Sample comparison of BÜHLMANN fCAL Turbo and OC-FCa faecal calprotectin methods.

Background: Faecal calprotectin is an inflammatory marker used to triage patients for further investigation with suspected inflammatory bowel disease (IBD). Our current method requires faecal samples be sent to the laboratory, where calprotectin is extracted before analysis. This is a time-consuming, potential bottleneck in the pathway. We have recently evaluated the OC-SENSOR PLEDIA fCAL method that uses the same sampling device as used in some bowel cancer screening and symptomatic colorectal cancer programmes that detect faecal haemoglobin. The below study is a comparison of the OC-FCa method with the BÜHLMANN fCAL Turbo which is used routinely within BSPS.

Method: 150 homogenised and 110 non-homogenised faecal samples were loaded into OC-Sampling Bottle 3 and BÜHLMANN CALEX cap sampling devices. The samples were then analysed on their respective systems according to manufacturer's instructions.

Results: The OC-FCa assay had a mean positive bias of 67.3% (homogenised) and 88.4% (non-homogenised). Homogenised samples showed substantial agreement between the methods for normal (<50 µg/g) and elevated (150+µg/g) risk categories (k = 0.794, k = 0.788, respectively) and moderate agreement for borderline (51-150 µg/g) (k = 0.25) according to the current Berkshire and Surrey Pathology Service (BSPS) guidelines. Non-homogenised samples had none to slight agreement for normal and borderline values (k = 0.02 for both) and moderate agreement for elevated (k = 0.596).

Conclusion: The OC-FCa method is a viable alternative for faecal calprotectin testing, but requires an adjustment to clinical cut-off values due to the lack of standardisation and strong positive bias. A clinical comparative study is required to assess the impact of patients collecting their own samples into the devices, as this may negate any potential degradation samples may exhibit during transit to the laboratory.