We used the latest available NHANES dataset (2011–2012) for derivation. MAC was measured in the right arm at the midpoint between the tip of the olecranon and the acromion, with the arm hanging loosely. Weight was measured digitally in kilograms, with subjects wearing a standard disposable gown and underwear. We included all subjects aged over 12 months and extracted age and anthropometric data for each subject, including weight, height, MAC, upper arm length, upper leg length, waist circumference and sagittal abdominal diameter.
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Full details of the extremely in-depth sampling and examination methods are available on their website. It combines interviews and physical examinations to collect health data for a nationally representative sample of the civilian population. NHANES is a programme of studies designed to assess the health and nutritional status of adults and children in the USA. This study was an analysis of publicly available National Health and Nutrition Examination Survey (NHANES) datasets, downloaded from the CDC website. This study therefore aimed to derive and validate MAC-based formula for weight estimation for use in all age groups. Our hypothesis was that MAC could provide the basis of an acceptable weight estimation tool for use in adults, adolescents and children. 1 In 2012, the Mercy Tape was developed, which uses a combination of measurements of both MAC and humeral length to estimate weight, and was more precise than any other method in children aged ≤16 years. It performed as well as BT in older children, but poorly in preschool children. This was a simple formula derived in children of Chinese school: weight in kg=(MAC in cm−10)×3. 7 Although MAC has long been known to correlate with weight, no MAC-based weight estimation tool was published until 2010. WHO guidelines use a cut-off of 11.5 cm as one criterion in the diagnosis of severe acute malnutrition, and MAC is increasingly used in adolescents and adults too, especially in pregnant women and people living with HIV. Mid-arm circumference (MAC) is widely used as an indicator of childhood nutrition status in resource-limited countries. 6 As for ABF, wide ranges of weight for height in adults will preclude the use of adult weight estimation methods based on height alone. These older children are either too tall to fit the dimensions of the tape, or if they do fit, their height does not correlate with weight as strongly as it does in younger children. 5 However, the tape is unsuitable for use in most children aged over 10 years. The latest version of the tape extends to 150 cm, as well as providing an estimate of weight according to the height of children, and classifies children into colour-coded groups corresponding to appropriate sets of equipment sizes and drug doses. The most commonly used height-based method of weight estimation is the Broselow tape (BT). Wide ranges of weights for adults of the same age preclude the use of ABF for adults. 4 However, none of these is reliable for children aged beyond 10–12 years. For children aged 6–12 years, weight in kg=(3×age)+7. 3 The APLS method uses two different formulae according to the age group of the child, as defined by the child's age last birthday: for children aged 1–5 years, weight in kg=(2×age)+8. 1, 2 Many drug and fluid regimens are weight dependent in all ages, but as yet there are no weight estimation tools for use in adults.Īge-based formulae (ABF) for paediatric weight estimation include those used in the APLS course. Most of these are age-based or height-based and are less reliable with increasing age. Because it is rarely possible to weigh a child in time-critical situations, it is customary to rely on a method of weight estimation and several tools have been developed for this purpose. In paediatric resuscitation, appropriate drug and fluid doses, equipment selection and ventilator settings are generally dependent on the weight of children. It is, therefore, important to estimate weight when it cannot be measured directly. However, many drugs used in time-critical situations do require more precise dosing according to weight, for example, local anaesthetics, induction agents, suxamethonium, gentamicin and other antibiotics or low molecular weight heparins. In adult medicine, it is common practice (although unlikely to be good practice) for many drugs to be given as a single adult dose, whether the patient weighs 50 or 100 kg.