Can we use mid upper arm anthropometry to detect malnutrition in medical inpatients? A validation study

Background and aims Mid upper arm anthropometry (MUAA) is often used as a measure of nutritional status to detect changes in body composition. The aim of this study was to investigate the reliability and validity of MUAA including mid arm circumference (MAC) and triceps skin fold thickness (TSFT) to determine the usefulness in clinical practice. Method We measured MUAA in 158 consecutive admissions along with subjective global assessment (SGA) and body mass index (BMI). Inter- and intra-rater reliability was evaluated in an additional 50 patients. Results The sensitivity and specificity of MUAA < 5th percentile was compared with SGA and BMI. MAC and TSFT had a low sensitivity and a high specificity with low positive predictive values when compared with criterion values which were BMI <= 18 and SGA-C. The intra-class correlation coefficient for inter- and intra-rater reliability for MAC were 0.98 (95% CI 0.96-0.98) and 0.99 (95% CI 0.98-0.99) respectively and for TSFT were 0.97 (95% CI 0.91-0.97) and 0.98 (95% CI 0.95-0.98) respectively. Conclusion MUAA < 5th percentile had a high specificity but low sensitivity when compared with indicators of malnutrition. Although MUAA could be reliably measured, it has poor validity and is thus unlikely to be a good predictor of clinical outcome. Percentiles based on healthy populations do not generalize well to the individuals seen in clinical practice.