Determination of urinary 2,5-hexanedione in the general Italian population

Objective: Determination of the urinary levels of 2.5-hexanedione (2,5-HD) was performed in subjects belonging to the Italian general population to define the reference value for this metabolite. Materials and methods: Urine samples were collected from 123 healthy Italian subjects who had not been occupationally exposed to n-hexane or methyl-n-butyl ketone (60 men and 63 women; 53 living in urban areas and 70 living in rural areas; 36 smokers and 87 nonsmokers; 65 aged above 35 years and 58 aged below 35 years). The determinations were performed by a gas chromatography method using a flame ionization detector (FID). A quality-control step was realized by analysis of 78 of these samples by high-performance liquid chromatography (HPLC) with UV detection. Results and discussion: The distribution of 2,5-HD concentration was log-normal and the corresponding centiles at the 95% confidence interval were as follows: the 50th centile, 0.270 mg/l for men and 0.191 mg/l for women; the 75th centile, 0.352 and 0.330 mg/l, respectively, for men and women; and the 95th centile, 0.762 and 0.582 mg/l, respectively, for men and women. The reference value, calculated as the upper unilateral 95% tolerance interval at 95% of confidence, was 0.795 mg/l for men and 0.627 for women.