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

Abstract

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 (p = 0.036) and a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score > 4.0 (p = 0.047). Loss of vascular pattern in the ileum (LVPI) was observed in approximately 70.0% of patients (p = 0.005), which was associated with PFC and abdominal bloating (p = 0.020). LVPI was also linked to microscopic inflammation (p = 0.012) and PFC with abdominal pain (p = 0.007). HFC was significantly associated with alterations in the ileal mucosa (p = 0.009) and LVPI (p = 0.001). Additionally, HFC and diarrhea were associated with LVPI in 27.3% of patients (p = 0.037) and with erosions in the ileum (p = 0.031). Chronic ileal inflammation correlated with HFC (p = 0.015), ASDAS-CRP > 2.1 (p = 0.09), LVPI (p = 0.001), and villous atrophy (p = 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.