Bacteraemia coincides with low citrulline concentrations after high-dose melphalan in autologous HSCT recipients

Mucosal damage to the intestines induced by myeloablative conditioning for allogeneic PBSC transplant (PBSCT) can be determined by the concentration of citrulline, which is a functional marker of small intestinal enterocytes. Low citrulline concentrations in blood coincide with and are a response to severe mucosal barrier injury. We treated 29 patients with high-dose melphalan 200 mg/m(2) (Mel-200) to prepare for an autologous PBSCT and collected plasma samples from each patient starting before the myeloablative regimen and three times per week thereafter until discharge. The baseline citrulline concentration was 27.6 mM+/-4.0 (mean+/-95% confidence interval; CI), and citrulline concentrations declined rapidly thereafter reaching a nadir averaging 6.7 mM+/-2.7, 12 days after starting Mel-200. Citrulline concentrations, only increased gradually and were still low (12 mM+/-4) at discharge. A total of 20 patients developed fever, which was associated with bacteraemia in 10 cases. Their mean citrulline concentrations were lower at 5.5 mM+/-1.5 than were those of patients without bacteraemia (10.2 mM+/-3.9). Importantly, neither the number of preceding neutropenic days nor the mean C-reactive protein (CRP) concentration at the onset of fever was different between these two groups. In conclusion, citrulline concentrations rapidly decline after Mel-200 reflecting intestinal mucosal barrier injury. Low citrulline, rather than the duration of neutropenia, is associated with bacteraemia indicating the importance of an intact mucosal barrier in neutropenic patients.