Consider an incontinent patient with a red, weeping area across both buttocks. One nurse records a Stage 2 pressure injury, the next records incontinence-associated dermatitis, and both entries can look reasonable on the chart. They lead to different care plans. Pressure injury staging is usually taught as a description of depth, but in practice it works as a treatment decision, and a wrong label sends the treatment in the wrong direction.
The stage determines what clinicians believe is damaged and why, and the decisions about offloading, dressings and debridement all follow from that belief.
The staging system published by the National Pressure Injury Advisory Panel (NPIAP, 2016) defines a pressure injury as localised damage to the skin and underlying tissue, usually over a bony prominence or related to a device, caused by pressure or pressure combined with shear. Each stage describes how deep that damage goes. Stage 2 is partial-thickness skin loss with a viable, pink or red, moist wound bed. Stage 3 and Stage 4 involve full-thickness loss.
The same definitions also say what each stage is not, and many of the errors that change treatment happen in that second half.
They differ in cause: a Stage 2 pressure injury is produced by pressure and shear, while incontinence-associated dermatitis (IAD) is an irritant contact dermatitis produced by urine or faeces on the skin.
The NPIAP definition is explicit that Stage 2 should not be used to describe moisture-associated skin damage, including IAD, intertriginous dermatitis, medical adhesive-related skin injury, or traumatic wounds such as skin tears, burns and abrasions (NPIAP, 2016). The difficulty is that both conditions favour the same territory, the skin over the sacrum and buttocks, and both can present as red, broken, painful skin.
| Feature | Stage 2 pressure injury | Incontinence-associated dermatitis |
|---|---|---|
| Cause | Pressure and shear, often with an adverse microclimate | Prolonged contact with urine or faeces |
| Typical location | Over a bony prominence or under a device | Perineum, genital area, buttocks, gluteal fold, inner thighs, skin folds |
| Shape and edges | Usually a single area, localised to the point of pressure | Diffuse or patchy, poorly defined edges |
| Depth | Partial-thickness loss with exposed dermis | Persistent redness, with or without superficial skin loss |
| Key condition | Occurs with or without incontinence | Cannot be IAD if the person is not incontinent |
| First-line management | Relieve pressure and shear, manage the wound bed | Manage the incontinence, cleanse, protect and restore the skin barrier |
Sources: NPIAP (2016); Beeckman et al. (2018); Clinical Excellence Commission (2021).
The patient receives wound care for a pressure injury they may not have, while the cause of the skin damage continues.
Management of IAD is built on containing or treating the incontinence, cleansing the skin with a pH-appropriate product after each episode, protecting it with a barrier product, and supporting barrier repair (Clinical Excellence Commission, 2021). A wound dressing placed over inflamed perineal skin addresses none of that. The same guidance warns that piling layers between the patient and the support surface raises heat, moisture and friction, and with them the risk of pressure injury.
The error also runs the other way. When a genuine Stage 2 injury on the sacrum is recorded as moisture damage, the care plan shifts towards continence products and creams, and the pressure that caused the wound may not be relieved. Because the two can coexist in the same patient, the Clinical Excellence Commission advises applying combined prevention for both when the cause of erythema is unclear, then reviewing the response.
A number is written down for a depth nobody has actually seen, and the decision about removing slough or eschar is made on a false premise.
NPIAP (2016) classifies a full-thickness wound as unstageable when slough or eschar obscures the extent of tissue loss; once it is removed, a Stage 3 or Stage 4 injury is revealed. Recording Stage 3 too early can understate a wound that later proves to involve muscle, tendon or bone. The definitions also carry a clear exception: stable eschar that is dry, adherent and intact, without erythema or fluctuance, on the heel or on an ischaemic limb should not be softened or removed. That rule only protects the patient if the wound has been correctly identified as unstageable in the first place.
It costs time, because the treatment that matters most, removing pressure from the area at once, is delayed while the damage beneath the skin progresses.
A deep tissue pressure injury appears as persistent, non-blanchable deep red, maroon or purple discolouration, or as a blood-filled blister, and results from intense or prolonged pressure and shear at the bone-muscle interface (NPIAP, 2016). Pain and temperature change often come before the colour change. Stage 1 explicitly excludes purple or maroon discolouration for this reason. If the discolouration is charted as Stage 1 or as bruising, the area may stay under load. The wound can then evolve rapidly to reveal the full extent of tissue damage.
Less reliable than the definitions suggest, although the evidence has gaps of its own.
A European study of nurses classifying pressure ulcer photographs found low overall agreement, with a kappa of 0.33; grade 3 lesions were regularly classified as grade 2, and non-blanchable erythema was often assessed as blanchable (Beeckman et al., 2007). In a later trial of an educational tool for differentiating pressure ulcers from IAD, nurses classified 44.5% of photographs correctly at baseline; after training, the intervention group reached 63.2%, compared with 53.1% in the control group (Beeckman et al., 2010). The Ghent Global IAD Categorisation Tool, tested across 30 countries, achieved a kappa of 0.65 for its two main categories but 0.41 across all four sub-categories (Beeckman et al., 2018).
These studies have a shared limitation. They measure agreement on photographs, not at the bedside, where clinicians can touch the skin, test blanching, ask about pain and review continence history. Bedside accuracy may be better or worse; the data do not settle it. There is also no point-of-care test that separates IAD from pressure injury, so the assessment still rests on visual inspection and clinical judgement (Clinical Excellence Commission, 2021).
A few questions asked before the stage is written down will catch many of the errors described above.
Is the person incontinent, and does the damage follow the area exposed to urine or faeces rather than a bony prominence? Are the edges diffuse or distinct? Is the wound bed visible, or is slough or eschar hiding it? Is any discolouration purple or maroon rather than red, and is the area painful or warmer than the surrounding skin? When the answer is uncertain, a second assessor and a dated reassessment are more useful than a confident number.
Dressing choice comes after these questions, not before them. A stage-by-stage guide such as the one published by ABeWER is useful precisely because it assumes the stage is right, which is why differentiating moisture damage from a Stage 2 injury comes first.
Staging looks like a description of depth, but it decides the treatment. Moisture damage called Stage 2 receives wound care instead of continence and skin barrier care, an unstageable wound called Stage 3 risks the wrong decision about eschar, and a missed deep tissue injury stays under pressure. The NPIAP definitions already list what each stage is not, and checking a wound against that list takes less time than correcting a care plan built on the wrong stage.
Beeckman, D. et al. (2007) 'EPUAP classification system for pressure ulcers: European reliability study', Journal of Advanced Nursing, 60(6), pp. 682–691.
Beeckman, D. et al. (2010) 'Pressure ulcers and incontinence-associated dermatitis: effectiveness of the Pressure Ulcer Classification education tool on classification by nurses', Quality and Safety in Health Care, 19(5), e3.
Beeckman, D. et al. (2018) 'Towards an international language for incontinence-associated dermatitis (IAD): design and evaluation of psychometric properties of the Ghent Global IAD Categorisation Tool (GLOBIAD) in 30 countries', British Journal of Dermatology, 178(6), pp. 1331–1340.
Clinical Excellence Commission (2021) Incontinence Associated Dermatitis (IAD): Best Practice Principles. Sydney: NSW Health.
National Pressure Injury Advisory Panel (2016) NPIAP Pressure Injury Stages. Available at: npiap.com.
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