In a sample of 8th and 11th grade children at one rural 
school located in Oregon, USA we demonstrate that 
measured anthropometric values are needed for accurate 
surveillance of body mass index (BMI). Gender and 
grade adjusted quantile regression analysis showed the 
median self-reported BMI (calculated from reported 
height and weight) was 1.39 ± 0.43 kg/m2 lower than that 
of measured anthropometric data, p<0.001, and the 75th 
percentile was 1.90 ± 0.77 kg/m2 lower in self-reported 
data, p<0.05). The bias in self-reported data increases as 
BMI increases, underestimating rural population obesity 
prevalence among youth. School nurses are poised to 
systematically and longitudinally assess students that may 
not have regular access to health care.