Obesity Alters Routine Blood Tests in Children

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Obesity may play a greater role in routine pediatric laboratory tests than previously thought, affecting how these tests should be interpreted. A study in The Journal of Clinical Endocrinology & Metabolism found that the condition affects 24 routine blood tests such as lipids, liver function, inflammation markers and iron—70% of the blood tests studied, according to the study’s first author, Victoria Higgins, PhD, of The Hospital for Sick Children and The University of Toronto in Canada.

The study is the first comprehensive analysis of obesity’s effects on routine blood tests in a large pediatric community cohort. “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 in a statement.

Nearly 19% of all children in the United States are obese, putting youths at risk for host of conditions such as diabetes, high blood pressure, dyslipidemia, and sleep apnea. Higgins and her team recruited 1,332 healthy children and teens ages 5 to 19 from the greater Toronto area with body mass indexes (BMI) ranging from 13.4-65 kg/m² to assess the influence of three adiposity measures on 35 common biochemical markers.

Investigators did a comparative analysis of serum biomarker levels in children with normal, overweight, and obese BMIs, looking at the association between each marker and BMI, waist circumference (WC), and waist-to-height ratio (WHtR z) scores. They also created reference intervals for all of the markers before and after removing the obese or overweight subjects.

“The most notable finding from our study was that the majority of the routinely assessed serum biomarkers measured were associated with weight status,” Higgins told CLN Stat. Adjusting for age and sex, 24 routine lab tests were significantly associated with BMI, WC and/or WHtR z-scores:

Thirteen of the markers differed significantly among the three BMI categories: ALT, apoB, C3, C4, ChE, hsCRP, GGT, haptoglobin, HDL-C, iron, transferrin, triglycerides, and uric acid. Of these, the researchers particularly did not expect that haptoglobin, transferrin, iron, and uric acid would have been affected by obesity, according to Higgins.

Investigators also discovered that there was a profound sex difference in the effect of obesity on some routinely assessed biomarkers. “For example, ALT increased and HDL-C decreased in males with increasing obesity, but not in females,” said Higgins.

Investigators could not confirm whether these altered levels reflect indolent disease. Clinicians, however, should be aware of the effect of weight status on several laboratory tests, cautioned Higgins. Laboratory professionals in the meantime should be aware of their patient populations and the impact BMI can have on the normal levels of routine blood tests. “It is important to understand these effects when communicating with physicians to provide appropriate guidance,” she added.

Future research involves looking into these altered biomarker levels, and what they mean for obese individuals in terms of health or disease. “This is important to determine how best these individuals should be included in reference populations used to establish reference intervals or if reference intervals should be stratified by BMI to represent people with obesity who would have a different normal range of values,” Higgins said.

She would also like to explore what the effect would be on disease classification and patient outcomes if BMI-stratified reference intervals for some routine biomarkers were implemented in the clinical setting.