Thioguanine nucleotides (6-TGN) and methylmercaptopurine (MeMP) are two important metabolites of thiopurine medications such as mercaptopurine (6MP) and azathioprine.

The laboratory tests for these metabolites are quoted in units of pmol/8×10^8 RBCs. (Picomoles per 800,000,000 red blood cells). Such as in this paper.

Why not quote the amount in units of 10^9 RBCs which would seem to be a more rounded number?

  • I'm unfamiliar with that particular choice of units, but I expect it has something to do with how many RBCs are in some standardized aperture.
    – De Novo
    Feb 1 '19 at 22:18
  • It seems odd because things like white blood cell counts and platelet counts are in units of 10^9 / L
    – Karl
    Feb 1 '19 at 22:47
  • Yes, I expect the measurement for these metabolites uses a different process. Units in different clinical laboratory values are not necessarily going to be the same unless they use the same process (sometimes even if they do), and this isn't the only example of odd units. Consider, for example, the Todd unit. Additionally, in clinical medicine, units are often dropped entirely.
    – De Novo
    Feb 2 '19 at 7:49
  • It looks as though the results of purine metabolites have been tweaked to give a value in the integer range. Feb 5 '19 at 22:34
  • @GrahamChiu: I'm not sure what you mean specifically. The advised range for 6-TGN is between 235 to 450 pmol/8×10^8 RBCs.
    – Karl
    Feb 7 '19 at 12:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.