Review article: the assessment of liver function using breath tests

Melatonin enhances the restoration of neurological impairments and cognitive deficits during drug withdrawal in methamphetamine-induced toxicity and endoplasmic reticulum stress in rats

Methamphetamine (METH) is a psychostimulant with a very high addiction rate. Prolonged use of METH has been observed as one of the root causes of neurotoxicity. Melatonin (Mel) has been found to have a significant role in METH-induced neurotoxicity. This study aimed to investigate the restorative effect of Mel on behavioral flexibility in METH-induced cognitive deficits. Male Sprague-Dawley rats were randomly assigned to be intraperitoneally injected with saline (control) or Meth at 5 mg/kg for 7 consecutive days. Then, METH injection was withdrawn and rats in each group were subcutaneously injected with saline or Mel at 10 mg/kg for 14 consecutive days. The stereotypic behavioral test and attentional set-shifting task (ASST) were used to evaluate neurological functions and cognitive flexibility, respectively. Rats developed abnormal features of stereotyped behaviors and deficits in cognitive flexibility after 7 days of METH administration. However, post-treatment with Mel for 14 days after METH withdrawal dramatically ameliorated the neurological and cognitive deficits in METH-treated rats. Blood biomarkers indicated METH-induced systemic low-grade inflammation. Moreover, METH-induced endoplasmic reticulum (ER) stress in the prefrontal cortex was diminished by melatonin supplementation. These findings might reveal the therapeutic potential of Mel in METH toxicity-induced neurological and cognitive deficits.

A systematic review on the detection of volatile organic compounds in exhaled breath in experimental animals in the context of gastrointestinal and hepatic diseases

BACKGROUND

Analysis of volatile organic compounds (VOCs) in exhaled breath has the potential to serve as an accurate diagnostic tool for gastro-intestinal diseases. Animal studies could be instrumental as a preclinical base and subsequent clinical translation to humans, as they are easier to standardize and better equipped to relate specific VOCs to metabolic and pathological processes. This review provides an overview of the study design, characteristics and methodological quality of previously published animal studies on analysis of exhaled breath in gastrointestinal and hepatic diseases. Guidelines are provided for standardization in study design and breath collection methods to improve comparability, avoid duplication of research and reduce discomfort of animals in future studies.

METHODS

PubMed and Embase database were searched for animal studies using exhaled breath analysis to detect gastro-intestinal diseases. Risk of bias was assessed using the SYRCLE's risk of bias tool for animal studies. Information on study design, standardization methods, animal models, breath collection methods and identified VOCs were extracted from the included studies.

RESULTS

10 studies were included (acute liver failure n = 1, non-alcoholic steatohepatitis n = 1, hepatic ischemia n = 2, mesenteric ischemia n = 2, sepsis and peritonitis n = 3, colitis n = 1). Rats were used in most of the studies. Exhaled breath was mostly collected using invasive procedures as tracheal cannulation or tracheostomy. Poor reporting on standardization, breath collection methods, analytical techniques, as well as heterogeneity of the studies, complicate comparison of the different studies.

CONCLUSION

Poor reporting of essential methodological details impaired comprehensive summarizing the various studies on exhaled breath in gastrointestinal and hepatic diseases. Potential pitfalls in study design, and suggestions for improvement of study design are discussed which, when applied, lead to consistent and generalizable results and a reduction in the use of laboratory animals. Refining the methodological quality of animal studies has the potential to improve subsequent clinical trial design.

Serum Levels of Adropin Improve the Predictability of MELD and Child-Pugh Score in Cirrhosis: Results of Proof-of-Concept Clinical Trial

Adropin is a peptide that was suggested to have a role in cirrhosis. The present study aimed to determine the ability to use serum adropin levels to improve their prediction accuracy as an adjunct to the current scores. In a single-center, proof-of-concept study, serum adropin levels were determined in thirty-three cirrhotic patients. The data were analyzed in correlation with Child-Pugh and MELD-Na scores, laboratory parameters, and mortality. Adropin levels were higher among cirrhotic patients that died within 180 days (1,325.7 ng/dL vs. 870.3 ng/dL, p = 0.024) and inversely correlated to the time until death (r ² = 0.74). The correlation of adropin serum levels with mortality was better than MELD or Child-Pough scores (r ² = 0.32 and 0.38, respectively). Higher adropin levels correlated with creatinine (r ² = 0.79. p < 0.01). Patients with diabetes mellitus and cardiovascular diseases had elevated adropin levels. Integrating adropin levels with the Child-Pugh and MELD scores improved their correlation with the time of death (correlation coefficient: 0.91 vs. 0.38 and 0.67 vs. 0.32). The data of this feasibility study suggest that combining serum adropin with the Child-Pugh score and MELD-Na score improves the prediction of mortality in cirrhosis and can serve as a measure for assessing kidney dysfunction in these patients.

Liver fat accumulation more than fibrosis causes early liver dynamic dysfunction in patients with non-alcoholic fatty liver disease

INTRODUCTION

In Non-Alcoholic Fatty Liver Disease (NAFLD), events driving early hepatic dysfunction with respect to specific metabolic pathways are still poorly known.

METHODS

We enrolled 84 subjects with obesity and/or type 2 diabetes (T2D). FibroScan® served to assess NAFLD by controlled attenuation parameter (CAP), and fibrosis by liver stiffness (LS). Patients with LS above 7 kPa were excluded. APRI and FIB-4 were used as additional serum biomarkers of fibrosis. The stable-isotope dynamic breath test was used to assess the hepatic efficiency of portal extraction (as DOB₁₅) and microsomal metabolization (as cPDR₃₀) of orally-administered (¹³C)-methacetin.

