Accurate estimation of a child's weight is necessary in the ED, particularly to enable accurate drug dosage, equipment size and counter shock voltage calculation in a critically ill child. Several methods have been developed for estimating children's weight, some based on age (for example, Argall, APLS, Best Guess formulae) and some on length/height (for example, Broselow tape). A suggested alternative is asking a parent to estimate the child's weight.
We found that parent estimation, where they were willing to estimate, was the most accurate method for estimation of a child's weight, with 78% accurate to within 10% of measured weight. Three previous studies have reported similar accuracy.9,10,11
It should be noted that 11% of parents declined to provide an estimate. The reasons for this were not explored in the study. It may also depend on which parent is asked as one (more likely the mother) many have more knowledge of their child's weight than the other. Our study design did not allow us to test this.
Our measurements were performed on children in lower Australasian Triage Scale groups indicating non‐critical illness or injury. Parents, who may have been able to provide a weight estimate in less stressful conditions, may not be as capable if their child were critically unwell. In some critically unwell children a parent may not actually be present when resuscitative measures are commenced. Somewhat paradoxically it is precisely this group of children in whom we need to obtain weights via means other than scales.
Of the remaining methods, we found the Broselow tape to be the most accurate, estimating weight to within 10% tolerance in 61% of cases. Other studies report similar predictive accuracy.15,16,17
The Broselow Tape, created in 1986, is somewhat limited as it only applies to children who are between 46–145 cm in length and between 3–34 kg in weight. It also assumes a particular body habitus and may be less accurate with very thin or obese children. It has also been reported that the tape performs less well in some ethnic groups, notably Maori and Pacific island peoples.5
Of the age‐based formulae, the Best Guess method was most accurate with both the Argall and APLS formulae performing poorly. The APLS formula has also been shown to perform poorly by other studies.6,7,17
The Argall formula had not previously been tested.
While parent estimate maintained its accuracy across the weight range, the Argall and APLS methods' performance dropped off sharply with increasing weight, particularly above 40 kg. The Broselow tape also performed less well at higher weights which may be due to body habitus and ethnicity as discussed previously.5
This study has some limitations that must be considered when interpreting the results. This was a convenience sample and excluded seriously ill children, and may therefore have been biased. We did not collect data on socioeconomic status or parent educational level. The sample is derived from a single, multi‐ethnic Australian study site and may not be generalisable to other settings. Most data were collected when the principal researcher was available to do so. This limited participant numbers and potentially introduced bias. More representative sampling may have been achieved with a larger sample size or a multicentre design. We did not have sufficient sample size to validly compare ethnic or BMI subgroups.
Based on the available data, it would seem appropriate to use parent estimate of their child's weight, if they are prepared to give it, as the first option for weight estimation in a sick child who cannot be weighed. Where that is not available and the child fits within the Broselow tape's limits, its use would be the most appropriate second choice. If an aged‐based formula is the only option the Best Guess formulae are preferred.