Cutting edge

July 9, 1999

Assessing patients' vulnerability to pressure sores is a major problem for the NHS. New research into the risks they face could help By the standards of most academic disciplines, nursing research is in its infancy. It is only in the past few years that nursing education has moved completely into the higher education sector and nursing schools have had to take account of national research agendas. In the past most nursing research was either about nurses or nursing students. What little research was carried out about nursing practice usually concentrated on the organisational management of care delivery rather than the care that was actually delivered.

Fortunately, with the help of the evidence-based practice agenda that is beginning to dominate all the National Health Service research funding agencies and the clinical governance policy drivers of the Department of Health, all this is beginning to change. Clinical nursing research is becoming the cutting edge of nursing research. Studies have revisited time-honoured areas of nursing concern: pressure sores, nutrition, wound care, continence and mobility. Re-examining these areas with a research eye has often led to challenging findings.

Take research into pressure sores. For many years pressure sores have been seen as a major problem in the NHS, not only because of the cost of treating them but also because of the personal suffering they cause. Pressure sore risk assessment tools have been developed to assess the vulnerability of patients and to direct the preventive resource to the right patient group. The number of pressure sore risk scales in existence is more than 17; however, the majority of these scales have not been subjected to rigorous scrutiny in terms of their reliability and validity.

Work carried out by myself and colleagues Bill Watson from the University of Northumbria and Margaret Cook, a staff nurse at Sunderland City Hospitals NHS Trust, illustrates the problems in this area. We designed a study to assess the inter-rater reliability of one of the most widely used pressure sore risk assessment scales in the UK - the Waterlow scale. Inter-rater reliability is an estimate of the degree to which two or more independent raters are consistent in their judgements and is an important part of the development of standard measuring instruments. Unfortunately, this work had never been carried out on the Waterlow scale. This scale consists of six sub-scales, each being allocated a risk score, and the total risk score is the sum of all the sub-scale risk scores. The total score indicates the degree of risk facing that person with regard to his or her potential to develop pressure damage. The higher the score, the greater the risk.

Our study assessed the inter-rater reliability of the Waterlow scale as it was used in clinical practice. While a number of methods are available to measure inter-rater reliability, this study called for the use of two methods: percentage of agreement and median correlation. We found a wide variation in the scores that a number of nurses gave to the same patient. In some cases patients' scores could vary from "not at risk" to "very high risk", even though the patient's actual condition remained unchanged. The problem with this is that if pressure sore prevention resources are allocated on the basis of risk score, then the variability in scores has implications for the assessment of the effectiveness of the tool as well as financial implications for resource use.

To an extent, increasing the training of nursing staff in the use of the assessment tool will lead to improvements in its inter-rater reliability. However, to date there has been an assumption within nursing that pressure sore assessment tools are self-explanatory and therefore little training in their use is needed. Our research therefore has considerable implications for practice and education alike.

Claire Hale is head of the division of nursing and professor of clinical nursing at the University of Leeds.

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