This article outlines the significance of pressure ulcers (PUs) and the importance of PU risk assessment tools (PURATs). The National Wound Care Strategy Programme (NWCSP) recommendation (NWCSP, 2023) to use the Pressure Ulcer Risk Primary Or Secondary Evaluation Tool (PURPOSE-T), developed by the Clinical Trial Research Unit (CTRU) at the University of Leeds, is discussed (Nixon et al, 2015; CTRU, 2019).
The NWCSP (2023: 2.2) stated:
‘Everyone receiving care from a health or care professional should be screened for pressure ulcer risk using the PURPOSE-T tool, or other validated risk assessment tool that, as a minimum, contains the same risk factors.’
In this article, the validity and reliability of the PURPOSE-T is critically analysed, and recommendations made regarding its implementation and the importance of the risk assessment informing patients' PU prevention care plans.
Context
PUs are defined by the European Pressure Ulcer Advisory Panel (EPUAP), the Pan Pacific Pressure Injury Alliance (PPPIA) and the National Pressure Injury Advisory Panel (NPIAP) (2019: 16) as:
‘Localized damage to the skin and/or underlying tissue, as a result of pressure or pressure in combination with shear. Pressure injuries usually occur over a bony prominence but may also be related to a medical device or other object.’
The prevalence of PUs is reported to be about 12.8% globally (Li et al, 2020) and they have a significant impact on the individual, affecting the person physically, emotionally and socially (Gorecki et al, 2009). Further studies reported the impact of PUs relating to three areas, in terms of the patient's anxiety around the PU, the health professional and the care delivery environment (Gorecki et al, 2012). Importantly, those with PUs have an increased risk of infection, prolonged hospitalisation and increased mortality (Young, 2021). Indeed, in a systematic review of articles published over the past 15 years on the impact of PUs, Roussou et al (2023) identified 14 studies and concluded that PUs affect patients' quality of life, especially at a psychological level.
PUs complicate the patient's general health condition and significantly influence their dependency on their supportive environment and health services, with reduced autonomy, increased insecurity and decreased mental wellbeing.
PUs have a significant financial as well as individual personal cost, and Dealey et al (2012) stated that, in the UK alone, the mean cost of healing per patient ranged from £1214 for category 1 pressure damage (non-blanchable erythema) to £14 108 for category 4 (full-thickness tissue loss with exposed muscle, tendon or bone). Guest et al (2017) estimated that the annual cost of PUs in the UK is £531.14 million. It would be appropriate to assume that the costs would be significantly higher today.
Thus, PUs remain a significant clinical and financial concern and there is a recognised desire to reduce the incidence as well as the clinical and financial cost of PUs, as outlined in a NWCSP document (2018). Coleman et al (2018) observed that, in clinical practice, structured risk assessment remains a key component of PU prevention and treatment. NHS Resolution (2022) has attributed this financial burden to the lack of standardised PU risk assessment.
The National Institute for Health and Care Excellence (NICE) (2014) identified the importance of undertaking a PU risk assessment (PURA) using a PURA tool (PURAT). Similarly, this is recognised by the EPUAP, NPIAP and PPPIA (2019). However, it has been noted that there is no evidence that the use of risk assessment scales decreases pressure ulcer incidence (Pancorbo-Hidalgo et al, 2006; Moore and Patton, 2019).
Pressure ulcer risk assessment
PURATs have been developed to enable clinicians to predict the risk of individuals developing PUs. These tools traditionally use checklists and numerical scores that categorise patients into low, medium, or high risk (Norton et al, 1975; Waterlow, 1985; Bergstrom et al, 1987). Although Kottner and Balzerb (2010) identified more than 100 risk factors described in the literature, NICE (2014) described the main risk factors as significantly limited mobility, significant loss of sensation, inability to reposition independently, significant cognitive impairment, an existing or previous PU and malnutrition. Therefore, developing PUs involves a complex interplay of factors (Coleman et al, 2013).
