[Calprotectin levels in patients with idiopathic inflammatory bowel disease comparison of two commercial tests].

BACKGROUND: Fecal calprotectin test is a simple, non-invasive, rapid and inexpensive diagnostic tool allowing differentiation between GIT functional disorders and inflammatory conditions and relapse prediction in non-specific inflammatory bowel disease. In the last year, commercially available ELISA diagnostic kits, using either monoclonal or polyclonal antibodies against a heterodimeric complex, calprotectin, for the detection of fecal calprotectin, started to be marketed.

OBJECTIVE: To compare two ELISA kits for the detection of fecal calprotectin differing from each other in the used type of antibody (monoclonal versus polyclonal).

MATERIAL AND METHODS: Two ELISA kits were assessed: Calprotectin ELISA (Bühlmann, Basel, Switzerland) using a monoclonal antibody against calprotectin and PhiCal Calprotectin ELISA (R-Biopharm, Darmstadt, Germany) using a polyclonal antibody against calprotectin. We analyzed fecal eluates from patients with Crohn's disease (CD, n=36) and ulcerous colitis (UC, n=29) and from healthy controls (n=98). Data were analyzed using software Statistica CZ 8.0 (Statsoft, Tulsa, U.S.A.) and measurement variability parameters (linearity, repeatability, stability) and test sensitivity and specificity were established and the methods were compared.

RESULTS: The two kits showed adequate accuracy (intra- and inter-assay variation < 10%). The dilution linearity test indicated superiority of the Calprotectin ELISA Bühlmann kit, in particular for high calprotectin levels. The results of the two methods showed good correlation: Pearson's correlation coefficient r = 0.83, limit difference according to Bland-Altman plot ranged from 17% to 30%. Diagnostic sensivity rates were 79% for the Calprotectin ELISA Bühlmann kit and 74% for the Calprotectin ELISA R-Biopharm kit, the test specificity rates were 87% and 84%, respectively.

CONCLUSIONS: Both of the tested kits have comparably good measurement parameters, the Bühlmann kit using monoclonal antibody against calprotectin showed higher sensitivity and specificity. In view of their availability, sensitivity and performance, the fecal calprotectin ELISA kits are helpful diagnostic tools for clinical practice.