Calprotectin, a sensitive marker of inflammation, is robustly assessed in plasma from patients with early or established rheumatoid arthritis by use of different laboratory methods

Abstract

Calprotectin (S100A8/S100A9, MRP8/MRP14) is a major leukocyte protein found to be more sensitive than C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR) as a marker of inflammation in patients with rheumatoid arthritis (RA). The present objective was to explore the robustness of calprotectin assessments by comparing two different laboratory methods assessing calprotectin in plasma samples from patients with early or established RA. A total of 212 patients with early RA (mean (SD) age 52(13.3) years, disease duration 0.6(0.5) years) and 177 patients with established RA (mean (SD) age 52.9(13.0) years, disease duration 10.0(8.8) years) were assessed by clinical, laboratory, and ultrasound examinations. Frozen plasma samples (−80 °C) were analysed for calprotectin levels at baseline, 1, 2, 3, 6 and 12 months by use of either enzyme-linked immunosorbent assay (ELISA) or fluoroenzyme immunoassay (FEIA). The ELISA technique used kits from Calpro AS and the FEIA technology was assessed on an automated Thermo Fisher Scientific instrument. The results showed high correlations between the two methods at baseline and during follow-up, with Spearman correlation at baseline 0.93 (p < 0.001) in the early and 0.96 (p < 0.001) in the established RA cohorts. The correlations between each of the two calprotectin assessments and clinical examinations had similar range. Calprotectin correlated well with clinical examinations, with at least as high correlations as CRP and ESR. The present study showed similar results for the two analytical methods, supporting the robustness of calprotectin analyses, and suggest calprotectin in plasma to be included in the assessments offered by clinical routine laboratories.

Keywords:

• Calprotectin
• rheumatoid arthritis
• enzyme-linked immunosorbent assay
• fluoroenzyme immunoassay
• ultrasound

Acknowledgements

We acknowledge Inge Dale at Calpro, Marianne Eidsheim at the Broegelmann Research Laboratory, Ellen Moholt and Camilla Fongen at Diakonhjemmet Hospital, and the ARCTIC study group of early RA: Hallvard Fremstad, Tor Magne Madland, Åse Stavland Lexberg, Hilde Haukeland, Erik Rødevand, Christian Høili, Hilde Stray, Anne Noraas, Inger Johanne Widding Hansen, and Gunnstein Bakland. We also acknowledge our study nurses Anne Katrine Kongtorp and Britt Birketvedt who were important in the organization and assessments of the established RA cohort. We acknowledge Patricia Fischer for measurements on the Thermo Fisher Scientific instrument. Thanks for ongoing support with the calprotectin assay from the development team at Thermo Fisher Scientific, especially Laura Steller and Bernhard Hoermann.

Disclosure statement

Hilde Berner Hammer has honorary for teaching from AbbVie, UCB, Lilly and Novartis. Sigve Lans Pedersen has no competing interests to declare. Maria Jonsson has no competing interests to declare. Linda Mathsson-Alm is employee at Thermo Fisher Scientific. Isabel Gehring is employee at Thermo Fisher Scientific. Joe Sexton has no competing interests to declare. Espen A. Haavardsholm: have received grants from Norwegian Regional Health Authorities (interregional KLINBEFORSK grants), grants from The South-Eastern Norway Regional Health Authority and personal fees from Pfizer, AbbVie, Celgene, Novartis, Janssen, Gilead, Eli-Lilly and UCB. Johan Askling has received grant/research support from AbbVie, AstraZeneca, Bristol Myers Squibb, Eli Lilly, Janssen, Merck, Pfizer, Roche, Samsung Bioepis, Sanofi, and UCB.

Data availability statement

The data will be shared if there is a reasonable request for it.

Additional information

Funding

This project was supported by Vinnova, Innovationsfonden and The Research Council of Norway, under the frame of Nordforsk [Grant agreement no. 90825, Project NORA]. Hilde Berner Hammer was funded by The Research Council of Norway to the study: NORA - Personalized medicine in RA by combining genomics, biomarkers, clinical and patient-derived data from the Nordic countries [project number 299511]. The study was funded by Centres for Clinical Treatment Research and the Research Council of Norway [project number 328657].