Is neutropenia required for effective maintenance of remission during azathioprine therapy in inflammatory bowel disease?

Background Azathioprine is an effective treatment for maintaining remission in inflammatory bowel disease (IBD). It is a matter of debate as to whethe r neutropenia is required during azathioprine therapy to achieve more effec tive disease remission. We evaluated whether neutropenia during azathioprin e therapy reduced relapse rates in IBD patients. Patients and methods This retrospective study was based on a total of 173 I BD (96 Crohn's disease (CD), 77 ulcerative colitis (UC)) patients who were stable on azathioprine for a minimum of 6 months. Median duration of follow -up was 4.0 years (range 0.6-21 years). The lowest neutrophil counts during treatment for these patients were recorded. Relapse rates per year of foll owup were compared in non-neutropenic patients (neutrophil count > 2.5 x 10 (9), n = 129) and neutropenic patients (neutrophil count less than or equal to 2.5 x 109, n = 44) groups, and survival curves for cumulative remission rates compared by log-rank test. Results Mean relapse rate per year of follow-up for the non-neutropenic gro up was 0.19/year (SD = 0.37/year) compared with the neutropenic group 0.28/ year (SD = 0.43/year) (P = NS). Analysis was performed on UC and CD subgrou ps, and relapse rates were not significantly different. The cumulative remi ssion per cent determined by Kaplan-Meier survival analysis showed no diffe rence between non-neutropenic and neutropenic groups by log-rank analysis, for UC and CD as well as for all IBD patients. Conclusion Neutropenia less than or equal to 2.5 x 10(9) while on azathiopr ine does not reduce the relapse rates of IBD patients who were established on azathioprine therapy compared with neutrophil counts > 2.5 x 10(9). (C) 2001 Lippincott Williams & Wilkins.