Calprotectin is a zinc and calcium binding protein that is derived mostly from neutrophils and monocytes. It can be detected in tissue samples, body fluids, and stools, making it a potentially valuable marker of neutrophil activity. Fecal calprotectin levels are increased in intestinal inflammation and may be useful for distinguishing inflammatory from noninflammatory causes of diarrhea.

Fecal calprotectin testing has been used to distinguish between organic and functional intestinal disease. Some authors consider fecal calprotectin to be a marker of neutrophilic intestinal inflammation rather than a marker of organic disease and believe the appropriate use of the marker is to use it to distinguish between inflammatory (IBD) and non-inflammatory bowel disease. In clinical practice, the test might be suitable for selecting patients with IBD symptoms for endoscopy, i.e. deciding which patients do not require endoscopy

Inflammatory bowel disease (IBD) is a chronic inflammatory condition typically associated with the symptoms of diarrhea, defecation urgency, and sometimes rectal bleeding and abdominal pain. There are 2 main forms of the disorder, Crohn disease and ulcerative colitis. Noninvasive diagnosis of inflammatory intestinal disease is difficult because the clinical manifestation of intestinal disorders and colon cancer are relatively nonspecific. For example, a patient presenting with diarrhea or abdominal pain has a wide range of diagnostic possibilities. Endoscopy with histology is the criterion standard method for diagnosing bowel inflammation. Limitations of this approach are that it is invasive, with an associated risk of adverse events, and not well-tolerated by some patients.

There is, thus, a need for simple, accurate, noninvasive tests to detect intestinal inflammation. Potential noninvasive markers of inflammation fall into several categories, including serologic and fecal. Serologic markers such as C-reactive protein and antineutrophil cytoplasmic antibodies tend to have low sensitivity and specificity for intestinal inflammation because they are affected by inflammation outside of the gastrointestinal (GI) tract. Fecal markers, in contrast, have the potential for being more specific to the diagnosis of GI tract disorders, because their levels are not elevated in extradigestive processes. Fecal leukocyte testing has been used to evaluate whether there is intestinal mucosal inflammation. The level of fecal leukocytes can be determined by the microscopic examination of fecal specimens; however, leukocytes are unstable and must be evaluated promptly by skilled personnel. There is interest in identifying stable proteins in stool specimens, which may be representative of the presence of leukocytes, rather than evaluating leukocyte levels directly.

Fecal calprotectin is 1 protein that could possibly be used as a marker of inflammation. It is a calcium- and zinc-binding protein that accounts for approximately 60% of the neutrophils’ cytoplasmic proteins. It is released from neutrophils during activation or apoptosis/necrosis and has a role in regulating inflammatory processes. In addition to potentially higher sensitivity and specificity than serologic markers, another advantage of fecal calprotectin as a marker is that it has been shown to be stable in feces at room temperature for up to 1 week, leaving enough time for patients to collect samples at home and send them to a distant laboratory for testing. In contrast, lactoferrin, also a potential fecal marker of intestinal inflammation, is stable at room temperature for only about 2 days. 

Among potential disadvantages of fecal calprotectin as a marker of inflammation are that fecal calprotectin levels increase after use of nonsteroidal anti-inflammatory drugs, that levels may change with age, and that bleeding (eg, nasal, menstrual) may cause an elevated fecal calprotectin level. Moreover, there is uncertainty about the optimal cutoff to distinguish between IBD and noninflammatory disease. 

Fecal calprotectin testing has been used to differentiate between organic and functional intestinal disease. Some authors consider fecal calprotectin to be a marker of neutrophilic intestinal inflammation rather than a marker of organic disease and believe the appropriate use of the marker is to distinguish between IBD and non-IBD. In practice, the test might be suitable for selecting patients with IBD symptoms for endoscopy, ie, deciding which patients do not require endoscopy. Fecal calprotectin testing has also been proposed to evaluate the response to IBD treatment and for predicting relapse. If found to be sufficiently accurate, results of calprotectin testing could potentially be used to change treatment, such as adjusting medication levels.

There is a commercially available enzyme-linked immunosorbent assay (ELISA) test measuring fecal calprotectin levels, the PhiCal™ (Genova Diagnostics). Recent literature from Europe and Canada has also discussed a rapid test for fecal calprotectin that could be used in the home or doctor’s office. At least 1 product, the Bühlmann Quantum Blue® Calprotectin Rapid Test, is being marketed outside of the United States; rapid tests have not been FDA approved for use in the United States.  

