Elevated Calprotectin Levels Reveal Loss of Vascular Pattern and Atrophy of Villi in Ileum by Digital Chromoendoscopy and Magnification Colonoscopy in Patients with Spondyloarthritis Without Having Inflammatory Bowel Disease.

Objective: This study aimed to establish a correlation between fecal calprotectin levels (FC) and intestinal inflammation in patients with spondyloarthritis without inflammatory bowel disease.

Methods: A total of 180 SpA patients were included in the study of them 20.6% required Digital chromoendoscopy (DCE). FC, C-reactive protein (CRP), HLA-B*27 and clinical indices were assessed.

Results: Positive fecal calprotectin (PFC) and high fecal calprotectin (HFC) levels were observed in 27.0% and 16.0% of patients, respectively. HFC correlated with a Bath Ankylosing Spondylitis Functional Index (BASFI) score > 4.0 ( = 0.036) and a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score > 4.0 ( = 0.047). Loss of vascular pattern in the ileum (LVPI) was observed in approximately 70.0% of patients ( = 0.005), which was associated with PFC and abdominal bloating ( = 0.020). LVPI was also linked to microscopic inflammation ( = 0.012) and PFC with abdominal pain ( = 0.007). HFC was significantly associated with alterations in the ileal mucosa ( = 0.009) and LVPI ( = 0.001). Additionally, HFC and diarrhea were associated with LVPI in 27.3% of patients ( = 0.037) and with erosions in the ileum ( = 0.031). Chronic ileal inflammation correlated with HFC ( = 0.015), ASDAS-CRP > 2.1 ( = 0.09), LVPI ( = 0.001), and villous atrophy ( = 0.014). Factorial analysis of mixed data (FAMD) identified significant associations between micro/macroscopic changes in chronic inflammation and HFC (CC = 0.837); increased levels of CRP and microscopic acute inflammation (CC = 0.792); and clinical activity scores of ASDAS-CRP and BASDAI (CC = 0.914).

Conlusions: FC levels were significantly elevated in patients with SpA, particularly those with LVPI, suggesting their potential as a valuable biomarker for managing SpA when joint manifestations coincide with ileal villous atrophy. This indicates a shared immune pathway linked to chronic gut damage.