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Influence of clinical parameters on the results of 13 C‐octanoic acid breath tests: examination of different mathematical models in a large patient cohort
Author(s) -
Keller J.,
Andresen V.,
Wolter J.,
Layer P.,
Camilleri M.
Publication year - 2009
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1111/j.1365-2982.2009.01340.x
Subject(s) - excretion , breath test , medicine , linear regression , gastroenterology , ingestion , regression analysis , endocrinology , mathematics , statistics , helicobacter pylori
It is assumed, although not proven, that 13 CO 2 ‐excretion following ingestion of 13 C‐octanoic acid ( 13 C‐OA) does not only depend on gastric emptying (GE) but also on absorption and metabolism of 13 C‐OA and endogenous CO 2 ‐production. Our aims were (i) to test the effects of patient characteristics and of diseases that may impair 13 C‐OA‐metabolism on GE parameters. (ii) To compare different GE endpoints. Therefore, we investigated effects of age, gender, BMI and diseases with potential impact on 13 C‐OA‐metabolism (including pancreatic, liver and lung disease, diabetes, IBD) on cumulative 4h‐ 13 CO 2 ‐excretion (4h‐CUM) and T ½ calculated by non‐linear regression model (NL, determined by shape of breath test curve) and generalized linear regression model (GLR, reflects absolute 13 CO 2 ‐excretion) in 1279 patients and 19 healthy controls who underwent a standardized 13 C‐OA‐breath test. Digestive and metabolic disturbances hardly influenced 4h‐CUM or T ½ calculated by NL or GLR models. In the multivariate linear regression models, 4h‐CUM was significantly predicted by diabetes adjusted for age, gender and IBD but influence of these parameters was small ( R 2 = 0.028, P < 0.0001). T ½ NL and 4h‐CUM were weakly correlated, even after exclusion of tests with unrealistically high estimates for T ½ NL ( n = 1095, R 2 = 0.029, P < 0.0001). Conversely, 4h‐CUM was closely associated with T ½ GLR (exponential correlation, R 2 = 0.774, P < 0.00001, n = 1279). We conclude that influences of digestive and metabolic disturbances on 13 CO 2 ‐excretion following 13 C‐OA‐application are generally low. Thus, our findings resolve an important criticism of methods using absolute 13 CO 2 ‐excretion for evaluation of 13 C‐OA‐breath tests and suggest that such models may correctly identify T ½ in a mixed patient population.