Modified 13C-octanoate breath test and impact of sampling points

Gastric emptying in patients with autoimmune pancreatitis

OBJECTIVES

Autoimmune pancreatitis (AIP) and its extrapancreatic lesions seem to be clinical manifestations of organs involved in IgG4-related systemic disease. To clarify whether the stomach is a target organ, gastric function was evaluated in patients with AIP.

METHODS

In 6 patients with AIP, gastric emptying was assessed by Carbon 13 (¹³C) acetate breath test before and after steroid therapy. Based on 4-hour breath samples, the half ¹³CO₂ excretion time (T(1/2)) and the time of maximal excretion (T(max)) were calculated as gastric emptying parameters. Data of 20 healthy volunteers were used as controls. The number of IgG4-positive plasma cells in gastrofiberscopic biopsy specimens was counted before and after steroid therapy.

RESULTS

Both T(1/2) and T(max) in patients with AIP decreased significantly after steroid therapy (T(1/2): 1.89 ± 0.21 hours vs 1.69 ± 0.15 hours, P = 0.046; and T(max): 1.1 ± 0.2 hours vs 0.96 ± 0.2 hours, P = 0.027), and became similar to those of the controls (T(1/2): 1.69 ± 0.32 hours and T(max): 0.98 ± 0.2 hour). The number of IgG4-positive plasma cells infiltrating the gastric mucosa decreased after steroid therapy.

CONCLUSIONS

Gastric emptying was impaired in patients with AIP and improved to the reference range after steroid therapy. The stomach may be a target organ of IgG4-related systemic disease.

Stable isotope breath tests for assessing gastric emptying: A comprehensive review

A stable isotope ([(13)C]) breath test is a promising method for assessing gastric emptying, but it has not been pervasive yet in Japan. We think that there are some barriers to its popularization, including the uncertainty concerning its theoretical backgrounds, the ambiguity of analyzing and interpreting the data, and the lack of standard protocols for breath sampling. The aim of the present review is to break through these barriers. We hope this article could make the [(13)C]-gastric breath test more maneuverable for and more accessible to researchers and clinicians.

Gastric emptying: a comparison of three methods

OBJECTIVE

A better understanding of the clinical relevance of delayed gastric emptying (e.g. in diabetes) requires a simple, easily accessible and inexpensive method for measuring it. Two "new" methods for measuring gastric emptying of liquids (the paracetamol absorption test and the 13C-acetate breath test) are compared with the gold standard (gastric emptying scintigraphy (GES)).

MATERIAL AND METHODS

The three techniques were used simultaneously in 10 healthy subjects. A gastric emptying time-retention curve was drawn for each technique and the results were compared at the 75%, 50% and 25% retention quartiles.

RESULTS

Agreement was found between the paracetamol absorption test and GES (p=0.95; Hotelling's T 2 test). Using the Wagner-Nelson one compartment correction produced a retention curve for the 13C-acetate breath test statistically significantly below GES (p<0.01).

CONCLUSION

In healthy subjects, the paracetamol absorption test produced results comparable to those of liquid GES, but not to the results of the 13C-acetate breath test.

Is the pattern of solid-phase gastric emptying different between genders?

BACKGROUND

In the 13C-octanoate breath test, the shape of the 13CO2 excretion curve in the ascending portion reflects a pattern of gastric emptying (GE). Recent scintigraphic studies have revealed an overall delay in solid GE in fertile women compared with men. However, it remains unknown whether women have a different GE pattern compared with men. As a symptomatic delay in solid GE is specific to the female gender, it could be hypothesized that the 13CO2 excretion curve is different in shape between genders.

MATERIALS AND METHODS

Because the ascending gradient of the 13CO2 excretion curve is often biphasic, the dual function of y(t) = ( a1 . tb1 + a2 . tb2) e(-K.t) was applied to fit the breath data, where a1, b1, a2, b2, and K are constants. Assessed on the 4 h-based breath samples obtained after ingestion of a 320-kcal muffin containing 100 mg 13C-octanoate, the time versus 13CO2 excretion curve was created from 31 adult volunteers (15 men and 16 women). The curve shape was characterized by the dual function, and was compared between genders.

RESULTS

In both genders, the ascending gradient exhibited the biphasic feature, characterized by an initial steep rise and the subsequent blunted increase, while the descending gradient followed the monotonous decay. The initial rise was steeper and the subsequent increase was more blunted in women than in men.

CONCLUSION

Women exhibit a gender-specific pattern of the 13CO2 excretion profile. A possible explanation for this gender difference is that the post-gastric feedback regulation is more potent in women than in men.

