A total of 496 children was studied. The range
of metabolite concentrations seen (6-
thioguanine nucleotides) ranged from 0 to
1410 pmol/108 red blood cells, with a median
value of 301. Nine children (2%) were found to
have completely undetectable metabolites on
one or more occasions. A further four children
had less than 50 pmol/108 (and were thus at the
limit of the assay sensitivity), 10 had values
between 50 and 100 pmol/108
, and 21 between
100 and 150 pmol/108
. All patients within this
range would give cause for concern about the
adequacy of treatment