RESULTS

NAFLD occurred in 45%, 65.9%, and 91.3% of normal weight, overweight, and obese subjects, respectively. Biomarkers of liver fibrosis were comparable across subgroups, and LS was higher in obese, than in normal weight subjects. DOB₁₅ was 23.2 ± 1.5‰ in normal weight subjects, tended to decrease in overweight (19.9 ± 1.0‰) and decreased significantly in obese subjects (16.9 ± 1.3, P = 0.008 vs. normal weight). Subjects with NAFLD had lower DOB₁₅ (18.7 ± 0.9 vs. 22.1 ± 1.2, P = 0.03) but higher LS (4.7 ± 0.1 vs. 4.0 ± 0.2 kPa, P = 0.0003) than subjects without NAFLD, irrespective of fibrosis. DOB₁₅ (but not cPDR₃₀) decreased with increasing degree of NAFLD (R = -0.26; P = 0.01) and LS (R = -0.23, P = 0.03). Patients with T2D showed increased rate of NAFLD than those without T2D but similar LS, DOB₁₅ and cPDR₃₀.

CONCLUSIONS

Overweight, obesity and liver fat accumulation manifest with deranged portal extraction efficiency of methacetin into the steatotic hepatocyte. This functional alteration occurs early, and irrespective of significant fibrosis and presence of T2D.

Liver Function-How to Screen and to Diagnose: Insights from Personal Experiences, Controlled Clinical Studies and Future Perspectives

Acute and chronic liver disease is a relevant problem worldwide. Liver function plays a crucial role in the course of liver diseases not only in estimating prognosis but also with regard to therapeutic interventions. Within this review, we discuss and evaluate different tools from screening to diagnosis and give insights from personal experiences, controlled clinical studies and future perspectives. Finally, we offer our novel diagnostic algorithm to screen patients with presumptive acute or chronic liver disease in the daily clinical routine.

mRNA and lncRNA expression profiles of liver tissues in children with biliary atresia

Progressive liver fibrosis is the most common phenotype in biliary atresia (BA). A number of pathways contribute to the fibrosis process so comprehensive understanding the mechanisms of liver fibrosis in BA will pave the way to improve patient's outcome after operation. In this study, the differentially expressed profiles of mRNAs and long non-coding RNAs from BA and choledochal cyst (CC) liver tissues were investigated and analyzed, which may provide potential clues to clarify hepatofibrosis mechanism in BA. A total of two BA and two CC liver tissue specimens were collected, the expression level of mRNAs and lncRNAs was detected by RNA sequencing. Differentially expressed mRNAs (DEmRNAs) were functionally annotated and protein-protein interaction networks (PPI) was established to predict the biological roles and interactive relationships. Differentially expressed lncRNAs (DElncRNAs) nearby targeted DEmRNA network and DElncRNA-DEmRNA co-expression network were constructed to further explore the roles of DElncRNAs in BA pathogenesis. The expression profiles of significant DEmRNAs were validated in Gene Expression Omnibus database. A total of 2,086 DEmRNAs and 184 DElncRNAs between BA and CC liver tissues were obtained. DEmRNAs were enriched in 521 Gene Ontology terms and 71 Kyoto Encyclopedia of Genes and Genomes terms which were mainly biological processes and metabolic pathways related to immune response and inflammatory response. A total of five hub proteins (TYRO protein tyrosine kinase binding protein, C-X-C motif chemokine ligand 8, pleckstrin, Toll-like receptor 8 and C-C motif chemokine receptor 5) were found in the PPI networks. A total of 31 DElncRNA-nearby-targeted DEmRNA pairs and 2,337 DElncRNA-DEmRNA co-expression pairs were obtained. The expression of DEmRNAs obtained from RNA sequencing were verified in GSE46960 dataset, generally. The present study identified key genes and lncRNAs participated in BA associated liver fibrosis, which may present a new avenue for understanding the patho-mechanism for hepatic fibrosis in BA.

Peppermint protocol: first results for gas chromatography-ion mobility spectrometry

The Peppermint Initiative seeks to inform the standardisation of breath analysis methods. Five Peppermint Experiments with gas chromatography-ion mobility spectrometry (GC-IMS), operating in the positive mode with a tritium 3H 5.68 keV, 370 MBq ionisation source, were undertaken to provide benchmark Peppermint Washout data for this technique, to support its use in breath-testing, analysis, and research. Headspace analysis of a peppermint-oil capsule by GC-IMS with on-column injection (0.5 cm3) identified 12 IMS responsive compounds, of which the four most abundant were: eucalyptol; β-pinene; α-pinene; and limonene. Elevated concentrations of these four compounds were identified in exhaled-breath following ingestion of a peppermint-oil capsule. An unidentified compound attributed as a volatile catabolite of peppermint-oil was also observed. The most intense exhaled peppermint-oil component was eucalyptol, which was selected as a peppermint marker for benchmarking GC-IMS. Twenty-five washout experiments monitored levels of exhaled eucalyptol, by GC-IMS with on-column injection (0.5 cm3), at t=0 min, and then at t+60, t+90, t+165, t+285 and t+360 min from ingestion of a peppermint capsule resulting in 148 peppermint breath analyses. Additionally, the Peppermint Washout data was used to evaluate clinical deployments with a further five washout tests run in clinical settings generating an additional 35 breath samples. Regression analysis yielded an average extrapolated time taken for exhaled eucalyptol levels to return to baseline values to be 429 ± 62 min (± 95% confidence-interval). The benchmark value was assigned to the lower 95 % confidence-interval, 367 min. Further evaluation of the data indicated that the maximum number of volatile organic compounds (VOC) discernible from a 0.5 cm3 breath sample was 69, while the use of an in-line biofilter appeared to reduce this to 34.

