1. McComb, W. Dwight Jr MD, FACP

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For any wound, the first priority is to determine its etiology. Once the cause is identified, applying a standardized assessment method tool can guide further diagnostic workup and therapy, supply information about risk, and even have significant financial implications. This is particularly true for diabetic foot ulcers (DFUs) and pressure injuries (PIs). Because DFUs and PIs are so common, it is critical that healthcare providers be proficient in using accepted assessment strategies. For DFUs, one commonly used tool is the grading scale proposed by Wagner.1 For PIs, the predominant classification method is the staging system set forth by the National Pressure Injury Advisory Panel (NPIAP).2 Although these two systems differ in structure and are designed for entirely different wound types, the similarities between them are sufficient to cause confusion at times. In this article, the author briefly summarizes the two systems and highlights their differences as a result of noticing confusion among the staff at his facilities.



In persons with diabetes, compromise of normal foot anatomy and function can be caused by myriad conditions, including but not limited to neuropathy, arthropathy, and peripheral vascular disease. The Wagner grading system helps to both identify feet that are at high risk and classify wounds once they develop.


Although other classification systems for DFUs have been proposed and even validated,3,4 the Wagner system is still in widespread use. This is particularly true among centers offering hyperbaric oxygen therapy (HBOT), an adjunctive therapy for DFUs that includes the Wagner grading system in its eligibility criteria.5 In addition, many outcome studies6 and clinical guidelines7 referencing HBOT as a treatment for DFUs use the Wagner grading system.


The Wagner system consists of six grades, beginning with Grade 0 and progressing to Grade 5.


* Grade 0 - Pre-ulcerative/high-risk foot (has no break in the skin)


* Grade 1 - Superficial ulcer (involves epidermis, dermis, or subcutaneous tissue)


* Grade 2 - Deep to tendon, bone, or joint (penetrates through the subcutaneous tissue)


* Grade 3 - Deep with abscess/osteomyelitis (goes as deep as Grade 2 but with infection)


* Grade 4 - Forefoot gangrene (requires at least a partial amputation)


* Grade 5 - Whole foot gangrene (requires at least a below-the-knee amputation)




The NPIAP PI staging system has been widely incorporated at an international level and has increasingly been used as a basis for treatment, coding, outcome comparison, and even reimbursement,2,8 making proper staging of PIs more important than ever.


Like the Wagner system, the NPIAP staging system uses Arabic numerals. Unlike the Wagner system, which is a risk assessment tool and thus assigns a number for feet considered to be at risk but without injury, the NPIAP staging system is for injury classification purposes only. It does, however, have terminology for damaged-but-intact skin as well as tissue injuries where obscured wound depth precludes staging. Another difference is that the NPIAP staging system does not incorporate the presence or absence of infection in any of its criteria (Table).


The NPIAP staging system consists of four numbered stages and two descriptive terms.


* Stage 1 - Intact skin with a localized area of discolored epidermis which may be nonblanchable erythema or may appear differently in darkly pigmented skin (does not break the skin)


* Stage 2 - Partial thickness skin loss with exposed dermis (does not penetrate to the subcutaneous tissue)


* Stage 3 - Full thickness skin loss (penetrates into but not through the subcutaneous tissue)


* Stage 4 - Full thickness skin and tissue loss (penetrates through the subcutaneous tissue with exposed or directly palpable fascia, muscle, tendon, ligament, cartilage, or bone)


* Unstageable full thickness tissue injury - Obscured full-thickness skin and tissue loss (cannot visualize the depth of the injury)


* Deep tissue pressure injury - Persistent nonblanchable deep red, maroon, or purple discoloration (cannot discern the full depth by inspection; skin may be intact or nonintact)




Even though the Wagner grading system and NPIAP staging system are for different injury/ulcer types and are in many ways disparate in their overall approach to assessment, the fact that they both rely on wound depth as determined by tissue type and use Arabic numbers assigned according to the level of tissue injury can lead to confusion. After encountering this many times in both inpatient and outpatient settings, the author created a graphic (Figure) that juxtaposes the two systems to highlight their differences. It may be useful as a learning resource and as a reference at the point of care and other locations where documentation is performed.

Figure. WAGNER GRADI... - Click to enlarge in new windowFigure.

Proper assessment in the form of grading DFUs and staging PIs is important for optimizing patient care and because it relates to quality standards, which have an ever-growing impact on reimbursement and access. Extra attention to avoid confusion between the two classification systems is warranted.




1. Wagner FW Jr. The dysvascular foot: a system for diagnosis and treatment. Foot Ankle 1981;2(2):64-122. [Context Link]


2. Edsberg LE, Black JM, Goldberg M, McNichol L, Moore L, Sieggreen M. Revised National Pressure Ulcer Advisory Panel pressure injury staging system: revised pressure injury staging system. J Wound Ostomy Continence Nurs 2016;43(6):585-97. [Context Link]


3. Armstrong DG, Lavery LA, Harkless LB. Validation of a diabetic wound classification system. The contribution of depth, infection, and ischemia to risk of amputation. Diabetes Care 1998;21(5):855-9. [Context Link]


4. Monteiro-Soares M, Boyko EJ, Jeffcoate W, et al. Diabetic foot ulcer classifications: a critical review. Diabetes Metab Res Rev 2020;36(Suppl 1):e3272. [Context Link]


5. Centers for Medicare & Medicaid Services. National Coverage Determination. Hyperbaric Oxygen Therapy. April 3, 2017. Last accessed February 15, 2023. [Context Link]


6. Ennis WJ, Huang ET, Gordon H. Impact of hyperbaric oxygen on more advanced Wagner Grades 3 and 4 diabetic foot ulcers: matching therapy to specific wound conditions. Adv Wound Care (New Rochelle) 2018;7(12):397-407. [Context Link]


7. Huang ET, Mansouri J, Murad MH, et al. A clinical practice guideline for the use of hyperbaric oxygen therapy in the treatment of diabetic foot ulcers. Undersea Hyperb Med 2015;42(3):205-47. [Context Link]


8. Padula WV, Black JM, Davidson PM, Kang SY, Pronovost PJ. Adverse effects of the Medicare PSI-90 hospital penalty system on revenue-neutral hospital-acquired conditions. J Patient Saf 2020;16(2):e97-e102. [Context Link]