Comparison between the formula 1/2ABC and 2/3Sh in intracerebral parenchyma hemorrhage

Abstract

BACKGROUND AND PURPOSE: The 1/2ABC formula is the method most commonly used in clinical practice to rapidly estimate intracerebral hemorrhage (ICH) volume. We aimed to compare this method with the alternative ‘2/3Sh’ formula for both regularly and irregularly-shaped hematomas. METHODS: Computed tomography (CT) images from 344 ICH patients (median volume: 16•66 ml) were retrospectively reviewed. According to the maximum slice, the shape was classified into regular or irregular (multilobular, conical, and other). Volumes as determined by the 1/2ABC and 2/3Sh formulas were compared against the gold standard, computer-assisted planimetry, for various hematoma shapes. RESULTS: With the 1/2ABC method, errors were seen non-significantly more frequently for irregularly-shaped hematomas [OR: 2•85 (95% CI: 0•65‐12•50)]. The 1/2ABC method misclassified a greater proportion of hematomas as greater or less than 30 ml in volume: 7•0% (95% CI: 6•0‐9•9%). Both the 1/2ABC and 2/3Sh formulas correlated well with gold standard (correlation coefficients >0•9 for each shape). While there was no statistically significant measurement error bias for either method, the 95% confidence intervals of the limit of agreement for 2/3Sh were tighter: −0•22 ml (−4•7‐4•25 ml) versus 2•50 ml (−10•35‐15•34 ml). Measurement errors were significantly greater with the 1/2ABC method, for both regular and irregular hematomas [1•17 ml (0•48‐2•83 ml) versus 0•88 ml (0•42‐1•68 ml) and 2•65 ml (1•07‐5•88 ml) versus 0•99 ml (0•47‐2•28 ml); P<0•05, respectively], although the magnitude of error would only rarely be clinically relevant for regular hematomas. Errors were most evident in assessing multilobular-shaped hematomas [6•49 ml (3•35‐13•98 ml) versus 1•86 ml (0•96‐9•94 ml); P<0•001]. CONCLUSIONS: The 2/3Sh formula leads to fewer clinically-relevant hematoma volume misclassifications than the 1/2ABC formula, and is particularly superior in estimating volumes of irregularly-shaped hematomas.