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Background: Currently, objective tests are lacking that enable the extent and duration of intestinal mucosal damage induced by myeloablative chemotherapy to be determined. To address this problem, we explored a citrulline-based assessment score as this amino acid is a simple quantitative marker of intestinal failure., Patients and Methods: From March 2004 to June 2007, citrulline concentrations were determined at baseline and at least once weekly after the start of myeloablative chemotherapy until 30 days thereafter among 94 allogeneic or autologous haematopoietic stem-cell transplant recipients. The patients were divided into three groups according to the regimen they received: (i) carmustine, etoposide, cytarabine and melphalan/high-dose melphalan, (ii) cyclophosphamide and total body irradiation +/- antithymocyte globulin and (iii) idarubicin-containing regimens. Intestinal mucosal damage was described either by level of citrulline on each day, on the basis of different thresholds of citrulline indicating the severity of villous atrophy, or by area under the curve using reciprocal value of 10/citrulline., Results: Regimens that incorporated idarubicin induced the most severe intestinal toxicity. Scores based on the level of citrulline, using severity thresholds, and on the area under the reciprocal curve are able to discriminate between the damage induced by different high-dose chemotherapy regimens., Conclusion: A citrulline-based assessment score appears objective, validated, reproducible, reliable, specific and sensitive making it a suitable first choice for measuring and monitoring intestinal mucositis.

Background: Intestinal mucosal barrier injury (MBI), resulting from myeloablative conditioning for haematopoietic stem-cell transplantation (HSCT), is an important cause of morbidity. Despite its frequency, recognition presents a challenge, while the aetiology needs still to be unravelled. The relationship between enterocyte mass and enterocyte loss was explored by examining citrulline serum levels and by assessing circulating intestinal fatty acid-binding protein (I-FABP) and ileal bile acid-binding protein (I-BABP), proteins released by dying mature enterocytes., Patients and Methods: Thirty-four adult patients with haematological malignancy received allogeneic HSCT (HSCT day 0) 12 days after being given idarubicin, cyclophosphamide and total body irradiation as myeloablative conditioning, a regimen known to induce oral and intestinal MBI. Serum levels of citrulline, I-FABP and I-BABP were measured on HSCT days -12, -6, 0, +7, +14 and +21., Results: Myeloablative conditioning resulted in a significant decrease in serum citrulline with the nadir on HSCT day +7; thereafter, levels rose gradually. Simultaneously, a significant decrease in I-FABP and I-BABP levels occurred from the day of transplant until day +14., Conclusions: Simultaneous reduction and subsequent increase of citrulline and I-FABP and I-BABP levels following cytotoxic treatment show that enterocyte mass corresponds to lower rate of dying enterocytes, indicating reduced turnover of enterocytes. Assessment of enterocyte turnover and mass offers opportunities for evaluation of new MBI therapies.