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P526. Correlation of 6-TGN levels with clinical remission in patients with ulcerative colitis treated with azathioprine

C. Primas, W. Eigner, A. Eser, C. Gratzer, S. Reinisch, H. Vogelsang, G. Novacek, W. Reinisch, L. Kazemi-Shirazi, Medical University of Vienna, Dept. for Gastroenterology and Hepatology, Vienna, Austria

Background

6-thioguanine nucleotide (6-TGN) levels can be used for therapeutic drug monitoring in IBD. Whether 6-TGN levels correlate with clinical response is controversial.

Aim of this study is to evaluate a possible correlation of 6-TGN levels with clinical remission in ulcerative colitis.

Methods

Patients with endoscopically and histologically confirmed ulcerative colitis treated at a tertiary IBD center at the Medical University of Vienna on treatment with azathioprine (AZA) for whom 6-TGN levels were available were included. Disease activity was assessed by the partial MAYO score. Clinical remission was defined as a partial MAYO score of ≤2. 6-TGN levels were determined in with EDTA anticoagulated blood samples by high-performance liquid chromatography (HPLC) and expressed as pmol/8×108 red blood count (RBC). Therapeutic activity of AZA was defined as a cut off of ≥200 pmol RBC. Statistical analysis was performed using IBM SPSS 22.

Results

So far 65 patients with ulcerative colitis [median age: 33 y, range 18–74 y), 39 males (60%)] were included. Partial MAYO score was ≤2 in 34 patients (53.1%). The sensitivity, specificity, positive predictive value, negative predictive value of clinical remission in patients with a 6-TGN level of ≥200 were 62.9%, 60%, 64.7%, and 58.1% respectively. There was a trend towards clinical remission in patients with a 6-TGN level ≥200 (Chi-square-test, p = 0.066).

Conclusion

6-TGN levels may correlate with and predict clinical remission in patients with ulcerative colitis. More patients are needed to answer this question and this study is ongoing.