THE FATE OF INGESTED C-14 UREA IN THE UREA BREATH TEST FOR HELICOBACTER-PYLORI INFECTION

The metabolic fate of the radioactive carbon in the C-14-urea breath t est for Helicobacter pylori was investigated in 18 subjects. After ing estion of labelled urea, breath was sampled for 24 h, and urine was co llected for 3 days. Subjects were designated high or low expirers on t he basis of their breath counts, and this agreed well with H. pylori s erologic analyses. When given 185 or 37 kBq of C-14-urea, 51% (SD = 16 %, n = 11) of the label was recovered from the breath of high expirers , and 7% (SD = 3%, n = 7) from the breath of low expirers. The mean co mbined urinary and breath recovery for high expirers was 86% (SD = 7%) , and for low expirers it was 97% (SD = 3%). It is concluded that the long-term retention of C-14 from ingested C-14-urea is low. The result s enable a more accurate estimation to be made of radiation exposure r esulting from the C-14-urea breath test.