A novel CLIA-based assay for the quantification of calprotectin in human faecal samples: a validation and reliability study

Objectives Faecal calprotectin levels closely reflect the quantity of neutrophils within the intestinal lumen, enabling the sensitive detection of acute inflammatory responses in the gut. A novel, automated chemiluminescent immunoassay (CLIA) was developed for the quantification of faecal calprotectin.Methods All CHORUS CLIA Calprotectin reagents, both reagents and the recombinant protein used for the calibration of the test, were produced in-house. To validate the assay, the limit of detection (LoD) and quantification (LoQ), precision, and reliability were determined. The assay was compared with the Calprest (R) NG (Eurospital n. 9,069) by Spearman's correlation coefficient, Passing-Bablok, and Bland-Altman analyses.Results The assay was linear in the concentration range between the LoQ, and no differences emerged in the intra-assay and inter-assay precision; the LoD was 22.2 mg/kg. Compared to Calprest (R), CHORUS CLIA Calprotectin showed excellent agreement: the Passing Bablok equation was y=-0.5177 + 0.9954x with a Spearman correlation coefficient of 0.98 (95 %CI: 0.97-0.98). In the Bland-Altman test, the mean difference was -4.38 (95 %CI: -18.174-9.408) with upper and lower limits of 135.96 and -144.73, respectively.Conclusions CHORUS CLIA Calprotectin was accurate and reliable in determining the concentration of faecal calprotectin and may become a useful tool in clinical practice. The assay proves to be highly precise, robust, and capable of accurately measuring calprotectin across the full clinical range, reliably distinguishing between physiological and pathological levels. Comparative analysis confirms that the CHORUS CLIA Calprotectin assay delivers results in strong agreement with Calprest NG used as the reference method.