13 C Mixed Triglyceride Breath Test: A Noninvasive Method to Assess Lipase Activity in Children

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Abstract
Results from the 13 C mixed triglyceride (MTG) breath test correlate with duodenal lipase activity in adults. This noninvasive test is a potential screening and diagnostic tool for children with fat malabsorption. The aim of this study was to adapt the methodology of the MTG breath test to study test meals and sampling methods and to define normal values for healthy children of all age groups; premature and full-term infants have similar pancreatic lipase deficiencies. After parental consent was obtained, 12 premature infants (< 37 weeks gestation and with body weights > 2 kg), 12 full-term infants (1–6 months old), 20 children (3–10 years old), and 20 teenagers (11–17 years old) were tested. All children were thriving well, had no gastrointestinal or respiratory problems, and had not received any medication that contained natural 13 C. For the premature and full-term infants, a formula was prepared that had a low and stable natural 13 C content mixed with 100 mg 13 C-labeled MTG (1,3-distearyl, 2-[ 13 C-carboxyl] octanoyl glycerol) and 1 g polyethylene-glycol 3350. The best accepted test meal for children over 3 years old was a slice of white bread with 5 g butter and 15 g chocolate paste, mixed with 250 mg 13 C-labeled MTG, and a glass of 100 mL whole-fat milk. Children over 3 years old were able to blow through a straw in a vacutainer for collecting the breath samples. In children under 3 years old, expired air was collected by aspirating breath via a nasal prong. Carbon dioxide production was calculated according to weight, age, and sex. For healthy pediatric control participants, the mean values for cumulative excretion of 13 CO 2 as a percentage of the administered dose after 6 hours were 23.9 ± 5.2% in premature infants, 31.9 ± 7.7% in full-term infants, 32.5 ± 5.3% in children, and 28.0 ± 5.4% in teenagers. The mean value for healthy adults is 35.6% with a lower reference limit of 22.8%. Age-specific test meals and breath-sampling techniques for the MTG breath test were defined. The mean values for different age groups may serve as guidelines for normal values in the pediatric population. The cumulative values for expired 13 CO 2 were above the lower limit for adults, which suggests that preduodenal lipases compensates for pancreatic lipase deficiency in premature and full-term infants.