[Sensitivity and precision of the 13C-breath test]

Sensitivity and precision of the 13C-breath test were assessed by examining a couple of limiting factors caused by the sensitivity of the instrument used for 13CO2 analysis, endogenous fluctuation of 13CO2 abundance, and the residual CO2 in sample storing tubes, vacutainers, etc. For 13CO2 analysis, a mass spectrometer equipped with a dual inlet, a dual collector, and an automated pressure matching system, was used. 15 ml vacutainers were used for sample storage. Endogenous fluctuation of 13CO2 abundance, however, was measured by putting the breath samples directly into the evacuated CO2 purification system, instead of using vacutainers. Endogenous fluctuation (S.D. = 0.202%) was the most significant limiting factor, compared with instrumental limitation (0.085%), or with influence of the residual CO2 (0.136%). Consequently, the sensitivity of the 13C-breath test was figured out to be 0.52%. This sensitivity is about 1,000 times lower than that of 14C-breath test. The precision was linearly dependent on 13C increase from basal 13C observed after administration of 13C enriched compounds, delta 13C, and was determined to be expressed as 1.94 delta 13C.