Background: We sought to compare the differences of coefficient of fat absorption (CFA) and coefficient of nitrogen absorption (CNA) in healthy individuals and those with cystic fibrosis (CF) and to study the precision of CFA and CNA.
Methods: Sixteen healthy and 23 subjects with CF and pancreatic insufficiency ate a high-fat, high-protein diet for 72 hours; stool was collected between blue food dye markers to determine CFA and CNA. Subjects with CF withheld pancreatic enzymes. Tests were repeated on 5 of the CF and 10 of the healthy subjects.
Results: In healthy subjects, mean CFA was 93.5% ± 2.7%; mean CNA was 88.1% ± 5%. Median test-retest in 10 healthy subjects was +0.7% CFA (range, -8.1% to + 5.9%) and +0.9% CNA (range, -14.6% to +6.8%). For subjects with CF, mean CFA was 38.5% ± 14.7% and mean CNA was 52.2% ± 11.4%. Median test-retest change in 5 subjects with CF was -6.9% CFA (range, -19.7% to +42.8%) and +14.7% CNA (range, -6.4% to +42.8%).
Conclusions: CFA and CNA have inconsistent precision in CF. The limitations of CFA as a measure of steatorrhea correction in CF should be recognized in studies of pancreatic enzyme supplements.
Keywords: cystic fibrosis; malabsorption; pancreatic enzymes; pancreatic insufficiency; pancreatic sufficiency.