Feasibility of a breath test with a substrate of natural 13C-abundance and isotope-selective non-dispersive infrared spectrometry: a preliminary study

European guideline on indications, performance and clinical impact of 13 C-breath tests in adult and pediatric patients: An EAGEN, ESNM, and ESPGHAN consensus, supported by EPC

INTRODUCTION

13 C-breath tests are valuable, noninvasive diagnostic tests that can be widely applied for the assessment of gastroenterological symptoms and diseases. Currently, the potential of these tests is compromised by a lack of standardization regarding performance and interpretation among expert centers.

METHODS

This consensus-based clinical practice guideline defines the clinical indications, performance, and interpretation of 13 C-breath tests in adult and pediatric patients. A balance between scientific evidence and clinical experience was achieved by a Delphi consensus that involved 43 experts from 18 European countries. Consensus on individual statements and recommendations was established if ≥ 80% of reviewers agreed and <10% disagreed.

RESULTS

The guideline gives an overview over general methodology of 13 C-breath testing and provides recommendations for the use of 13 C-breath tests to diagnose Helicobacter pylori infection, measure gastric emptying time, and monitor pancreatic exocrine and liver function in adult and pediatric patients. Other potential applications of 13 C-breath testing are summarized briefly. The recommendations specifically detail when and how individual 13 C-breath tests should be performed including examples for well-established test protocols, patient preparation, and reporting of test results.

CONCLUSION

This clinical practice guideline should improve pan-European harmonization of diagnostic approaches to symptoms and disorders, which are very common in specialist and primary care gastroenterology practice, both in adult and pediatric patients. In addition, this guideline identifies areas of future clinical research involving the use of 13 C-breath tests.

Mulberry leaf extract decreases digestion and absorption of starch in healthy subjects-A randomized, placebo-controlled, crossover study

PURPOSE

Mulberry (Morus alba L.) leaf tea has recently received much attention as a dietary supplement due to the wide range of putative health benefits, such as antidiabetic effects. Nevertheless, data evaluating its influence on carbohydrate metabolism in humans are scarce. The present study aims to investigate the effect of mulberry leaf extract supplementation on starch digestion and absorption in humans.

MATERIALS AND METHODS

The study comprised of 25 healthy subjects, aged 19-27 years. In all subjects, a starch 13C breath test was performed twice in a crossover and single blind design. Subjects were initially randomized to ingest naturally 13C-abundant cornflakes (50g cornflakes+100ml low fat milk) either with the mulberry leaf extract (36mg of active component-1-deoxynojirimycin) or the placebo and each subject received the opposite preparation one week later.

RESULTS

The cumulative percentage dose recovery was lower for the mulberry leaf extract test than for the placebo test (median [quartile distribution]: 13.9% [9.9-17.4] vs. 17.2% [13.3-20.6]; p=0.015). A significant decrease was detectable from minute 120 after the ingestion.

CONCLUSIONS

A single dose of mulberry leaf extract taken with a test meal decreases starch digestion and absorption. These findings could possibly be translated into everyday practice for improvement of postprandial glycemic control.

Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study

Green tea is known worldwide for its beneficial effects on human health. However, objective data evaluating this influence in humans is scarce. The aim of the study was to assess the impact of green tea extract (GTE) on starch digestion and absorption. The study comprised of 28 healthy volunteers, aged 19 to 28 years. In all subjects, a starch (13)C breath test was performed twice. Subjects randomly ingested naturally (13)C-abundant cornflakes during the GTE test (GTE 4 g) or placebo test. The cumulative percentage dose recovery (CPDR) was significantly lower for the GTE test than for the placebo test (median [interquartile range]: 11.4% [5.5-15.5] vs. 16.1% [12.7-19.5]; p = 0.003). Likewise, CPDR expressed per hour was considerably lower in each point of the measurement. In conclusion, a single dose of green tea extract taken with a test meal decreases starch digestion and absorption.

Combined oral contraceptives affect liver mitochondrial activity

OBJECTIVES

To examine liver mitochondrial function in women using combined oral contraceptives (COCs) containing ethinylestradiol.

METHODS

A breath test after oral administration of 1 mg/kg (13)C-alpha-ketoisocaproic acid ((13)C-KICA) and 20 mg/kg L-leucine was performed twice: (i) in 15 women on day 14, 15, 16, 17 or 18 of COC intake, and between day 1 and 5 of the withdrawal bleeding; and (ii) in 15 regularly menstruating females not taking hormonal contraceptives: during the luteal phase, between the 18th and the 22nd day of the cycle, and again between day 1 and 5 of the menstruation.

