Fecal Calprotectin

Fecal calprotectin, a calcium- and zinc-binding neutrophilic cytosolic protein, is found in proportion to the degree of inflammation present. Fecal calprotectin is resistant to colonic bacterial degradation, is evenly distributed and stable in stool for up to 1 week at room temperature, and can be measured by a commercially available enzyme-linked immunosorbent assay (ELISA) with less than 5 g of stool. Calprotectin plays a regulatory role in the inflammatory process and is a very sensitive marker for detection of inflammation in the gastrointestinal tract. Unfortunately, results from the ELISA test take 5 to 7 days to process, which obviates the ability to make a bedside diagnosis or make timely management decisions. Recently, however, Calpro,™ has developed a rapid test (not yet US Food and Drug Administration approved) that can be done within minutes and correlates well ( r =0.92, P <.001) with its conventional ELISA equivalent.

Insurance coverage for fecal calprotectin may not always occur, depending on specific policies, and out-of-pocket cost can run about $340. For example, Blue Cross and Blue Shield as well as United Healthcare consider this testing to be “investigative.” Current procedural terminology (CPT) code for ordering this test is 83520.

Fecal Lactoferrin

Fecal lactoferrin is an iron-binding protein that is similar to fecal calprotectin in that it is neutrophil derived, has antimicrobial properties, and is available through commercial ELISA testing. Lactoferrin is a major component of neutrophil secondary granules, released upon neutrophil activation and degranulation, and is resistant to proteolysis in the feces. Insurance coverage is slightly better, and out-of-pocket costs are lower compared with calprotectin, running around $90 to $180. For example, Cigna Healthcare considers fecal lactoferrin testing as medically necessary as part of an evaluation of diarrhea but does not cover it because it considers the testing “experimental, investigational, or unproven.” CPT codes for ordering this test include 83630 and 83631.

Differentiating Inflammatory Bowel Disease from Irritable Bowel Syndrome

In a patient presenting with abdominal pain and diarrhea, it can be difficult to ascertain if the etiology is organic or functional. It is common for some symptoms of inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) to overlap, and endoscopic evaluation is used to distinguish between the two. A biomarker that is specific for IBD can prevent those patients with IBS from undergoing unnecessary endoscopic evaluation.

Lactoferrin concentrations have been shown to be increased in active ulcerative colitis (UC) and Crohn disease (CD) with 93% correlation of levels to disease activity; lactoferrin level was also elevated in inactive IBD, above levels from IBS patients and healthy controls. Overall, sensitivity of fecal lactoferrin for IBD was 78% (95% confidence interval [CI], 69%–83%), and the specificity was 90% (95% CI, 83%–96%), correlating well with endoscopic and histologic grading of disease activity. Moreover, elevated fecal lactoferrin was 100% specific in ruling out IBS.

Lactoferrin tested in 177 patients was significantly higher in those with active IBD compared with those with inactive disease, IBS patients, those with enteric infection, and healthy volunteers. The sensitivity and specificity of fecal lactoferrin were 92% and 88%, respectively, for UC, and 92% and 80%, respectively, for CD.

Another comparison study of 139 patients (54 with IBS, 42 with UC, and 43 with CD), found that UC and CD patients with active inflammation had significantly higher levels of lactoferrin and calprotectin compared with those with inactive disease ( P <.05) and with IBS ( P <.05). This study, however, found an overall diagnostic accuracy in IBD of 80.0% for lactoferrin greater than 7.05 μg/mL and 80.0% for calprotectin greater than 48 μg/mL, for the respective clinical disease scores. Calprotectin had the highest diagnostic accuracy in CD (81.4%), whereas lactoferrin was superior in UC (83.3%).

Both fecal calprotectin and lactoferrin have been found to be quite accurate in diagnosing inflammatory disease. In discriminating IBS, Schoepfer and colleagues found that calprotectin and lactoferrin were 89% and 91% accurate, respectively. Overall accuracy for discrimination of IBS from patients with Crohn disease in remission (Crohn Disease Activity Index [CDAI]<150) was 90% for both lactoferrin and calprotectin. Calprotectin and lactoferrin were significantly elevated in patients with Crohn disease with CDAI greater than 150 compared with those in remission. In a comparison study, both fecal calprotectin and lactoferrin had similar sensitivity (78%, 80%), specificity (83%, 85%), PPV (86%, 87%), and accuracy (80%, 81%), respectively.

