Methodological issues in the development and use of instruments to assess patient nutritional status or the level of risk of nutritional compromise

This paper presents the results of an appraisal of the evidence for the effectiveness of methods of nutritional assessment currently in use by nurses and from this develops concepts which may be applied to many areas of nursing practice. The paper first shows how the approach to nutritional assessment by nurses has changed over time, producing the present search for methods which are relatively quick and easy to use. It then describes the limited nature of the evidence of effectiveness of these methods and considers the reasons for this situation. It suggests that the difficulty of validation is an important factor and describes the three most common approaches to validation, showing how problems arise from lack of clarity in the definition of terms and the assumption of a simple relationship between the level of risk of nutritional compromise and actual nutritional status. In conclusion, it is suggested that these difficulties illustrate principles applicable to many areas of nursing care, and a definition of 'segments' of care processes, each with well-defined purposes and outcome measures, is proposed. Such an approach will help to demonstrate the complexity and value of nursing activity.