RESULTS

In women on COCs the maximum (13)C elimination in breath air (Dmax) was higher (26.8 ± 1.6%/h) than during withdrawal bleeding (23.5 ± 1.2%/h; p = 0.012). The time to reach the Dmax was similar on the two study days: 33.3 ± 2.4 min during the phase of pill intake vs. 37.0 ± 2.5 min during the pill-free interval. The one-hour cumulative breath (13)C elimination was greater after two weeks of COC intake than during the withdrawal bleeding: 17.49 ± 1.03% vs. 15.32 ± 0.85% (p = 0.024). In the control group no menstrual cycle phase-dependent fluctuations in the results of the (13)C-KICA breath test were observed.

CONCLUSION

The metabolism of (13)C-alpha-ketoisocaproic acid augments during the intake of COCs containing ethinylestradiol, reflecting enhanced liver mitochondrial metabolic activity.

13C-methacetin breath test reproducibility study reveals persistent CYP1A2 stimulation on repeat examinations

AIM: To find the most reproducible quantitative parameter of a standard ¹³C-methacetin breath test (¹³C-MBT).

METHODS: Twenty healthy volunteers (10 female, 10 male) underwent the ¹³C-MBT after intake of 75 mg ¹³C-methacetin p.o. on three occasions. Short- and medium-term reproducibility was assessed with paired examinations taken at an interval of 2 and 18 d (medians), respectively.

RESULTS: The reproducibility of the 1-h cumulative ¹³C recovery (AUC_0-60), characterized by a coefficient of variation of 10%, appeared to be considerably better than the reproducibility of the maximum momentary ¹³C recovery or the time of reaching it. Remarkably, as opposed to the short gap between consecutive examinations, the capacity of the liver to handle ¹³C-methacetin increased slightly but statistically significantly when a repeat dose was administered after two to three weeks. Regarding the AUC_0-60, the magnitude of this fixed bias amounted to 7.5%. Neither the time gap between the repeat examinations nor the gender of the subjects affected the ¹³C-MBT reproducibility.

CONCLUSION: ¹³C-MBT is most reproducibly quantified by the cumulative ¹³C recovery, but the exactitude thereof may be modestly affected by persistent stimulation of CYP1A2 on repeat examinations.

Interference of acute cigarette smoking with [¹³C]methacetin breath test

It is essential to establish whether and how environmental factors affect the reliability of [(13)C]methacetin breath test ((13)C-MBT). In 12 healthy volunteers (smokers), a standard (13)C-MBT with 75 mg [(13)C]methacetin was performed twice in random order: on a control day without smoking and on another day with smoking two cigarettes antecedently. A considerable flattening of the curve of the momentary (13)C recovery within the expiratory air was observed when the (13)C-MBT was performed after smoking. The maximum of the momentary (13)C recovery, D(max), decreased from 37.20±2.58 to 25.39±2.29% dose/h (p=0.00052). Moreover, the time to reach D(max) was prolonged after cigarette smoking (26.5±3.1 vs. 16.5±1.9 min, p=0.0199). The curve of the cumulative (13)C recovery on the cigarette smoking day appeared to be shifted downwards, and statistically significant differences relative to the control situation were found between the 24th and 75th minute following [(13)C]methacetin administration. Smoking cigarettes immediately prior to the (13)C-MBT diminishes the ability of the liver to handle methacetin, and hence a possibility of such an interaction should be excluded in order to interpret the results of the test correctly.

(13)C breath tests for the assessment of exocrine pancreatic function

The secretin-pancreozymin test is regarded as the most accurate of the pancreatic exocrine function tests but is cumbersome, time consuming, and invasive because it requires duodenal intubation and hormonal stimulation of the pancreas. Fecal analysis of fat, fecal elastase, or chymotrypsin are more practicable but far less sensitive to detect early stages of pancreatic exocrine insufficiency. Several (13)C-labeled substrates that are digested by pancreatic enzymes have been proposed for breath tests, thus assessing the intraluminal activity of pancreatic enzymes and therewith the pancreatic exocrine function. Particularly in pediatrics, (13)C breath tests are suited not only for diagnosis of pancreatic exocrine disorder, but also for therapy control under pancreatic enzyme substitution. However, the costs of substrates, the high time expenditure, and the lack of standardization still limit the clinical use of these breath tests. This review aims to place into perspective the traditional pancreatic exocrine function tests and the newer (13)C breath tests.

Exact profiles of (13)CO(2) recovery in breath air after per oral administration of [(13)C]methacetin in two groups of different ages

The aim of this study is to determine if age is a factor influencing the results of a [(13)C]methacetin breath test ((13)C-MBT). Two groups of healthy volunteers, each comprising six men and six women, but differing in average age (Y=young, 25.1+/-0.6 years, MA=middle-aged;, 46.0+/-2.1 years) orally took 75 mg [(13)C]methacetin. Samples of expiratory air for (13)CO(2) measurement were collected up to 48 h after intake of the substrate. A maximum momentary (13)CO(2) breath exhalation of 37.0+/-2.6%dose/h was observed at 18 min (median, range: 9-30 min) in the young subjects and of 38.4+/-2.5%dose/h at 18 min (median, range: 12-30 min) in the middle-age volunteers. The cumulative (13)C elimination in expiratory air was statistically significantly higher in the MA compared with the Y group as from 75 min up to 180 min, indicating a greater microsomal metabolic efficiency of the liver in the middle-aged healthy subjects. Gender, use of hormonal contraception, cigarette smoking, or body mass index did not modify the age-related effect on the cumulative (13)C elimination in breath air. The study results imply a necessity of composing control groups well matched with regard to the age structure for a proper interpretation of clinical (13)C-MBT results.

