Skin and Wound Assessment Instruments

This group divides by what is being tracked. Risk prediction tools such as the Braden Scale identify people likely to develop a pressure ulcer, so that prevention can be started before there is anything to treat. Healing and status measures such as the Pressure Ulcer Scale for Healing and the Bates-Jensen Wound Assessment Tool track an existing wound over time. Classification systems such as the European Pressure Ulcer Advisory Panel categories describe depth and tissue involvement at a point in time and are not designed to measure change.

The dermatology instruments answer a different question again. The Psoriasis Area and Severity Index and the Eczema Area and Severity Index grade extent and severity by clinician assessment, while the Dermatology Life Quality Index asks the patient what the condition does to their life. The Patient and Observer Scar Assessment Scale is unusual in collecting both perspectives on the same scar in parallel.

Classification systems are frequently misused as outcome measures. Pressure ulcer categories describe tissue depth and are not a scale: a category 3 ulcer that improves does not become a category 2, because the classification is not reversible. Healing has to be measured with an instrument designed for it.

Clinician-rated severity indices carry a reliability cost. Area estimation by eye is the weakest component of both the psoriasis and eczema indices, and agreement between raters is only moderate. In multi-site studies this is managed with rater training and, increasingly, standardised photography. Patient-reported quality of life measures avoid the reliability problem and answer a different question, which is why both are usually collected.

Check that the instrument matches the task: risk, healing, or classification. Substituting one for another is the most common error in this area and produces results that cannot be interpreted.

Check the photographic and measurement protocol if wound size is an endpoint. Lighting, angle, distance and whether a scale marker is in frame all affect measured area, and without a fixed protocol the between-visit variation swamps the change being measured.

Check licensing on the dermatology quality of life instruments, several of which are commercially controlled with separate academic and commercial terms. Finally, record the anatomical site. Healing rates and the meaning of a given severity score both vary by site, and a heel and a sacral ulcer are not comparable observations.

Can pressure ulcer categories be used to measure healing?

No. The classification describes tissue depth at a point in time and is not reversible: a healing category 3 ulcer does not become category 2. Use a healing measure such as the Pressure Ulcer Scale for Healing instead.

What is the difference between a risk tool and an assessment tool?

A risk tool such as the Braden Scale predicts who is likely to develop a wound, so it is applied before there is one. An assessment tool describes a wound that already exists. They answer different questions and are not interchangeable.

How reliable are area-based severity indices?

Moderately. Estimating affected body surface area by eye is the least reliable component of both the psoriasis and eczema indices. Rater training and standardised photography improve agreement, and multi-site studies should plan for both.

Should I collect clinician severity or patient quality of life?

Usually both. They correlate imperfectly, and a condition covering a small body area can have a large effect on daily life. Reporting only clinician-rated severity misses the outcome patients care about most.