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Pressure Ulcers/Injuries - Classification/Staging

Pressure Ulcers/Injuries - Classification/Staging

Pressure Ulcers/Injuries - Classification/Staging



This topic provides details on two of the most used classification systems for pressure ulcer/injury (PU/PI): the classification created by the National Pressure Injury Advisory Panel (NPIAP, formerly National Pressure Ulcer Advisory Panel or NPUAP) and the system adopted by the Centers for Medicare and Medicaid Services (CMS). For an introduction and assessment of PU/PI including epidemiology, risk factors, etiology, pathophysiology, history, physical examination, diagnosis, differential diagnoses, documentation and ICD-10 coding, see "Pressure Ulcers/Injuries - Introduction and Assessment".


The NPIAP classification, updated in 2016, is the most widely adopted classification for pressure ulcers/injuries (PUs/PIs).[1][2][3] In the U.S., CMS allows nursing homes to adopt the NPIAP guidelines in their clinical practice and nursing documentation. However, CMS requires nursing homes to utilize CMS' adapted version of the NPIAP guidelines when coding the Minimum Data Set (MDS) system. Stage definitions of the MDS version do not perfectly correlate with each stage as described by NPIAP. For coding purposes, the MDS should be coded according to the definitions stated in the Medicare MDS 3.0 RAI Manual, transcribed below.[4]


Table 1A summarizes the NPIAP and Medicare MDS Classification/Stages and provides representative drawings/pictures of each stage. Table 1B provides a printable version of Table 1A, in addition to Stage 2 PU/PI common differential diagnoses. Table 2 compares stages and definitions of PU/PI classification as per the NPIAP (2016) [2] and Medicare MDS 3.0 RAI Manual (2018)[4], used in long term care facilities (nursing homes). Guidance on PU/PI staging is provided thereafter. 

Table 1A. Summary of the NPIAP and Medicare MDS Classification/Stages with representative drawings/pictures  (click on images to enlarge). NPIAP: National Pressure Ulcer Advisory Panel, MDS: Classification adapted by Medicare, to be used when entering information in the Minimum Data Set (MDS) system, used by nursing homes. Text in red indicates differences in nomenclature between these two systems (ulcers versus injury).   
NPIAP and Medicare MDS Codes/Stages Schematic Drawings (NPIAP copyright & used with permission) Representative Picture
  • Stage 1 Pressure Injury: Non-blanchable erythema of intact skin (NPIAP and MDS M0300A)

  • Stage 2 Pressure Injury: Partial-thickness skin loss with exposed dermis (NPIAP)
  • Stage 2 Pressure Ulcer: Partial-thickness skin loss with exposed dermis (MDS M0300B)

  • Stage 3 Pressure Injury: Full-thickness skin loss (NPIAP)
  • Stage 3 Pressure Ulcer: Full-thickness skin loss (MDS M0300C)

  • Stage 4 Pressure Injury: Full-thickness skin and tissue loss (NPIAP)
  • Stage 4 Pressure Ulcer: Full-thickness skin and tissue loss (MDS M0300D)

  • Unstageable Pressure Injury: Obscured full-thickness skin and tissue loss  (NPIAP)
  • Unstageable Pressure Ulcers Related to Slough and/or Eschar (MDS M0300F)

  • Deep Tissue Pressure Injury (NPIAP)
  • Unstageable Pressure Injuries Related to Deep Tissue Injury (MDS M0300G)

Additional definitions (not part of the NPIAP staging system)

  • Unstageable Pressure Ulcers/Injuries Related to Non-removable Dressing/Device (MDS M0300E)
  • Medical Device Related Pressure Injury (NPIAP)
  • Mucosal Membrane Pressure Injury (NPIAP)

Quick Reference Tool

See the 'Quick Reference Tool: Pressure Ulcers/Injury Staging and Common Differential Diagnosis' below (Table 1B)

Algorithm Quick Reference Pressure Ulcer Injury

Table 1B. Quick Reference Tool: Pressure Ulcers/Injury Staging and Common Differential Diagnosis


