# Validation of a Useful Tool for Screening for Overweight and Obesity in Pre-Adolescents
## 2 Materials and Methods  
Weight (Tanita BC-601 monitor, 0.1 kg), height (SECA stadiometer, 1 mm) and arm circumference measurements (SECA tape measure, 1 mm, and Doctors Without Borders designed MUAC tape, 1 mm) were taken according to the standards of the International Society for the Advancement of Kineanthropometry (ISAK) [11; 12; 23]. An observational study with a convenience sample was undertaken. The validation study of the MUAC measure was developed with a sample of 108 students described by age and sex. A total screening study sample of 360 students (175 boys and 185 girls) consisted of the 4 th (\(n=135,67\) boys and 68 girls, aged between 9 and 10 years), 5 th (\(n=118\), 58 boys and 60 girls, aged between 10 and 11) and 6 th (\(n=107\), 50 boys and 57 girls, aged between 11 and 12 years) courses. The analysis data were divided into courses by age and sex and the data were analysed to identify optimal cut-off values compared to the WHO height/weight percentile for each course [23; 24; 25]. All samples were collected in 5 schools in 3 towns in the province of Valencia (Spain). For the recruitment of students, voluntary participation in the study was requested through the school council in 5 public primary schools. Parents were subsequently notified in writing of their voluntary participation. Informed consent to the study was sent and requested to be signed to participate. Finally, 80% of the total sample of invited students participated. The measurements were taken during the 2018/2019 school year in the schools during school hours, starting with their first-class hour and before brunch time. To carry out the anthropometric measurements, the participants were divided into pairs of students and a supervising schoolteacher. The measurements were carried out in an empty and spacious auxiliary classroom.  
As for data analysis, the qualitative variable \"sex\" and the quantitative variables \"age\", \"height\", \"weight\" and brachial perimeter measured with \"tape measure\" and \"MUAC tape\" were obtained and the samples were categorised by courses (4 th, 5 th, and 6 th) and sex.  
The statistical software R-Studio 4.2.0 was used to calculate the mean value, standard deviation and range of values for quantitative variables and for sex and grade.  
To establish the correlation between the quantitative statistical values of \"tape measure\" and \"MUAC tape\", as well as the correlation between tape measure, MUAC tape measure and final percentile in relation to height percentile and weight percentile by age, sex, height and weight, the statistical software R-Studio was also used.  
From the quantitative variables, the variables \"cut-off percentile\", \"weight percentile\", \"body mass index\" and \"total percentiles\" were obtained for each age. Specific percentiles were calculated individually for each age, sex, weight and height using the web application \"Percentile Calculator\" of the \"Initiative for the Humanization of Childbirth and Lactate Care (IHAN)\", UNICEF Spain, based on the WHO Child Growth Standards [26].  
The study protocol was approved by the Human Research Ethics Committee (H1513343373169) of the University of Valencia and all procedures were conducted according to the Declaration of Helsinki. In addition, both the principals of the participating schools and the legal guardians of the participating students were informed. This research did not receive any specific grants from funding agencies in the public, commercial or non-profit sectors.