Comparison of methods used to measure serum iron in the presence of iron gluconate or iron dextran.

Monaghan et al. (6 ) in a Scottish population. Our study provides similar findings in an Italian population, without any differences between regional origins. Moreover, 7 of 16 subjects with the 7/7 genotype had STB within the reference interval. These data, in agreement with the recent study by Rudenski and Halsall (7 ), confirm that the Gilbert genotype is not always expressed. There is a need to establish health-associated reference values for quantities measured in the clinical chemistry laboratory, but the idea of health is problematic (8, 9). The high frequency of variant allele TA7 and its significant influence on STB suggests the desirability of exclusion of these subjects from the selection of reference individuals for bilirubin determination. In our 43 subjects homozygous for the wild-type TA6 allele, the upper limit of the conventional 95% reference interval was 14.4 mmol/L, compared with the upper limit of 17.1 mmol/L currently used in our laboratory (10 ).