Breath Biomarkers in Diagnostic Applications

The detection of chemical compounds in exhaled human breath presents an opportunity to determine physiological state, diagnose disease or assess environmental exposure. Recent advancements in metabolomics research have led to improved capabilities to explore human metabolic profiles in breath. Despite some notable challenges in sampling and analysis, exhaled breath represents a desirable medium for metabolomics applications, foremost due to its non-invasive, convenient and practically limitless availability. Several breath-based tests that target either endogenous or exogenous gas-phase compounds are currently established and are in practical and/or clinical use. This review outlines the concept of breath analysis in the context of these unique tests and their applications. The respective breath biomarkers targeted in each test are discussed in relation to their physiological production in the human body and the development and implementation of the associated tests. The paper concludes with a brief insight into prospective tests and an outlook of the future direction of breath research.

Prognostic Value of the 13 C-Methacetin Breath Test in Adults with Acute Liver Failure and Non-acetaminophen Acute Liver Injury

BACKGROUND AND AIMS

The 13 C-methacetin breath test (MBT) is a noninvasive, quantitative hepatic metabolic function test. The aim of this prospective, multicenter study was to determine the utility of initial and serial 13 C-MBT in predicting 21-day outcomes in adults with acute liver failure (ALF) and non-acetaminophen acute liver injury (ALI).

APPROACH AND RESULTS

The 13 C-MBT BreathID device (Exalenz Biosciences, Ltd.) provided the percent dose recovery (PDR) for a duration of 60 minutes after administration of 13 C-methacetin solution as the change in exhaled 13 CO2 /12 CO2 compared with pre-ingestion ratio on study days 1, 2, 3, 5, and 7. Results were correlated with 21-day transplant-free survival and other prognostic indices. A total of 280 subjects were screened for enrollment between May 2016 and August 2019. Median age of the 62 enrolled patients with adequate data was 43 years, 79% were Caucasian, 76% had ALF with the remaining 24% having ALI. The mean PDR peak on day 1 or day 2 was significantly lower in nonsurvivors compared with transplant-free survivors (2.3%/hour vs. 9.1%/hour; P < 0.0001). In addition, serial PDR peaks were consistently lower in nonsurvivors versus survivors (P < 0.0001). The area under the receiver operating characteristic curve (AUROC) of the 13 C-MBT in the combined cohort was 0.88 (95% CI: 0.79-0.97) and higher than that provided by King's College (AUROC = 0.70) and Model for End-Stage Liver Disease scores (AUROC = 0.83). The 13 C-MBT was well tolerated with only two gastrointestinal adverse events reported.

CONCLUSIONS

The 13 C-MBT is a promising tool to estimate the likelihood of hepatic recovery in patients with ALF and ALI. Use of the PDR peak data from the 13 C-MBT point-of-care test may assist with medical decision making and help avoid unnecessary transplantation in critically ill patients with ALF and ALI.

Adiponectin involved in portal flow hepatic extraction of 13C-methacetin in obesity and non-alcoholic fatty liver

Obesity and non-alcoholic fatty liver disease (NAFLD) are high prevalence, inter-related conditions at increased risk for advanced liver diseases and related mortality. Adiponectin and leptin have divergent roles in the pathogenesis of fat accumulation and NAFLD. However, the relationships between body and liver fat accumulation, early modification of liver function and unbalanced adipokine levels are still scarcely explored. We studied by (13C)-methacetin breath test ((13C)-MBT) 67 adults stratified according to body mass index, and to presence/absence of ultrasonographic nonalcoholic fatty liver disease (uNAFLD). uNAFLD was detected in 20%, 73% and 96% of normal weight, overweight and obese subjects, respectively. The delta over baseline after 15 min (DOB₁₅), a marker of hepatic extraction efficiency from portal blood flow, was lower in obese than in normal weight subjects, and in subjects with-, as compared to those without uNAFLD. The cumulative percent dose recovery after 30 min (cPDR₃₀), a marker of liver microsomal function, was lower in uNAFLD patients. DOB₁₅ was positively correlated with adiponectin levels in obese and in uNAFLD patients. uNAFLD patients also showed a positive correlation between cPDR₃₀ values and adiponectin. Our data indicate the existence of early alterations of liver function in obese and in patients with uNAFLD. These dysfunctions are linked to altered leptin/adiponectin balance and can be identified noninvasively by (13C)-MBT.

(13C)-Methacetin breath test provides evidence of subclinical liver dysfunction linked to fat storage but not lifestyle

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is characterised by the presence of hepatic steatosis in the absence of other causes of secondary hepatic fat accumulation, and is usually associated with visceral, metabolically active obesity. However, the subclinical effects of body and liver fat accumulation on liver function are still unclear.

METHODS

We used orally administered (¹³C)-methacetin and breath test to quantify the efficiency of hepatic extraction from portal blood flow and liver microsomal function in 81 participants, in relation to presence/absence of ultrasonographic NAFLD, extent of body fat accumulation, insulin resistance, dietary models, and lifestyle.

RESULTS

NAFLD was present in 23% of participants with normal weight, and prevalence increased with body fat and insulin resistance. Fat accumulation, NAFLD, and insulin resistance were associated with decreased hepatic extraction efficiency, and liver microsomal function was impaired in moderate-to-severe NAFLD. Caloric intake, dietary models, and lifestyles had a minor role in promoting functional changes.

