Re: Fecal Elastase: Pancreatic Status Verification and Influence on Nutritional Status in Children with Cystic Fibrosis.

Abstract

Cohen, et al. J Pediatr Gastroenterol Nutr 2005;40:438-44 To the Editor: In the April issue of the journal, Cohen et al. (1) aimed to assess fecal elastase-1 (FE) levels in young children with cystic fibrosis (CF) and pancreatic insufficiency (PI) and to explore the relationship between FE values and growth, nutrition, pulmonary status, and fat absorption over a 24 month period. The authors concluded that a substantial number of children with CF have a misclassified pancreatic status. Children with detectable FE concentrations had greater fat absorption, improved growth, and nutritional status over 24 months when compared with those with undetectable FE levels. The reported observation that residual pancreatic exocrine secretion as documented by detectable FE activity has a beneficial effect for CF patients and has important clinical significance. With respect to fat absorption, growth, nutritional, and skeletal maturity status, Cohen et al. (1), as expected, documented that the clinical course is more favorable in children with higher FE levels. The authors attributed better clinical status to lower fecal fat losses not to the difference in energy intake that was no-significantly higher in patients with residual FE concentrations. Fecal fat losses as assessed by coefficient of fat absorption were higher in patients with undetectable FE. Surprisingly, this finding was not confirmed by bomb calorimetry, which indicates there is no real difference between the two groups. The authors underlined that enzyme replacement therapy, although undoubtedly essential for those with severe steatorrhea, may have potential clinical and psychosocial adverse effects. These include the assumption that poor growth and nutritional status is a result of inadequate treatment of PI with the resultant possibility that other causes of nutritional failure may then be missed. On the basis of these results, a very important question has been raised regarding whether the patients with residual pancreatic secretion should be treated with pancreatic enzymes. This question will only be reliably answered by further studies. These will need to focus on those patients with residual pancreatic function but with mild steatorrhea or reduced levels of FE (<200 μg/g stool). Patients with mild steatorrhea are currently treated on the basis of clinical experience, whereas those with FE greater than 200 μg/g stool are unlikely to benefit from pancreatic enzyme therapy. Cohen et al. (1) also documented that 12% of preadolescent children who were diagnosed with PI and prescribed pancreatic enzymes were possibly misdiagnosed. A similar observation was also recently documented in a larger American multicenter study (2). The authors proved that a considerable percentage of both PI and pancreatic sufficient (PS) CF patients was misclassified. As in most of the centers participating in the Borowitz multicenter U.S. study, pancreatic function tests are seldom routinely performed in CF patients. The reliable determination of pancreatic status should be obligatory in all CF patients, and the FE test is a very useful predictor of pancreatic exocrine function (3,4). The measurement of FE concentration could serve as a screening test for maldigestion in CF (5), and, in addition, the test could be used for the longitudinal assessment of declining exocrine pancreatic function in PS patients (6). Beharry et al. (5) documented a high predictive value (99%) for ruling out PI in CF patients using a cutoff level of 100 μg/g of stool for FE measurement. In all but one Polish PI CF patient ever tested, FE concentrations lower than 200 μg/g have been found (7,8). The use by Cohen et al. (1) of stool trypsin concentrations lower than 80 μg/g of feces (in place of 72 hour fecal fat balance studies) to classify some patients as PI may have partly contributed to the high percentage of patients with detectable FE concentrations found in this group. On the other hand, as documented by Cohen et al., some of those patients with FE concentrations greater than 15 μg/g of feces, even when receiving pancreatic enzyme supplementation during the study, fulfill the criteria for PI. Jaroslaw Walkowiak Aleksandra Lisowska I Chair of Pediatrics Department of Gastroenterology and Metabolism Poznan University of Medical Sciences Poznan, Poland