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Arch Dis Child. 2007 October; 92(10): 938.
PMCID: PMC2083225

Estimating children's weights: a developing country perspective

We read with interest the study by Luscombe and Owens1 in which a new age‐based formula is proposed for estimating weight in paediatric resuscitation. However, as the authors admit, the study findings are limited to a specific UK population and may not apply elsewhere.

In contrast to the UK, where children's weights are increasing, in Malawi undernutrition is a significant problem with 48% of children under 5 years of age stunted, 22% underweight for age and 5% wasted (below −2 SD weight for height/length).2 Here and in other developing countries, it seems likely that an age‐based formula developed in a well nourished population will overestimate the weight of many children. As 95% of Malawian children are an appropriate length for their weight, measuring length may offer a better guide to estimating weight.

To test this assumption we retrospectively reviewed data on children aged 1–10 years admitted to the resuscitation area of the Queen Elizabeth Central Hospital accident and emergency department, Malawi over 1 month. We chose these children as they represent those most likely to receive treatment based on an estimated weight. We identified 148 children, of whom 100 had both age (in months) and weight recorded (measured during admission and recorded to the nearest 100 g). Mean age was 30.3 months (range 1–7 years) and mean weight was 11.1 kg (range 6–26 kg).

We then used the current formula (2×(age+4)) and the new formula proposed by Luscombe and Owens (3×age+7) to assess their accuracy against actual weight. The current formula overestimated weight by a mean of 10.6% (range +28.5 to –39%, where a negative value reflects an overestimate). The proposed formula overestimated weight by a mean of 17% (range +21 to –44%).

Most children requiring resuscitation were under 2 years of age. In older children (>5 years of age, n = 9), weight was overestimated to a greater extent using the proposed formula, by a mean of 30.9%, compared to an overestimate of 14% using the current formula. This may reflect the cumulative effect of age on stunting.

The formula recommended by Advanced Pediatric Life Support (APLS) has affected resuscitation training and treatment guidelines worldwide. For example 2×(age+4) has been used to recommend drug doses and fluid volumes for different age groups in the WHO guidelines for the integrated management of childhood illness (IMCI), guidelines used widely in the developing world.3

It should be remembered that in children with severe malnutrition, a major cause of child mortality worldwide, over‐resuscitation is dangerous, potentially precipitating fluid overload, cardiac failure and death.

We feel it is essential that should a new age‐based formula be adopted, especially by such an influential group as APLS, it be made clear that this formula only applies to a UK population and is not appropriate in many other settings.

Where stunting is common, the length of a child may better reflect their weight and we have evaluated a triage length tape previously.4 The length tape has the advantage that doses can be marked on it, reducing calculation error. However, for any tool to be useful it needs to be readily available and a simple age‐based equation meets this requirement well. WHO may wish to determine an appropriate, simple and validated equation for use in low resource settings.

Footnotes

Competing interests: None declared.

References

1. Luscombe M, Owens B. Weight estimation in resuscitation: is the current formula still valid? Arch Dis Child 2007. 92412–415.415 [PMC free article] [PubMed]
2. National Statistics Office Malawi demographic and health survey 2004. Zomba, Malawi: NSO, 2005
3. World Health Organization Management of the child with a serious infection or severe malnutrition: guidelines for first‐referral level in developing countries. Geneva: WHO, 2000
4. Molyneux E, Brogan R, Mitchell G. et al Children's weights: guess or measure by tape? Lancet 1999. 3541616

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