Calprotectin in ankylosing spondylitis – frequently elevated in feces, but normal in serum

Abstract

Objectives. To investigate indirectly the prevalence of intestinal inflammation in ankylosing spondylitis (AS) patients by assessing the levels of fecal calprotectin, to study levels of serum calprotectin in AS, and to correlate the concentrations of calprotectin in feces and serum with reported gastrointestinal symptoms, medication, and measures of disease activity. Methods. All patients fulfilling the Modified New York criteria of AS at the study centers were invited to participate. The patients answered questionnaires concerning medication, symptoms, and disease activity. Physical examination was performed, including back mobility tests. Samples of stools and blood were collected and analyzed for fecal and serum calprotectin. Results. Elevated levels of fecal calprotectin (>50 mg/kg) was found in 140 of 205 AS patients (68%). Levels of fecal calprotectin were associated with increasing age, disease duration, ESR, CRP, and serum calprotectin, but not with gastrointestinal symptoms. Fecal calprotectin was higher in patients using NSAIDs, salicylates, and proton pump inhibitors, but lower in patients using methotrexate and infliximab. Serum calprotectin levels were normal or low in 98% of AS patients and not different from the levels in healthy blood donors. Serum calprotectin levels were positively associated with ESR, CRP, WBC, and PLT. Conclusions. Two-thirds of AS patients had elevated levels of fecal calprotectin, without associated gastrointestinal symptoms. Serum calprotectin was mostly normal in AS, in contrast to various other inflammatory rheumatic diseases. We suggest that fecal calprotectin may be a marker for subclinical intestinal inflammation in AS and should be measured after stopping NSAIDs, but further endoscopic studies are needed.

Key Words::

• ankylosing spondylitis
• calgranulin
• calprotectin
• gut
• intestinal inflammation
• S100A8
• S100A9

Acknowledgements

We especially want to thank all the patients and blood donors who so willingly participated in the study. We are grateful to Annica Andersson at Department of Rheumatology and Inflammation Research, Sahlgrenska Academy at University of Gothenburg for analyzing serum calprotectin, and nurses Gunilla Håwi and Ingela Carlberg at Sahlgrenska University hospital, Camilla Johansson at Department of Rheumatology Borås and Birgitta Sharma at Department of Rheumatology Alingsås, for their assistance with the patients. This study has been supported by grants from The Health and Medical Care Executive Board of the Västra Götaland, Rune and Ulla Amlövs foundation for Rheumatology Research, Göteborg's Association Against Rheumatism, The Medical Society of Göteborg, the Medical Society of Göteborg, and the Region Västra Götaland (agreement concerning research and education of doctors), COMBINE, and the Margareta Rheumaresearch foundation. There are no financial supports, other benefits from commercial sources, or financial interests of any of the authors, which could create a potential conflict of interest with regard to the work.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.