13C-alpha-Ketoisocaproic acid breath test revisited: an in-depth reproducibility study advocates an extended breath sampling period

In this study we sought for a quantitative parameter which would offer the best reproducibility of a standard (13)C-alpha-ketoisocaproic acid ((13)C-KICA) breath test. On 3 separate days 14 healthy volunteers (7 females, 7 males) took orally 1 mg/kg body mass (13)C-KICA and 20 mg/kg body mass L-leucine. Samples of expiratory air for (13)CO(2) measurement with the use of isotope ratio mass spectrometry were collected every 5 min during the first hour and then at 70, 80, 90, 105, 120, 150, 180, 240, 300, 360, 540, 720, and 1440 min. Short-term reproducibility assessment involved paired examinations taken 3.5 days apart; paired examinations separated by 22 days (median) served for the medium-term reproducibility assessment. T(max), the time to reach the maximum momentary (13)C recovery (D(max)), showed an unsatisfactory reproducibility, and the D(max) displayed a fairly good reproducibility, whereas the cumulative (13)C recovery calculated for a time span within the range 0-90 and 0-120 min exhibited the best reproducibility. In no case did the medium-term reproducibility prove any worse than the short-term one. Taking into account its reproducibility, the cumulative (13)C recovery appears to be the most reliable parameter of the (13)C-KICA breath test.

13C-breath tests: current state of the art and future directions

13C-breath tests provide a non-invasive diagnostic method with high patient acceptance. In vivo, human and also bacterial enzyme activities, organ functions and transport processes can be assessed semiquantitatively using breath tests. As the samples can directly be analysed using non-dispersive isotope selective infrared spectrometers or sent to analytical centres by normal mail breath tests can be easily performed also in primary care settings. The 13C-urea breath test which detects a Helicobacter pylori infection of the stomach is the most prominent application of stable isotopes. Determination of gastric emptying using test meals labelled with 13C-octanoic or 13C-acetic acid provide reliable results compared to scintigraphy. The clinical use of 13C-breath tests for the diagnosis of exocrine pancreatic insufficiency is still limited due to expensive substrates and long test periods with many samples. However, the quantification of liver function using hepatically metabolised 13C-substrates is clinically helpful in special indications. The stable isotope technique presents an elegant, non-invasive diagnostic tool promising further options of clinical applications. This review is aimed at providing an overview on the relevant clinical applications of 13C-breath tests.

Variability of the 13C-acetate breath test for gastric emptying of liquids in healthy children

PURPOSE

Scintigraphy is considered as the "gold standard" for measuring gastric emptying (GE). The C-acetate breath test (C-ABT) offers an attractive alternative to measure GE of liquids as it is nonradioactive. The aim of this study was to assess the variability of the C-ABT for GE of liquids in healthy children using nondispersive infrared spectrometry (NDIRS).

METHODS

The C-ABT was repeated at least 2 times in 21 healthy children (6 girls and 15 boys), aged between 6.2 and 16.4 years, 2 to 7 days apart. After an overnight fast, a standardized milk drink, labeled with 50 or 100 mg C-acetate according to weight, was administered. Breath samples were taken before feeding, at 5-minute intervals for the first 40 minutes and at 10-minute intervals for the following 140 minutes after feeding. Breath samples were analyzed using NDIRS, and C recovery was used to calculate values for gastric half-emptying time (t1/2), time of peak C exhalation, or gastric lag phase (tlag) and gastric emptying coefficient (GEC). Intraindividual variabilities of the parameters t1/2, tlag, and GEC were expressed as coefficient of intrasubject variation (CV).

RESULTS

The median CV of t1/2 was 8.3% (CV range, 1.6%-16.2%; t1/2 interindividual range, 65-112 minutes; and t1/2 intraindividual range, 4-33 minutes). The median CV of tlag was 16.6% (CV range, 2.0%-26.6%; tlag interindividual range, 31-76 minutes; and tlag intraindividual range, 1-35 minutes). The median CV of GEC was 4.3% (CV range, 0.8%-15.7%; GEC interindividual range, 3.81-4.89; GEC intraindividual range, 0.08-1.31). The CVs of t1/2, tlag, and GEC were independent of age, sex, weight, height, and measured values of t1/2, tlag, and GEC.

CONCLUSIONS

The C-ABT using NDIRS is an easy, noninvasive, and nonradioactive procedure with a large intraindividual variation for measuring GE of liquids in healthy children, but comparable to the variation reported with other techniques.

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.