In yet another study, fecal calprotectin was found to be 95% sensitive (95% CI, 0.93–0.97) and 91% specific (95% CI, 0.86–0.91) for discriminating IBD from functional disorders. Tibble and coworkers found that an abnormal calprotectin test had an odds ratio (OR) for organic disease confirmed by imaging or endoscopic examination of 27.8 (95% CI, 17.6–43.7; P <.0001) compared with an odds ratio of 4.2 (95% CI, 2.9–6.1; P <.0001) and 3.2 (95% CI, 2.2–4.6; P <.0001) for elevated C-reaction protein (CRP) and erythrocyte sedimentation rate. This test also supports the utility of the fecal maker and Rome criteria for differentiating organic disease from functional disorder 1.

A meta-analysis by von Roon and colleagues found that the precision of fecal calprotectin for the diagnosis of IBD was superior to serologic markers such as CRP, erythrocyte sedimentation rate, anti- Saccharomyces cerevisiae antibody, perinuclear antineutrophil cytoplasmic antibody, and anti- Escherichia coli outer membrane porin C antibody.

A meta-analysis of 13 prospective studies (6 adult and 7 pediatric) found fecal calprotectin a useful screening tool for identifying patients who are most likely to need endoscopy for suspected inflammatory bowel disease. Screening by measuring fecal calprotectin levels would result in a 67% reduction in the number of adults requiring endoscopy and a lower, albeit still beneficial, 35% reduction in children to safely exclude IBD with 93% sensitivity and 96% specificity for adults, and 92% sensitivity and 76% specificity for children and teenagers.

Other Etiologies of Elevated Fecal Markers

Although fecal markers are good indicators of IBD compared with IBS, they are not specific for IBD; elevated levels have been found in other diseases ( Table 1 ). Studies showing elevations in fecal calprotectin have found, however, that levels in these other conditions are typically much lower (especially in noninfectious etiologies) than those found in active inflammatory bowel disease. Thus, the fecal markers are still useful, especially if the absolute levels are taken into consideration.

Differentiating Between Crohn Disease and Ulcerative Colitis

Currently, endoscopy, histology, imaging, and serologic testing are used to help differentiate between CD and UC. Although fecal markers are useful to differentiate between IBD and IBS, they have not been found to be useful to differentiate between CD and UC. One study of 48 patients found no statistical difference between Crohn and non-Crohn patients (ulcerative colitis [UC], indeterminate colitis [IC]) in the levels of fecal calprotectin (median, 760 μg/g; interquartile range [IQR], 325–1251 vs 419 μg/g; IQR, 91–1355, respectively, P = .64). Quail and colleagues also found no difference in gender (male vs female, 714 μg/g vs 1032.5 μg/g, P = .74) or age at IBD diagnosis with the calprotectin levels (Kruskal-Wallis test, P = .26). Unlike calprotectin, fecal lactoferrin may differentiate those with UC, which had significantly higher levels (mean, 1125 μg/g) than those with CD (mean, 440 μg/g; P = .04) in one study. However, another study showed similar fecal lactoferrin levels in patients with active CD (1035.25 μg/g) versus active UC (1126.29 μg/g).

Small Bowel Inflammation Versus Colon Inflammation

No significant data were found in the use of fecal markers to distinguish location of disease. However, the likelihood of differentiating between small bowel and colonic inflammation appears to be low, especially because these fecal markers appear unlikely to distinguish CD from UC patients.

Differentiating Inflammatory Bowel Disease from Irritable Bowel Syndrome

In a patient presenting with abdominal pain and diarrhea, it can be difficult to ascertain if the etiology is organic or functional. It is common for some symptoms of inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS) to overlap, and endoscopic evaluation is used to distinguish between the two. A biomarker that is specific for IBD can prevent those patients with IBS from undergoing unnecessary endoscopic evaluation.

Lactoferrin concentrations have been shown to be increased in active ulcerative colitis (UC) and Crohn disease (CD) with 93% correlation of levels to disease activity; lactoferrin level was also elevated in inactive IBD, above levels from IBS patients and healthy controls. Overall, sensitivity of fecal lactoferrin for IBD was 78% (95% confidence interval [CI], 69%–83%), and the specificity was 90% (95% CI, 83%–96%), correlating well with endoscopic and histologic grading of disease activity. Moreover, elevated fecal lactoferrin was 100% specific in ruling out IBS.

Lactoferrin tested in 177 patients was significantly higher in those with active IBD compared with those with inactive disease, IBS patients, those with enteric infection, and healthy volunteers. The sensitivity and specificity of fecal lactoferrin were 92% and 88%, respectively, for UC, and 92% and 80%, respectively, for CD.