Importantly, the plan of care must be individualised according to the risk and based upon the specific areas in the risk assessment where a need is identified. This can assist clinicians in making decisions to reduce or manage those risks; for example, an inadequate nutritional intake should initiate care planning that specifically includes how to manage this aspect. Thus, PURATs are made up of risk factors that are used to identify patients who are susceptible to developing a PU, enabling health professionals to exclude those not at risk and implement specific care for those who are at risk. The PURAT facilitates the development of appropriate care plans that support an individualised and evidence-based approach to preventive interventions and care. The overall aim is to identify people who are at risk of developing a PU and the level of risk.
Although it has been argued that many risk factors may contribute to developing a PU, primary factors indicate that certain groups are at greater risk of developing PUs (Moore and Cowman, 2008; 2012). Coleman (2013) recognised that there are only three factors that are of significance for developing a PU: mobility/activity, impaired perfusion and an existing or previous PU.
The PURPOSE-T
The development of the PURPOSE-T (Coleman et al, 2016) comprised five phases:
PURPOSE-T is described as an evidence-based PURAT that has been developed using robust research methods (Fletcher, 2023) and is currently recommended as best practice by the NWCSP (2023). Thus its clinical implementation is increasing.
The PURPOSE-T identifies individuals with existing PUs, as well as those individuals with no risk who can be quickly screened out (Coleman et al, 2018). This approach enables individuals in any setting to be assessed or screened, allowing the health professionals to make informed and appropriate decisions about their care.
PURPOSE-T: a three-step assessment process
Step 1: screening
This step allows the clinician to assess the patient and, if no risk is identified, no further risk assessment needs to be undertaken. This is extremely useful clinically because this process is quick to complete and can therefore be used across a range of settings where patients are seen for only a short period of time. The screening comprises assessment of:
The PURPOSE-T guidance recommends that the skin assessment is conducted and documented in those patients identified as being at risk of developing a PU and requires a description of the skin in both the screening and assessment phases (Fletcher, 2013). Top tips for assessing dark skin tone are discussed by Black and Simende (2020) and a best practice statement (Wounds UK, 2021) discusses PUs in dark skin tones.
Clinical judgement is required at this stage in differentiating between normal skin, vulnerable skin, those with a medical device in place and those with an existing PU. The terms ‘normal’ and ‘vulnerable’ to describe the skin requires knowledge of common skin states such as dry, paper-thin or moist, as well as a range of medications that affect the skin, including steroids, plus common skin conditions such as eczema, because clinicians are required to determine the differential diagnosis. Additionally and importantly, clinicians are encouraged to consider skin tone because early signs of pressure damage are less obvious and historically have not been identified (Wounds UK, 2021).
The third element of the screening is the use of clinical judgement to highlight any other risk factors that significantly affect the individual. If there is no score in this area, then no further risk assessment is recommended. Consequently, it is crucial to ensure accuracy in all three aspects of the screening.
Step 2: full assessment
This step requires nine sections to be completed and includes a range of options for each. The categories are:
Clinical judgement is required to complete step 2 and there is also the option for no problem being identified. There are colour-coded tick boxes:
Step 3: assessment decision
The assessment decision is based on the findings in step 2 and is colour coded, but is also subject to clinical decision making. The clinician should identify the colour boxes in step 2. If yellow or blue boxes only have been recorded, the number of boxes from each colour and clinical judgement will determine whether the patient is ‘at risk’ or ‘not currently at risk’ of developing a PU. If orange boxes have been ticked, the patient is at risk and the primary prevention pathway should be followed. If any pink boxes are recorded, the patient should follow the secondary prevention and treatment pathway. These lead to the assessment decision box:
Box 1 demonstrates the use of the PURPOSE-T.
Hypothetical case study using the PURPOSE-T
Mary Jones (not a real person), aged 81, was admitted to a medical ward via the hospital emergency department (ED) with flu, which had led to breathing difficulties. The following is a hypothetical use of the PURPOSE-T.
Step 1. Screening
These results would lead to yellow boxes being ticked on the PURPOSE-T, meaning Mrs Jones was potentially at risk of developing a pressure ulcer. The nurse would then progress to a full assessment.
Step 2. Full assessment
Taking these results into consideration, an assessment decision could then be made
Step 3: Assessment decision
As two orange boxes had been ticked, Mrs Jones would be assessed as having no pressure ulcer but to be at risk of developing one. She would require the primary prevention pathway.