CONCLUSIONS

The interplay between body fat accumulation, insulin resistance, and NAFLD is linked with altered hepatic extraction efficiency from blood flow and deranged microsomal function. Non-invasive diagnosis of subclinical alterations of liver function is relevant for primary and secondary prevention measures. Furthermore, the occurrence of NAFLD in lean individuals and the evidence that caloric intake, dietary models, and lifestyle played a minor role require further studies exploring the role of environmental factors in the natural history of these diseases.

LAY SUMMARY

Obesity is progressively increasing worldwide and is paralleled by fat accumulation in the liver (non-alcoholic fatty liver disease [NAFLD]), the most common chronic liver disease worldwide. NAFLD can alter liver structure and function, with a variety of consequences ranging from asymptomatic and subclinical alterations to cirrhosis and cancer. (¹³C)-Methacetin breath test, a non-invasive diagnostic tool, can reveal early subclinical alterations of liver dynamic function in individuals with obesity and in patients with NAFLD.

Exploring Liver Mitochondrial Function by 13C-Stable Isotope Breath Tests: Implications in Clinical Biochemistry

The liver is at the crossroad of key metabolic processes, which include detoxification, glycolipidic storage and export, and protein synthesis. The gut-liver axis, moreover, provides hepatocytes with a series of bacterial products and metabolites, which contribute to maintain liver function in health and disease. Breath tests (BTs) are developed as diagnostic tools for indirect, rapid, noninvasive assessment of several metabolic processes in the liver. BTs monitor the appearance of CO₂ in breath as a marker of a specific substrate metabolized in the liver, typically within microsomes, cytosol, or mitochondria. The noninvasiveness of BTs originates from the use of the, nonradioactive, naturally occurring stable isotope ¹³C marking a specific substrate which is metabolized in the liver, leading to the appearance of ¹³CO₂ in expired air. Some substrates (ketoisocaproic acid, methionine, and octanoic acid) provide information about dynamic liver mitochondrial function in health and disease. In humans, the application of ¹³C-breath tests ranges from nonalcoholic and alcoholic liver diseases to liver cirrhosis, hepatocarcinoma, preoperative and postoperative assessment of liver function, and drug-induced liver damage. ¹³C-BTs are an indirect, cost-effective, and easy method to evaluate dynamic liver function and gastric kinetics in health and disease, with ongoing studies focusing on further applications in clinical medicine.

Exhaled Breath Markers for Nonimaging and Noninvasive Measures for Detection of Multiple Sclerosis

Multiple sclerosis (MS) is the most common chronic neurological disease affecting young adults. MS diagnosis is based on clinical characteristics and confirmed by examination of the cerebrospinal fluids (CSF) or by magnetic resonance imaging (MRI) of the brain or spinal cord or both. However, neither of the current diagnostic procedures are adequate as a routine tool to determine disease state. Thus, diagnostic biomarkers are needed. In the current study, a novel approach that could meet these expectations is presented. The approach is based on noninvasive analysis of volatile organic compounds (VOCs) in breath. Exhaled breath was collected from 204 participants, 146 MS and 58 healthy control individuals. Analysis was performed by gas-chromatography mass-spectrometry (GC-MS) and nanomaterial-based sensor array. Predictive models were derived from the sensors, using artificial neural networks (ANNs). GC-MS analysis revealed significant differences in VOC abundance between MS patients and controls. Sensor data analysis on training sets was able to discriminate in binary comparisons between MS patients and controls with accuracies up to 90%. Blinded sets showed 95% positive predictive value (PPV) between MS-remission and control, 100% sensitivity with 100% negative predictive value (NPV) between MS not-treated (NT) and control, and 86% NPV between relapse and control. Possible links between VOC biomarkers and the MS pathogenesis were established. Preliminary results suggest the applicability of a new nanotechnology-based method for MS diagnostics.

Potential use of metabolic breath tests to assess liver disease and prognosis: has the time arrived for routine use in the clinic?

The progression of liver disease may be unique among organ system diseases in that progressive fibrosis compromises not only the sufficiency of hepatocyte mass but also impairs blood flow to the liver, resulting in porto-systemic shunting. Although liver biopsy as an assessment of fibrosis has become the key biomarker of and target for new therapies, it is invasive and subject to sampling error, and cannot quantify metabolic function or porto-systemic shunting. Measurement of the hepatic venous pressure gradient accommodates some of the deficiencies of biopsy but requires expertise not widely available and misses minor changes in hepatocellular mass and thereby information about metabolic function. Thus, an unmet need in clinical hepatology remains unfulfilled: a noninvasive biomarker which quantitates both the hepatocellular insufficiency and porto-systemic shunting inherent in progressive hepatic fibrosis. Ideally, such a biomarker should correlate with clinical endpoints including liver-related survival and cirrhotic complications, be performed at the point-of-care, and be affordable and easy to use. This review, an expert opinion, summarizes background and recent data suggesting that metabolic breath tests may now meet these requirements and have a valid place in clinical hepatology to supplant the time-honoured assessment of hepatic fibrosis.

Factors that influence the volatile organic compound content in human breath

BACKGROUND

Thousands of endogenous and exogenous volatile organic compounds (VOCs) are excreted in each breath. Inflammatory and deviant metabolic processes affect the level of endogeneous VOCs, which can serve as specific biomarkers for clinical diagnosis and disease monitoring. Important issues that still need to be tackled are related to potential confounding factors like gender and age and endogenous and exogenous factors, like f.i. smoking.

