Midupper Arm Circumference Outperforms Weight-Based Measures of Nutritional Status in Children with Diarrhea

Current WHO guidelines endorse using MUAC in community-based settings and WLZ in health facilities to diagnose children with SAM. In our study, a large proportion of children with diarrhea were misclassified with SAM when using WLZ whereas MUAC and MUACZ were found to have high agreement pre- and posthydration and were far less likely to misclassify children with SAM. Furthermore, dehydration status was found to have a significant impact on the accuracy of WLZ and WAZ, but no significant impact on the accuracy of MUAC or MUACZ. This difference may partially explain previous research, which has shown that MUAC and WLZ often identify different populations of children with malnutrition. A large study by WHO and UNICEF used both diagnostic criteria in a sample of 450,000 children aged 6–60 mo. WLZ and MUAC both identified a similar proportion of children with SAM: 3.22% and 3.27%, respectively. However, ∼60% of children who were classified as having SAM by one of these indicators were not classified as such by the other (4). These findings were confirmed by several subsequent studies (13, 16, 22, 23). Berkley et al. (16) postulated that one of the factors causing WLZ and MUAC to identify different populations of children could be related to hydration status. To examine the influence of dehydration, Berkley et al. (16) modeled the changes in WLZ with respect to National Center for Health Statistics standards for a hypothetical severely dehydrated child with 10% loss of body weight. They found that if a child’s usual z score was 0, then a 10% body weight loss would have reduced the WLZ by ∼1 z score (16). Our study validates this theory by showing that WLZ can vary based on the severity of dehydration in the child. Clinically, this is relevant in the diagnosis of children with severe malnutrition. Our study showed that 12–14% of children were misclassified with severe underweight or SAM using WAZ and WLZ, respectively. Previous research has found similar results of overdiagnosis of SAM using the WHO standard (15, 16). Misclassification is costly and can lead to overtreatment, poor resource use, and exacerbation of the burden of illness. Conversely, if providers are concerned that measures of undernutrition may not be accurate in children with diarrhea, they may delay treatment for undernutrition until after rehydration in some children who truly need it, with an attendant risk that they may never receive it. MUAC has many advantages in practical use. MUAC increases by only a small amount between 1 and 4 y of age, minimizing the effect of age on the measure’s ability to predict nutrition status (22). Furthermore, MUAC measurement tapes are cheap and more readily available in resource-limited environments than scales. Finally, they have shifted the diagnosis of undernutrition to the community level, because of their ease of use and the widespread availability of MUAC measurement tapes (24). Although there have been many studies on the diagnosis of SAM in the general population, there is a paucity of data on the diagnosis of malnutrition specifically in children with diarrhea, although these 2 conditions frequently present concurrently. To our knowledge, only one prior study has looked specifically at this population of children. Mwangome et al. (15) studied 3 measures of malnutrition in 325 children <5 y of age presenting with diarrhea to a rural hospital in Kenya. They found that every 1% change in weight with rehydration was associated with a change in MUAC of 0.40 mm, a change in MUACZ of 0.035, and a change in WLZ of 0.116 (15). Our study confirms their finding that WLZ is a poor indicator of undernutrition in children with diarrhea. However, in our study MUAC and MUACZ were not significantly affected by dehydration status. Unlike the study by Mwangome et al. (15) our study uses the posthydration stable weight as the proxy for preillness weight to determine the severity of dehydration on arrival. Mwangome et al. (15) compared arrival weight to a second weight performed 48 h after admission, making the assumption that all children achieved a stable weight by that time and that no children were under- or overhydrated. This assumption seems particularly unlikely given that 25% of the children enrolled in their study lost weight in the first 48 h after admission, suggesting inadequate rehydration in children with persistent diarrhea. In our study, only 2% of children lost weight in the rehydration unit, and these children were excluded from our analysis to avoid biasing our results. Our study finds MUAC and MUACZ to be the best diagnostic indicators for undernutrition in children presenting with diarrhea. Rapidly identifying vulnerable populations suffering from both diarrhea and undernutrition has important clinical implications. This high-risk population can receive targeted therapy for their severe malnutrition, such as protein-energy supplementation, while also receiving specialized ORS for their dehydration, such as ReSoMal (Nutriset, Normandy, France), developed specifically for children with severe malnutrition. Moreover, in community-based settings, it may not be possible to reassess the nutritional status of a child with diarrhea after rehydration, because they are only evaluated at a single point in time before being sent home with sachets of ORS. In these cases, MUAC or MUACZ can be used to confidently assess nutritional status, enabling prompt diagnosis and initiation of community-based nutritional supplementation, without requiring the child to return in several days for a repeat nutritional assessment after rehydration. Limitations. Children with bipedal edema and those with WAZ < −4 were not included in this study, because they are managed in a separate malnutrition unit at icddr,b, instead of the general rehydration unit used for all other children with diarrhea. Although this likely excluded the most severe cases of malnutrition (including those whose diagnoses were least likely to be affected by dehydration status), including them in our analysis would have presented additional complications. For instance, all children in the malnutrition unit receive supplemental nutrition, including locally made F75 and F100, so their change in weight could not be attributed solely to rehydration, making it more difficult to assess the degree of dehydration present on arrival. In addition, children with kwashiorkor may not experience the same weight gain because of loss of edema-related fluid on improvement in protein status. None of the children enrolled in our study received any high-calorie nutritional supplementary diet during their stay in the rehydration unit, as per icddr,b guidelines, so their percent weight change should accurately reflect their dehydration status on arrival. This study was also conducted at a single urban hospital in Bangladesh, and our results may not be generalizable to more rural populations or those in other settings. However, this particular hospital has a wide catchment area, encompassing a population of >17 million people in the city of Dhaka and surrounding rural and suburban districts. For this population, icddr,b functions as a primary center for diarrhea care, with >90% of patients presenting primarily and <10% transferred from other health facilities. Conclusions. Our study demonstrates that MUAC and MUACZ can be used to accurately identify undernutrition in children with diarrhea, regardless of their dehydration status. Conversely, WLZ and WAZ, traditional measures of malnutrition in children still used frequently at health facilities, are significantly affected by dehydration status and misclassify a large proportion of children with SAM and severe underweight. Based on these results, clinicians and community health care workers can confidently use MUAC or MUACZ to guide nutritional supplementation for children presenting with diarrhea in resource-limited settings.