Evaluating the concurrent validity of body mass index (BMI) in the identification of malnutrition in older hospital inpatients

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Ng, WL
Collins, PF
Hickling, DF
Bell, JJ
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2019
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Abstract

Background: Nutrition screening and assessment tools often include body mass index (BMI) as a component in identifying malnutrition risk. However, rising obesity levels will impact on the relevancy and applicability of BMI cut-off points which may require re-evaluation. This study aimed to explore the relationship between commonly applied BMI cut-offs and diagnosed malnutrition. Methods: Data (age, gender, BMI and Subjective Global Assessment (SGA) ratings) were analysed for 1152 inpatients aged ≥65 years across annual malnutrition audits (2011–2015). The receiver operation characteristic (ROC) curve analysed the optimal BMI cut-off for malnutrition and concurrent validity of commonly applied BMI cut-offs in nutritional screening and assessment tools. Results: Malnutrition prevalence was 36.0% (n = 372) using SGA criteria (not malnourished, moderate or severe malnutrition). Median age was 78.7 (IQR 72–85) years, median BMI 25.4 (IQR 21.8–29.7) kg/m2; 52.1% male and 51.2% overweight/obese. ROC analysis identified an optimal BMI cut-off of <26 kg/m2, 80.8% sensitivity and 61.5% specificity (AUC 0.802, 95% CI 0.773, 0.830; p < 0.0001). Commonly applied BMI cut-offs (between 18.5 and 23 kg/m2) failed to meet the alpha-priori requirement of 80% sensitivity and 60% specificity. However, BMI <23 kg/m2 had the highest agreement (κ = 0.458) with malnutrition diagnosed using the SGA. Conclusions: Both malnutrition and overweight/obesity are common in older inpatients. Continuing increases in the prevalence of overweight and obesity will impact on the sensitivity of BMI as a screening component for malnutrition risk. The current study suggests tools developed over a decade ago may need to be revisited in future.

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Clinical Nutrition

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38

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5

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Nutrition and dietetics

Science & Technology

Life Sciences & Biomedicine

Body mass index

Malnutrition

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Ng, WL; Collins, PF; Hickling, DF; Bell, JJ, Evaluating the concurrent validity of body mass index (BMI) in the identification of malnutrition in older hospital inpatients, Clinical Nutrition, 2019, 38 (5), pp. 2417-2422

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