Table 2. Pressure Ulcers/Injuries stages and additional definitions as per NPIAP (2016) and Medicare MDS 3.0 RAI Manual (2018) 
NPIAP 2016Medicare MDS 3.0 RAI Manual 2018
Stage 1 Pressure Injury: Non-blanchable erythema of intact skin. Intact skin with a localized area of non-blanchable erythema, which may appear differently in darkly pigmented skin. Presence of blanchable erythema or changes in sensation, temperature, or firmness may precede visual changes. Color changes do not include purple or maroon discoloration; these may indicate deep tissue pressure injury .
Stage 1 Pressure Injury: Non-blanchable erythema of intact skin. An observable, pressure-related alteration  of intact skin whose indicators, as compared to an adjacent or opposite area on the body, may include changes in one or more of the following parameters: skin temperature  (warmth or coolness); tissue consistency (firm or boggy); sensation (pain, itching); and/or a defined area of persistent redness in lightly pigmented skin, whereas in darker skin tones, the injury may appear with persistent red, blue, or purple hues. 
Stage 2 Pressure Injury: Partial-thickness skin loss with exposed dermis
Partial-thickness loss of skin with exposed dermis. The wound bed is viable, pink or red, moist, and may also present as an intact or ruptured serum-filled blister. Adipose (fat) is not visible and deeper tissues are not visible. Granulation tissue, slough and eschar are not present. These injuries commonly result from adverse microclimate and shear in the skin over the pelvis and shear in the heel.  This stage should not be used to describe moisture associated skin damage (MASD) including incontinence associated dermatitis (IAD), intertriginous dermatitis (ITD), medical adhesive related skin injury (MARSI), or traumatic wounds (skin tears, burns, abrasions).
Stage 2 Pressure Ulcer: Partial-thickness skin loss with exposed dermis:  Partial thickness loss of dermis presenting as a shallow open ulcer with a red-pink wound bed, without slough or bruising. May also present as an intact or open/ ruptured blister.
Stage 3 Pressure Injury: Full-thickness skin loss
Full-thickness loss of skin, in which adipose (fat) is visible in the ulcer and granulation tissue and epibole (rolled wound edges) are often present. Slough and/or eschar may be visible. The depth of tissue damage varies by anatomical location; areas of significant adiposity can develop deep wounds.  Undermining and tunneling may occur. Fascia, muscle, tendon, ligament, cartilage and/or bone are not exposed. If slough or eschar obscures the extent of tissue loss this is an Unstageable Pressure Injury.
Stage 3 Pressure Ulcer: Full-thickness skin loss:  Subcutaneous fat may be visible but bone, tendon or muscle is not exposed. Slough may be present but   does not obscure the depth of tissue loss. May include undermining or tunneling.
Stage 4 Pressure Injury: Full-thickness skin and tissue loss
Full-thickness skin and tissue loss with exposed or directly palpable fascia, muscle, tendon, ligament, cartilage or bone in the ulcer. Slough and/or eschar may be visible. Epibole (rolled edges), undermining and/or tunneling often occur. Depth varies by anatomical location. If slough or eschar obscures the extent of tissue loss this is an Unstageable Pressure Injury.
Stage 4 Pressure  Ulcer:  Full-thickness skin and tissue loss: Full thickness tissue loss with exposed  bone, tendon or muscle. Slough or eschar may be present on some parts of the wound bed. Often includes undermining and tunneling. 
Unstageable Pressure Injury: Obscured full-thickness skin and tissue loss
Full-thickness skin and tissue loss in which the extent of tissue damage within the ulcer cannot be confirmed because it is obscured by slough or eschar.  If slough or eschar is removed, a Stage 3 or Stage 4 pressure injury will be revealed. Stable eschar (i.e. dry, adherent, intact without erythema or fluctuance) on the heel or ischemic limb should not be softened or removed.
Unstageable Pressure Ulcers Related to Slough and/or EscharPressure ulcers that are covered with slough and/ or eschar, and the wound bed cannot be visualized 
Deep Tissue Pressure Injury (DTI): Persistent non-blanchable deep red, maroon or purple discoloration
Intact or non-intact skin with localized area of persistent non-blanchable deep red, maroon, purple discoloration or epidermal separation revealing a dark wound bed or blood filled blister. Pain and temperature change often precede skin color changes. Discoloration may appear differently in darkly pigmented skin.  This injury results from intense and/or prolonged pressure and shear forces at the bone-muscle interface.  The wound may evolve rapidly to reveal the actual extent of tissue injury, or may resolve without tissue loss. If necrotic tissue, subcutaneous tissue, granulation tissue, fascia, muscle or other underlying structures are visible, this indicates a full thickness pressure injury (Unstageable, Stage 3 or Stage 4). Do not use DTI to describe vascular, traumatic, neuropathic, or dermatologic conditions.
Unstageable Pressure Injuries Related to Deep Tissue Injury. Deep tissue injury may precede the development of a Stage 3 or 4 pressure ulcer even with optimal treatmentDeep tissue injury is described as purple or maroon area of discolored intact skin due to damage of underlying soft tissue. The area may be preceded by tissue that is painful, firm, mushy, boggy, warmer or cooler as compared to adjacent tissue. 

