Weight may affect doctors' ability to correctly interpret routine blood tests in children, according to a new study.

"We performed the first comprehensive analysis of the effect of obesity on routine blood tests in a large community population of children and found that almost 70 percent of the blood tests studied were affected," said the study author, Victoria Higgins from the University of Toronto in Ontario, Canada. "As clinical decisions are often guided by normative ranges based on a large healthy population, understanding how and which routine blood tests are affected by obesity is important to correctly interpret blood test results," Higgins said. The number of US youth who are overweight or obese has risen dramatically over the past three decades. The State of Obesity reports about 18.5 per cent of children are obese.

With the rising rates of obesity in children and teens becoming a major public health concern, it is important for patients and doctors to understand the potential influence of weight on routine blood tests. For the findings, published in The Journal of Clinical Endocrinology & Metabolism, the researchers studied over 1,300 otherwise healthy children and teenagers from the community in the Greater Toronto Area. They found that 24 routine blood tests are affected by obesity, including liver function tests, inflammation markers, lipids, and iron. According to the researchers, while it is unknown whether this effect of pediatric obesity reflects early disease, doctors should be aware of these findings when interpreting several blood tests in children.

"We hope our study results will assist pediatricians and family physicians to better assess children and adolescents with different degrees of overweight or obesity," Higgins said.