METHODS

The aim of this study was to systematically access the effect of endogenous and exogenous factors on VOC composition of exhaled breath. In the current study breath samples from 1417 adult participants from the LifeLines cohort, a general population cohort in the Netherlands, were collected and the total content of VOCs was measured using gas chromatography-time-of-flight-mass spectrometry. Breath samples were collected in Groningen and transferred to carbon tubes immediately. These samples were then shipped to Maastricht and measured in batches. VOCs profiles were correlated to 14 relevant characteristics of all participants including age, BMI, smoking and blood cell counts and metabolic parameters as well as to 16 classes of medications.

RESULTS

VOCs profiles were shown to be significantly influenced by smoking behavior and to a lesser extent by age, BMI and gender. These factors need to be controlled for in breath analysis studies. We found no evidence whatsoever in this 1417 subjects' cohort that white blood cell counts, cholesterol or triglycerides levels have an influence on the VOC profile. Thus they may not have to be controlled for in exhaled breath studies.

CONCLUSION

The large cohort of volunteers used here represents a unique opportunity to gauge the factors influencing VOCs profiles in a general population i.e. the most clinically relevant population. Classical clinical parameters and smoking habits clearly influence breath content and should therefore be accounted for in future clinical studies involving breath analysis.

In vitro development and validation of a non-invasive (13)C-stable isotope assay for ornithine decarboxylase

Oesophageal cancer is a significant cause of cancer related mortality, with increasing incidence worldwide. Ornithine decarboxylase (ODC) is an enzyme involved in polyamine synthesis and cellular proliferation, and ODC expression and activity has been implicated as a prognostic marker of oesophageal cancer. This study aimed to develop and optimise an in vitro (13)C-stable isotope assay for ODC activity as a non-invasive marker of oesophageal cancer. Experiments were performed in triplicate (n  =  3/group/cell line) using Caco2, HeLa, Flo-1, OE33, TE7 and OE21 cell lines (colorectal, cervical, oesophageal adenocarcinoma and oesophageal squamous carcinoma respectively). Following addition of 2mM (13)C-ornithine to cells, 10 ml gas samples were collected from the headspace every 20 min for a total of five hours. Gas samples were analysed using isotope ratio mass spectrometry to quantify (13)CO2. Assay specificity was determined using the selective ODC inhibitor, N-(4'-Pyridoxil)-Ornithine(BOC)-OMe (POB). All data is expressed as δ (13)CO2 from baseline. High ODC activity was detected by (13)C-ornithine assay in Caco2 (32.00  ±  1.12 δ (13)CO2) in contrast to HeLa cells (5.44  ±  0.14 δ (13)CO2) cells. POB inhibited activity in Caco2 cells to 12.87  ±  1.10 δ (13)CO2. Differential ODC activity was detected in all oesophageal cancer cells, and 53 h incubation of cell lines with POB reduced activity by 72%, 56%, 64% and 69% in the Flo-1, OE33, OE21 and TE7 cell lines respectively. We have shown that ODC activity can be selectively detected by a non-invasive, stable-isotope (13)C-ornithine assay. ODC activity was detected in all oesophageal cancer cell lines in vitro. Further studies are indicated to quantify ODC activity in oesophageal cancer patients.

Breathomics--exhaled volatile organic compound analysis to detect hepatic encephalopathy: a pilot study

The current diagnostic challenge with diagnosing hepatic encephalopathy (HE) is identifying those with minimal HE as opposed to the more clinically apparent covert/overt HE. Rifaximin, is an effective therapy but earlier identification and treatment of HE could prevent liver disease progression and hospitalization. Our pilot study aimed to analyse breath samples of patients with different HE grades, and controls, using a portable electronic (e) nose. 42 patients were enrolled; 22 with HE and 20 controls. Bedside breath samples were captured and analysed using an uvFAIMS machine (portable e-nose). West Haven criteria applied and MELD scores calculated. We classify HE patients from controls with a sensitivity and specificity of 0.88 (0.73-0.95) and 0.68 (0.51-0.81) respectively, AUROC 0.84 (0.75-0.93). Minimal HE was distinguishable from covert/overt HE with sensitivity of 0.79 and specificity of 0.5, AUROC 0.71 (0.57-0.84). This pilot study has highlighted the potential of breathomics to identify VOCs signatures in HE patients for diagnostic purposes. Importantly this was performed utilizing a non-invasive, portable bedside device and holds potential for future early HE diagnosis.

Use of the methacetin breath test to classify the risk of cirrhotic complications and mortality in patients evaluated/listed for liver transplantation

BACKGROUND & AIMS

The MELD score predicts short-term mortality in patients with cirrhosis; however, some patients with low scores develop complications and die unexpectedly. Consequently, we evaluated the diagnostic accuracy of the methacetin breath test (MBT), an assay of liver metabolic function, and the MELD score, to predict the risk of complications of cirrhosis and liver-related death.

METHODS

One hundred sixty-five patients with cirrhosis received oral (13)C-methacetin; (13)CO2 was measured in expired breath (BreathID; Exalenz). The cumulative percent dose recovery of (13)CO2 at 20 min with a threshold of ⩽0.55% (high-risk) and >0.55% (low risk) most accurately predicted liver-related death and the risk of cirrhotic complications within one year. MELD thresholds of ⩾15 and ⩾19 were also examined to predict the same endpoints.

RESULTS

Dose recovery ⩽0.55% and MELD ⩾19 both predicted liver-related death (HR 12.6 [95% CI 1.6-98.3]; p=0.016, and HR 5.5 [1.6-18.9]; p=0.007, respectively); MELD ⩾15 did not. Dose recovery ⩽0.55% (HR 1.9 [1.1-3.2]; p=0.03) also predicted the risk of ⩾1 complication(s), and was particularly able to foretell the risk of development/exacerbation of ascites (HR 4.7 [1.8-11.9]; p=0.001), which was not achieved by either MELD threshold. Finally, in patients with MELD <19, dose recovery ⩽0.55% predicted the risk of death (p=0.017), development of ⩾1 cirrhotic complication(s) (p=0.062), and development/exacerbation of ascites (p=0.0009).

