**Design and validation of a double-burden mid-upper arm circumference (MUAC) tape for South African children aged six to 24 months**
S. McLaren1, L. Steenkamp2, HD. McCarthy1
1. School of Human Sciences, London Metropolitan University, London, N7 8DB; 2. HIV and AIDS Research Unit, Nelson Mandela University, Gqeberha
The nutritional double burden of disease refers to a concurrent high prevalence of under- and overnutrition affecting many low and middle income countries (LMICs)(1). Mid-upper arm circumference (MUAC) and weight-for-height (WHZ) are used to identify children with severe acute malnutrition(2). However, current MUAC and WHZ cut-offs endorsed by the WHO show poor levels of agreement among different childhood populations(3), including South African children(4). Therefore, alternative MUAC cut-offs have been proposed, achieving improved agreement (5,6). Additionally, there is current interest in MUAC as a screening tool for overweight and obesity(7). Resources in LMICs, including equipment and personnel, are shared between under- and over-nourished children. Therefore, the aim of this study was to validate alternative MUAC cut-offs for South African children between six and 24 months old.
Data from 348 young children (aged between 6 and 24 months) were collected from community clinics and creches. Ethics approval (ref. no H15-HEA-DIET-003) and gatekeepers’ permission was obtained. Using WHZ categories defined by WHO(2) as the reference, MUAC cut-offs were proposed to define categories of nutritional status. Sensitivity, specificity, positive predictive value (PPV), negative predictive values (NPV) were calculated. The association between MUAC category and WHZ category allocation defined by the proposed MUAC cut-off values was assessed using a chi-square test, with Cramer’s V used to determine the strength of the association and a Kappa test to determine the level of agreement between the two indicators. Analyses were conducted using SPSS v25.
The mean age was 13.57 months (SD, 5.34) and 49.8% of the sample was male. Mean MUAC=15.32 cm (SD, 1.04) and mean WHZ=0.50 (SD, 0.99). WHZ ranged from -3.2 to 4.57.
MUAC<13.0 cm had a sensitivity of 100% and specificity of 99.1% (PPV=0.25, NPV=1.0) for WHZ<-3. MUAC between 13.1 and 13.8 cm had a sensitivity of 100% and specificity of 95.6% (PPV=0.117, NVP=1.0) for WHZ<-2. MUAC between 16.5 and 16.9 cm had a sensitivity of 11.1% and specificity of 86.8% (PPV=0.111, NPV=0.868) for WHZ>+2. MUAC>17.0 cm had sensitivity of 90.9%, specificity of 80.1% (PPV=0.235, NPV=0.992) for WHZ>+3. There was a significant agreement between MUAC and WHZ (Kappa= 0.255; p<0.001). There was a significant association between the proposed MUAC cut-off values and WHZ categories (Pearson Chi square = 233.52; df=16; n=348; p<0.001).  This association is strong (Cramer’s V= 0.410; p<0.001).
The double-burden MUAC tape proposed has potential for reducing resource requirements for screening for both under- and overnutrition in a South African context. Despite the poor performance of the tool for identifying overweight, it has a high sensitivity and specificity for acute malnutrition and obesity. These preliminary results are encouraging, but further research is warranted using a larger independent sample with a range of states of nutrition as well as against clinical outcomes.
References
1. UNICEF, World Health Organisation, World Bank Group (2021). _Joint child malnutrition estimates, key findings of the 2021 edition_.
2. WHO (2013). _Guideline: Updates on the management of severe acute malnutrition in infants and children_. Geneva, World Health Organization
3. Grellety E, Golden MH (2016) _BMC Nutr_ 2, 10.
4. McLaren SW, Steenkamp L, Venter D (2017) _S Afr J Clin Nutr_ 30:4, 118-119.
5. Laillou A, Prak S, de Groot R, et al. (2014) _PLoS ONE_ 9(7): e101159.
6. Tessema M, Laillou A, Tefera A, et al (2020) _PLoS ONE_ 15(4): e0230502.
7. Talma H, van Dommelen P, Schweizer JJ, et al (2019). _Arch Dis Child_** **104: 159-165.

Design and validation of a double-burden mid-upper arm circumference (MUAC) tape for South African children aged six to 24 months

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