayed margins, and (C) multinodular to separated. The ABC/2 technique was compared with computer-assisted planimetric analyses with regard to hematoma site and shape.
Results: The mean hematoma volume was 40.83+/-3.9 cm3 (ABC/2) versus 36.6+/-3.5 cm3 (planimetric analysis). Bland-Altman plots suggested equivalence of both estimation techniques, especially for smaller ICH volumes. The most frequent location was a deep hemorrhage (54%), followed by lobar (21%), cerebellar (14%) and brain stem hemorrhage (11%). The most common shape was round-to-ellipsoid (44%), followed by irregular ICH (31%) and separated and multinodular shapes (25%). In the latter, ABC/2 formula significantly overestimated volume by +32.1% (round shapes by +6.7%; irregular shapes by +14.9%; P ANOVA <0.01). Variation of the denominator toward ABC/3 in cases of irregularly and separately shaped hematomas revealed more a precise volume estimation with a deviation of -10.3% in irregular and +5.6% in separately shaped hematomas.
Conclusions: In patients with OAT-related ICH, >50% of bleedings are irregularly shaped. In these cases, hematoma volume is significantly overestimated by the ABC/2 formula. Modification of the denominator to 3 (ie, ABC/3) measured ICH volume more accurately in these patients potentially facilitating treatment decisions.