CONCLUSIONS

In this pilot study, methacetin breath testing predicted the risk of liver-related death and development/exacerbation of ascites more accurately than MELD ⩾15 or ⩾19. In patients with low MELD (<19points), MBT may be useful to identify patients in whom the frequency of clinical observation should be intensified.

Evaluation of Exalenz Bioscience's BreathID for Helicobacter pylori detection

Carbon-labeled urea breath tests, which have high sensitivity and specificity, are the preferred method used in epidemiological studies, screening dyspeptic patients and assessing eradication or recurrence of Helicobacter pylori infection. The principle of the (13)C-urea breath test relies upon the ability of the H. pylori urease to hydrolyze the orally administered (13)C-urea. The BreathID (Exalenz Bioscience Inc., Union, NJ, USA) provides a competitive solution for breath testing, including unique features such as automatic continuous breath collection and analysis. This is an unattended convenient test, with no human error as the correct part of the breath is collected and patients' assistance is not required. The test results are available in real time at the point of care and enable shortened breath testing procedures. Additionally, several studies showing expanded utility of the BreathID in pediatrics, after therapy and during proton pump inhibitors intake, further support the safety and performance of the BreathID in the diagnosis of H. pylori.

Activity of cytochrome P450 1A2 in relation to hepatic iron accumulation in transfusion-dependent β-thalassaemia major patients

BACKGROUND

Cytochrome P450 1A2 (CYP1A2) is a cytochrome enzyme with a pivotal role in hepatic drug metabolism. Data from CYP1A2((-/-)) mouse suggest that CYP1A2 plays a role in aspects of hepatic iron toxicity. The aim of this study was to assess the activity of CYP1A2 in relation to hepatic iron load in patients with transfusion-dependent β-thalassaemia major.

METHODS

The (13) C-methacetin continuous breath test was performed on 30 consecutive patients with transfusion-dependent β-thalassaemia major. CYP1A2 activity was measured by the rate at which the (13) C substrate is metabolized and exhaled expressed as percentage dose recovery (PDR) per hour. CYP1A2 activity was correlated with clinical and laboratory parameters and hepatic iron accumulation by T2* magnetic resonance imaging (T2*MRI).

RESULTS

Cytochrome P450 1A2 activity in patients with transfusion-dependent β- thalassaemia major was positivity correlated with plasma ferritin levels. No correlation was found with age, duration and amount of red blood cell transfusion and type of iron chelation therapy. Low CYP1A2 activity was negatively associated with hepatic iron accumulation (T2*MRI ≤ 6.3 ms); adjusted odds ratio (OR; 95% CI) for hepatic iron accumulation in patients with low CYP1A2 activity was 0.047 (0.003-0.72; P = 0.021). Of the six patients with decreased activity of CYP1A2, five had no hepatic iron accumulation and one had mild hepatic iron accumulation by T2*MRI.

CONCLUSION

Activity of CYP1A2 is associated with hepatic iron accumulation in patients with transfusion-depended β-thalassaemia major. Further studies are needed to assess the exact role of CYP1A2 in iron metabolism in human.

Review article: next generation diagnostic modalities in gastroenterology--gas phase volatile compound biomarker detection

BACKGROUND

The detection of airborne gas phase biomarkers that emanate from biological samples like urine, breath and faeces may herald a new age of non-invasive diagnostics. These biomarkers may reflect status in health and disease and can be detected by humans and other animals, to some extent, but far more consistently with instruments. The continued advancement in micro and nanotechnology has produced a range of compact and sophisticated gas analysis sensors and sensor systems, focussed primarily towards environmental and security applications. These instruments are now increasingly adapted for use in clinical testing and with the discovery of new gas volatile compound biomarkers, lead naturally to a new era of non-invasive diagnostics.

AIM

To review current sensor instruments like the electronic nose (e-nose) and ion mobility spectroscopy (IMS), existing technology like gas chromatography-mass spectroscopy (GC-MS) and their application in the detection of gas phase volatile compound biomarkers in medicine - focussing on gastroenterology.

METHODS

A systematic search on Medline and Pubmed databases was performed to identify articles relevant to gas and volatile organic compounds.

RESULTS

E-nose and IMS instruments achieve sensitivities and specificities ranging from 75 to 92% in differentiating between inflammatory bowel disease, bile acid diarrhoea and colon cancer from controls. For pulmonary disease, the sensitivities and specificities exceed 90% in differentiating between pulmonary malignancy, pneumonia and obstructive airways disease. These sensitivity levels also hold true for diabetes (92%) and bladder cancer (90%) when GC-MS is combined with an e-nose.

CONCLUSIONS

The accurate reproducible sensing of volatile organic compounds (VOCs) using portable near-patient devices is a goal within reach for today's clinicians.

Liver function breath tests for differentiation of steatohepatitis from simple fatty liver in patients with nonalcoholic Fatty liver disease

GOALS

We investigated the utility of liver function breath tests [C-Aminopyrine Breath Test (C-ABT), C-Galactose Breath Test (C-GBT)], for the diagnosis of nonalcoholic steatohepatitis (NASH) among nonalcoholic fatty liver disease (NAFLD) patients.

BACKGROUND

Liver biopsy is currently the gold standard for the differentiation between simple fatty liver (NAFL) and NASH in NAFLD patients.

