AIM: To investigate possibility and clinical application of fecal calprotectin in determining disease activity of ulcerative colitis (UC).

METHODS: The enzyme-linked immunosorbent assay (ELISA) was used to measure the concentrations of calprotectin in feces obtained from 66 patients with UC and 20 controls. C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), acid glycoprotein (AGP) were also measured and were compared with calprotectin in determining disease activity of UC. The disease activity of UC was also determined by the Sutherland criteria.

RESULTS: The fecal calprotectin concentration in the patients with active UC was significantly higher than that in the inactive UC and in the controls (402.16 ± 48.0 &mgr;g/g vs 35.93 ± 3.39 &mgr;g/g, 11.5 ± 3.42 &mgr;g/g, P < 0.01). The fecal calprotectin concentration in the inactive UC group was significantly higher than that in the control group (P < 0.05). A significant difference was also found in the patients with active UC of mild, moderate and severe degrees. The area under the curve of the receiver operating characteristics (AUC^ROC) was 0.975, 0.740, 0.692 and 0.737 for fecal calprotectin, CRP, ESR and AGP, respectively. There was a strong correlation between the fecal calprotectin concentration and the endoscopic gradings for UC (r = 0.866, P < 0.001).

CONCLUSION: Calprotectin in the patient’s feces can reflect the disease activity of UC and can be used as a rational fecal marker for intestinal inflammation in clinical practice. This kind of marker is relatively precise, simple and noninvasive when compared with other commonly-used markers such as CRP, ESR and AGP.

Ulcerative colitis (UC) is a chronic, idiopathic inflammatory bowel disease characterized by remission of disease activity. The incidence and the prevalence rates of UC are increasing in China[1]. It is important to accurately evaluate intestinal mucosa inflammation in the management of these patients, particularly for the assessment of therapeutic effectiveness. Colonoscopy and biopsy are useful in the assessment of intestinal mucosa inflammation of patients with UC, but these examinations can be a heavy burden to the patient[23]. Clinical evaluations including laboratory tests such as C-reactive protein (CRP)[4–6], erythrocyte sedimentation rate (ESR)[7], acid glycoprotein (AGP)[8], and platelet count[910], have been used for the determination of disease activity of UC, but none of them are specific for gut inflammation[11]. Therefore, a new marker that will be more sensitive and specific for determination of disease activity of UC is urgently needed in clinical practice.

An alternative approach to the assessment of the presence of intestinal inflammation[12] is to analyze the whole gut lavage fluid or to quantitate the protease resistant neutrophil derived proteins such as lactoferrin[1314] in the patient’s feces, and this approach can be non-invasive for the patient. Calprotectin is one of these proteins. It is a major protein in the neutrophilic granulocytes and the macrophages[15], which accounts for 60% of the total protein in the cytosol fraction in these cells[1617]. This kind of protein can resist metabolic degradation caused by intestinal bacteria, and the protein is relatively stable in stools for up to one week at room temperature[18]. It can differentiate between patients with organic or non-organic intestinal disease, and can be useful in detecting colorectal cancer and inflammatory disorders, and can also be useful in predicting a relapse of inflammatory bowel disease[19].

Our study was aimed at the measurement of the concentration of calprotectin in the feces of the UC patient and at the comparison of it with commonly-used markers in clinical practice, such as CRP, ESR and AGP.

Chronic relapsing and remitting inflammation of the gastrointestinal tract is the hallmark of UC. One of the most prominent histological features observed in UC is infiltration of the neutrophils into the inflamed mucosa at an early stage of inflammation. The neutrophils are major sources of inflammatory cytokines, chemokines proteases, active lipids, and reactive oxygen derivatives, as well as a full complement of factors needed to exacerbate mucosal inflammation and tissue injury[22–25] The fecal calprotectin excretion of indium-labeled autologous granulocytes has for a long time been suggested as the gold standard test in assessing bowel inflammation in inflammatory bowel disease. However, as it involves an exposure to radiation and prolonged fecal collection, which is unpopular with patients and laboratory staff, it is only used as a research tool. In patients with inflammatory bowel disease, a three day excretion of indium-labeled granulocytes correlated well with a daily excretion and a one-off fecal calprotectin level[26].

In this study, we focused on the evaluation of any relationship that might exist between the mucosal neutrophil infiltration represented by calprotectin, CRP, ESR, AGP and the UC disease activity represented by the Sutherland criteria. The DAI score of UC is the sum score of the following four parameters (each scoring between nought and three, making 12 the worst score): stool frequency, rectal bleeding, mucosa appearance, and physician’s global assessment[27]. It reflects the clinical representation of UC and is the most extensive and simplest DAI. It is adopted by the guidelines for the management of inflammatory bowel disease in the fourth Asia Pacific Digestive Week[28]. Our results showed that fecal calprotectin concentrations were significantly higher in the patients with active UC than in the patients with inactive UC and in the controls. In addition, our results showed that fecal calprotectin concentration was higher in the patients with inactive UC than in the controls. In the patients with UC, the fecal calprotectin concentration had a better correlation with DAI than the CRP, ESR or AGP concentration.

The ROC curve is adopted not only to ensure the right cut-off point, but also to compare the diagnostic values of two or more diagnostic tests. The ROC analysis on the fecal calprotectin concentrations under these circumstances, showed that a cut-off point of 50.0 &mgr;g/g for calprotectin had a 91.9% sensitivity and a 79.4% specificity for making a differentiation between active UC and inactive UC. These were significantly better than those obtained with CRP, ESR and AGP.

In this study, ELISA was used to determine the fecal calprotectin concentrations in the patients with UC and in the controls. In comparison to endoscopy this method is simple, noninvasive and inexpensive. However, fecal calprotectin can only reflect the excretion of neutrophils. Many infective diseases can cause a large number of neutrophils to infiltrate, so that fecal calprotectin is elevated in a number of organic gastroenterological disorders[29–31]. Therefore, fecal calprotectin is not desirable as a method that is required to differentiate efficiently between UC and infective colitis, so it cannot take the place of an endoscope in diagnosing UC. Regardless of how sensitive the calprotectin technique may be in the detection of disease activity in patients with previously diagnosed UC, its greater potential use is in identifying patients with UC and in differentiating between patients with UC and patients with non-inflammatory disorders, still requires further study.

In conclusion, the determination of fecal calprotectin is an objective approach to grading the mucosal disease activity in patients with inflammatory bowel disease. The advantages of fecal calprotectin are simplicity, noninvasiveness, and relatively low cost. Fecal calprotectin can be useful not only in research but also in clinical practice.