Sensitivity and Precision of the ¹³C-Breath Test

Abstract

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, Δ¹³C, and was determined to be expressed as 1.94 Δ¹³C.