Intraindividual variability in red blood cell thiopurine methyltransferase activity.
OBJECTIVE
Long-term (13 weeks) and circadian (24 hours) intraindividual variability in red blood cell (RBC) thiopurine methyltransferase (TPMT) activity in healthy subjects was studied.


METHODS
RBC TPMT activity was measured radiochemically.


RESULTS
The variability in RBC TPMT activity was low and was only slightly higher than the imprecision of he TPMT assay. Mean long-term intraindividual variability in RBC TPMT activity was 6.5% (CV) (n = 46). Mean intraindividual circadian variability in RBC TPMT activity was 6.4% (CV) (n = 18).


CONCLUSIONS
In contrast to what has been observed in children with acute lymphoblastic leukaemia, the intraindividual variability in RBC TPMT activity in healthy subjects was low. The reported changes in baseline RBC TPMT activity in patients are probably therefore due to drugs, disease, assay variation or other, unidentified factors.
Giverhaug
T
T
Department of Pharmacology, University of Tromsø, Norway.
Klemetsdal
B
B
Lysaa
R
R
Aarbakke
J
J
D000328:Adult; D002940:Circadian Rhythm; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008780:Methyltransferases / Q000378:metabolism*; D008875:Middle Aged; D015203:Reproducibility of Results
D008780:Methyltransferases; C022745:thiopurine methyltransferase