(188) Body Mass Index Versus Mid-upper Arm Circumference: Can We Replace The Gold Standard?

Background: Body Mass Index (BMI) has long been used as a measure and predictor of health in the general population. For patients with cystic fibrosis (CF), it has been established as the gold standard for nutrition assessment due to an optimal BMI correlating with better lung function, measured by forced expiratory volume in one second (FEV₁). However, as in the general population, BMI use in CF patients has limitations, especially around lean body mass versus fat mass¹. The rise of obesity rates in CF prompted our investigation of a better predictor of nutritional status within the CF pediatric population². Mid-Upper Arm Circumference (MUAC) is an established measure of pediatric nutrition status and is a predictor of fat mass^3. In 2021, our care center began including MUAC measurements as a part of our nutrition assessment in pediatric CF patients. The objective of this study was to compare BMI and MUAC nutrition assessment methods within the CF pediatric patients.

Methods: An IRB approved, single center, retrospective analysis was performed on 87 patients, average age 10.71 +/- 4.25 years. Data were collected on BMI, MUAC and FEV1 from April 2021 to March 2022. Correlation was assessed between BMI Z- scores and MUAC Z scores and also with FEV1. Subsequent visit BMI, MUAC, and FEV1measurements were obtained in 34 patients.

Results: BMI Z- scores and MUAC Z- scores had statistically significant positive linear correlation. MUAC Z- scores identified more patients as malnourished compared to BMI Z- scores. At baseline visit, out of 75 CF patients who were identified as well-nourished via BMI Z- scores, MUAC Z- scores identified 12 out of those 75 (16%) as having either mild or moderate malnutrition (Cohen kappa statistic= 0.46 [95% CI, 0.27-0.65]). FEV1 did not differ significantly between those who were identified as well-nourished by both BMI and MUAC versus those who were identified as malnourished by MUAC only. FEV1 value from baseline visit was a better predictor of the FEV1 value at the subsequent visit regardless of BMI or MUAC at baseline visit.

Conclusions: Based on our review, these results lend support to prior evidence that MUAC values identify a greater number of patients as malnourished. However, due to the small sample size and retrospective nature of this review, a larger, multicenter study on MUAC as a nutrition assessment method in CF patients is necessary to determine correlation between MUAC and lung function.

Acknowledgements:

References: 1) Soltman S, Hicks RA, Naz Khan F, Kelly A. Body composition in individuals with cystic fibrosis. J Clin Transl Endocrinol. 2021 Oct 30;26:100272. doi: 10.1016/j.jcte.2021.100272. PMID: 34804808; PMCID: PMC8586800.

2) Kutney KA, Sandouk Z, Desimone M, Moheet A. Obesity in cystic fibrosis. J Clin Transl Endocrinol. 2021 Nov 17;26:100276. doi: 10.1016/j.jcte.2021.100276. PMID: 34868883; PMCID: PMC8626670.

3) Chomtho S, Fewtrell MS, Jaffe A, Williams JE, Wells JC. Evaluation of arm anthropometry for assessing pediatric body composition: evidence from healthy and sick children. Pediatr Res. 2006 Jun;59(6):860-5. doi: 10.1203/01.pdr.0000219395.83159.91. Epub 2006 Apr 26. PMID: 16641219.