The policy was created with a literature search using MEDLINE through February 2011 and updated regularly with a literature review. The most recent literature review was performed through June 1, 2015. The key literature is summarized in the following section.

Assessment of a diagnostic technology typically focuses on 3 parameters: (1) technical performance; (2) diagnostic performance (sensitivity, specificity, and positive and negative predictive value) in appropriate populations of patients; and (3) demonstration that the diagnostic information can be used to improve patient outcomes (clinical utility). 

Technical performance of a device is typically assessed with 2 types of studies, those that compare test measurements with a criterion standard, and those that compare results taken with the same device on different occasions (test-retest). 

Diagnostic performance is evaluated by the ability of a test to accurately diagnose a clinical condition compared with the criterion standard. The sensitivity of a test is the ability to detect a disease when the condition is present (true positive), while specificity indicates the ability to detect patients who are suspected of disease but who do not have the condition (true negative). Evaluation of diagnostic performance, therefore, requires independent assessment by the 2 methods in a population of patients suspected of disease but who do not all have the disease. 

Evidence related to improvement of clinical outcomes with use of this testing assesses the data linking use of a test to changes in health outcomes (clinical utility). While, in some cases, tests can be evaluated adequately using technical and diagnostic performance, when a test identifies a new or different group of patients with a disease, randomized trials are needed to demonstrate impact of the test on the net health outcome.

Technical Performance

The U.S. Food and Drug Administration (FDA) substantial equivalence determination decision summary for the PhiCal test includes data on technical performance.¹ 

For example, data on test reproducibility were obtained with 2 samples representing the low and high ends of the reportable range of the test. Each sample was extracted 24 times and all extracts were tested. The coefficients of variation (CV) were 12.6% for the low-end sample and 12.1% for the high-end sample. In an analysis of interassay precision, 10 samples (5 positive, 5 negative) were each extracted 5 times from individual pools of stool. Each extract was assayed in 5 replicates on 5 separate runs on different days. The CV range was 5.8% to 20.1%. The findings indicate that the assay is reproducible within acceptable limits along the reportable range.  Diagnostic Performance

Diagnosis of IBD

Several systematic reviews evaluating the accuracy of fecal calprotectin testing for diagnosing inflammatory bowel disease (IBD) have been published. Most recently, in 2015, Menees et al published a systematic review of studies evaluating the ability of fecal calprotectin and other markers to identify patients with IBD and to distinguish between IBD and irritable bowel syndrome (IBS).² The authors included prospective cohort studies that used the enzyme-linked immunosorbent assay (ELISA) test for fecal calprotectin (not the point-of-care test) and used Manning or Rome criteria for IBS diagnosis. Sixtyseven studies were reviewed in detail and 12 met the inclusion criteria. Eight studies on fecal calprotectin had data suitable for analysis. Studies included a total of 1062 participants, 565 with IBD, 259 with IBS, and 239 healthy controls. The authors found that the likelihood of IBD increased as the level of fecal calprotectin increased, with a maximal predictive value of 78.7% at 1000 μ/g. A patient with a fecal calprotectin level below 40 μg/g had 1% chance or less of having IBD. However, no fecal calprotectin level could accurately exclude the possibility of IBS. The predictive value of fecal calprotectin for IBS was 11.6% at 20 μg/g and 7.6% at 1000 μg/g. 

In 2013, Waugh et al in the U.K. published a meta-analysis as part of the national Health Technology Assessment program.³ The investigators searched for studies using fecal calprotectin tests to evaluate inflammation of the lower intestine in newly presenting patients compared with a reference standard, preferably histology. Studies on both laboratory-based and point-of-care tests were included. Studies using fecal calprotectin tests to monitor disease progression or response to treatment were excluded. The authors assessed 83 full-text articles for eligibility and 28 were deemed eligible and included in the quantitative synthesis. Studies were pooled when there were a minimum of 4 using the same calprotectin cutoff. A pooled analysis of 5 studies using fecal calprotectin to differentiate between IBD and IBS in adults at a cutoff of 50 μg/g had a combined sensitivity of 0.93 (95% confidence interval [CI], 0.83 to 0.97) and a combined specificity of 0.94 (95% CI, 0.73 to 0.99). A pooled analysis of 6 studies using fecal calprotectin to differentiate between IBD and non-IBD in adults and children had a combined sensitivity of 0.99 (95% CI, 0.95 to 1.00) and a combined specificity of 0.74 (95% CI, 0.59 to 0.86). The authors concluded that calprotectin testing is a reliable method for differentiating between inflammatory and noninflammatory disease of the bowel. They noted that most studies have been done in specialty settings. A limitation of the evidence, noted in the review, is that the optimal cutoff for calprotectin tests is not known; most studies used the cutoff of 50 μg/g and did not evaluate other potential cutoffs. Accordingly, the authors recommended using the 50 μg/g cutoff and reevaluating this cutoff as additional evidence accumulates. 

