Utility of Mid-Upper Arm Circumference in Diagnosing Malnutrition in Children With Cystic Fibrosis.

Background: Standardized diagnostic indicators for malnutrition using growth percentile z-scores (weight for length or body mass index [BMI]) and mid-upper arm circumference (MUAC) z-scores are being used in clinical practice; however, their application to the pediatric cystic fibrosis (CF) population is not well described. In this study, we aim to compare growth percentile z-scores and MUAC z-scores in diagnosing and classifying malnutrition in children with CF and assess the relationship between their degree of malnourishment and corresponding pulmonary function tests (PFTs).

Methods: In this retrospective observational outpatient study of 49 pediatric CF patients, data were collected on baseline characteristics, anthropometrics, and PFTs over 12 months. Agreement in malnutrition diagnoses was quantified by Cohen κ statistics. Pearson test assessed the correlation between MUAC and BMI z-scores as well as PFTs and anthropometrics. Serial anthropometrics and PFTs were obtained and compared for a subset of patients (n = 28).

Results: Growth percentile and MUAC z-scores were positively correlated in diagnosing malnutrition (Pearson correlation r = 0.87), but MUAC z-scores identified more patients as malnourished compared with growth percentile z-scores (49% vs 12%, Cohen κ of 0.22 [95% CI, 0.04-0.40]). There was no significant relationship between anthropometrics and PFTs. MUAC z-scores increased significantly over time, but BMI z-scores did not show this trend.

Conclusions: Our small-scale data suggest a promising role for MUAC z-scores in classifying malnutrition and in measuring changes in nutrition status over time in pediatric CF.