Size does matter – Age-related weight estimation in “tall n’ thin” and “tiny n’ thick” children and a new habitus-adapted alternative to the EPLS-formula

doi:10.1016/j.resuscitation.2014.04.032

Resuscitation

Volume 85, Issue 9, September 2014, Pages 1174-1178

https://doi.org/10.1016/j.resuscitation.2014.04.032 Get rights and content

Abstract

Aim of the study

Weight in kilograms is a required parameter in the emergency medical care of children. In emergent situations, obtaining an accurate weight is often not possible. In such situations, weight can be estimated by using an age-dependent formula such as the EPLS-formula (age in years + 4) × 2. As recently recognized for emergency tapes, the habitus of the child has a major influence on weight estimation. In this study, the performance of various age-dependent formulas is to be investigated, with special regard to children demonstrating non-normal growth.

Methods

The performance of various formulas for weight estimation in children growing along the 5th, 50th, and 95th percentile is investigated based on a mathematical model compared to the WHO and CDC reference percentiles using ICC and Bland–Altman methods. Additionally, a new formula for children demonstrating non-normal growth is derived by regression analysis and tested: f × age in years + 6 with the factor f being 2 for “tall n’ thin”, 3 for normal and 4 for “tiny n’ thick” children.

Results

All previously published formulas lack precision when applied to children outside the 50th percentile. The new habitus-adapted formula shows a better performance for children growing along the 5th or 95th percentile.

Conclusions

The new formula provides enhanced precision in weight estimation and can help in reducing, e.g. drug dosing errors. It should be used for weight estimation in children demonstrating non-normal weight development and in situations when superior methods such as weighing or habitus-adapted emergency tapes are not applicable.

Introduction

Weight in kilograms (kg) is a required parameter in the emergency medical care of sick or injured children.¹ In cardiac arrest, defibrillation energy and most drug doses are calculated based on weight in kilograms. In non-critical medical situations, such as planned surgery or in-patient care in hospitals, weight can and should be measured. In life-threatening and prehospital situations, weighing is commonly not an option as it is time-consuming and requires repositioning the patient onto a scale. Parental weight estimation remembering the last weighing is the next best option,² followed by weight estimation using a length-weight correlation as in the Broselow tape.3, 4 European pediatric life support (EPLS) courses by the European Resuscitation Council (ERC) suggest the use of an age-weight-correlation by an age-dependent formula, commonly referred to as the EPLS-formula⁵: [(age in years + 4) × 2]. Several other formulas for weight estimation based on age have been reported in the literature. The basic principle of age-dependent formulas is the theory that a lone and sick or injured, yet awake child might correctly tell the health provider his age, but not his weight.

In pediatrics, growth is usually expressed by using percentiles. The 50th percentile resembles the mean weight or length for given age.11, 12 All formulas have been developed by referencing normal-sized and normal-weighted children.¹³ Therefore, they lack accuracy in children demonstrating a non-normal growth – specifically thinner-than-usual or thicker-than-usual children. Weight estimation using a length-weight correlation, such as the Broselow-tape, has the same limitation. This has recently been recognized and led to the development of tools like the PAWPER-tape6, 7 or the Mercy-method-tape (ClinicalTrials NCT01709500) that incorporate other parameters like habitus or mid-arm circumference⁸ for a more precise and differentiated estimation. The American Heart Association advocates in their actual guidelines for Pediatric Advanced Life Support (PALS) the use of tapes, though stating that habitus might be an important consideration.⁹

The incorporation of habitus into an age-dependent formula has yet to be introduced. This led the authors of this article to the idea of developing a new as-simple-as-possible formula for age-dependent weight estimation that can be also used in children with non-normal weight. In this article, the performance of the commonly used formulas in children with lean, normal and sturdy habitus is examined followed by the presentation of a new formula for weight estimation. This is based on the standard percentiles for growth in childhood by the World Health Organization (WHO) and the Center for Disease Control (CDC).