In 2010, van Rheenen et al published a meta-analysis on studies conducted in adults and/or children.⁴ The authors only included studies that met the following methodologic criteria: used prospective study design, included patients with suspected bowel disease, obtained stool samples before endoscopy, and evaluated all patients endoscopically with histological verification of segmental biopsies. Thirteen studies met eligibility criteria; 6 were conducted in adults and 7 in children and adolescents. IBD was confirmed by the reference test in 215 of 670 (32%) of adults and 226 of 371 (61%) of the children. Eleven studies used the PhiCal test; 7 of the 11 (64%) used a cutoff of 50 μg/g for a positive calprotectin test, and the remainder used cutoffs ranging from 24 to 100 μg/g. In the adult studies, the pooled sensitivity and specificity of the fecal calprotectin test for distinguishing between IBD and non-IBD was 93% (95% CI, 85% to 97%) and 96% (95% CI, 79% to 99%), respectively. For children and teenagers, the corresponding numbers were a sensitivity of 92% (95% CI, 84% to 96%) and a specificity of 76% (95% CI, 62% to 86%). Specificity was significantly lower in children and teenagers than in adults (p=0.048).

Use of the fecal calprotectin test significantly changed the posttest probability of IBD in both age groups. In adults, an abnormal calprotectin test increased the probability of IBD from a pretest probability of 32% to a posttest probability of 91% (95% CI, 77% to 97%). Similarly, a normal calprotectin test reduced the probability from 32% to 3% (95% CI, 1% to 11%). In children and teenagers, an abnormal calprotectin test increased the probability of IBD from 61% to 86% (95% CI, 78% to 92%) and a normal calprotectin test reduced the probability from 61% to 15% (95% CI, 7% to 28%). 

The investigators calculated that, in a hypothetical population of 100 adults with suspected IBD (and a prevalence of 32%), fecal calprotectin testing would result in 30 true positives, 65 true negatives, 3 false positives, and 2 false negatives. If only patients with a positive test received endoscopy, 33 of 100 (33%) would receive endoscopy including 3 patients without disease. Two patients with disease would be missed. In a hypothetical population of 100 children with suspected IBD (and a prevalence of 61%), there would be 56 true positives, 30 true negatives, 9 false positives, and 5 false negatives. Nine of 100 without disease would get endoscopy and 5 patients with disease would be missed. In a lower prevalence population, the positive predictive value of fecal calprotectin testing would be lower; accordingly, the authors did not recommend use of the test to screen asymptomatic patients or use of the test in a primary care setting. It is also worth noting that, when 95% CIs were taken into account, the data were consistent with a posttest probability of having IBD with a negative fecal calprotectin test as high as 11% in adults and 28% in children. The authors commented that, due to the relatively small number of studies meeting their eligibility criteria, they were unable to examine different test cutoffs. Seven of 13 (54%) used the manufacturer’s recommended cutoff of 50 μg/g, but the remaining studies used cutoffs ranging from 24 to 100 μg/g. The authors also stated that, despite their efforts to include patients most likely to be potential candidates for the test, none of the studies used a clear diagnostic algorithm to select patients at highest risk of IBD. 

An earlier meta-analysis of studies on the diagnostic accuracy of fecal calprotectin testing in children and adults was published by Van Roon et al in 2007.⁵ The authors included studies that evaluated fecal calprotectin with histologic diagnosis of Crohn disease (CD), ulcerative colitis (UC), or/and colorectal cancer. An addition to eligibility criteria was that studies include a control group either of healthy people or people with IBS. The authors identified 30 studies with a total of 5983 participants (3393 of whom were healthy controls). Nine studies (n=1297) provided data on the ability of fecal calprotectin to distinguish between IBD versus no IBD using a cutoff of 50 μg/g to indicate a positive test. The pooled sensitivity was 89% (95% CI, 86% to 91%) and the pooled specificity was 81% (95% CI, 78% to 84%). Stratifying by age group, a pooled analysis of 6 studies conducted in adults (n=1030) using the 50 μg/g cutoff, calculated a sensitivity of 71% (95% CI, 67% to 75%) and specificity of 80% (95% CI, 77% to 83%). When findings from the 3 studies with children (n=201) were pooled, the sensitivity was 83% (95% CI, 73% to 90%) and specificity was 85% (95% CI, 77% to 91%). Four studies (n=328) provided data on differentiating between IBD and no IBD in adults and/or children using a calprotectin cutoff of 100 μg/g. The pooled sensitivity was 98% (95% CI, 93% to 99%) and the pooled specificity was 91% (95% CI, 86% to 95%). The authors noted that there may have been spectrum bias in the studies included in the review. That is, studies using fecal calprotectin to differentiate between IBD and non-IBD had differing proportions of patients with mild versus severe disease, and this could have affected the sensitivity and specificity of the test.