Short- and medium-term reproducibility of gastric emptying of a solid meal determined by a low dose of 13C-octanoic acid and nondispersive isotope-selective infrared spectrometry

AIM: To evaluate the reproducibility of a modified ¹³C breath test-based measurement of solid phase gastric emptying (GE) within the frames of a simple-repeated measure study protocol.

METHODS: Twelve healthy subjects (6 females and 6 males, mean age 24.9 ± 0.7 years) were recruited to undergo three identical GE examinations. In six subjects the first two examinations were performed 2 d apart, and the third session was carried out at a median interval of 19.5 d (range 18 - 20 d) from the second one. In another six subjects the first two measurements were taken 20 d apart (median, range: 17-23 d), whereas the third session took place 2 d after the second one. Probes of expiratory air collected before and during six hours after intake of a solid meal (378 kcal) labelled with 75 μL (68 mg) ¹³C-octanoic acid, were measured for ¹³CO₂ enrichment with the nondispersive isotope-selective infrared spectrometry NDIRS apparatus.

RESULTS: Taking coefficients of variation for paired examinations into account, the short-term reproducibility of the GE measurement was slightly but not significantly better than the medium-term one: 7.7% and 11.2% for the lag phase (T-Lag), 7.3% and 10.9% for the gastric half emptying time (T½). The least differences in GE parameters detectable at P = 0.05 level in the 12 paired examinations were 9.6 and 15.6 min for T-Lag, 11.6 and 19.7 min for T½ by a two-day or two to three-week time gap, respectively.

CONCLUSION: The low-cost modification of the breath test involving a lower dose of ¹³C-octanoic acid and NDIRS, renders good short- and medium-term reproducibility, as well as sensitivity of the measurement of gastric emptying of solids.

Analytical techniques in biomedical stable isotope applications: (isotope ratio) mass spectrometry or infrared spectrometry?

An overview is presented of biomedical applications of stable isotopes in general, but mainly focused on the activities of the Center for Liver, Digestive and Metabolic Diseases of the University Medical Center Groningen. The aims of metabolic studies in the areas of glucose, fat, cholesterol and protein metabolism are briefly explained, as well as the principle of breath testing and the techniques to study body composition and energy expenditure. Much attention is paid to the analytical considerations based upon metabolite concentrations, sample size restrictions, the availability of stable isotope labelled substrates and dose requirements in relation to compound-specific isotope analysis. The instrumental advantages and limitations of the generally used techniques gas chromatography/reaction/isotope ratio mass spectrometry and gas chromatography/mass spectrometry are described as well as the novelties of the recently commercialised liquid chromatography/combustion/isotope ratio mass spectrometry. The present use and future perspective of infrared (IR) spectrometry for clinical and biomedical stable isotope applications are reviewed. In this respect, the analytical demands on IR spectrometry are discussed to enable replacement of isotope ratio mass spectrometry by IR spectrometry, in particular, for the purpose of compound-specific isotope ratio analysis in biological matrices.

WAGNER-NELSON METHOD FOR ANALYSING THE ATYPICAL DOUBLE-PEAKED [13CO2] EXCRETION CURVE IN THE [13C]-OCTANOATE GASTRIC EMPTYING BREATH TEST IN HUMANS

1. In the [(13)C]-octanoic acid breath test, the time versus pulmonary [(13)CO(2)] excretion rate curve is analysed using mathematical curve-fitting techniques to calculate gastric emptying parameters. Thus, the goodness-of-fit highly influences the accuracy of the breath test. However, a double-peaked [(13)CO(2)] excretion curve, which occasionally develops owing to the presence of an interval of quiescent gastric emptying (the plateau phase), is likely to be fitted poorly. 2. In pharmacokinetics, the Wagner-Nelson method has been used to describe precisely the absorption kinetics of orally administered drugs and its reliability is independent of the nature of gastric emptying. A recent study has shown the potential of the Wagner-Nelson method to generate a realistic gastric emptying flow curve from [(13)CO(2)] excretion data. In the present report, we have demonstrated that the Wagner-Nelson method can visualize the plateau emptying phase responsible for the cases of double peaks. 3. Wagner-Nelson analysis applied to the breath test described precisely the characteristic emptying pattern of the two emptying phases being interrupted by the plateau phase. Conventional analysis for the breath test failed to detect the plateau phase. 4. The Wagner-Nelson method is a useful tool for analysing atypical double-peaking [(13)CO(2)] excretion curves.