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McLaren, Shawn, Steenkamp, Liana and Venter, Danie (2017) Use of Mid Upper-Arm Circumference (MUAC) as screening tool in an urban township in the Eastern Cape: rationale for testing changed cut-off values to identify malnutrition. South African Journal of Clinical Nutrition, 30 (4). pp. 118-119. ISSN 1607-0658
Introduction
Children with a weight-for-height z-score (WHZ) < -3 standard deviations (SD) of the World Health Organisation (WHO) standard for children less than 60 months of age have a higher mortality compared to children with a WHZ > -3 SD of this standard. The WHO therefore recommends the use of a WHZ of below -3 SD to identify children with SAM.
The mid-upper arm circumference (MUAC) cut-off values of 11.5 cm and 12.5 cm are used globally as screening tools to identify SAM and MAM, respectively, in children between six and 60 months of age. According to the WHO and UNICEF the WHZ and MUAC may be used interchangeably as a screening tool to identify malnourished infants and children, as they reveal a very similar prevalence of SAM in the field. However, more recent data indicate that there may be little overlap between the children identified with SAM and MAM by WHZ and those identified using the MUAC cut-offs. Therefore, more recently the recommendation is to use WHZ and MUAC measurements as independent but complementary admission criteria for SAM.
Methods
In this descriptive study with a cross-sectional design, data from a convenience sample of 400 infants and young children younger than 24 months were gathered from five clinics and 15 early childhood development (ECD) centres in Motherwell, Nelson Mandela Bay Health District (NMBHD) from October 2015 to February 2016. The Pearson correlation co-efficient (r) was used to measure the strength or degree of the relationship between variables. Sensitivity and specificity tests were used on the data with the existing recommended MUAC cut-off values as well as new calculated MUAC cut-off values to determine whether the new MUAC cut-off values were more sensitive in the identification of children affected by wasting, without including false negatives (children without SAM or MAM).
Results
The current WHO MUAC cut-off values to identify MAM have a high specificity, but performed poorly when tested for sensitivity. The r-value (0.78) for the relationship between WHZ and MUAC suggests a dependent relationship between these two indicators. The least squares regression formula (Y = 15.409 + 0.803x (males); Y = 15.13 + 0.83x (females)) was then used to predict where WHZ = -2 is most likely to correspond with a MUAC value in cm. The new predicted MUAC values of 13.8 cm (males) and 13.5 cm (females) were subsequently tested for sensitivity and specificity. The sample was too small to calculate sensitivity for both genders, but 96.4% specificity was achieved for females. A sensitivity of 100% and specificity of 94.5% was achieved with the male MUAC cut-off. Thus, the proposed cut-offs identified all of the wasted children (WHZ < -2), while identifying an acceptably low number of false positives
Conclusion
The current WHO MUAC cut-off values lacked the sensitivity to identify cases of MAM in a South African urban township population. A revised, single MUAC cut-off value for males and females younger than two years may increase the correct diagnosis of MAM, thus providing health workers the opportunity to prevent SAM. This new cut-off value should be tested in the field with larger samples
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