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P195. Leukocyte scintigraphy as a tool to measure inflammatory load in ulcerative colitis

J.F. Brandse1, R. Bennink2, S. Van Eeden3, P.A. Baars4, M. Löwenberg1, C.Y. Ponsioen1, G.R. van den Brink1, G. D'Haens1, 1Academic Medical Center, Inflammatory Bowel Disease Centre, Amsterdam, Netherlands, 2Academic Medical Center, Nuclear Medicine, Amsterdam, Netherlands, 3Academic Medical Center, Pathology, Amsterdam, Netherlands, 4Academic Medical Center, Clinical Immunology, Amsterdam, Netherlands

Background

Assessing inflammatory activity is essential in therapeutic decision making in Ulcerative Colitis (UC). Although leukocyte scintigraphy has been suggested as a potential method to image inflammatory activity, novel state-of-the-art scintigraphy including SPECT-CT has not been validated for the measurement of inflammatory load in UC in comparison with other inflammatory markers.

We aimed to prospectively validate leukocyte SPECT-CT as a tool to measure and quantify inflammatory load in patients with different extent and severity of UC.

Methods

UC patients with an indication for ileocolonoscopy were included. Within 1 week and without any changes in therapy both colonoscopy (Mayo score, UCEIS) with biopsies (Geboes score) and leukocyte scintigraphy were performed. In addition, serum C-reactive protein and fecal calprotectin (Bühlmann ELISA) were measured and clinical questionnaires (CCAI, Mayo) were collected. Patients' peripheral blood leukocytes were isolated and labelled with 200 (188–220) MBq technetium-99m HMPAO. SPECT combined with a low-dose CT was performed 60 min after reinjection of labelled cells. To quantify inflammation in each colon segment the maximum uptake of leukocytes was calculated as a ratio to the mean uptake in bone marrow of 4 lumbar vertrebrae and expressed as SPECT inflammation classification of each colon segment and a Summed Activity Score (SAS) for the inflammatory activity in all 5 colonic segments.

Results

Twenty-six UC patients were studied. 3/26 were using anti-TNF, 4/26 thiopurines, 3/26 prednisone and 20/26 5-ASA at inclusion. At endoscopy 12/26 (46%) of patients had pancolitis, 8/26 (31%) left-sided colitis and 6/26 (23%) proctitis. According to endoscopic Mayo score, 1/26 (4%) of patients had inactive, 5/26 (19%) mild, 8/26 (31%) moderate or 12/26 (46%) severe disease. The median (IQR) full Mayo score was 7 (5–10), CCAI: 6 (2–9), serum CRP 4.1 mg/L (1.7–12.5) and fecal Calprotectin 449 ug/g (245–1142). According to SPECT-CT patients were classified as having 9/26 Mild, 12/26 Moderate, 5/26 Severe disease for their most affected colon segment. Significant correlations (Spearman) were observed between this SPECT inflammation classification and endoscopic Mayo: r 0.54 (P < 0.01), UCEIS r 0.56 (P < 0.01) and histologic Geboes score r 0.59 (P < 0.01). The Summed Activity Score correlated better with fecal calprotectin r 0.55 (P < 0.01) than with CRP: r 0.24 (P = 0.24), CCAI: r 0.43 (P < 0.05) or clinical Mayo: r 0.54 (P < 0.01).

Conclusion

SPECT-CT classification of disease severity of the most inflamed colon segment is correlated with both endoscopic and histologic scores for UC. The total inflammatory load in Ulcerative Colitis at SPECT-CT is better reflected by fecal calprotectin compared to serum CRP.