Validity and reliability
Clinical decision making should be based on the best and most up-to-date research evidence (Abu-Baker et al, 2021). Understanding this concept in terms of a valid and reliable PURAT can support sound clinical decision making and improve patient outcomes (Majid et al, 2011; Siedlecki and Albert, 2017).
Traditionally, the evidence supporting the use of PURATs has been demonstrated to be poor, and their use has been reported to be ineffective, leading to a lack of efficient interventions for most patients (Schoonhoven et al, 2002; Pancorbo-Hidalgo et al, 2006; Coleman et al, 2013). Coleman et al (2013) found there is a lack of consensus on the reliability and validity of PURATs, suggesting that there is often an over-prediction of risk. Indeed, Coleman et al (2016) noted that the variation in the development methods of PURATs has led to the inconsistent inclusion of risk factors and thus concerns about content validity.
The value of any PURAT is how accurately it does what it purports to do. It is essential for it to measure what it was intended to measure and for users to know how accurate the data or results are (Charalambous et al, 2018; Ahmed and Ishtiaq, 2021). It is therefore essential to consider both the validity and reliability of the PURPOSE-T.
Validity
PURPOSE-T could be assessed as having face validity because, on the face of it, it would appear to assess the probability of an individual developing a PU (Charalambous et al, 2018; Wynn and Holloway, 2019). This face validity can be useful to help inform a health professional's clinical judgement, which has been recognised as being equally as effective as using a PURAT (Moore and Patton, 2019). Although this is likely to help with compliance, mainly because of the ease with which the tool can be used (Bannigan and Watson, 2009), face validity is deemed as low evidence of a quality validity tool.
Content validity of a PURAT is concerned with how well a measurement tool covers important parts of the health components to be measured and whether all aspects that are relevant have been considered (Coleman, 2013). The content validity of PURATs has been found to be poor because many do not agree on what the risk factors are, as has been demonstrated by Coleman et al (2013).
Coleman et al (2013) initially conducted a systematic review of primary research that identified risk factors independently predictive of PU development in adult patient populations. They concluded that overall, there was no single factor that led to the risk of developing a PU but that it was the ‘interplay’ of the risk factors that increased the risk. A better understanding of these risk factors would enable clinicians to identify patients at high risk of developing a PU and thus preventive measures could be targeted at individuals more appropriately, leading to effective use of resources both clinically and financially (Coleman et al, 2013). In a systematic review (Coleman et al, 2013) 54 625 abstracts were identified but only 54 met the study's criteria, with a total of seven studies considered high quality, based on the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement (2025). The small number of studies alone highlights the need for an alternative evidence-based PURAT for clinicians to be reassured that they are basing decisions around care on evidence-based practice as advocated by NICE (2014). Coleman et al (2013) argued that this review indicated the need for the development of a conceptual framework to bring together epidemiological, physiological, and biomechanical evidence.
The development of the PURPOSE-T was based on a five-fold approach as previously discussed. The consensus approach demonstrated good content validity as compared to other tools whose authors developed them based on their individual perceptions of the key factors surrounding PU development.
Criterion validity is an important aspect of determining whether a PURAT has diagnostic accuracy at predicting an outcome that is expected by comparison to other available PURATs. Although PURPOSE-T is recommended by NWCSP, there is currently no gold standard PURAT for comparison, and it is estimated that there are approximately 40 different PURATs available to clinicians to access (Kottner and Balzer, 2010).
This lack of a gold standard PURAT may lead to clinicians relying on their clinical judgement or opinion when assessing PURPOSE-T's convergent validity. Convergent validity (sometimes known as congruent validity) – a sub type of construct validity – tests whether constructs that are expected to be related are in fact related. This means that the PURPOSE-T should not be relied on in isolation and it would be prudent to use other forms of reliability tools alongside it to strengthen the reliability overall. There is no other tool like PURPOSE-T neither are any other PURATs the same (Coleman et al, 2018; Wynn and Holloway, 2019).
Predictive validity is concerned with sensitivity and specificity (Swift et al, 2020). Predictive validity measures how well a tool can predict future outcomes and relies on sensitivity (true positives) and specificity (true negatives). Ethical dilemmas can arise when trying to get conclusive results, for example false positives (high sensitivity/low specificity) can lead to over-diagnosis and/or unnecessary interventions and false negatives (high specificity/low sensitivity) might miss critical factors leading to delays in treatments or prevention measures. However, adopters of the PURPOSE-T (Clough, 2015; Hultin, 2022a) demonstrated that it contributed to a decrease in PU incidence in their clinical areas, which could be argued to demonstrate a high sensitivity in identifying patients at risk of PU injury.
