1. Improving the Accuracy of the ABC/2 Estimation Technique in Spontaneous Supratentorial
Intracerebral Hemorrhage
Wendy Ziai, MD, MPH, Saman Nekoovaght-Tak; Joshua F. Betz, John Muschelli, Ryan Noel Fisico, Ximin Li, Daniel F. Hanley, MD for the MISTIE and CLEAR investigators
Department of Neurology, Division of Brain Injury Outcomes, Johns Hopkins University School of Medicine, Baltimore, MD
Introduction Results
Conclusion
Methods
References and Disclosures
Empirical evidence from a large international population of
supratentorial ICH patients suggests that on average, ABC/2 over-
estimates ICH volumes by 20%. Using an approximation of ABC/
2.4 provides a simple way to correct this bias. Shrinking the C-axis
of the ellipse may also improve fit, but the optimal adjustment
depends on hematoma size. Using a denominator of 2.4 is a
simple, objective way to improve rapid ICH assessment with the
existing measurement paradigm, which is consistent in both large
and small hematomas. Further research is necessary to determine
how ABC/2.4 compares with other approximation methods.
The range of ICH volumes using planimetry was 0.02 – 134.29 mL (median 11.6mL; IQR [5.6, 23.9]). In MISTIE II (M2) patients, mean hematoma
volume was 45.72 ± 27.1 (SD) cm3 using ABC/2 vs. 39.48 ± 19.58 cm3 using planimetry. In CLEAR III (C3) patients, mean hematoma volume was
11.11±8.30 (ABC/2) vs. 9.58±7.10 cm3 (planimetry). Method 1: The optimal denominator for the ABC approximation without adjusting C was 2.39 in
M2 patients (95% CI 2.33, 2.46) and 2.37 in C3 patients (95% CI 2.31, 2.42). When these samples are combined, the optimal denominator was
2.39 (95% CI 2.35, 2.42). Method 2: Without any correction to the denominator, the optimal adjustment for C was a decrease of 0.8352 in M2
patients (95% CI -0.976, -0.694) and a decrease of 0.5277 in C3 patients (95% CI -0.595, -0.46). Method 3: In regression models adjusting C and
the denominator, the optimal adjustment for C was an increase of 0.5707 in M2 patients (95% CI -0.215, 1.635), and an increase of 0.0485 in C3
patients (95% CI -0.383, 0.235). The optimal value of the denominator in these models was 2.64 in M2 patients (95% CI 2.29, 3.13) and 2.39 in C3
patients (95% CI 2.21, 2.62). Method 1 provided the best adjustment for ABC/2 using the optimal denominator 2.4. Overall (including both M2 and
C3 CTs) the mean difference between planimetry and ABC/2 was -3.02 mL (95% CI -3.57, -2.48), and the mean difference between planimetry and
ABC/2.4 was 0.42 mL (95% CI 0.02, 0.80). The mean percentage difference between planimetry and ABC/2 was -21.3% (95% CI -24.4%, -18.2%)
vs. -1.1% (95% CI -3.7%, 1.5%) between planimetry and ABC/2.4.
While the ABC/2 formula is the most common method of
approximating intracerebral hemorrhage (ICH) volumes, ABC/2
has been reported to overestimate clot volume with increasing
error for larger hematomas. This has led to several modifications
of the ABC/2 method, including modification of the denominator
and modification of the C-axis. We investigated the optimal way to
correct for the over-estimation of ABC/2 in a large, international
population of ICH patients.
We assessed the diagnostic computed tomography (CT) scans of
373 patients enrolled in the MISTIE II (Minimally Invasive Surgery
plus rt-PA of Intracerebral Hemorrhage Evacuation Phase II)
(N=100) and CLEAR III (Clot Lysis: Evaluating Accelerated
Resolution of Intraventricular Hemorrhage Phase III) (N=273)
clinical trials across 60 sites using planimetry and ABC/2 where:
A= Largest hemorrhage diameter on axial image (cm)
B= Largest diameter perpendicular to A (cm)
C = [Number of Slices] x [Slice Thickness] (cm)
We evaluated three methods of adjusting elliptical approximations of
ICH volume using linear and nonlinear regression: changing the
denominator (method 1), changing the C-axis (method 2), or
changing both (method 3):
Method 1: Volume = β(ABC)
Method 2: Volume = AB(C - γ )/2
Method 3: Volume = β(AB ( C-γ ))
1. R.U. Kothari, T. Brott, J.P. Broderick, W.G. Barsan, L.R. Sauerbeck, M. Zuccarello et al.
The ABCs of measuring intracerebral hemorrhage volumes. Stroke, 27 (1996), pp. 1304–1305
2. J.M. Gebel, C.A. Sila, M.A. Sloan, C.B. Granger, J.P. Weisenberger, C.L. Green et al. Comparison of the
ABC/2 estimation technique to computer-assisted volumetric analysis of intraparenchymal and subdural
hematomas complicating the GUSTO-1 trial.Stroke, 29 (1998), pp. 1799–1801
3. Wang CW, Juan CJ, Liu YJ, Hsu HH, Liu HS, Chen CY, et al. Volume-dependent overestimation of
spontaneous intracerebral hematoma volume by the ABC/2 formula. Acta Radiol. 2009;50:306–311
The CLEAR-III trial is supported by grant NIH/NINDS 5U01 NS062851 to Dr. Hanley
MISTIE sponsored by NINDS R01N5046309. Donations from Genentech, inc.& Codman, inc.