RT Journal Article SR Electronic T1 Measurement of thiopurine methyltransferase activity and azathioprine metabolites in patients with inflammatory bowel disease JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 665 OP 670 DO 10.1136/gut.49.5.665 VO 49 IS 5 A1 P W Lowry A1 C L Franklin A1 A L Weaver A1 M Gennett Pike A1 D C Mays A1 W J Tremaine A1 J J Lipsky A1 W J Sandborn YR 2001 UL http://gut.bmj.com/content/49/5/665.abstract AB BACKGROUND Measurement of 6-thioguanine nucleotide concentrations may be useful for optimising treatment with azathioprine and 6-mercaptopurine.METHODS We conducted a study of 170 patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine to determine the relationship between 6-thioguanine nucleotide concentrations and both disease activity, as measured by the inflammatory bowel disease questionnaire (active disease <170, remission ⩾170) and leucopenia. Blood was submitted for whole blood 6-thioguanine nucleotide concentration and leucocyte count.RESULTS Mean (SD) inflammatory bowel disease questionnaire score was 176 (32). There was no correlation between inflammatory bowel disease questionnaire scores and 6-thioguanine nucleotide concentrations (r s=−0.09, p=0.24). Median 6-thioguanine nucleotide concentrations in 56 patients with active disease and 114 patients in remission were similar (139v 131 pmol/8×108 red blood cells; p=0.26). There was no correlation between 6-thioguanine nucleotide concentrations and leucocyte counts.CONCLUSIONS In patients with inflammatory bowel disease treated with azathioprine or 6-mercaptopurine, 6-thioguanine nucleotide concentrations did not correlate with disease activity, as measured by the inflammatory bowel disease questionnaire, or leucocyte count. These findings are discrepant with most previous studies, possibly due to selection of responding patients who tolerated the medications. A prospective, randomised, dose optimisation trial using 6-thioguanine nucleotide concentrations is warranted.6-TGN6-thioguanine nucleotidesAZAazathioprine6-MP6-mercaptopurineCDCrohn's diseaseUCulcerative colitis6-MMP6-methylmercaptopurineTPMTthiopurine methyltransferaseRBCred blood cellALLacute lymphoblastic leukaemiaIBDinflammatory bowel diseaseIBDQinflammatory bowel disease questionnaireWBCwhite blood cell5-ASA5-aminosalicylic acid