Performance of alternative measures to body mass index in the assessment of moderate and severe under-nutrition among acutely unwell patients hospitalized in a TB ward in the Philippines: A cross-sectional study.

Laura V White,Sharon E Cox,Nathaniel Lee,Naomi R Saludar,Tansy Edwards,Flora P Marin

doi:10.1371/journal.pone.0215968

Abstract

Body mass index (BMI) kg/m2 is a key screening tool for under-nutrition in adults, but difficult to obtain in immobile or unwell patients, particuarly in low resource settings, due to inability to accurately measure both weight and height. Mid-upper arm circumference (MUAC) is used to assess under-nutrition in children under 5 years but no standardised cut-off values exist for adults. In a cohort of adult Filipino patients admitted to a tuberculosis ward we assessed (i) cut-offs for MUAC to predict moderate under-nutrition (BMI <17kg/m2), (ii) the performance of limb lengths to predict height and; (iii) associations of body fat percentage from skinfolds and hand grip-strength with BMI. In 303 patients with MUAC and BMI at admission, aged 18–80 years (mean = 45.5, SD:14.8), BMI ranged from 11.2–30.6 kg/m2 and 141 (46.5%) had BMI <17.0 kg/m2. Using receiver operator curves, MUAC cut-offs were identified as <20.5cm for males (sensitivity: 89%, specificity: 84%) and <18.5cm for females (sensitivity: 91%, specificity: 89%), for BMI<17.0 kg/m2. Using published equations, knee height had the lowest mean difference between predicted and measured heights compared to ulnar or demi-span: (-0.98 cm, 95% CI: -1.51/-0.44). Both grip-strength and body fat percentage were positively associated with BMI, in separate linear regression models with exposure-age-sex interactions (adjusted-R-squared values: 0.15, 0.66, respectively). MUAC can predict moderate acute under-nutrition with high positive predictive value. Further research is required to determine the performance of alternative measures to BMI to predict mortality or adverse outcomes in acutely unwell patients.

Highlights

Under-nutrition is a common risk factor for mortality among hospitalized patients [1] in both low and high resource settings
The primary analysis was to demonstrate the association between Mid-upper arm circumference (MUAC) and body mass index (BMI) and cut-off values for MUAC best corresponding to a BMI classification of under-nutrition (BMI
BMI was available for 303 (87%) of 348 enrolled patients who survived to day 3 of admission (Fig 1) of whom 69.5% were male and 9.2% were aged more than 65 years (Table 1)

Summary

Introduction

Under-nutrition is a common risk factor for mortality among hospitalized patients [1] in both low and high resource settings. Under-nutrition is associated with prolonged length of stay, increased likelihood of re-admission [2] and higher risk of infections [3]. Diagnosis and intervention for under-nutrition can result in reduced costs, morbidity and mortality [4, 5]. Screening for under-nutrition on admission, to identify patients at risk and those who require nutrition interventions should occur for all patients. Several ‘nutrition scores’ such as the subjective global assessment (SGA) and the malnutrition universal screening tool ‘MUST’ exist but rely on body mass index (BMI) to determine accurate risk classification [6]. BMI is widely used in nutrition screening, obtaining accurate weight or height measurements among severely unwell or immobile inpatients is often not feasible

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