Presentation: Patient requiring thiopurine methyltransferase genotyping for thiopurine treatment

A 28-year-old woman with left-sided ulcerative colitis has had two disease flares requiring steroid therapy in the last year. During her most recent flare, one month ago, she was hospitalised and received a blood transfusion due to severe anaemia. She is being reviewed in clinic to commence azathioprine.

• The British Society of Gastroenterology (BSG) recommends that all patients being considered for thiopurine therapy should have an assessment of their TPMT status.
• Currently, genomic testing is not recommended for this, as serum TPMT is the most clinically useful assay.

• Once TMPT status is assessed, the BSG recommends that thiopurines should be avoided in patients with low TPMT enzyme activity.
• The dose of thiopurine should be reduced to 50% in those with intermediate thiopurine activity.
• Daily dosage should also be reduced in patients with significant renal impairment.
• Where a patient has previously had genomic testing for their TMPT status, for example through a clinical trial, please refer to Results: Patient with a known TPMT and/or NUDT15 genotype requiring thiopurines for non-malignant indications.

For clinicians

• NICE: Azathioprine

References:

• Lamb CA, Kennedy NA, Raine T and others. ‘British Society of Gastroenterology consensus guidelines on the management of inflammatory bowel disease in adults‘. Gut 2019: volume 68, pages s1–s106. DOI: 10.1136/gutjnl-2019-318484
• Warner B, Johnston E, Arenas-Hernandez M and others. ‘A practical guide to thiopurine prescribing and monitoring in IBD‘. Frontline Gastroenterology 2018: volume 9, issue 1, pages 10–15. DOI: 10.1136/flgastro-2016-100738

For patients

• Crohn’s & Colitis UK: Azathioprine and mercaptopurine