Section snippets

Materials and methods

For regression analysis, a linear regression model was applied onto the same reference database in order to produce a formula for weight as a function of age in years, separately for the 5th, 50th and 95th percentile. For goodness of fit testing, coefficient of determination R² and analysis of variance were performed.

The reference percentiles for children aged 1–12 years are shown in Fig. 1. Using these data as reference, the authors compared the results of various age-dependent formulas and

Results

The performance of the various formulas described in the literature is shown in Fig. 1 and Table 1. The authors also added the simplest formula [kg = 4 × years], which is a simplification of the best guess method into analysis.

The displayed ICC-value represents the absolute correlation between the reference values and the results of the shown formula. The colored background of cell in Table 1 represents the goodness of correlation as indicator for the quality of the formulas performance. The

Discussion

The EPLS-formula is the most commonly referred age-dependent formula. Imprecise estimations, especially in populations with growth differing from the United States 13, 14, 15, have led to the development of several other formulas.¹⁶ The “Advanced Life Support Group” (ALSG) changed their recommendation for an age-dependent formula in the 5th edition of their “advanced pediatric life support” (APLS) course manual¹⁷ from the EPLS-formula to a more complex one (see Table 1). Each of the various

Conflict of interest statement

The authors state that they have no conflicts of interest.

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Cited by (13)

