BACKGROUND: Undernourished people have an increased risk of premature mortality from both infectious and non-communicable diseases. Aside from screening purposes, assessment of nutritional status is a useful tool in management and evaluation of various chronic diseases. Body-Mass-Index (BMI) is today the most commonly used marker of nutritional status however, this method presents a challenge in many low resource settings and immobile patients. Mid-upper arm circumference (MUAC) is another anthropometric measure that requires minimal equipment and little training. So far, MUAC cutoffs for undernutrition are well established in children < 5 years but there is still no consensus for a specific cutoff in adults. The objective of this study was to compare MUAC with BMI and suggest a MUAC cut-off corresponding to a BMI of 18.5 kg/m2 to identify underweight in adults.

METHODS: A cross-sectional study was conducted at two urban public hospitals in Nepal. The following variables where collected: MUAC, weight, height, sex, age and self-reported medical history.

EXCLUSION CRITERIA: < 19 years of age, pregnancy and oedema. Sensitivity and specificity for a MUAC value corresponding to BMI < 18.5 was calculated. ROC analysis was performed for male and female as well as Pearson's correlation of MUAC and BMI.

RESULTS: A total of 302 people between 18 and 86 years of age, 197 women and 105 men, were included. Of these, 90 people suffered from rheumatic heart disease. MUAC was highly correlated with BMI in both women r = 0.889 and men r = 0.846. Best statistically derived MUAC cutoff corresponding to a BMI < 18.5 kg/m2 was 24.5 cm (Youdens Index = 0.75; sensitivity 92.86; specificity 82.48), with high predictive value (AUROCC> 0.9). The setting based optimal MUAC cutoff was also 24.5 cm. No considerable variation was found in sex- and disease specific subgroups.

CONCLUSION: MUAC is strongly correlated with BMI in adults in Nepal. For simplicity, a MUAC of 24.5 cm is the optimal statistically and setting based cutoff in both women and men to identify underweight (BMI < 18.5 kg/m2).