Fig. 3.

An excellent linear correlation was observed between LP½ and cumulative 4 h-¹³C-exhalation (R²=0.774, p<0.00001) (A). LP½ is the linear predictor which is calculated as weighted sums of ¹³CO₂ production rates (derived from 3 breath samples, only) and is defined as the reciprocal of T½_GLR. Accordingly, an identically tight, yet exponential correlation was observed between cumulative 4 h-¹³C-exhalation and T½_GLR (B). For the vast majority of breath test data (all tests with cumulative ¹³CO₂-excretion between 40 and 200 μmol, n=1209, equivalent to 94.5% of all tests) a highly significant linear correlation could also be established (solid line, R²=0.711, p<0.00001). Only the extremes with very low (n=27) or high (n=43) cumulative ¹³CO₂-excretion markedly deviate from this approximately linear part of the curve.