Drug dosing errors in simulated paediatric emergencies – Comprehensive dosing guides outperform length-based tapes with precalculated drug doses
2020, African Journal of Emergency Medicine
Citation Excerpt :
Some experts advocate the use of pre-calculated drug dosing regimes for emergency drugs based on best estimation weight calculations based on age [25]. Although age-based weight estimation might still be practised in some settings, many experts consider it to be dangerously inaccurate, vulnerable to calculation errors and no longer appropriate for clinical use, especially since other – and better – methods are available [26–29]. These formulas are also not advocated by the leading international resuscitation organisations [9].
The accuracy of drug dosing calculations during medical emergencies in children has not been evaluated extensively. The objectives of this study were to evaluate the accuracy of drug dose calculations using the Broselow tape, the PAWPER XL tape plus its companion drug-dosing guide, a custom-designed mobile phone app and no drug-dosing aid (control group).
This was a prospective study in which 32 emergency medicine volunteers participated in eight simulations of common paediatric emergency conditions, using children models. The participants used the three methods to estimate the children's weight and calculate drug doses. The accuracy of and time taken for the drug dose determinations were then evaluated for each of the methods.
The overall accuracy of drug dose determinations was extremely and potentially dangerously low in the control group in which no dosing guide was used as well as in the Broselow tape group (<20% of doses were correct). The accuracy was significantly higher with the PAWPER XL tape group and the mobile app group (47% and 31% respectively). The times taken to obtain the required information did not differ in a clinically meaningful magnitude.
Both an accurate weight estimation and a dosing guide with comprehensive information were necessary to produce an accurate prescription. The information on the Broselow tape was not sufficient for this purpose. The current guidelines recommending the use of tapes with limited information should be revised. The results from the comprehensive dosing guides were substantially better, but still had a lower proportion of accurate prescriptions than desirable. The role of training in every aspect of the emergency paediatric weight estimation and drug dosing procedure cannot be underestimated and should be routine in any environment where emergency care may be needed.
Paediatric weight estimation by age in the digital era: optimising a necessary evil
2018, Resuscitation
Citation Excerpt :
Two studies have evaluated how the addition of an assessment of body habitus could improve the accuracy of age-based weight estimation methods. These are (where Z = age in years):The Erker formula [22]Wt = (2 × Z) + 6 For ‘tall ‘n thin’ childrenWt = (3 × Z) + 6 For ‘normal’ childrenWt = (4 × Z) + 6 For ‘tiny ‘n thick’ children The Wells ‘derived formula’ [7]HS1: Wt = (1.9 × Z) + 5.8HS2: Wt = (2.3 × Z) + 5.8HS3: Wt = (2.4 × Z) + 7.5HS4: Wt = (2.9 × Z) + 8.3HS5: Wt = (3.7 × Z) + 8.1
Age-based weight estimation methods are regularly used in paediatric emergency medicine despite their well-established inaccuracy.
Determine the potential improvement in accuracy achievable by the use of a new mobile application, based on CDC/WHO weight-for-age centile data, which incorporates a gender assignment, a body habitus assessment, and which is capable of an age-in-months based calculation.
A theoretical, simulated validation study, comparing the performance of the widely used APLS/EPALS formulae against two contemporary habitus-adjusted methods, and the Helix Weight Estimation Tool. 1,070,743 children from the 2015/2016 UK National Child Measurement Program dataset, aged between 4 and 5 and 11 and 12 years, had age-based weight estimates made by all five methods.
Primary outcomes were the percentage of weight estimations within 10%, 20%, and those greater than 20% discrepant from actual weight for each method. Our theoretical, gender-dependent, habitus-adjusted method performed better than all other methods across all error thresholds. The overall number of estimations within 10% was 70.4%, and within 20% was 95.45%. The mean percentage error was −1% compared to actual weight.
The use of a digital tool incorporating a subjective assessment of body habitus, gender assignment, and the ability to estimate weight based on age-in-months might be able optimise the process of paediatric weight estimation by age, making this practice as safe and accurate as possible for the occasions when weight estimation by age is chosen over length-based methods.
It is time to abandon age-based emergency weight estimation in children! A failed validation of 20 different age-based formulas
2017, Resuscitation
Citation Excerpt :
Although the statistical relationship between age and weight is less linear and less close than that between length and weight, age-based weight estimation could potentially be improved by taking habitus into account. This has already been shown in a theoretical study, but no validation studies have proven the concept [19]. Our primary objective was to evaluate the accuracy of every published weight-estimation formula in our study population (both age- and length-based).
When children’s weight cannot be measured during medical emergencies, it must be estimated, as weight is required for many interventions. Age-based formulas are the oldest weight estimation systems in children, but have been shown to be very inaccurate in many studies. This aim of this study was to evaluate the accuracy of age- and length-based formulas and to see if a measure of body habitus could be used to improve the performance of these formulas.
This was an analysis of data from a sample of 1085 children aged from 1 month to 16 years, collected from four Emergency Departments in Johannesburg, South Africa. Basic demographic and anthropometric data was collected and each child had a visual assessment of body habitus, quantified as a habitus score. Weight estimates from 20 existing age-based formulas and two length-based formulas were then compared against measured weight to determine their accuracy. Age- and length-based, habitus-modified models were developed and similarly evaluated.
A systematic review and meta-analysis of the accuracy of weight estimation systems used in paediatric emergency care in developing countries
2017, African Journal of Emergency Medicine
Citation Excerpt :
Many of these methods were derived from populations of well- or over-nourished children and have been shown to lack accuracy and consistency of performance, especially between different populations [12–14]. To limit the degree of underestimation of weight in high-income country populations, newer age-based formulas have been developed over the last decade to accommodate for the increasing prevalence of obesity in children [15,16]. The Broselow tape has also been updated and modified (to the current version: 2011 edition A) to reduce the risk of underestimation of weight [17].
When weight cannot be measured during the management of medical emergencies in children, a convenient, quick and accurate method of weight estimation is required, as many drug doses and other interventions are based on body weight. Many weight estimation methodologies in current use have been shown to be inaccurate, especially in low- and middle-income countries with a high prevalence of underweight children. This meta-analysis evaluated the accuracy of weight estimation systems in children from studies from low- and middle-income countries.
Articles from low- and middle-income countries were screened for inclusion to evaluate and compare the accuracy of existing systems and the newer dual length- and habitus-based methods, using standard meta-analysis techniques.
The 2D systems and parental estimates performed best overall. The PAWPER tape, parental estimates, the Wozniak method and the Mercy method were the most accurate systems with percentage of weight estimates within 10% of actual weight (PW10) accuracies of 86.9%, 80.4%, 72.1% and 71.4% respectively. The Broselow tape (PW10 47.1%) achieved a moderate accuracy and age-based estimates a very low accuracy (PW10 11.8–47.5%).
The PAWPER tape, the Wozniak method and the Mercy method achieved an acceptable level of accuracy in studies from low- and middle-income countries and should preferentially be used and further advanced for clinical emergency medicine practice. Parental estimates may be considered if the regular caregiver of the child is present and a recent measured weight is known. The Broselow tape and age-based formulas should be abandoned in low- and middle-income country populations as they are potentially dangerously inaccurate.
Weight Estimation Methods in Children: A Systematic Review
2016, Annals of Emergency Medicine
Citation Excerpt :
We screened the abstracts of 131 studies and excluded 16 after screening and an additional 35 after full-text review (Figure). We thus included 80 studies on the topic of estimating weight in pediatric patients that met our inclusion criteria in this review.2,4,6-83 Studies were published from 1986 to 2016 and were conducted in 23 countries, although more were from the United States.
We seek to collect, review, evaluate, and synthesize the current literature focusing on all published methods of pediatric weight estimation.
We conducted a literature review using PubMed and Web of Science databases, and the Google Scholar search engine, with the “similar articles” feature, as well as review of the bibliographies of identified studies. We excluded studies estimating weight of neonates, predominantly adults without separate information for children, child self-reported weight, and studies estimating outcomes other than weight. Quantitative outcomes of accuracy (proportion within 10% of actual weight), mean percentage error, and mean bias were preferred.
Eighty studies met inclusion criteria with predominant methods: parent or health care worker weight estimation, age-based formulae, and length-based estimation without (eg, Broselow) or with adjustment for body habitus (eg, Pediatric Advanced Weight-Prediction in the Emergency Room, Mercy). Parent estimation was the most accurate at predicting total (actual) body weight, with length-based methods with habitus adjustment next. Length-based methods outperformed age-based formulae, and both tended to underestimate the weight of children from populations with high obesity rates and overestimate the weight of children from populations with high malnourishment rates. Health care worker estimation was not accurate.
Parent estimation and length-based methods with adjustment for body habitus are the most accurate methods to predict children’s total (actual) body weight. Age-based formulae and length-based methods without habitus adjustment likely tend to predict ideal body weight.
Predictive Models for Calculating Body Weight and Assessing the Likelihood of Overweight and Obesity in Young Children
2023, Paediatrics Eastern Europe