MATERIALS AND METHODS

Thirty-six patients with histologically proven NAFLD (NAFL:16, NASH:20) underwent C-ABT and C-GBT. The results were expressed as the percentage of administered C dose recovered per hour (%dose/h) and as cumulative percentage of administered C dose recovered over time (%cumulative dose). Histologic lesions were scored according to Brunt and Kleiner's classifications.

RESULTS

C-ABT results correlated inversely with activity grade (r=-0.650, P=0.001), NAFLD activity score (r=-0.473, P=0.026), and fibrosis stage (r=-0.719, P=0.001). Compared with NAFL, NASH patients had significantly lower %dose/h and %cumulative dose at 60, 90, and 120 minutes (always P<0.04) by C-ABT. C-ABT %dose/h and %cumulative dose at 120 minutes could predict the presence of NASH (area under the receiver operating characteristic curve: 0.762 and 0.741, respectively). In contrast, there was no significant association between C-GBT results and any patient characteristic.

CONCLUSIONS

In the NAFLD patients, decreased and delayed liver microsomal function, as assessed by C-ABT, is associated with more severe necroinflammation and fibrosis, whereas C-ABT results at 120 minutes may be helpful for the diagnosis of NASH.

Assessment of hepatic detoxification activity: proposal of an improved variant of the (13)c-methacetin breath test

Breath tests based on the administration of a (13)C-labeled drug and subsequent monitoring of (13)CO2 in the breath (quantified as DOB - delta over baseline) liberated from the drug during hepatic CPY-dependent detoxification are important tools in liver function diagnostics. The capability of such breath tests to reliably indicate hepatic CYP performance is limited by the fact that (13)CO2 is not exclusively exhaled but also exchanged with other compartments of the body. In order to assess this bias caused by variations of individual systemic CO2 kinetics we administered intravenously the test drug (13)C-methacetin to 25 clinically liver-healthy individuals and monitored progress curves of DOB and the plasma concentration of (13)C-methacetin. Applying compartment modelling we estimated for each individual a set of kinetic parameters characterizing the time-dependent exchange of the drug and of CO2 with the liver and non-hepatic body compartments. This analysis revealed that individual variations in the kinetics of CO2 may account for up to 30% deviation of DOB curve parameters from their mean at otherwise identical (13)C-methacetin metabolization rates. In order to correct for this bias we introduced a novel detoxification score which ideally should be assessed from the DOB curve of a 2-step test ("2DOB") which is initialized with the injection of a standard dose of (13)C-labeled bicarbonate (in order to provide information on the actual CO2 status of the individual) followed by injection of the (13)C-labeled test drug (the common procedure). Computer simulations suggest that the predictive power of the proposed 2DOB breath test to reliably quantity the CYP-specific hepatic detoxification activity should be significantly higher compared to the conventional breath test.

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.

Rapid "breath-print" of liver cirrhosis by proton transfer reaction time-of-flight mass spectrometry. A pilot study

The aim of the present work was to test the potential of Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS) in the diagnosis of liver cirrhosis and the assessment of disease severity by direct analysis of exhaled breath. Twenty-six volunteers have been enrolled in this study: 12 patients (M/F 8/4, mean age 70.5 years, min-max 42-80 years) with liver cirrhosis of different etiologies and at different severity of disease and 14 healthy subjects (M/F 5/9, mean age 52.3 years, min-max 35-77 years). Real time breath analysis was performed on fasting subjects using a buffered end-tidal on-line sampler directly coupled to a PTR-ToF-MS. Twelve volatile organic compounds (VOCs) resulted significantly differently in cirrhotic patients (CP) compared to healthy controls (CTRL): four ketones (2-butanone, 2- or 3- pentanone, C8-ketone, C9-ketone), two terpenes (monoterpene, monoterpene related), four sulphur or nitrogen compounds (sulfoxide-compound, S-compound, NS-compound, N-compound) and two alcohols (heptadienol, methanol). Seven VOCs (2-butanone, C8-ketone, a monoterpene, 2,4-heptadienol and three compounds containing N, S or NS) resulted significantly differently in compensate cirrhotic patients (Child-Pugh A; CP-A) and decompensated cirrhotic subjects (Child-Pugh B+C; CP-B+C). ROC (Receiver Operating Characteristic) analysis was performed considering three contrast groups: CP vs CTRL, CP-A vs CTRL and CP-A vs CP-B+C. In these comparisons monoterpene and N-compound showed the best diagnostic performance.

CONCLUSIONS

Breath analysis by PTR-ToF-MS was able to distinguish cirrhotic patients from healthy subjects and to discriminate those with well compensated liver disease from those at more advanced severity stage. A breath-print of liver cirrhosis was assessed for the first time.

Effects of ergot alkaloids on liver function of piglets as evaluated by the (13)C-methacetin and (13)C-α-ketoisocaproic acid breath test

Ergot alkaloids (the sum of individual ergot alkaloids are termed as total alkaloids, TA) are produced by the fungus Claviceps purpurea, which infests cereal grains commonly used as feedstuffs. Ergot alkaloids potentially modulate microsomal and mitochondrial hepatic enzymes. Thus, the aim of the present experiment was to assess their effects on microsomal and mitochondrial liver function using the ¹³C-Methacetin (MC) and ¹³C-α-ketoisocaproic acid (KICA) breath test, respectively. Two ergot batches were mixed into piglet diets, resulting in 11 and 22 mg (Ergot 5-low and Ergot 5-high), 9 and 14 mg TA/kg (Ergot 15-low and Ergot 15-high) and compared to an ergot-free control group. Feed intake and live weight gain decreased significantly with the TA content (p < 0.001). Feeding the Ergot 5-high diet tended to decrease the 60-min-cumulative ¹³CO₂ percentage of the dose recovery (cPDR₆₀) by 26% and 28% in the MC and KICA breath test, respectively, compared to the control group (p = 0.065). Therefore, both microsomal and mitochondrial liver function was slightly affected by ergot alkaloids.