Another comparison study of 139 patients (54 with IBS, 42 with UC, and 43 with CD), found that UC and CD patients with active inflammation had significantly higher levels of lactoferrin and calprotectin compared with those with inactive disease ( P <.05) and with IBS ( P <.05). This study, however, found an overall diagnostic accuracy in IBD of 80.0% for lactoferrin greater than 7.05 μg/mL and 80.0% for calprotectin greater than 48 μg/mL, for the respective clinical disease scores. Calprotectin had the highest diagnostic accuracy in CD (81.4%), whereas lactoferrin was superior in UC (83.3%).

Both fecal calprotectin and lactoferrin have been found to be quite accurate in diagnosing inflammatory disease. In discriminating IBS, Schoepfer and colleagues found that calprotectin and lactoferrin were 89% and 91% accurate, respectively. Overall accuracy for discrimination of IBS from patients with Crohn disease in remission (Crohn Disease Activity Index [CDAI]<150) was 90% for both lactoferrin and calprotectin. Calprotectin and lactoferrin were significantly elevated in patients with Crohn disease with CDAI greater than 150 compared with those in remission. In a comparison study, both fecal calprotectin and lactoferrin had similar sensitivity (78%, 80%), specificity (83%, 85%), PPV (86%, 87%), and accuracy (80%, 81%), respectively.

In yet another study, fecal calprotectin was found to be 95% sensitive (95% CI, 0.93–0.97) and 91% specific (95% CI, 0.86–0.91) for discriminating IBD from functional disorders. Tibble and coworkers found that an abnormal calprotectin test had an odds ratio (OR) for organic disease confirmed by imaging or endoscopic examination of 27.8 (95% CI, 17.6–43.7; P <.0001) compared with an odds ratio of 4.2 (95% CI, 2.9–6.1; P <.0001) and 3.2 (95% CI, 2.2–4.6; P <.0001) for elevated C-reaction protein (CRP) and erythrocyte sedimentation rate. This test also supports the utility of the fecal maker and Rome criteria for differentiating organic disease from functional disorder 1.

A meta-analysis by von Roon and colleagues found that the precision of fecal calprotectin for the diagnosis of IBD was superior to serologic markers such as CRP, erythrocyte sedimentation rate, anti- Saccharomyces cerevisiae antibody, perinuclear antineutrophil cytoplasmic antibody, and anti- Escherichia coli outer membrane porin C antibody.

A meta-analysis of 13 prospective studies (6 adult and 7 pediatric) found fecal calprotectin a useful screening tool for identifying patients who are most likely to need endoscopy for suspected inflammatory bowel disease. Screening by measuring fecal calprotectin levels would result in a 67% reduction in the number of adults requiring endoscopy and a lower, albeit still beneficial, 35% reduction in children to safely exclude IBD with 93% sensitivity and 96% specificity for adults, and 92% sensitivity and 76% specificity for children and teenagers.

Other Etiologies of Elevated Fecal Markers

Although fecal markers are good indicators of IBD compared with IBS, they are not specific for IBD; elevated levels have been found in other diseases ( Table 1 ). Studies showing elevations in fecal calprotectin have found, however, that levels in these other conditions are typically much lower (especially in noninfectious etiologies) than those found in active inflammatory bowel disease. Thus, the fecal markers are still useful, especially if the absolute levels are taken into consideration.

Differentiating Between Crohn Disease and Ulcerative Colitis

Currently, endoscopy, histology, imaging, and serologic testing are used to help differentiate between CD and UC. Although fecal markers are useful to differentiate between IBD and IBS, they have not been found to be useful to differentiate between CD and UC. One study of 48 patients found no statistical difference between Crohn and non-Crohn patients (ulcerative colitis [UC], indeterminate colitis [IC]) in the levels of fecal calprotectin (median, 760 μg/g; interquartile range [IQR], 325–1251 vs 419 μg/g; IQR, 91–1355, respectively, P = .64). Quail and colleagues also found no difference in gender (male vs female, 714 μg/g vs 1032.5 μg/g, P = .74) or age at IBD diagnosis with the calprotectin levels (Kruskal-Wallis test, P = .26). Unlike calprotectin, fecal lactoferrin may differentiate those with UC, which had significantly higher levels (mean, 1125 μg/g) than those with CD (mean, 440 μg/g; P = .04) in one study. However, another study showed similar fecal lactoferrin levels in patients with active CD (1035.25 μg/g) versus active UC (1126.29 μg/g).

Small Bowel Inflammation Versus Colon Inflammation

No significant data were found in the use of fecal markers to distinguish location of disease. However, the likelihood of differentiating between small bowel and colonic inflammation appears to be low, especially because these fecal markers appear unlikely to distinguish CD from UC patients.