View all citing articles on Scopus

^☆: A Spanish translated version of the summary of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.04.032.

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Clinical PaperSize does matter – Age-related weight estimation in “tall n’ thin” and “tiny n’ thick” children and a new habitus-adapted alternative to the EPLS-formula☆

Abstract

Aim of the study

Methods

Results

Conclusions

Introduction

Section snippets

Materials and methods

Results

Discussion

Conflict of interest statement

Ann Emerg Med

Surg Clin North Am

Resuscitation

Arch Pediatr

J Nutr

Resuscitation

Ann Emerg Med

Am J Emerg Med

Resuscitation

Guidelines on paediatric dosing on the basis of developmental physiology and pharmacokinetic considerations

Clin Pharmacokinet

Analysis of parental and nurse weight estimates of children in the pediatric emergency department

Pediatr Emerg Care

ERC: EPLS – European Pediatric Life Support: ERC manual for health care workers dealing with paediatric resuscitation

The PAWPER tape: a new concept tape-based device that increases the accuracy of weight estimation in children through the inclusion of a modifier based on body habitus

Resuscitation

Optimizing emergency drug dosing in children

Acad Emerg Med

Part 14: Pediatric Advanced Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

Circulation

Clinical Paper
Size does matter – Age-related weight estimation in “tall n’ thin” and “tiny n’ thick” children and a new habitus-adapted alternative to the EPLS-formula☆