6-TGN and 6-MMPN

Referred to Berkshire & Surrey Pathology Services, Frimley Park Hospital NHS Foundation Trust, Portsmouth Road, Frimley, Surrey GU16 7UJ

Alternative names, keywords

Thioguanine nucleotides and methylmercaptopurine nucleotides, TGN, MeMP, 6 TGN, 6-MMPN, thiopurine metabolites.

Samples required

EDTA blood (purple cap/ yellow cap ring, 4 mL tube). Smaller tubes are available for paediatric samples.

4 weeks to steady state after starting/changing dose. No need to take sample at specific time relative to last dose.

Test indications

May be helpful to check whether therapeutic concentrations are being achieved, especially in patients heterozygous for TPMT on reduced dose regimes.

Reference range

TGN therapeutic range: 235-450 pmol/8x108 red blood cells.

MeMP concentrations over 5700 pmol/8x108 red blood cells have been reported to confer an increased risk of hepatotoxicity.

Turnaround time

Referral lab quotes turnaround time of 5 days, however additional time must be allowed for packing, dispatch and delivery of sample, and return and processing of results.


Biochemistry (Referrals)