Several systematic reviews were limited to studies in the pediatric population. In 2014, Henderson et al focused on studies of pediatric patients undergoing an initial investigation for suspected IBD.⁶ The authors identified 8 studies that reported fecal calprotectin levels before endoscopic investigation of IBD in patients younger than 18 years. Six studies used a fecal calprotectin cutoff of 50 μg/g and the other 2 used a cutoff of 100 μg/g. In their quality assessment, only 3 studies were judged to have a representative spectrum of patients and only 3 studies clearly reported that they used an acceptable reference standard (ie, upper and lower endoscopy in all patients). Findings from the 6 studies were pooled. The pooled sensitivity and specificity of fecal calprotectin in identifying patients with IBD were 97.8% (95% CI, 94.7% to 99.6%) and 68.2% (50.2% to 86.3%), respectively. A 2012 meta-analysis by Kostasis et al identified a total of 37 studies conducted with children.⁷ Three studies were excluded because they did not report sufficient information about fecal calprotectin levels, which left 34 studies in the review. Studies were included in the review regardless of sample size or methodologic characteristics. Study findings were not pooled due to heterogeneity. The sensitivity of studies using fecal calprotectin to identify children with IBD ranged from 12.5% to 100% and specificity ranged from 58.3% to 100%. When the analysis was limited to patients with newly diagnosed and untreated IBD (ie, similar to the population included in the Henderson meta-analysis), the sensitivity of fecal calprotectin ranged from 73.5% to 100% and the specificity ranged from 65.9% to 100%. 

Representative diagnostic test studies using the fecal calprotectin test are described next.

In 2015, Kennedy et al in the U.K. retrospectively evaluated the diagnostic accuracy of fecal calprotectin for diagnosing IBD by examining medical records at 2 teaching hospitals in Scotland.⁸ The study included patients ages 16 to 60 years who were presenting for the first time with gastrointestinal (GI) symptoms and had undergone fecal calprotectin testing prior to diagnosis. Medical records were reviewed to identify diagnostic information using measures such as Lennard-Jones criteria for diagnosing IBD and Rome III criteria to classify IBS patients. If no diagnosis was recorded in the medical record, 2 gastroenterologists blinded to the fecal calprotectin test results reviewed clinical notes. Patients with an organic diagnosis or who had a full colonoscopy (n=467) were censored at the time of medical record review. A total of 895 patients were included in the final analysis. Of these, 566 (63.2%) were diagnosed with a functional disorder, 91 (10.2%) were diagnosed with IBD, and the remaining patients had other GI conditions or did not have a final diagnosis. Fecal calprotectin levels were significantly higher in patients diagnosed with IBD (median, 1251 μg/g) than those with a functional diagnosis (median, 20 μg/g) or other GI condition (median, 50 μg/g). According to receiver operator characteristic (ROC) analysis, the area under the curve (AUC) was 0.97 for distinguishing between IBD and functional disease. Using the manufacturer’s recommended cutoff of 50 μg/g, the sensitivity and specificity of fecal calprotectin for identifying IBD versus functional disorder were 97% (95% CI, 90% to 99%) and 74% (95% CI, 70% to 77%), respectively. At a cutoff of 70 μg/g, sensitivity remained at 97% (95% CI, 90% to 99%) and the specificity was 80% (95% CI, 76% to 83%). 

A 2012 study from Switzerland by Manz et al included 575 consecutive adult patients with abdominal discomfort from a single center who were referred for endoscopy.⁹ A fecal sample was collected within 24 hours of undergoing colonoscopy or sigmoidoscopy. Fecal calprotectin was measured using a commercially available ELISA test by staff blinded to the endoscopic findings. The gastroenterologists who conducted endoscopies were blinded to fecal calprotectin test results. A total of 538 of 575 (94%) patients were included in the analysis; 37 patients were excluded because they did not complete the study protocol. Endoscopies yielded clinically significant findings in 212 of 538 (39%) of patients. Median calprotectin levels were higher in patients with clinically significant findings (97 μg/g) than in patients with normal endoscopic findings (10 μg/g; p<0.001). Using a cutoff of 50 μg/g, the fecal calprotectin test had a sensitivity of 73% and specificity of 93% for identifying clinically significant disease. ROC analysis yielded an AUC of 0.88 (95% CI, 0.85 to 0.90). 

Otten et al in the Netherlands published a study in 2008 evaluating the ability of fecal calprotectin and lactoferrin to discriminate between IBD and IBS.¹⁰ The study included 144 adult patients who were referred for colonoscopy or sigmoidoscopy due to lower GI abdominal complaints. A fecal sample was obtained before endoscopy. Endoscopy data were not available for 5 patients; 114 of the remaining 139 (82%) were diagnosed with either IBD (n=23) or IBS (n=91) and were included in the analysis. At a cutoff of 50 mg/kg, the PhiCal ELISA calprotectin test had a sensitivity of 95.7% (95% CI, 76.0% to 99.8%) and a specificity of 86.8% (95% CI, 77.7% to 92.7%) for distinguishing between IBD and IBS in the 114 patients. In contrast, an ELISA test measuring lactoferrin (cutoff, 7.25 mg/mL) had a sensitivity of 78.3% (95% CI, 55.8% to 91.7%) and specificity of 90.1% (95% CI, 81.6% to 95.1%). 

In 2008, Sidler et al published a study conducted in Australia that included 61 children ages 2 to 18 years referred for endoscopy for GI tract symptoms suggestive of organic disease.¹¹ Children with an established diagnosis of an organic GI tract disease were excluded. Stool samples were collected before endoscopy. Thirty-one children (51%) were diagnosed with IBD and 30 were diagnosed with a non-IBD condition. At a cutoff of 50 mg/kg, fecal calprotectin had a sensitivity of 100% and a specificity of 67% for differentiating between IBD and non-IBD conditions. At a cutoff of 200 mg/kg, fecal calprotectin had a sensitivity of 90% and a specificity of 97%. 

Section Summary

A number of well-conducted studies have been published that evaluate the accuracy of fecal calprotectin levels for diagnosing IBD. Additionally, several systematic reviews of these studies have been published. In general, the studies indicate that the commercially available test is reasonably accurate for use in patients with clinical suspicion of disease. Studies varied in the cutoff of fecal calprotectin used to indicate the presence of disease. As reported in systematic reviews, the greatest amount of evidence exists for the cutoff of 50 μg/g; however, an optimal cutoff for diagnosing IBD is not yet clear from the available studies. Moreover, most studies have been conducted in specialty care; there is less evidence on the diagnostic accuracy of fecal calprotectin tests in the primary care setting. 

Evaluating Response to Treatment

Several studies have evaluated the accuracy of calprotectin and other fecal markers for predicting treatment outcome in patients with bowel disease. For example, a 2010 prospective multicenter study by Turner et al examined the ability of 4 fecal markers to predict steroid refractoriness in 101 children with severe UC.¹² The markers were fecal calprotectin, lactoferrin, M2-pyruvate kinase (M2-PK), and S100A12. Stool samples were obtained from children when they were admitted to the hospital for intravenous steroid treatment. Twenty-six patients (26%) subsequently failed steroid treatment within a median of 10 days. Levels of all fecal markers were elevated at baseline. The mean value of fecal calprotectin at sampling for patients who later responded to treatment was 3307 μg/g and for those who failed treatment it was 7516 μg/g; this difference was statistically significant (p=0.039). The ability of the fecal markers to predict treatment response was assessed using ROC analysis. An ROC of greater than 0.7 was considered fair, 0.8, good, and greater than 0.9, excellent at discriminating between steroid responders and nonresponders. The ROC values for the markers were 0.64 for calprotectin, 0.51 for lactoferrin, 0.75 for M2-PK, and 0.39 for S100A12; only M2-PK was considered to be at least a “fair” marker. In addition, a clinical scoring system known as the Pediatric Ulcerative Colitis Activity Index had an AUC of 0.81. 

A 2012 study by Molander et al in Finland included 60 patients with IBD (34 had CD, 26 had UC).¹³ The study evaluated whether a normal fecal calprotectin level after induction therapy predicted the response to maintenance therapy 1 year later. Patients, all of whom had an elevated fecal calprotectin level at baseline (mean, 810 μ1 (52%) of patients had a normal fecal calprotectin value and 29 (48%) had an elevated fecal calprotectin. Forty-eight patients used maintenance therapy for approximately 1 year; the other 12 stopped due to lack of response. At the 1-year follow-up, 26 of the 31 (84%) patients with normal fecal calprotectin after induction were in clinical remission compared with 11 of 29 (38%) of those with an elevated fecal calprotectin level after induction (p<0.001). Using ROC analysis, a fecal calprotectin level of 139 μg/g after induction therapy was selected as the best cutoff to predict risk of having clinically active disease at 1 year. Using this cutoff, there was a sensitivity of 72%, a specificity of 80%, and AUC was 0.84. 

A 2008 study by Wagner et al in Sweden included 40 patients with IBD who had symptoms of relapse.¹⁴ Two patients were excluded, leaving 27 with UC and 11 with CD. All patients were evaluated clinically before and after treatment (4 and 8 weeks), and patients with UC also underwent endoscopy. Treatment of relapse was individualized; most patients received topical and/or systemic 5-aminosalicylic acid. Fecal samples were obtained at baseline and at 4 and 8 weeks after starting treatment for recurrence. Samples were tested for fecal calprotectin levels (>50 μg/g was considered to be positive), as well as for fecal myeloperoxidase (MPO) and fecal eosinophil protein X (EPX). Mean fecal calprotectin levels in UC patients were 5600 μg/g at baseline, 1730 μg/g at 4 weeks, and 1820 μg/g at 8 weeks. Mean levels in CD patients were 5010 μg/g at baseline, 2440 μg/g at 4 weeks and 1460 μg/g at 8 weeks. In UC patients, a complete response (CR) was defined as return of clinical and endoscopic scores to normal. Fourteen of 27 (52%) of UC patients experienced a CR after 4 weeks and 21 of 27 (78%) had a CR after 8 weeks. There was a statistically significant decline in fecal calprotectin levels in complete responders (p<0.01) with UC, and this was not observed in partial or nonresponders. In the CD group, 9 of 11 (81%) had a CR after 4 weeks and 10 of 11 (91%) after 8 weeks. The change in fecal calprotectin levels in complete responders was not statistically significant. Normalized fecal calprotectin levels at the end of the study predicted a CR in 100% of patients. However, elevated fecal calprotectin levels were inconclusive. Elevated fecal calprotectin levels were found in 10 of 21 patients with UC and 6 of 9 patients with CD who responded to treatment by the end of the study. These elevated levels were not likely to indicate an imminent relapse. Patients with continued high levels of fecal calprotectin were followed retrospectively, and none was found to have had a relapse within 3months of conclusion of the study. There was a strong correlation in fecal calprotectin values at all time periods and values of MPO and EPX.  

Section Summary

The available data on using fecal calprotectin testing to predict response to treatment are preliminary investigations. Potential cutoff values derived from study data would need to be verified using other samples of patients. Cutoffs varied among studies. In addition, common limitations of the studies predicting response to treatment are that none provided data on how treatment decisions and/or health outcomes would differ with and without use of the test.

Assessment of Disease Activity

Two recent meta-analyses have reviewed studies on fecal calprotectin testing to identify IBD patients with active disease. A 2015 meta-analysis by Mosli et al evaluated the diagnostic accuracy of fecal calprotectin in adults and children with previously diagnosed UC or CD who had active disease confirmed by endoscopy.¹⁵ A total of 19 studies with 1069 UC patients and 1033 CD patients met eligibility criteria. Individual studies used a variety of cutoffs for fecal calprotectin, ranging from 6 to 280 μg/g. Pooled sensitivity and specificity estimates for fecal calprotectin were 88% (95% CI, 84% to 90%) and 73% (95% CI, 66% to 79%), respectively. The AUC for fecal calprotectin was 89% (95% CI, 86% to 91%). In 2014, Lin et al published a meta-analysis limited to studies of adults diagnosed with IBD.¹⁶ The studies evaluated fecal calprotectin for monitoring IBD activity and use of an endoscopic scoring system as the reference standard. Ten studies with 744 UC patients and 727 CD patients met eligibility criteria. The authors selected the cutoff value from each study that had the highest diagnostic accuracy and used this estimate for the pooled analyses. Pooled sensitivity of fecal calprotectin for identifying active disease versus remission was 85% (95% CI, 82% to 87%). Pooled specificity was 81% (95% CI, 77% to 84%). Cutoff values for testing positive for fecal calprotectin ranged from 30 to 274 ?g/g in individual studies. At the manufacturer’s recommended cutoff of 50 ?g/g, pooled sensitivity was 92% and pooled specificity was 60%. At a cutoff of 100 μg/g, pooled sensitivity was 84% and pooled specificity was 66%. 

Section Summary

Two meta-analyses of studies using fecal calprotectin testing to distinguish between IBD patients with active disease and those in remission had a relatively high diagnostic accuracy. However, the cutoff for a positive fecal calprotectin test varied widely and there is a lack of data on the clinical utility of this application of fecal calprotectin testing, eg, how findings would impact decisions for endoscopic monitoring.

Predicting Relapse 

In 2012, Mao et al published a meta-analysis of studies evaluating fecal calprotectin in predicting relapse of IBD.¹⁷ Their systematic review included prospective studies of adult patients that measured fecal calprotectin at relapse, included estimates of diagnostic accuracy (eg, sensitivity, specificity), and based their definition of relapse on clinical activity indices or endoscopic findings. The authors identified 11 studies; on closer examination, 4 of these were found not to meet their inclusion criteria. Thus, 6 studies with 672 patients were included in the meta-analysis. Five of them included patients with both CD and UC and the sixth study included only patients with CD. In all studies, fecal calprotectin was measured when patients were in clinical remission and was used to predict relapse 1 year later. The pooled sensitivity and specificity of fecal calprotectin to predict relapse of IBD was 78% (95% CI, 72% to 83%) and 73% (95% CI, 68% to 77%), respectively. The pooled area under the ROC curve was 0.83. The authors concluded that the diagnostic test performance was not as high as expected but advantages of fecal calprotectin assessment are that it is a simple and noninvasive test. They noted that limitations of the studies were that remission was based on subjective clinical activity indices and that additional prospective studies using endoscopic relapse were needed.

Representative trials are described next. 

A 2013 prospective study by Yamamoto et al in Japan studied 80 UC patients who had been in remission for at least 3 months and were taking mesalamine as maintenance therapy.¹⁸ Fecal calprotectin levels were measured at the beginning of the study. At 12-month follow-up, 21 (26%) patients had relapsed. The mean calprotectin level was 172.7 μg/g in patients who relapsed and 135.5 μg/g in patients who remained in remission (p=0.02). Based on levels in study patients, the authors selected 170 μg/g as a cutoff for calprotectin to evaluate diagnostic accuracy. Using this cutoff, fecal calprotectin had a sensitivity of 76% and a specificity of 76% for predicting relapse. 

In 2013, Lasson et al in Sweden published findings of a prospective study of newly diagnosed UC patients.¹⁹ After an initial workup, patients were monitored over 3 years, with planned follow-up after 3 months and yearly thereafter. Fecal calprotectin was monitored at each visit. Relapse was defined as an increase in symptoms of sufficient severity to justify changing treatment. A total of 101 patients were eligible to participate. Twenty-eight patients were subsequently excluded due to a missing stool sample at 3 months, 3 did not meet diagnostic criteria for UC, and 1 was lost to follow-up. Thus, 69 patients (68%) were included in the 1-year analysis. During the first year, 24 patients (35%) did not experience a relapse of UC. These patients had a significantly lower median level of fecal calprotectin at 3 months (102 μg/g) than patients with relapsing UC (263 μg/g). Sixty-seven patients were included in the 2- and 3-year analyses. The 3-month fecal calprotectin levels were significantly higher in patients with relapsing disease at 2 years than those with mild disease. There was no a significant relationship between fecal calprotectin and relapsing disease at 3 years. The authors found that the 3-month fecal calprotectin concentration of 169 μg/g yielded the greatest sensitivity and specificity to predict relapse at 1 year (64.4% and 70.8%, respectively). The optimal cutoff of fecal calprotectin for predicting relapsing disease at 2 years was 262 μg/g (sensitivity, 51.1%; specificity, 81.8%). 

A 2009 study by Gisbert et al in Spain included 163 patients (89 CD, 74 UC) who had been in remission for at least 6 months.²⁰ One sample of fecal calprotectin was obtained at baseline, and patients were followed for 12 months. Mean baseline level of fecal calprotectin was 153 μg/g (range, 6-1217 μg/g); levels were not reported for UC versus CD patients. During the follow-up period, 13 of 74 (18%) UC patients and 13 of 89 (15%) CD patients experienced a relapse severe enough to warrant a change in treatment. Mean levels of calprotectin were significantly higher in patients who relapsed compared with those who did not. In CD patients, mean levels were 266 μg/g in relapsing patients and 145 μg/g in nonrelapsing patients (p=0.002). Corresponding values in UC patients were 213 μg/g and 126 μg/g, respectively (p=0.03). A cutoff of 150 μg/g for fecal calprotectin was found to best predict relapses of IBD. At 150 μg/g, fecal calprotectin had 31% sensitivity and 91% specificity for predicting UC and 28% specificity and 93% specificity for predicting CD. 

Section Summary

A 2012 meta-analysis of 6 prospective studies found a pooled sensitivity of 78% and a pooled specificity of 73% of the fecal calprotectin test in predicting relapse in IBD patients in remission. Cutoff values of fecal calprotectin have varied in the studies, and studies have tended to base definitions of remission on subjective clinical remission indices, rather than endoscopic data. In addition, like the studies on predicting response to treatment, the impact of fecal calprotectin testing on health outcomes in UC and CD patients in remission has not been evaluated in controlled studies.

Clinical Utility 

Clinical utility for all potential uses of the test is best evaluated by prospective controlled studies, ideally randomized controlled trials (RCTs), evaluating the impact of the test on patient management decisions and/or health outcomes. For example, there is interest in studies that evaluate whether the endoscopy rate is decreased when fecal calprotectin testing is used to evaluate patients with suspected IBD and in studies that compare health outcomes in patients managed with and without use of fecal calprotectin testing. 

No studies evaluating clinical utility of fecal calprotectin testing for diagnosis of IBD, the FDA-cleared indication, were identified. However, 1 RCT has examined the value of fecal calprotectin testing for managing patients with UC at high risk of relapse. This prospective nonblinded study, published by Lasson et al in 2015, included adults with UC who were on maintenance treatment with oral 5aminosalicylate (5-ASA) medication and who had at least 1 flare-up during the previous year.²¹ Patients were randomized in a 3:2 ratio to an intervention that based medication dosing decisions on fecal calprotectin levels and a usual care control group. Both groups submitted fecal samples at baseline and on a monthly basis. In the intervention group, a cutoff of 300 ?g/g of calprotectin was used as the cutoff for escalating the dose of 5-ASA to the maximally tolerable dose. The high dose of 5-ASA was continued

3 months and then was reduced when the fecal calprotectin was less than 200?g/g. The primary outcome was the rate of relapse at 18 months; relapse was defined as a Mayo score of 2 or less, with no single variable greater than 1. At 1 year, 18 of 51 patients (35.3%) in the intervention group and 20 of 40 (50%) in the control group experienced at least 1 relapse. The difference between groups was not statistically significant (p=0.23). The authors noted that 10 of the 18 patients in the intervention group had a relapse but did not have a fecal calprotectin value above the cutoff for medication dosage escalation and, in the subgroup of patients who did have values of 300 ?g/g or more, there was a significantly lower rate of relapse in the intervention group than in the control group (28.6% and 57.1%, respectively). Future RCTs could prospectively evaluate the clinical utility of a lower cutoff of fecal calprotectin. 

Section Summary

No controlled studies have evaluated the clinical utility of fecal calprotectin measurement used to diagnose IBD. A single RCT has been published to date evaluating the relapse rate in patients with UC whose medication doses were managed with and without fecal calprotectin test results and, in its primary analysis, found no significant difference in relapse at 18 months. 

Summary of Evidence

Numerous studies have evaluated the ability of fecal calprotectin testing to distinguish between patients with inflammatory bowel disease (IBD) and non-IBD, the U.S. Food and Drug Administration?approved indication for the fecal calprotectin test. Generally, studies have shown that the fecal calprotectin test is reasonably accurate for this purpose when used in an appropriate patient population, ie, patients with clinical suspicion of IBD based on examination and history. Studies have also examined the association between fecal calprotectin levels and the response to treatment or risk of relapse in patients known to have IBD. However, studies have used various cutoffs to indicate an abnormally high fecal calprotectin level for diagnosing or monitoring patients. Although the greatest amount of evidence exists for the cutoff of 50 μg/g, the optimal cutoff remains unknown. Moreover, most diagnostic accuracy studies have been conducted in the specialty care setting, and there is insufficient evidence of accuracy in the primary care setting where disease level is likely lower. Furthermore, only 1 prospective comparative study has evaluated the clinical utility of fecal calprotectin testing. That study did not find a statistically significant difference in the relapse rate when patients with ulcerative colitis were managed with and without use of fecal calprotectin test results to guide medication dosage.