Is Fecal Calprotectin an Accurate Marker of Inflammation in Cystic Fibrosis?

Background: There is increasing evidence that intestinal inflammation plays a major role in gastrointestinal symptoms in cystic fibrosis (CF). Fecal calprotectin is a marker that is elevated in several gastrointestinal inflammatory diseases, but little is known about its value in CF. We aimed to look for associations of elevated fecal calprotectin among CF patients and whether its level correlates with the clinical manifestations of CF. Methods: A single stool specimen was collected from 62 patients with CF. Fecal calprotectin was measured using the commercially available ELISA kits (PhiCal test). Clinical data were collected from patients’ records and CF registry. Results: There were no significant differences between CF patients with normal and abnormal fecal calprotectin levels. However, patients who were not receiving inhaled antibiotics had higher fecal calprotectin levels than those who were. Conclusion: Elevated fecal calprotectin may not accurately predict intestinal inflammation in CF. However, the fact that it was elevated in both pancreatic sufficient and insufficient groups supports the concept of “cystic fibrosis enteropathy” regardless of the pancreatic status. Background: Cystic fibrosis (CF) is the most common cause of pancreatic insufficiency (PI) in children. Between 85% 90% of CF patients have PI and malabsorption. These patients are typically treated with pancreatic enzyme replacement therapy (PERT). However, CF patients with pancreatic sufficiency (PS), and patients with PI who receive adequate PERT, may have persistent abdominal symptoms. It has been suggested that other poorly understood non pancreatic confounding factors are likely contributors [1]. There is no specific noninvasive test to prove the presence of intestinal inflammation. Several studies have shown evidence of intestinal inflammation in CF. Increased amounts of inflammatory markers were found in whole gut lavage indicating immune activation in the intestinal mucosa of CF patients [2-4]. A study using wireless capsule endoscopy (WCE) showed varying degrees of inflammatory findings including edema, mucosal breaks and ulcerations in most adult patients with CF [5]. Calprotectin, a protein found mainly in neutrophils, but also in monocytes and macrophages, is released during neutrophil activation or death. Calprotectin can be measured in plasma as well as other body fluids but is six times more concentrated in feces than in blood [6, 7]. Fecal calprotectin (FC) is thus an inflammatory marker that is elevated in a variety of inflammatory intestinal diseases such as Crohn’s disease and CF [5, 7, 8]. Canani et al showed a correlation between FC with the histologic grade of mucosal inflammation observed at endoscopy in patients with inflammatory bowel disease (IBD). In their study FC was a more accurate predictor of active mucosal inflammation than clinical scores and serum markers [8]. Similarly, Bruzesse et al showed that intestinal mucosal inflammation is a major feature of cystic fibrosis. A comparison of 30 CF patients and 15 IBD patients with 30 healthy controls showed that the first 2 groups had significantly higher mean FC than controls [9]. The present study was performed to determine the frequency of elevated FC in CF patients, and to determine whether there are any associations with different characteristics such as pancreatic status, gastrointestinal morbidities, pulmonary function tests (PFTs) and pulmonary exacerbations. We also evaluated whether FC values differ between patients who receive certain treatments (PERT, probiotics and antibiotics) and those who do not. Methods: Between January 2009 – November 2010 all patients attending the CF clinic at the Children’s Hospital of Wisconsin were requested to provide a stool specimen for the study at their next clinic visit regardless of their age, CF mutations, pancreatic status or severity of disease. Sixty two patients participated. The samples were stored at (-60 C) until analysis. FC is stable at room temperature for up to 1week [8, 10, 11]. Clinical data were collected from patients’ medical records and CF registry. Data collected included: age at CF diagnosis (years); age at sample collection (years); spirometry parameters including forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1) and forced expiratory flow 25%-75% (FEF25-75%); gender; ethnicity; diagnosis (classic CF, or CF related metabolic syndrome CRMS); body mass index (normal, obese, overweight); symptoms (abdominal pain, gas, vomiting, fever, pulmonary exacerbation); stool characteristics (frequency, consistency); hospitalizations; morbidities (meconium ileus, surgery, bowel resection, distal intestinal obstruction syndrome (DIOS); antibiotic use (inhaled, intravenous, oral); pancreatic enzyme supplementation; probiotic use; and pancreatic function (PI versus PS ). Calprotectin Assay: The coded stool samples were thawed, aliquots of 80-120 mg were taken and then a quantitative measurement was done using commercially available ELISA kits (PhiCal test). ELISA steps were all completed according to the instructions of the manufacturer. This study was approved by the institutional review board of the Children’s Hospital of Wisconsin and consent and/or assent was obtained from patients and/or parents as appropriate.