Using the Mercy Method for Weight Estimation in Indian Children

Development and Validation of a Weight Estimation Tool for Acutely Ill Children Who Cannot be Weighed

OBJECTIVES

To develop and validate weight estimation tools using mid upper arm circumference (MUAC) and body length, and determine accuracy and precision of Broselow tape in children 6 mo to 15 y of age.

METHODS

Data of 18,456 children aged 6 mo to 5 y and 1420 children aged 5 to 15 y were used to develop linear regression equations using length and MUAC to estimate weight. These were validated on prospectively enrolled populations of 276 and 312 children, respectively. Accuracy was measured by Bland-Altman bias, median percentage errors, and percentage of predicted weight within 10% of true weight. Broselow tape was tested on the validation population.

RESULTS

Gender specific equations were developed which estimated weight within 10% of true weight in 69.9% (64.1-75.2%) and 65.7% (60.1-70.9%) of children aged 6 mo to 5 y, and 5 to 15 y, respectively. Broselow tape predicted weight within 10% of the true weight in 40.5% (34.7-46.6%) and 32.5% (26.7-38.7%) of children aged 6 mo to 5 y and 5 to 15 y, respectively.

CONCLUSIONS

The model developed from MUAC and length accurately estimated weight in children aged 6 mo to 15 y, and is potentially useful during emergencies. The Broselow tape frequently overestimated weight in authors' setting.

Validation study on a prediction formula to estimate the weight of children & adolescents with special needs aged 2-18 years old

BACKGROUND

This study aims to validate two predictive formulas of weight estimating strategies in children with special needs, namely the Cattermole formula and the Mercy formula.

METHODOLOGY

A cross-sectional study with a universal sampling of children and adolescents with special needs aged 2-18 years old, diagnosed with cerebral palsy, down syndrome, autism and attention-deficit/hyperactivity disorder was conducted at Community-Based Rehabilitation in Central Zone Malaysia. Socio-demographic data were obtained from files, and medical reports and anthropometric measurements (body weight, height, humeral length, and mid-upper arm circumference) were collected using standard procedures. Data were analysed using IBM SPSS version 26. The accuracy of the formula was determined by intraclass correlation, prediction at 20% of actual body weight, residual error (RE) and root mean square error (RMSE).

RESULT

A total of 502 children with a median age of 7 (6) years were enrolled in this study. The results showed that the Mercy formula demonstrated a smaller degree of bias than the Cattermole formula (PE = 1.97 ± 15.99% and 21.13 ± 27.76%, respectively). The Mercy formula showed the highest intraclass correlation coefficient (0.936 vs. 0.858) and predicted weight within 20% of the actual value in the largest proportion of participants (84% vs. 48%). The Mercy formula also demonstrated lower RE (0.3 vs. 3.6) and RMSE (3.84 vs. 6.56) compared to the Cattermole formula. Mercy offered the best option for weight estimation in children with special needs in our study population.

Weight estimation in two groups of Ghanaian children with chronic diseases using Broselow, Mercy, PAWPER XL and PAWPER XL-MAC tapes

Introduction

The performance of various weight estimation methods in children with sickle cell disease (SCD) and heart disease (HD) has not been studied. We aimed to determine and compare the accuracies of the Broselow, Mercy, PAWPER XL and PAWPER XL-MAC tapes in Ghanaian children with no known chronic diseases (controls), SCD and HD.

Methods

We prospectively recruited 631 children (199 with HD, 209 SCD and 223 controls) from the Komfo Anokye Teaching Hospital (KATH). Their weights were estimated using the Broselow, Mercy, PAWPER XL and PAWPER XL-MAC tapes. These estimated weights were compared to measured weight using mean percentage error (MPE), the proportion of weight estimates within ±10% (P10) and ±20% (P20) of measured weight. Bland-Altman limits of agreement (LOA) were determined to assess the precision of weight estimation and agreement with measured weight.

Results

The PAWPER XL, Mercy and PAWPER XL-MAC were the most accurate in all groups of children studied. All methods except the Broselow tape (BT), which performed best in the control group, had their best performance among children with SCD with negligible critical error rates (proportion of children with weight estimates > 20% of their actual weight). The P20 in the various groups of children using the BT were 88.36%, 80.21% and 51.10% respectively in the control, SCD and HD groups. The Mercy, PAWPER XL and PAWPER XL MAC tapes were generally above 90% in all groups.