Medical Device Related Pressure Injury: This term describes an etiology. Medical device related pressure injuries result from the use of devices designed and applied for diagnostic or therapeutic purposes. The resultant pressure injury generally conforms to the pattern or shape of the device. The injury should be staged using the staging system above.

Unstageable Pressure Ulcers/Injuries Related to Non-removable Dressing/Device : PU/PI covered by a non-removable dressing/device, which includes for example, a primary surgical dressing that cannot be removed, an orthopedic device, or cast. Ulcer is staged using the staging system above when dressing/device is removed and wound bed is visualized 

Mucosal Membrane Pressure Injury:  Mucosal membrane pressure injury is found on mucous membranes with a history of a medical device in use at the location of the injury. Due to the anatomy of the tissue these ulcers cannot be staged.



General Guidance on PU/PI Staging

Guidance on PU/PI staging provided by the NPIAP and CMS is consolidated below: 
  • The NPIAP classification is intended for documentation of ulcers resulting from pressure and/or shear, and not ulcers with other etiologies. [2][5]
  • Verify that there is clinical agreement in PU/PI classification amongst health professionals responsible for classifying PU/PI.[5] 
  • Differentiate between blanchable (normal reactive hyperemia) and non-blanchable (Stage 1 PU/PI). Blanchable erythema is seen when a skin area that is reddened turns pale as a result of applying pressure with a finger or plastic disc and preventing blood flow to the region. As the pressure is released, skin turns red again.[5]( Figure 1). It is important to note that blanchable erythema or changes in sensation, temperature, or firmness may precede visual changes and represent an opportunity to implement offloading and pressure redistribution strategies before further skin damage occurs.

Fig. 1. Blanchable erythema (normal reactive hyperemia) and non-blanchable erythema (Stage 1 PU/PI) (click to enlarge). NPIAP copyright & used with permission

  • According to the NPIAP, when classifying a PU/PI, the clinician has the following options [6]:     
    • 1) If the type of tissue injured in the wound base can be visualized or directly palpated, numerically classify as Stage 1 or 2 or 3 or 4, based on the deepest tissue type exposed. 
    • 2) If the wound base cannot be evaluated, classify as: 
      • Deep Tissue Pressure Injury (DTI) when the skin is intact with deep red, purple or maroon discoloration or blood blister(s).   
      • Unstageable when the base is obscured by slough or eschar.     
    • 3) If on a mucosal membrane, document, but do not stage
  • To stage each PU/PI, consider the deepest anatomical point that is visible or palpable when staging. [4] If a PU/PI's tissues are obscured such that the depth of soft tissue damage cannot be observed, it is considered to be unstageable [4] Stage of a PU/PI can only be determined when enough slough and/or eschar is removed to expose the anatomic depth of soft tissue damage involved. [7] (Figures 2 and 3)

