Thiopurine Metabolites (6-TGN, 6-MMPN)

Clinical Background:

The immunosuppressive effect of thiopurine drugs (like azathioprine) is mediated primarily by the cytotoxic metabolite 6TGN, and incorporation of these false bases into DNA. Accumulation of high levels of 6TGN is also responsible for some side effects of thiopurine drugs and has been associated with leucopaenia.
Measurement of 6MMPN helps to distinguish patients who are underdosed or non-compliant (6-MMPN levels appropriately low) from those demonstrating resistance to thiopurine drugs, i.e. preferentially metabolising thiopurine drugs to inactive 6MMPN rather than 6-TGN (6-MMPN disproportionately increased).
In resistant patients, increasing the azathiopurine dose is not helpful and further increases 6-MMPN levels, predisposing to hepatotoxicity.

Discipline:

Haematology

Haematology
Specimen Container Adult:

EDTA whole blood

EDTA whole blood
Specimen Container Paediatric:

EDTA whole blood

EDTA whole blood
Minimum Volume Adult:

4 mL

4 mL
Minimum Volume Paediatric:

4 mL

4 mL
Sample Stability:

Process upto 10 days from sample collection
Stability – 7 days refrigerated
3 days room temperature

Process upto 10 days from sample collection
Stability – 7 days refrigerated
3 days room temperature
Transport Requirements:

First class post

First class post
Add On Test:

tnu-tr.bloodsciencesadditions@nhs.net (external)

tnu-tr.bloodsciencesadditions@nhs.net (external)
Reference Ranges:

TGN: 235 - 450 pmol/8x10*8 RBCs. Maximum drug efficacy.
6MMPN: >5700 pmol/8x10*8 RBCs- increased risk of hepatoxicity.

TGN: 235 - 450 pmol/8x10*8 RBCs. Maximum drug efficacy.
6MMPN: >5700 pmol/8x10*8 RBCs- increased risk of hepatoxicity.
Routine Contact Name:

Duty biochemist
Routine Telephone:

Freeman: 0191 244 8889

RVI: 0191 282 9719

Freeman: 0191 244 8889

RVI: 0191 282 9719
Routine Email:

nuth.dutybiochemist@nhs.net

Thiopurine Metabolites (6-TGN, 6-MMPN)

Clinical Background:

Test Details

Availability:

Turn Around: