Fat Malabsorption in Cystic Fibrosis: Comparison of Quantitative Fat Assay and a Novel Assay Using Fecal Lauric/Behenic Acid

Abstract

Objectives-The "gold standard" for the diagnosis of fat malabsorption, the 72 hour fat balance study, requires a three day collection to generate a coefficient of fat absorption (CFA). We hypothesized that, a new test using behenic acid (behenate test) as a nonabsorbable lipid marker may provide a facile means to assess fat absorption. The study proposed to answer two questions: 1) whether the "behenate test" correlated with the "gold standard" and 2) whether the CFA improved when taking pancreatic enzymes during meals instead of prior to them.Methods-The study compared the "behenate test" with the gold standard in 15 cystic fibrosis patients during three arms which require 3-4 day hospitalizations: one taking pancreatic enzymes prior to meals, one taking pancreatic enzymes during meals, and one off of pancreatic enzymes.Results-The mean CFA was 78.3% when pancreatic enzymes were taken during meals and 80.4% when pancreatic enzymes were taken prior to meals. Correlation between the CFA and the "behenate test" for collections during all 3 arms was r 2 = 0.219 (p= 0.001). Conclusion-1)Timing of ingestion of pancreatic enzymes does not significantly alter the CFA. 2) Although the CFA correlates with the "behenate test", the correlation is not robust enough to justify its replacement of the "gold standard." It is unclear whether the poor correlation between tests relates to intermeal variability in fat excretion,or other factors; however the "behenate test" may be suitable as a screening test for detection of fat malabsorption.

Malabsorption blood test: Assessing fat absorption in patients with cystic fibrosis and pancreatic insufficiency

“…In adult patients with chronic pancreatitis, Dominguez‐Munoz et al in 2005 showed, using the C mixed triglyceride breath test, that enzymes taken with meals or at the end of the meal improved fat absorption compared with when taken before meals. In contrast, Dorsey et al in 2010, showed in CF and PI that there was no difference in the CFA when enzymes were taken during meals or before meals . The difference in these results may be related to the various methodologies used, diagnosis, disease severity, and that the CFA is not a highly reliable test.…”

“…With these limitations, CFA is underutilized or avoided in most clinical care and research settings. Several alternative tests for assessment of fat malabsorption have been explored including mixed triglyceride, dipeptide breath tests, stable and radioactive isotope tests, spot stool fat level, stool behenate levels, secretin‐cholecystokinin–stimulated pancreatic challenge test, and secretin‐stimulated magnetic resonance cholangiopancreatography . All have limitations and have failed to gain wide acceptance as accurate or practical alternatives to the 72‐hour stool and diet collection.…”

Cystic fibrosis: An update for clinicians. Part 2: Hepatobiliary and pancreatic manifestations

“…SPB is a component of fat used in commercial production of fried snack foods and serves as a nonabsorbable lipid marker. The stool lauric acid: behenic acid ratio provides an assessment of fat absorption which correlates with CFA, but it is not sufficiently robust to replace CFA …”

“…The stool lauric acid: behenic acid ratio provides an assessment of fat absorption which correlates with CFA, but it is not sufficiently robust to replace CFA. 75 Treatment of PI. The objectives of pancreatic enzyme replacement therapy (PERT) are to correct macro-and micronutrient maldigestion, alleviate abdominal symptoms attributable to maldigestion, help establish normal stools and bowel habits, and sustain normal growth and nutritional status.…”

Cystic Fibrosis-Related Oxidative Stress and Intestinal Lipid Disorders

“…Without treatment, fat malabsorption leads to malnutrition, failure to thrive, fat-soluble vitamin (A, D, E, and K) inadequacy, and essential fatty acid deficiency (EFAD) (40,96).…”