Fig. 2 Unstageable sacral PU/PI covered with eschar                                                                    

Fig. 3 Sacral PU/PI - Stage 4. Debridement of eschar reveals f ull-thickness skin and tissue loss

  • Stable eschar (i.e., dry, adherent, intact without erythema or fluctuance) on the heels serves as “the body’s natural (biological) cover” and should only be removed after careful clinical consideration, including ruling out ischemia.[7]  (Figure 4)

Fig. 4. Unstageable ulcer in the heel, covered with stable eschar

  • Do not reverse or back stage, that is, change a PU/PI stage as it heals.[4][8] Clinical standards do not support reverse staging or backstaging as a way to document healing, as it does not accurately characterize what is occurring physiologically as the ulcer heals. PUs/PIs do not heal in a reverse sequence, that is, the body does not replace the types and layers of tissue (e.g., muscle, fat, and dermis) that were lost during PU/PI development before they re-epithelialize. Stage 3 and 4 PUs/PIs fill with granulation tissue. This replacement tissue is never as strong as the tissue that was lost and hence is more prone to future breakdown. A Stage 4 ulcer will always be a Stage 4, even after it heals (i.e, healed/closed Stage 4 PU/PI).[4][8]
    • To document signs of improvement, clinicians can describe characteristics of the wound (i.e., depth, width, presence or absence of granulation  tissue, etc.) or use a validated pressure ulcer healing tool, such as the PUSH tool. [4][8]
  • When examining PU/PI in individuals with darkly pigmented skin, rely on assessment of skin temperature, change in tissue consistency and pain rather than identification of non-blanchable erythema in Stage 1, inflammatory redness from cellulitis or discoloration from deep tissue injury.[5] Sub-epidermal moisture is an important adjunctive assessment strategy.[3]
  • Deep tissue injury (DTI): Once a deep tissue injury opens to an ulcer, reclassify the ulcer into the appropriate stage.[4] 
  • Medical device-related PU/PI: it is suggested that medical device-related PU/PI due to pressure of nasogastric/nasoenteric tubes on the skin of the nasal vestibule and exterior nose be  staged as a PU/PI (stage 1-4, unstageable or deep tissue injury) and not as mucosal membrane pressure injuries. The nasal vestibule is lined by skin with hair follicles, sebaceous glands and sweat glands, and terminates at the limen nasi posteriorly. [9]  

Coding Guidance for "Present on Admission" PU/PI in Acute Care Setting

According to Coding Clinic and Medicare report on coding for hospital acquired conditions [10][11], if a lower stage PU/PI was recognized on admission and progressed to a higher stage ulcer during the hospital stay, the ulcer would be coded at the higher stage and would be confirmed as "present on admission". That is, if for instance a Stage 1 PU/PI is diagnosed and documented upon admission but progresses to PU/PI Stage 3 during hospital stay, this PU/PI would be coded as a Stage 3 that was "present on admission" [NOTE: a lower stage PU/PI such a Stage 1 PU/PI needs to be recognized and documented as such at the time of admission].

