A prospective single centre pilot evaluation of a serum calprotectin assay in unselected GI patients

Background: Whilst C-reactive protein (CRP) is an established serum marker of inflammation, its use in gastroenterology has been limited by its poor sensitivity and specificity for GI disease. Faecal calprotectin (FC) has been adopted into mainstream GI practice as a sensitive but non-specific marker of intestinal inflammation. However, stool samples collection for FC can be challenging and the possibility of utilising a sensitive and specific serum biomarker of intestinal inflammation in luminal gastroenterology is an attractive prospect. This work investigates the performance of serum calprotectin (SC) compared to current biomarkers, FC and CRP, in an unselected cohort of patients attending our GI unit.

Methods: Patients attending in and outpatients within an adult GI service who submitted a stool sample for FC analysis were identified. A total of 109 who had a serum sample obtained within one day of stool sample collection had the serum analysed for CRP and SC and the correlation between these biomarkers was investigated.

Results: The intraclass correlation coefficient (ICC) between SC, FC and CRP was 0.10, 95% CI -0.09-0.28 and 0.18, 95% CI -0.01-0.35, respectively. The ICC between FC and CRP was 0.18, 95% CI -0.01-0.35.

Conclusions: Our data reveals that there is no significant correlation between SC and FC, nor between SC and CRP in a large unselected cohort of GI patients. Therefore, as a serum biomarker for intestinal inflammation, SC is unlikely to be of clinical utility and the search for an appropriate serum GI biomarker continues.