(210) Mid-Upper Arm Circumference in Children with CF: Changes Seen with Highly Effective Modulator Therapy

Background: Highly effective triple modulator therapy (elexacaftor-tezacaftor-ivacaftor) [ETI] has dramatically changed the clinical course for people with cystic fibrosis (CF) with recent clinical trials suggesting positive impact on nutrition for most children and adults using the modulators [1,2]. Our previous study has shown that mid upper arm circumference (MUAC) is a more sensitive indicator of nutritional status in children with CF, with more being diagnosed as malnourished while using MUAC compared to standard anthropometric measures such as body mass index (BMI) or weight for length (WFL) z scores [3]. In this is study, we aimed to assess the impact of highly effective modulators on MUAC in children with CF.

Methods: In this single center retrospective chart review study, we compared the anthropometrics, MUAC z sores and BMI/WFL z scores, as well as lung function measures (Forced expiratory volume in 1 second, FEV₁) before and after taking the ETI in children between 6 and 18 years of age between January 2020 and March 2022. Children with complete sets of nutrition and spirometry within 6 months pre- and post- the introduction of ETI were included. Children who were non-adherent with modulators were excluded.

Results: 15 children with an average age of 10.6±2.6yrs were included. 33% were female, and only 4 children had double delta F508 mutations. 4 patients were on other modulators prior to introduction of ETI. Growth percentile z scores and MUAC z scores were positively correlated in diagnosing malnutrition (Pearson’s correlation r = 0.80 and 0.84 respectively) before and after introduction of modulators. MUAC z scores identified 6 patients as malnourished whereas growth percentile z scores identified 4 patients as malnourished (40% vs. 26.7%). No patients moved from malnourished (6/15) to well-nourished with ETI therapy with a median follow up between measurements of 6.3 months. Of the 6 patients in the malnourished category based on MUAC z score, 3/6 remained in the mild malnourished, 2/6 improved from moderate to mild malnourished and 1/6 patient worsened from mild to moderate malnourished. Out of 4 children (4/15) in the malnourished category based on the BMI/WFL z scores, one patient moved from mild malnourished to well-nourished, 2 remained in the same category. One worsened from mild to moderate malnourished category in both BMI/WFL and MUAC z score group. FEV₁ improved by at least 10% in 6/15 patients and remained stable in rest of the patients. We did not observe any significant correlation between anthropometrics and lung function metrics.

Conclusions: Our data suggests that MUAC z scores are more sensitive in classifying malnutrition in children with CF. Highly effective modulators stabilize or improve lung function quickly, but nutritional status may take longer to improve. Close monitoring of nutritional status using MUAC in addition to standard anthropometrics has added utility in monitoring and addressing nutrition on ETI therapy.

Acknowledgements: Audrey Chikalla, Rachel Phong

References: [1] Bass R, Brownell J, et al; The Impact of Highly Effective CFTR Modulators on Growth and Nutrition status. Nutrients 2021; 13: 2907.



[2] Petersen M, Begnel L, et al.; Effect of elexacaftor-tezacaftor-ivacaftor on body weight and metabolic parameters in adults with cystic fibrosis. Journal of Cystic Fibrosis 2022; 21: 265-271.

[3] Phong R, Taylor S, et al; Utility of Mid-Upper Arm Circumference in Diagnosing Malnutrition in Children with Cystic Fibrosis. Nutr. Clin Pract 2020; 35(6): 1904-1100.