To improve diagnostic accuracy the ABCD rule of lesion screening is widely used based on asymmetry (A), border (B), color (C), and differential structure (D) measuring.
• A total dermatoscopic value (TDV) results from the calculation
TDV = A·1,3 + B·0,1 + C·0,5 + D·0,5
• This score contributes to the differentiation between benign and malignant lesions:
1,00 - 4,75 – benign skin lesion
4,75 - 5,45 – suspicious
More than 5,45 – melanoma
A – Asymmetry of Shape, Structure and Color. The lesion is divided in four regions and there is symmetry inspected across x or y axis. If asymmetry is only by one axis it gives 1 point and if on both axis there are 2 points calculated. So for shape, structure and color, there can be 6 points maximum.
Border and Color
For measuring border irregularities the lesion is divided in 8 regions. If in one particular region color is ends strictly with boundary of lesion there is one point. If lesion color changes smoothly to skin color then there is 0 points. So for B there can be maximum 8 points.
For color there can be as many points as many colors there can be found on lesion. Usually there are 6 main colors, so total 6 points for C.
Dermatological Structure D
Thera are 5 main structures noticed in lesions. No structures – smooth color – 1 point, net structure another 1 point, tree like boundaries another 1 point, dots – 1 point and globules 1 point. Total 5 points can be. In some literature there can be diameter of lesion measured for D. If diameter is more than 6 mm it can be stated as suspicious.
When looking in Total Dermatological Value formula, there are obvious that the main criteria are Asymmetry. It is usually the main screening option. It is easy to inspect yourself using this methodology. If there is any concern, it is better to visit your doctor.