Discussion

The Mercy, PAWPER XL and PAWPER XL-MAC tapes performed significantly better than the BT in all groups of children studied. These methods of weight estimation performed best in children with SCD with very little critical error.

Pediatric weight estimation: validation of the PAWPER XL tape and the PAWPER XL tape mid-arm circumference method in a South African hospital

Objective

The primary aim of this study was to prospectively compare the performance of the Broselow tape, Mercy method, pediatric advanced weight prediction in the emergency room extra-long (PAWPER XL) tape, and PAWPER XL mid-arm circumference (MAC) method in estimating the weight of children from a low-income setting. The secondary aim was to analyze the time taken to perform each method.

Methods

This analyzed a convenience study sample of 300 children aged 0 to 18 years at the Baragwanath Hospital in South Africa. Weight estimations were obtained using each of the weight estimation systems on each child. These weight estimations were then compared against the actual weight to determine bias, precision, and accuracy of the estimation methods.

Results

The PAWPER XL tape and PAWPER XL-MAC methods performed the best and provided estimated weights within 10% of the actual weight in 62.7% and 67.3% of cases, respectively, followed by the Mercy method (56.5%) and Broselow tape (43.9%). The use of MAC improved the accuracy of estimation, especially in heavier and taller children. The median times taken to perform measurements using the Broselow tape, Mercy method, PAWPER XL tape, and PAWPER XL-MAC method were 11.3 seconds, 34.7 seconds, 9.3 seconds, and 33.9 seconds respectively.

Conclusion

The PAWPER XL tape and PAWPER XL-MAC methods were the most accurate methods of estimating weight in this group of children. These methods may be considered in preference to the Broselow tape or the Mercy method for emergency weight estimation in low socioeconomic status populations.

Mercy TAPE for Calculation-Free Height Estimation in Pediatric Rehabilitation Patients

BACKGROUND

In children, height is an essential element of a pediatric assessment, yet this measure is less likely to occur in nonambulatory children or those with unique disabilities. There is compelling support for surrogate measures; however, many of these are accompanied by limitations.

OBJECTIVE

This study was conducted to evaluate whether the U.S. Food and Drug Administration (FDA)-cleared Mercy TAPE could be adopted for height estimation.

DESIGN

Development and external validation of a height-estimation method were conducted with retrospectively collected data in nonrehabilitation children. Testing of the model was performed prospectively in a pediatric rehabilitation population.

SETTING

U.S. pediatric rehabilitation outpatient clinic.

PARTICIPANTS

Data from 19 407 children were used to develop the model. Data from an independent cohort of 1472 children were used for external validation, and the model was tested in 195 pediatric rehabilitation patients. Of the 195 patients, 57% required no wheelchair, 18% could ambulate independently for short distances, 17% could ambulate with an assistive device, and 8% were full-time wheelchair users.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASUREMENTS

Relative error (RE), percentage error (PE), and percent predicted within 10% and 20% of actual height.

RESULTS

Height estimated with the modified Mercy TAPE was highly predictive of actual height in nonrehabilitation children in the United States (RE [mean ± SD]: 1.1 ± 5.7 cm; PE [mean ± SD]: 1.0 ± 4.7%). In rehabilitation patients, height was underestimated to a greater extent (RE [mean ± SD]: 3.0 ± 7.4 cm; PE [mean ± SD]: -2.1 ± 5.6%).

CONCLUSIONS

The Mercy TAPE offers a reasonable approximation of height in ambulatory children, although it slightly underestimates height in the pediatric rehabilitation population. Consequently, this and other surrogate measures may be less suited to examining growth against a reference ambulatory population and more suited to following individual children over time.

How well does the Best Guess method predict children's weight in an emergency department in 2018-2019?

OBJECTIVE

For seriously ill children, weight is often required to direct critical interventions. As it is not always feasible to measure weight in emergencies, age-based weight prediction formulae may be used as an alternative. The Best Guess formulae, derived in Australia, have been shown to be among the most accurate age-based methods in Australian children. They were validated in 2010. The present study aims to re-validate the Best Guess formulae and compare their performance to the previous validation cohort.

METHODS

A prospective observational study was conducted in the paediatric ED of a community teaching hospital. It included a convenience sample of children aged 1 month to 10 years who presented between July 2018 and April 2019. Seriously ill children were excluded. Data collected included measured weight, height, gender, age and ethnic group. The outcomes of interest were predictive performance of Best Guess formulae and comparison of predictive accuracy with a 2005 cohort from the same ED.

