New insights on the use of mini nutritional assessment: Impact of alternative calf circumference cutoffs

Abstract

Background & aims: The Mini Nutritional Assessment - Short Form (MNA_SF) is an easy, quick, and validated tool for screening and diagnosing malnutrition among older individuals. Despite its clinical relevance, using body mass index (BMI) and a universal calf circumference (CC) cutoff might pose limitations. Therefore, our study aimed to investigate the potential of using sex-specific and BMI-adjusted CC cutoff values within the MNA-SF to classify nutritional status and assess its prognostic significance.

Methods: Older patients hospitalized with varied diagnoses were included. BMI and CC measurements were conducted by registered dietitians. MNA-SF, which considers either BMI or CC, was utilized to classify nutritional status. Patients scoring 0-7 points were classified as malnourished. Four different approaches for MNA-SF were considered: Traditional: i) using BMI, ii) the alternative/surrogate using a non-sex specific CC < 31 cm; Newly adapted approaches: iii) using sex-specific CC cutoff values ≤ 34 cm for men and ≤33 cm for women, without BMI adjustment factors; iv) using sex-specific BMI-adjusted CC cutoff values ≤ 34 cm for men and ≤33 cm for women. BMI adjustment factors were: -3 cm of CC for BMI 25-29.9 kg/m², -7 cm for BMI 30-39.9 kg/m², and -12cm for BMI ≥40 kg/m². The prevalence of nutritional categories across different MNA-SF approaches was estimated. Cox regression analysis and Receiver Operating Characteristic (ROC) curve analysis were performed to evaluate and compare their predictive significance for overall survival.

Results: This study included 242 patients (58.8 % men, median age of 68 years, interquartile range: 64 to 74). Cancer was the most frequent reason for hospitalization (36.6 %). Scores in MNA-SF were significantly lower when using sex-specific unadjusted & BMI-adjusted CC. The frequency of malnutrition ranged from 21.9 % (MNA-SF using BMI) to 41.7 % (MNA-SF_{adj.CC≤34/33}). The incidence of mortality was significantly higher among malnourished patients classified using the sex-specific unadjusted (58.2 %) and BMI-adjusted CC approaches (63.3 %), compared to 38.2 % and 40 % when using BMI and the non-sex-specific CC < 31 cm, respectively. All approaches had similar survival prediction (area under the ROC curves 65-67 %), and were independently associated with mortality. Using BMI-adjusted CC with sex-specific cutoff values (≤33/34) within the MNA-SF significantly improved survival prediction sensitivity (63.6 % versus 38.2 % with BMI and 40 % with CC < 31). Malnourished patients classified by MNA-SF using sex-specific and BMI-adjusted CC cutoff values ≤ 33/34 exhibited the highest risk of mortality based on hazard ratios, compared to those classified by MNA-SF using BMI or CC < 31.

Conclusion: Our study demonstrates that using sex-specific, unadjusted, and BMI-adjusted CC cutoffs values within MNA-SF classified a greater number of patients at risk of or already experiencing malnutrition, as well as a higher incidence of mortality among malnourished individuals. These methods showed greater sensitivity and achieved a more balanced trade-off between sensitivity and specificity compared to traditional approaches (using BMI or CC < 31). Pending future validation, these approaches have potential to offer a more reliable alternative for assessing nutritional status and improving prognostication in this population.

Keywords: Aging; Body mass index; Calf circumference; MNA adjusted; Malnutrition; Survival.