# ABC/2

**ABC/2** is a fast and simple method for estimating the volume of intracerebral haemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software. Intracerebral haemorrhage volume is an important predictor of morbidity and mortality (and thus trial eligibility) which is often under-reported ^{1}. It has been well-validated and correlates highly with volumes calculated by planimetric techniques ^{2,3}.

## On this page:

#### Formula

First described by Kwak et al ^{4 }and popularised by Kothari et al ^{2}:

- A x B x C / 2
- A = greatest haemorrhage diameter in the axial plane
- B = haemorrhage diameter at 90º to A in the axial plane
- C = originally described as the number of CT slices with haemorrhage multiplied by the slice thickness, but can simply be substituted with the craniocaudal diameter of the haemorrhage where there is access to multiplanar reformats
^{1}

If the measurements are made in centimetres (cm), then the volume will be in cubic centimetres (cm^{3}).

##### Mathematical basis

The above formula is a simplified version of the formula for the volume of an ellipsoid, which is:

- 4/3 π x (A/2) x (B/2) x (C/2)
- where A, B and C are the three diameters of the ellipsoid

If π is estimated as 3, then the formula can be simplified to ABC/2.

#### Interpretation

A baseline intracerebral haemorrhage volume of >50-60 mL is a poor prognostic marker ^{1,5}.

#### Practical points

There are some pitfalls with the ABC/2 method:

- assumes an ellipsoid lesion (and thus the more the lesion deviates from this morphology the more inaccurate the calculated volume will be)
- overestimates oral anticoagulant-related intracerebral haemorrhage volumes (because they are often irregular in shape)
^{3}- an ABC/3 formula has been suggested for these lesions
^{3}although has not yet been validated

- an ABC/3 formula has been suggested for these lesions