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Poster presentations: Clinical: Diagnosis and Outcome 2020

P151 Can two different faecal calprotectin assays be used interchangeably in inflammatory bowel disease treatment?

E. Van Wassenaer MD1, K. Diederen1, A. Kindermann1, E.M.M. van Leeuwen2, G.R. D’Haens3, M.A. Benninga1, B.G.P. Koot1

1Emma Children’s Hospital- Amsterdam UMC- University of Amsterdam, Pediatric Gastroenterology, Amsterdam, The Netherlands, 2Amsterdam UMC- University of Amsterdam, Department of Experimental Immunology, Amsterdam, The Netherlands, 3Amsterdam UMC- University of Amsterdam, Gastroenterology and Hepatology, Amsterdam, The Netherlands

Background

Faecal calprotectin (FC) is a broadly used sensitive biomarker for intestinal inflammation in inflammatory bowel disease (IBD) patients. However, in practice, interpretation of results can be complicated due to the use of different assays to determine FC. There is a lack of data comparing different FC assays. This study aimed to assess the agreement between two different assays for determining FC in patients with IBD.

Methods

Between January and April 2017, faecal samples of known IBD patients were tested with two assays: (1) EliA 2 Calprotectin, (Thermo Fisher Scientific Phadia, Sweden) and (2) ELISA tests (EK-Cal, Bühlmann Laboratories, Switzerland). FC measurements >1800 mg/kg were displayed as 1800, as the EK-Cal test could not measure higher values. Samples were not homogenised before testing, and they were tested on the same day. Inter-assay variability was first displayed in a Bland-Altman plot, and then difference in the categorisation of the FC result(1: 0–250 mg/kg, 2: 250–500 mg/kg, 3: >500 mg/kg) was assessed with the linear weighted Kappa (κ). Values for agreement were judged as follows: κ <.0: poor, .0-.20: slight, .21-.40: fair, .41-.60: moderate, .61-.80: substantial, >.80: almost perfect.

Results

A total of 171 patients (mean age 33 years (range: 7–81), 92 (54%) female, 117 (68%) Crohn’s disease, 53 (31%) ulcerative colitis, 1 (1%) IBD-U) were included in this study. Median FC levels were 242 mg/kg (range: 4−1800), and the mean difference between the two assays was 89 mg/kg (range: -1341 – 1140). The mean difference was largest in the high FC category, (3: 200 mg/kg, n = 60), and smallest in the low FC category (1: 5 mg/kg, n = 82)). There was no systematic difference between the two assays (Figure 1). In five out of 171 (3%) patients there was a difference of two categories between the two assays and in 25 out of 171 (15%), there was a difference of one category. There was substantial agreement between the two assays (κ=.78).

Conclusion

There is no systematic difference in FC measurements between the Phadia and EK-Cal assay in this cohort of IBD patients, and agreement between the two is substantial. This suggests that these two assays can be used interchangeably for monitoring IBD patients in clinical practice.