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P311. Thiopurine metabolite monitoring and allopurinol combination therapy: current utilisation and influence on Australian gastroenterology IBD practice

K.C.P. Sze, W.S.W. Ng, S.J. Connor, Liverpool Hospital & University of NSW, Dept. of Gastroenterology, Sydney, Australia

Background

Thiopurines (TP) are a mainstay of inflammatory bowel disease (IBD) management. Thiopurine methyltransferase (TPMT) testing and TP metabolites monitoring have been suggested to predict individual variation in TP metabolism and response to therapy. However, prospective data to confirm the clinical benefits of metabolites guided dosing is still limited. Guidelines around TP monitoring are also lacking. This study aims to evaluate current Australian gastroenterologists' (GEs) practice in TP use for IBD, including TPMT testing, full blood count (FBC) monitoring, TP metabolites testing, allopurinol combination therapy, and how these practices have changed clinical outcomes.

Methods

An anonymous survey was distributed to GEs by email and at various meetings across Australia over a 6 month period.

Results

168 responses were received, of which 137 were complete. Most respondents (79%) tested TPMT levels, and most but not all tested this prior to initiating TP (89%). The majority still prescribed TP if TPMT levels were intermediate or low (98.4%; 71.3%), and were more likely to exercise caution by reduced dosing (57%; 96.6%) and/or increased frequency of FBC monitoring (34.7%; 73.6%). FBC monitoring intervals upon initiation of TP varied, especially in the 1st month. A vast majority (88%) used TP metabolites, and of these, 80.4% were using the results for metabolite guided dose adjustments to optimize response, not just for non-response to standard dosing. 88% have to wait more than 1 week for metabolite results. Those not testing metabolites cited lack of availability or cost as the main reasons, and almost all of these respondents would use it otherwise. The majority of respondents found that metabolite guided dose adjustments had improved clinical response rates, reduced complication rates (80.6% and 61.2% of respondents respectively), and had altered their clinical practice (79%). Allopurinol combination therapy was prescribed by the majority of respondents (71%), and of these, 83% would use it in “shunters” irrespective of liver function test abnormalities, whilst 36.6% would use it for TP side effects irrespective of metabolite levels.

Conclusion

The vast majority of Australian GEs are using TP metabolite monitoring, or would, were it more readily available. The majority are using metabolite guided dose adjustments with associated subjective improvements in clinical response rates and reduced complication rates. Allopurinol combination therapy is also used by the majority of GEs. Prospective data to confirm what is reflected in current practice and standardized recommendations for TP metabolite monitoring and allopurinol combination therapy are readily awaited.