RESULTS

A total of 961 patients were included; 42% girls, median age 3 years. The sample was ethnically diverse. Mean percent difference in weight was -3.3% with the formulae usually over-estimating weight. Overall, agreement within 10% was 41.8%; agreement within 20% was 72.6%. Predictive accuracy was not significantly different between the cohorts.

CONCLUSION

The Best Guess method has not reduced in accuracy as a weight estimation method in emergent situations in this Australian cohort, despite a tendency to slightly over-estimate children's weight. Further study is needed to test the Best Guess method's accuracy in ethnic subgroups.

A validation of the PAWPER XL-MAC tape for total body weight estimation in preschool children from low- and middle-income countries

Importance

The PAWPER tape system is one of the three most accurate paediatric weight estimation systems in the world. The latest version of the tape, which does not rely on a subjective assessment of habitus, is the PAWPER XL-MAC method which uses length and mid-arm circumference (MAC) to estimate weight. It was derived and validated in a population in the USA and has not yet been fully validated in a population from a resource-limited setting.

Objective

The objective of this study was to evaluate the performance of the PAWPER XL-MAC tape weight estimation system in a large dataset sample of children from resource-limited settings.

Methods

This was a “virtual” study in which weight estimates were generated using the PAWPER XL-MAC tape and Broselow tape 2007B and 2011A editions in a very large open access dataset. The dataset contained anthropometric information of children aged 6 to 59 months from standardised nutritional surveys in 51 low- and middle-income countries. The performance of PAWPER XL-MAC method was compared with the Broselow tape and a new length- and habitus-based tape, the Ralston method.

Main outcomes and measures

The bias of the weight estimation methods was assessed using the mean percentage error (MPE) and precision using the 95% limits of agreement (LOA) of the MPE. The overall accuracy was denoted by the percentage of weight estimates falling within 10% and 20% of actual weight (abbreviated as p10 and p20 respectively).

Results

The MPE (LOA) for the PAWPER XL-MAC tape, the Broselow 2007B and 2011A and Ralston method were 1.9 (-15.3, 19.2), 5.4 (-15.9, 26.7), 7.7 (-13.3, 30.5) and -0.7 (-20.2, 19.3) respectively. The p10 and p20 for each method were 79.3% and 96.9% for the PAWPER XL-MAC tape, 64.3% and 91.0% for the Broselow tape 2007B, 55.5% and 85.9% for the Broselow tape 2011A and 67.4 and 94.0% for the Ralston method respectively. The PAWPER XL-MAC system was statistically significantly more accurate than the Broselow tape 2011A, the Broselow tape 2007B and the Ralston method. The relative difference in accuracy (p10) was 43% (odds ratio 4.4 (4.4, 4.5), p<0.001), 23% (odds ratio 2.9 (2.8, 2.9), p<0.001) and 18% (odds ratio 1.8 (1.8, 1.8), p<0.001) compared to each method, respectively.

Conclusions and relevance

The PAWPER XL-MAC tape performed well in this study and was statistically significantly more accurate than both the Broselow tape editions and the Ralston method. This difference was substantial and clinically important. The tape did not perform as well at extremes of habitus-type, however, and might benefit from recalibration.

The accuracy of paediatric weight estimation during simulated emergencies: The effects of patient position, patient cooperation, and human errors

INTRODUCTION

The effect of patient position and patient cooperation on the accuracy of emergency weight estimation systems has not been evaluated previously. The objective of this study was to evaluate weight estimation accuracy of the Broselow tape, the PAWPER XL tape, the Mercy method, and a custom-designed mobile phone App in a variety of realistic simulated paediatric emergencies.

METHODS

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 each of the four methods to estimate the children's weight. The accuracy of and time taken for the weight estimations were evaluated for each method. A regression analysis determined the effects of patient position and cooperation on weight estimation accuracy. Evaluation of subgroups of best-performers and worst-performers among the participants provided information on the effects of human user-error on weight estimation accuracy.

RESULTS

The Broselow tape, Mercy method, App and the PAWPER XL tape achieved percentages of weight estimation within 10% of actual weight in 47.7, 57.3, 68.1, and 73.0% of estimations, respectively. Patient position and cooperation strongly impacted the accuracy of the Broselow tape, had a minimal effect on the Mercy method and the App, and had no effect on the PAWPER XL tape. The best performing participants achieved very high accuracy with all methods except the Broselow tape.

