Nutritional domains in frailty tools: Working towards an operational definition of nutritional frailty.

Different methods have been proposed for the assessment of the nutritional status in frailty phenotypes. In the present narrative review article, we have summarized the number and specifications of nutritional items in existing frailty tools, in order to develop a possible means of assessment and operational definition of the nutritional frailty phenotype. In six different databases until December 2019, we searched for original articles regarding frailty tools (i.e., scales, indexes, scores, questionnaires, instruments, evaluations, screening, indicators), analyzing each tool regarding nutritional items. We identified 160 articles describing 71 frailty tools. Among the selected frailty tools, 54 were community-based (70 %), 17 hospital-based (22 %), 4 validated in long-term care institutions for older adults (LTCIOA) (5.1 %) and 2 validated in both community- and hospital-based settings, including LTCIOA (2.5 %). Fifty-two of these tools (73 %) included at least one nutritional item. Twenty-two (42 %) reported two or more nutritional items. The items were grouped in the following categories: A) anthropometric measurements, B) laboratory measurements, and C) other nutritional-related measurements. Anthropometric measurements stood out compared to all other items. Nutritional items are included in the majority of frailty tools, strengthening the concept that they may have a direct implication on an increased risk of adverse health-related outcomes in frail subjects. This supports the development of the concept of nutritional frailty as an independent frailty phenotype. Subsequent steps will be to assess the contribution of each nutritional item to a possible operational definition of nutritional frailty and define the items that may best identify this new frailty phenotype.