Overall, although the development of a robust evidence-based PURAT is undoubtedly useful, PURATs have been found to be unable to predict the causality of pressure damage or have an impact on the incidence or severity of PUs (Pancorbo-Hidalgo et al, 2006; Moore and Patton, 2019).
Reliability
Reliability is defined as the consistency of a method in measuring something, that is to say if the same result can be obtained consistently by applying the same methodology in similar conditions (Siedlecki and Albert, 2017; Ahmed and Ishtiaq, 2021). Coleman et al (2018) evaluated the inter-rater reliability and the test-retest reliability of the PURPOSE-T, to understand whether it is consistent when used over time. The method applied to determine the inter-rater and test-retest reliability was Cohen's kappa, which is the preferred statistical measure for when two or more raters both apply a criterion based on a tool, in this case PURPOSE-T (McHugh, 2012).
Coleman et al (2018) found good inter-rater reliability, which was tested using a simple kappa score (0.71) and weighted kappa score (0.76) for the assumption that all the nurses would use the PURPOSE-T in a similar way. Coleman et al (2018) also determined that test-retest reliability was very good. They found agreement in the baseline and follow-up assessments using PURPOSE-T to be 92%. Using both a simple kappa score (0.87) and a weighted kappa score (0.89) they also attempted to minimise recall bias from clinicians by ensuring there was sufficient time between test and retest, recording a mean average of 3 days (Coleman et al, 2018).
It is interesting that Coleman et al (2014) identified three direct causal factors of PU: immobility, skin/PU status and perfusion but the inter-rater reliability of the three: immobility, perfusion and sensory perception, were moderate on the kappa score (0.41-0.6). This could suggest a lack of clinical knowledge by the clinicians when completing the PURAT or problems with its usability.
Implementation of PURPOSE-T
The PURPOSE-T and several resources are available via the registration page (CTRU, 2025) (https://ctru.leeds.ac.uk/purpose/purpose-t/) and includes the following:
A study evaluating the feasibility of implementing an electronic version of PURPOSE-T was published by Hultin et al (2022b). The research, involving 30 nursing staff, was undertaken in a Swedish hospital ward. Importantly, more patients were identified as being at risk and more nursing interventions were prescribed compared to the previously used PURAT. The focus group (n=23) identified that all staff were satisfied with the PURPOSE-T. A limitation to this study was the small number of participants, highlighting the need for further studies.
Discussion
It is estimated that there are approximately 40 different PURATs available to clinicians to access (Kottner and Balzer, 2010). Thus, it is imperative that standardisation is achieved if clinicians are able to articulate what good care looks like in this area (Moore and Patton, 2019; NWCSP, 2023). However, comparing any new PURAT against a gold standard is impossible because no gold standard exists among the PURATs available. This may be due to the lack of consensus around their development (Black et al, 1999).
Empirical evidence supporting the validity of PURPOSE-T appears stronger than that of other PURATs; however, PURPOSE-T has only been validated for use in the general adult populations and not in children, critically unwell patients or psychiatric populations. Therefore further evaluations would be needed to determine whether this PURAT is the gold standard and thus to be recommended as the primary PURAT in clinical practice.
A practical difficulty that may be encountered is adapting the PURPOSE-T to the electronic patient record when other tools are already historically embedded (Fletcher, 2023). Furthermore, the guidance around its implementation at a national or even international level have not yet been agreed, thus this may have an impact on the usability of the PURAT in clinical practice both now and in the future (Moore and Patton, 2019; Hultin et al, 2022a; 2022b).
Conclusion
The development of PURPOSE-T was based on a systematic review of the evidence, involved national and international experts, pre-testing and field testing, and was undertaken in partnership with service users. Clinicians seeking to adopt PURPOSE-T in their clinical area would greatly benefit from clear strategy guidance and access to early adopters to support its implementation. Importantly, early adopters have a unique opportunity to gather data on patient outcomes to demonstrate its clinical benefit.