Impact of new tool on dosing pediatric meds

June 11, 2015

Something as basic as obtaining an accurate weight on a young patient can be a monumental task in disadvantaged areas, or in emergency situations. Yet accurate weights are critical in terms of medication dosing, fluid volumes, device sizing, and many other treatments and applications.

Something as basic as obtaining an accurate weight on a young patient can be a monumental task in disadvantaged areas, or in emergency situations. Yet accurate weights are critical in terms of medication dosing, fluid volumes, device sizing, and many other treatments and applications.

To address this problem, Susan M. Abdel-Rahman, PharmD, Children's Mercy Hospitals and Clinics of Kansas City, Missouri, has developed a new tool to assess children’s weight without the use of a scale, and it has proved in studies to be effective within 10% of a weight determined on a traditional scale method.

“We can comfortably say, at present, that we have the most accurate and robust weight estimation strategy available,” Abdel-Rahman says.

Using the principals of a tape measure, the Mercy TAPE translates the length of the child and circumference of the upper arm into a weight that is displayed on the device. The “TAPE” name stands for “TAking the guesswork out of Pediatric weight Estimation,” and the principal is based on the Mercy Method, which estimates weight based on the length and circumference of the upper arm.

The Mercy TAPE puts a twist on the Mercy Method, however, and utilizes humeral length and mid-upper arm circumference to determine weight rather than body length, which can be challenging to obtain from uncooperative or combative children, or age. Each measurement is associated with a unique number that is reported on the device, and when the numbers are added together you have the weight of the child. 

The device can be printed on any flexible, nonstretchable medium such as paper, coated paper, fiberglass, and more to create a disposable or semipermanent tool, according to the study. Although the Mercy TAPE could have limited use in settings where providers are illiterate or use no written language, the researchers note that the device could be modified to utilize colors and symbols that correspond with medication doses, intervention strategies, or weight targets.

“With minimal instruction, first-time users can learn to identify the anatomic landmarks, and for the practiced user the entire process takes about 18 seconds,” Abdel-Rahman says. “The benefit is access to a highly accurate weight estimate on which you can base treatment decisions even if you don’t have a scale.”

NEXT: How effective is the tool? 


In a clinical trial to determine the efficacy of the device, 624 participants ranging in age from 2 months to 16 years were weighed, and 2 different models of the Mercy TAPE outperformed the Broselow tape overall. According to the study, the Broselow method was successful in obtaining weights for only 415 of the 624 children because the remaining subjects were taller than the Broselow measurement device. “Broselow demonstrated a larger mean error and mean percentage error than the Mercy TAPEs and overestimated weight in children who were underweight and underestimated weight in those who were overweight and obese,” the study notes.

“The Broselow method predicted fewer children within 10% of their actual weight compared to both TAPEs and fewer children within 20% of actual when compared with the 2D-TAPE,” according to study findings.

“It is too common for existing weight estimation methods to produce 2- to 3-fold errors in weight. For many medicines, this could result in a child receiving no benefit from the drug or alternatively experiencing serious or life-threatening toxicities,” says Abdel-Rahman. “The Mercy Method should allow doctors to deliver doses of medicine to children with more accuracy than ever before, and significantly reduce the risk of improper medication use in these critical settings.”

Abdel-Rahman says the Mercy TAPE was developed as a result of a collaboration with the World Health Organization to define pediatric medication dosages for priority conditions such as tuberculosis and malaria. During the course of their work in reviewing dosages, Abdel-Rahman and her team found that providers in many disadvantaged or remote areas did not have access to functional and reliable methods of obtaining accurate weights without severe limitations.

“We appreciated an opportunity to develop a more robust tool that spanned a broader age range, performed comparably irrespective of nutritional status, and was applicable to children of varying geographic origin,” Abdel-Rahman says. “A weighing scale remains the gold standard for obtaining weight so the Mercy TAPE is designed to provide an estimate of weight when access to a scale is not available.”

The Mercy TAPE is inexpensive, lightweight, and portable, and can be used with a child sitting up, lying down, or cradled in their parent’s arms, she says. There are no facility requirements for use such as level surfaces or electricity, so it is operational in any setting where the user can read and interpret numbers.

NEXT: What does the FDA say?


One billion of the world’s 2.2 billion children live in poverty, and 270 million are without access to basic healthcare services. For example, Abdel-Rahman points out that only 32% of health facilities in Uganda have suitable pediatric scales.

“The Mercy TAPE is meant to impact the lives of these children. However, it may also impact the lives of children in developing countries. In the United States, there are an estimated 8 million emergency room visit by children under the age of 15 that occur in hospitals which do not routinely care for children,” she says. “There are also over 600,000 ambulance transports involving children. Notably, less than 20% of transport vehicles meet performance measures for essential pediatric equipment. In these settings, the Mercy TAPE can provide accurate patient weights to practitioners with who are less familiar with children.”

The Mercy TAPE was patented by Abdel-Rahman in November 2013 and recently earned 510(k) clearance from the US Food and Drug Administration (FDA) as a medical device. Prior to the 16-month FDA clearance process, Abdel-Rahman says her team performed 5 validation studies in 3 countries on the Mercy TAPE. She says validation studies are currently under way in West Africa and South Asia, and that her group is also working with international partners including UNICEF to facilitate additional feasibility studies. Abdel-Rahman says philanthropic support has allowed her team to gift Mercy TAPE devices to healthcare providers in more than a dozen countries.

The full study was published in the Annals of Emergency Medicine in 2013.