Clinical evaluation of the OC-Sensor Pledia calprotectin assay.

Objectives: Faecal calprotectin (f-Cal) and faecal haemoglobin (f-Hb) are important tests for evaluation of gastrointestinal disease. Samples for measurement of f-Hb are taken by the patient directly into a specimen collection device containing stabilising buffer, which can be placed directly onto the analyser in the laboratory. Samples for f-Cal are usually sent in screw top pots and often require time-consuming extraction procedures prior to analysis. OC-FCa calprotectin is a new assay which uses the same specimen collection device and analyser as our current f-Hb assay. Analytical evaluation has already shown it to perform well but to have a positive bias. This study was a clinical evaluation to investigate the diagnostic test performance and cut-off suitable for its use in the diagnosis of IBD.

Methods: OC-FCa calprotectin was measured in a convenience sample of 603 patients in whom f-Hb had been requested and was found to be ≥10 μg/g. Clinical outcomes were obtained from notes, radiological reports and endoscopy and histology reports.

Results: A total of 425 patients completed clinical investigations; IBD was diagnosed in 49 and other colorectal pathology in 161. Median f-Cal in patients with IBD was 1,660 μg/g, significantly different (p<0.01) from those with other colorectal pathology (192 μg/g) or normal findings (157 μg/g). ROC curve analysis showed AUC of 0.898 with sensitivity of 91.8% and specificity of 79.3% at a cut-off of 600 μg/g.

Conclusions: The new OC-FCa calprotectin assay performed well for the diagnosis of IBD using a cut-off of 600 μg/g.