The MDS requires you to stage a wound based on how it appears at the time you assess it, which requires "reverse staging." This approach affects RUG reimbursement as a wound heals. Stage 1. A persistent area of skin redness (without a break in the skin) that does not disappear when pressure is relieved. Stage 2. A partial thickness loss of skin layers that presents clinically as an abrasion, blister, scab or shallow crater. Stage 3. A full thickness of skin is lost, exposing the subcutaneous tissues. Presents as a deep crater with or without undermining adjacent tissue. Stage 4. A full thickness of skin and subcutaneous tissue is lost, exposing muscle or the bone.