  • It may appear inconsistent to report a Stage 3 PU/PI as "present on admission" (POA) since the PU/PI gradually deteriorated during the hospital stay. However, because the lower stage ulcer was recognized and documented upon admission, the indicator "present on admission" (POA) should be used by coders. In terms of coding and POA reporting, a pressure ulcer is only coded and reported once, at its highest stage.[11]
  • In 2008, CMS introduced a claim-level payment penalty that denied increased reimbursement for discharge records that contained a documented hospital-acquired condition (HAC). [12][13] PU/PIs Stages 3 and 4 are one of the 14 HACs subject to payment penalty. However, this list of reportable events excludes a PU/PI of lower stage that progressed to Stage 3 or 4, if the lower stage was recognized upon admission.[11]
  • Under the 2008 CMS HAC payment provision, hospitals are required to report a corresponding POA indicator for each PU/PI diagnosis. Possible values for the POA indicator include among others [12][14]:
    • "Y", indicating that the diagnosis was present at the time of admission
    • "N", indicating that the diagnosis was not POA (i.e., and thus considered a HAC).
  • Current coding guidelines for the POA indicator allow HACs to be coded as POA for conditions diagnosed during the admission that were clearly present but not diagnosed until after admission occurred.[14] See other POA Criteria in Appendix I of the CDC ICD-10-CM Official Guidelines for Coding and Reporting FY 2019.[14]
  • Despite these coding guidelines issued by CMS, CDC, Coding Clinic, reports [10][11][14] show that there are variances in interpretation among acute care facilities, so clinicians might want to confirm local practice with their specific coding/billing department. 


5/5/21Added Quick Reference Tool: Pressure Ulcers/Injuries Staging and Differential Diagnosis
11/19/19Added section 'Coding Guidance for "Present on Admission" PU/PI in Acute Care Setting'

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  1. Raetz JG, Wick KH et al. Common Questions About Pressure Ulcers. American family physician. 2015;volume 92(10):888-94.
  2. The National Pressure Ulcer Advisory Panel - NPUAP. National Pressure Ulcer Advisory Panel (NPUAP) announces a change in terminology from pressure ulcer to pressure injury and updates the stages of pressure injury . 2016;.
  3. NPIAP. Prevention and Treatment of Pressure Ulcers/Injuries: Clinical Practice Guideline. The International Guideline, 3rd Edition (2019) . 2019;.
  4. Centers for Medicare & Medicaid Services. Long-Term Care Facility Resident Assessment Instrument 3.0 User’s Manual . 2018;.
  5. National Pressure Ulcer Advisory Panel (NPUAP), European Pressure Ulcer Advisory Panel (EPUAP), and Pan Pacific Pressure Injury Alliance (PPPIA) et al. Prevention and Treatment of Pressure Ulcers: Clinical Practice Guidelines and Quick Reference Guide. 2014. .;.
  6. National Pressure Injury Advisory Panel. NPUAP Position Statement on Staging - 2017 Clarifications . 2017;.
  7. CMS. State Operations Manual State Operations Manual - Appendix PP - Guidance to Surveyors for Long Term Care Facilities . 2017;.
  8. National Pressure Ulcer Advisory Panel. The Facts about Reverse Staging in 2000The NPUAP Position Statement . 2012;.
  9. Richbourg L. Meet Me in the Nasal Vestibule: A View From Here. Journal of wound, ostomy, and continence nursing : official publication of The Wound, Ostomy an.... 2017;volume 44(6):513-514.
  10. Catherine L. Snow, MPH Linda Holtzman, MHA Hugh Waters, PhD Nancy T. McCall, ScD Michael Halpern, MD Lisa Newman, MSPH John Langer, PhD Terry Eng, MS Carolyn Reyes Guzman, MPH RTI International et al. Medicare report:  Accuracy of Coding in the HospitalAcquired Conditions–Present on Admission Program . 2012;.
  11. . Coding Clinic Fourth Quarter . 2008;.
  12. Squitieri L, Waxman DA, Mangione CM, Saliba D, Ko CY, Needleman J, Ganz DA et al. Evaluation of the Present-on-Admission Indicator among Hospitalized Fee-for-Service Medicare Patients with a Pressure Ulcer Diagnosis: Coding Patterns and Impact on Hospital-Acquired Pressure Ulcer Rates. Health services research. 2018;volume 53 Suppl 1():2970-2987.
  13. The Centers for Medicare and Medicaid Services. Hospital-Acquired Conditions . 2016;.
  14. The Centers for Disease Control. ICD-10-CM Official Guidelines for Coding and Reporting FY 2019 . 2019;.
Topic 1182 Version 1.0