DISCUSSION

The Mercy method, the App, and the PAWPER XL tape achieved exceptionally high accuracy even in uncooperative and sub-optimally positioned children when used by the best-performing participants. Human error, from inexperience and inadequate training, had the most significant impact on accuracy. The Mercy method was the most subject to human error, and the PAWPER XL tape, the least. Adequate training in using weight estimation systems is essential for paediatric patient safety.

Accuracy of weight estimation by the Broselow tape is substantially improved by including a visual assessment of body habitus

BackgroundThe Broselow tape (BT) has been shown to estimate weight poorly primarily because of variations in body habitus. The manufacturers have suggested that a visual assessment of habitus may be used to increase its performance. This study evaluated the ability of habitus-modified models to improve the accuracy thereof.MethodsA post hoc analysis of prospectively collected data from four hospitals in Johannesburg, South Africa, on a population of 1,085 children. Sixteen a priori models generated a modified weight estimation or drug dose based on the BT weight and a gestalt assessment of habitus.ResultsThe habitus-modified method suggested by the manufacturer did not improve the accuracy of the BT. Five dosing and four weight-estimation models were identified that markedly improved dosing and weight estimation accuracy, respectively. The best dosing model improved dosing accuracy (doses within 10% of correct dose) from 52.0 to 69.6% and reduced critical dosing errors from 16.5 to 4.3%. The best weight-estimation model improved accuracy from 59.4 to 81.9% and reduced critical errors from 11.8 to 1.9%.ConclusionThe accuracy of the BT as a drug-dosing and weight-estimation device can be substantially improved by including an appraisal of body habitus in the methodology.

Estimating the weight of children in Nepal by Broselow, PAWPER XL and Mercy method

BACKGROUND

Resuscitation of a critically-ill child requires an accurate weight for fluids and medication dosing; however, weighing children on a scale while critically ill is not always practical. The objective of this study is to determine the accuracy of three different weight estimation methods (Broselow, PAWPER XL and Mercy tape) of children presenting to Patan Hospital, Nepal.

METHODS

This was a prospective, cross-sectional study that included children presenting to the emergency department and under-fourteen outpatient clinic at Patan Hospital. Measured weight was compared to estimated weight of Broselow, PAWPER XL, and Mercy tapes. The mean percentage error and percentage of estimated weights that were within 10% (PW10) and 20% (PW20) of actual weight were calculated. Acceptable accuracy was determined as a PW10>70% and PW20>95%. A Bland-Altman analysis was done to determine agreement between each weight estimation method and actual weight.

RESULTS

The study included 813 children. The mean age was 4.2 years (ranging from 4 days to 14 years) with 60% male. The mean percentage error (MPE) for Broselow, PAWPER XL and Mercy were -1.0% (SD 11.8), 0.7% (10.5) and 4.2% (11.9) respectively. The predicted weight within 10% was highest for the PAWPER XL (71.5%) followed by Broselow (63.2%) and Mercy (58.1%). The predicted weight within 20% of actual weight was 95.2%, 91.5% and 91.3% for PAWPER XL, Broselow and Mercy respectively.

CONCLUSION

The PAWPER XL tape was the only method found to be accurate in estimating the weight of Nepalese children.

A Weight Estimation Strategy for Preterm and Full-Term Infants

Weight is the foremost marker of health outcomes in infants; however, the majority of community workers and health care providers in remote, resource-constrained settings have limited access to functional scales. This study develops and validates a simple weight estimation strategy for infants that addresses the limitations of current approaches. Circumferential and segmental anthropometric measures were evaluated for their relationship to infant weight and length. Data derived from 2097 US infants (n = 1681 for model development, n = 416 for validation). Statistical and practical considerations informed final measurement selection. Head circumference and chest circumference demonstrated the best correlations with weight (r = 0.89) and length (r = 0.94 and 0.93), and were among the most reproducible as reflected by intraclass correlation coefficients (>0.98). The head circumference and chest circumference combination offered better goodness-of-fit and smaller limits of agreement than did either measure alone. The final model predicted weight within 10% and 15% of actual for 84% and 94% of infants, respectively, with no bias for postnatal age (P = .76), gestational age (P = .10), and sex (P = .25). The model requires simple summation to generate a weight estimate and can be embodied as a low-cost, paper-based device.

A systematic review and meta-analysis of the accuracy of weight estimation systems used in paediatric emergency care in developing countries

Introduction

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.

Methods

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.

Results

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%).

Conclusions

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.

