For those not familiar with this system, its based on PEDIS:
P = perfusion
E = extent or size
D = depth or tissue loss
I = infection
S = sensation or neuropathy
Infection has the following grades:
Grade 1: no signs or symptoms of infection
Grade 2: in subcutaneous tissue only
Grade 3: extensive erythema, infection of deeper tissue
Grade 4: systemic inflammatory response indicating severe infection
The full guidelines are here:
Diagnosis and Treatment of Diabetic Foot Infections