Background: We evaluated the (pre-)analytical and diagnostic performance of two automated fecal calprotectin (FC) immunoassays, Liaison® Calprotectin (Diasorin) on Liaison® XL and fCAL™ turbo (Bühlmann laboratories AG) on Cobas C501 (Roche Diagnostics), and compared it with our established Bühlmann ELISA method.
Methods: Our study comprised 229 consecutive patients with clinical suspicion of inflammatory bowel disease (IBD).
Results: All assay related stool extraction procedures showed excellent correlation with the established method, but the new stool extraction devices tend to give higher results as compared with stool weight methods. Both automated assays demonstrated good performance in terms of precision (CVt≤8.1%), accuracy (bias≤6.7%) and total error (≤16.4%). Method comparison with established enzyme linked immunosorbent assay (ELISA) showed good correlation (rs>0.925), but regression analysis showed significant proportional differences. Diagnostic performance characteristics with regard to diagnosis of IBD were good and in line with other reports. In addition, we were able to show that optimization of manufacturer's cut-off and moreover, the introduction of a gray zone resulted in a significant increase of post-test probability.
Conclusions: In conclusion, the newly developed stool extraction device protocols showed acceptable and comparable performance to the stool weight method. Overall, the automated Liaison® Calprotectin and fCAL™ turbo assay showed good analytical and diagnostic performance for detection of IBD.
Keywords: Crohn’s disease; biomarker; calprotectin; diagnostic performance; extraction; feces; immunoassay; inflammatory bowel disease; likelihood ratio; ulcerative colitis.