The accuracy of emergency weight estimation systems in children-a systematic review and meta-analysis

The safe and effective administration of fluids and medications during the management of medical emergencies in children depends on an appropriately determined dose, based on body weight. Weight can often not be measured in these circumstances and a convenient, quick and accurate method of weight estimation is required. Most methods in current use are not accurate enough, but the newer length-based, habitus-modified (two-dimensional) systems have shown significantly higher accuracy. This meta-analysis evaluated the accuracy of weight estimation systems in children. Articles were screened for inclusion into two study arms: to determine an appropriate accuracy target for weight estimation systems; and to evaluate the accuracy of existing systems using standard meta-analysis techniques. There was no evidence found to support any specific goal of accuracy. Based on the findings of this study, a proposed minimum accuracy of 70% of estimations within 10% of actual weight (PW10 > 70%), and 95% within 20% of actual weight (PW20 > 95%) should be demonstrated by a weight estimation system before being considered to be accurate. In the meta-analysis, the two-dimensional systems performed best. The Mercy method (PW10 70.9%, PW20 95.3%), the PAWPER tape (PW10 78.0%, PW20 96.6%) and parental estimates (PW10 69.8%, PW20 87.1%) were the most accurate systems investigated, with the Broselow tape (PW10 55.6%, PW20 81.2%) achieving a lesser accuracy. Age-based estimates achieved a very low accuracy. Age- and length-based systems had a substantial difference in over- and underestimation of weight in high-income and low- and middle-income populations. A benchmark for minimum accuracy is recommended for weight estimation studies and a PW10 > 70% with PW20 > 95% is suggested. The Mercy method, the PAWPER tape and parental estimates were the most accurate weight estimation systems followed by length-based and age-based systems. The use of age-based formulas should be abandoned because of their poor accuracy.

New age-based weight estimation formulae for Japanese children

BACKGROUND

Although dosing and sizing of resuscitation drugs and equipment are mostly weight based, time is usually insufficient to weigh critically ill children. Many age-based weight estimation formulae for emergency use have been developed worldwide, but there is no specific formula for Japanese children. The aim of this study was therefore to develop and validate age-based formulae for estimating the bodyweight of children living in Japan.

METHODS

A total of 370 980 measurements of bodyweight were obtained from 39 547 participants aged 12-155 months. They participated in a national survey, called the Longitudinal Survey of Babies in the 21st Century, which started in 2001. We created the new original weight estimation formulae for children living in Japan, called the Japanese Pediatric Assessment of Normal weight (JAPAN) formulae, using 75% of measurements that were randomly selected from the total measurements. To check the validity of the formulae, we applied the JAPAN formulae, the Park et al. formula for Korean children, and the commonly used Nelson formula for the remaining 25% of measurements. The mean absolute error and the root mean square error (RMSE) were calculated for each scale.

RESULTS

The JAPAN formulae performed better than the two other formulae among Japanese children, with a mean absolute error and RMSE of 0.83 and 1.08 (kg), respectively. The performance of the Park et al. formulae for Korean children was poor for children living in Japan.

CONCLUSIONS

The newly developed JAPAN formulae for age-based weight estimation are appropriate for children living in Japan.

Evaluation of the accuracy of common weight estimation formulae in a Zambian paediatric surgical population

Limited resources and access to healthcare in sub-Saharan Africa are associated with high rates of malnourished children, although many countries globally are demonstrating increasing childhood obesity. This study evaluated how well current age- or height-based formulae estimate the weight of children undergoing surgery in Zambia. All children under 14 years of age presenting for elective surgery at the University Teaching Hospital, Lusaka, had both height and weight measured. Their actual weight was compared against estimated weight from various formulae. The Broselow tape outperformed all the age-based formulae, demonstrating the lowest median percentage error of -5.8%, with 46.0% of estimates falling within 10% of the actual measured weight (p < 0.001). Of the 1111 children who were eligible for World Health Organization growth standard appraisal, 88 (8%) met the weight criteria for severe acute malnutrition. Our results are consistent with other studies in finding that the Broselow tape is the best estimator of weight in a lower middle-income country, followed by the original Advanced Paediatric Life Support formula if the Broselow tape is unavailable.

Weight Estimation Tool for Children Aged 6 to 59 Months in Limited-Resource Settings

Importance

A simple, reliable anthropometric tool for rapid estimation of weight in children would be useful in limited-resource settings where current weight estimation tools are not uniformly reliable, nearly all global under-five mortality occurs, severe acute malnutrition is a significant contributor in approximately one-third of under-five mortality, and a weight scale may not be immediately available in emergencies to first-response providers.

