External Quality Control Clinical Trial
Official title:
Collection of Blood Samples for Use in an External Quality Assurance (EQA) Scheme for Thiopurine S-methyl Transferase (TPMT) Activity and Thiopurine Metabolites, 6-thioguanine Nucleotides (6TGN) and 6-methyl Mercaptopurine Nucleotides (6MMPN).
Participation in EQA schemes, where available, is mandatory for the United Kingdom
Accreditation Service (UKAS). No EQA scheme currently exists for TPMT and thiopurine
metabolites, which is a potential shortcoming of these tests. A pilot of this project has
been awarded funding by Clinical Pathology Accreditation (CPA).
The purpose of this work is to collect samples for an EQA scheme for whole blood TPMT
(activity and genotype) and thiopurine metabolites, which will be run in collaboration with
UK NEQAS (United Kingdom National External Quality Assessment Service), and facilitate a
comprehensive world-wide service that enables laboratories providing these tests to fulfil
quality goals and ultimately provide optimal patient care.
The thiopurine S-methyl transferase (TPMT) enzyme is involved in the breakdown of thiopurine
drugs (such as azathioprine), which are commonly used to treat inflammatory bowel disease
and autoimmune diseases. Different individuals in the population have different, genetically
determined, levels of TPMT. An individual with absent TPMT activity has a high risk of
serious side effects from thiopurine drug treatment. In routine practice, TPMT activity in
the blood is measured before starting patients on thiopurine drugs to determine an effective
and safe starting dose.
Thiopurine metabolites are the breakdown products of thiopurine drugs and are monitored in
the blood of patients on thiopurine drugs to optimise their drug dose.
These tests are performed by laboratories across Britain and around the world. It is
important for patient care that the results are of high quality and consistent across
different centres. One way of assessing this is through an EQA scheme. No EQA scheme
currently exists for TPMT/thiopurine metabolites, which is a potential shortcoming of the
tests.
Venous blood collected from NHS staff volunteers and SWBH outpatients, who have had TPMT
measured as part of their routine care, will be distributed to participating laboratories
every two months. Where it is not possible to find suitable blood donors, pooled surplus
blood samples from the laboratory will be used instead. The laboratories will test the
samples and return results to UK NEQAS for comparison. A report will be compiled allowing
them to compare themselves with other centres and make changes where necessary.
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