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

Dorsey, Jill*; Buckley, Donna; Summer, Suzanne; Jandacek, Ronald J; Rider, Therese; Tso, Patrick; Narkewicz, Michael R§; Heubi, James E

Journal of Pediatric Gastroenterology & Nutrition: April 2010 - Volume 50 - Issue 4 - p 441–446
doi: 10.1097/MPG.0b013e3181b18308
Original Articles: Hepatology and Nutrition

Objectives: The gold standard for the diagnosis of fat malabsorption, the 72-hour fat balance study, requires a 3-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 2 questions: first, whether the behenate test correlated with the gold standard and, second, whether the CFA improved when taking pancreatic enzymes during meals instead of taking them before meals.

Patients and Methods: The study compared the behenate test with the gold standard in 15 patients with cystic fibrosis during 3 arms that require 3- to 4-day hospitalization: first, taking pancreatic enzymes before meals; second, taking it during meals; and third, without taking it.

Results: The mean CFA was 78.3% when pancreatic enzymes were taken during meals and 80.4% when these enzymes were taken before meals. Correlation between the CFA and the behenate test for collections during all 3 arms was r2 = 0.219 (P = 0.001).

Conclusions: Timing of ingestion of pancreatic enzymes does not significantly alter the CFA. Although the CFA correlates with the behenate test, the correlation is not robust enough to justify replacement of the gold standard by this test. 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 the detection of fat malabsorption.

*Nemours Children's Clinic, Jacksonville, FL, USA

Division of Pediatric Gastroenterology, Hepatology, and Nutrition, General Clinical Research Center, Cincinnati Children's Hospital Medical Center, USA

Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA

§Sections of Pediatric Gastroenterology and Nutrition and of Pediatric Pulmonology, Department of Pediatrics, University of Colorado School of Medicine, Aurora.

Received 13 February, 2009

Accepted 26 May, 2009

Address correspondence and reprint requests to James E. Heubi, MD, General Clinical Research Center, Cincinnati Children's Hospital Medical Center, 3333 Burnet Av, Cincinnati, OH 45208 (e-mail:

Financial support was received as grant no. RR00069 from the Cystic Fibrosis Foundation and the General Clinical Research Center.

The authors report no conflicts of interest.

© 2010 Lippincott Williams & Wilkins, Inc.