Objective

To determine the accuracy and precision of mid-upper arm circumference (MUAC) and height as weight estimation tools in children under five years of age in low-to-middle income countries.

Design

This was a retrospective observational study. Data were collected in 560 nutritional surveys during 1992–2006 using a modified Expanded Program of Immunization two-stage cluster sample design.

Setting

Locations with high prevalence of acute and chronic malnutrition.

Participants

A total of 453,990 children met inclusion criteria (age 6–59 months; weight ≤ 25 kg; MUAC 80–200 mm) and exclusion criteria (bilateral pitting edema; biologically implausible weight-for-height z-score (WHZ), weight-for-age z-score (WAZ), and height-for-age z-score (HAZ) values).

Exposures

Weight was estimated using Broselow Tape, Hong Kong formula, and database MUAC alone, height alone, and height and MUAC combined.

Main Outcomes and Measures

Mean percentage difference between true and estimated weight, proportion of estimates accurate to within ± 25% and ± 10% of true weight, weighted Kappa statistic, and Bland-Altman bias were reported as measures of tool accuracy. Standard deviation of mean percentage difference and Bland-Altman 95% limits of agreement were reported as measures of tool precision.

Results

Database height was a more accurate and precise predictor of weight compared to Broselow Tape 2007 [B], Broselow Tape 2011 [A], and MUAC. Mean percentage difference between true and estimated weight was +0.49% (SD = 10.33%); proportion of estimates accurate to within ± 25% of true weight was 97.36% (95% CI 97.40%, 97.46%); and Bland-Altman bias and 95% limits of agreement were 0.05 kg and (-2.15 kg; 2.24 kg). The height model fitted for MUAC classes was accurate and precise. For MUAC < 115 mm, the proportion of estimates accurate to within ± 25% of true weight was 97.15% (95% CI 96.90%, 97.42%) and the Bland-Altman bias and 95% limits of agreement were 0.08 kg and (-1.21 kg; 1.37 kg). For MUAC between 115 and 125 mm, the proportion of estimates accurate to within ± 25% of true weight was 98.93% (95% CI 98.82%, 99.03%) and Bland-Altman bias and 95% limits of agreement were 0.05 kg and (-1.15 kg; 1.24 kg). For MUAC > 125 mm, the proportion of estimates accurate to within ± 25% of true weight was 98.33% (95% CI 98.29%, 98.37%) and Bland-Altman bias and 95% limits of agreement were 0.05 kg and (-2.08 kg; 2.19 kg).

Conclusions and Relevance

Models estimating weight from height alone and height with MUAC class in children aged 6–59 months in a database from low-to-middle income countries were more accurate and precise than previous weight estimation tools. A height-based weight estimation tape stratified according to MUAC classes is proposed for children aged 6–59 months in limited-resource settings.

Evaluation of the Mercy weight estimation method in Ouelessebougou, Mali

Background

This study evaluated the performance of a new weight estimation strategy (Mercy Method) with four existing weight-estimation methods (APLS, ARC, Broselow, and Nelson) in children from Ouelessebougou, Mali.

Methods

Otherwise healthy children, 2 mos to 16 yrs, were enrolled and weight, height, humeral length (HL) and mid-upper arm circumference (MUAC) obtained by trained raters. Weight estimation was performed as described for each method. Predicted weights were regressed against actual weights. Agreement between estimated and actual weight was determined using Bland-Altman plots with log-transformation. Predictive performance of each method was assessed using residual error (RE), percentage error (PE), root mean square error (RMSE), and percent predicted within 10, 20 and 30% of actual weight.

Results

473 children (8.1 ± 4.8 yr, 25.1 ± 14.5 kg, 120.9 ± 29.5 cm) participated in this study. The Mercy Method (MM) offered the best correlation between actual and estimated weight when compared with the other methods (r² = 0.97 vs. 0.80-0.94). The MM also demonstrated the lowest ME (0.06 vs. 0.92-4.1 kg), MPE (1.6 vs. 7.8-19.8%) and RMSE (2.6 vs. 3.0-6.7). Finally, the MM estimated weight within 20% of actual for nearly all children (97%) as opposed to the other methods for which these values ranged from 50-69%.

Conclusions

The MM performed extremely well in Malian children with performance characteristics comparable to those observed for U.S and India and could be used in sub-Saharan African children without modification extending the utility of this weight estimation strategy.