Interpretation of non-invasive breath tests using (13)C-labeled substrates--a preliminary report with (13)C-methacetin

Non-invasive breath tests can serve as valuable diagnostic tools in medicine as they can determine particular enzymatic and metabolic functions in vivo. However, methodological pitfalls have limited the actual clinical application of those tests till today. A major challenge of non-invasive breath tests has remained the provision of individually reliable test results. To overcome these limitations, a better understanding of breath kinetics during non-invasive breaths tests is essential. This analysis compares the breath recovery of a ¹³C-methacetin breath test with the actual serum kinetics of the substrate. It is shown, that breath and serum kinetics of the same test are significantly different over a period of 60 minutes. The recovery of the tracer ¹³CO₂ in breath seems to be significantly delayed due to intermediate storage in the bicarbonate pool. This has to be taken into account for the application of non-invasive breath test protocols. Otherwise, breath tests might display bicarbonate kinetics despite the metabolic capacity of the particular target enzyme.

Clinical utility of 13C-liver-function breath tests for assessment of hepatic function

13C-Liver-function breath tests have been used in clinical diagnostics and, to a limited extent, to investigate hepatic function. From a practical perspective, tests such as the 13C-aminopyrine and 13C-methacetin breath tests are simple to administer, safe, and relatively inexpensive to perform. Surprisingly, they have not entered the mainstream of clinical practice, because they are perceived to lack the specificity and adequate precision needed to give accurate results in real time. The dynamic nature of 13C-liver-function breath tests, their possible versatility in terms of assessing a range of different liver functions, and the ease with which they can be repeated to follow relative changes in liver function with time, all imply the potential for wider clinical application. Therefore, there is a need for these tests to be critically evaluated and their potential clinical application be tested systematically against defined objectives. We describe refinements in the methodology of the tests and propose several situations in which currently reliable methods for assessment of liver function do not exist and where 13C-liver-function breath tests might be of use. We propose that use has been constrained by practical methodological considerations which could be addressed to offer tests better suited to routine application in the out-patient or community setting.

Continuous 13C-methacetin breath test differentiates biliary atresia from other causes of neonatal cholestasis

BACKGROUND AND AIM

Distinguishing biliary atresia (BA) from other causes of neonatal cholestasis (NC) is challenging. Continuous BreathID C-methacetin breath test (MBT) is a novel method that determines liver function. Methacetin is metabolized uniquely by the liver and CO2 is measured passively, through a nasal cannula in the exhaled breath. The aim of this study was to assess the ability of MBT to differentiate BA from other causes of NC.

METHODS

MBT was performed in infants with NC before any invasive procedure. Percent dose recovered (PDR) peak and time to peak (TTPP) of C recovered were correlated with blood test results and degree of fibrosis on liver biopsy.

RESULTS

Fifteen infants were enrolled in the study. Eight were eventually diagnosed as having BA. MBT showed that infants with NC from various causes reached the PDR peak after 44.5 ± 6.7 minutes, whereas infants with BA reached the PDR peak value after 54.7 ± 4.3 minutes (P < 0.005). This suggested low cytochrome P450 1A2 activity in the BA group. The area under the curve (AUC) was 0.95 (95% confidence interval [CI] 0.83-1), sensitivity of 88%, and specificity of 100%.

CONCLUSIONS

This pilot study shows that MBT can differentiate between BA and other causes of NC by time to peak of methacetin metabolism. The results suggest that MBT may be used as part of the diagnostic algorithm in infants with liver disease. Larger-scale studies should be conducted to confirm these initial observations.

Comparison of two dosage regimens of the substrate for the [13C]methacetin breath test

The [(13)C]methacetin breath test ([(13)C]MBT)--a valuable non-invasive tool dedicated to the assessment of the liver metabolic capacity--still needs standardisation. The aim of this study was to check whether currently used dosage regimens of [(13)C]methacetin provide concordant [(13)C]MBT results in subjects with an atypical body constitution. Healthy volunteers: low body mass<55 kg (eight women), and high body mass>95 kg (eight large body frame men) were recruited. They underwent [(13)C]MBT on separate days, taking in random order [(13)C]methacetin: a fixed 75 mg dose (FX75), or a 1 mg kg(-1) body mass-adjusted dose (BMAD). Samples of expiratory air for (13)CO(2) measurement were collected over 3 h. The maximum momentary (13)C elimination in breath air occurred earlier and was higher following BMAD than with FX75 in the low body mass females (T (max) 14.6 ± 1.0 min vs. 22.1 ± 2.4 min, p = 0.019; D (max) 41.9 ± 2.9 % dose h(-1) vs. 36.6 ± 3.6 % dose h(-1), p = 0.071). In the high body mass men, T (max) remained unchanged, whereas D (max) was slightly higher with BMAD compared to FX75 (21.5 ± 3.2 min vs. 23.0 ± 3.0 min; 38.5 ± 2.9 % dose h(-1) vs. 32.3 ± 2.5 % dose h(-1)). It is concluded that in subjects with a body constitution outside the general population average, the dosage of the substrate may affect some results of the [(13)C]MBT. The dosage-related differences appear, however, to be insignificant if the result of the [(13)C]MBT is reported as a cumulative (13)C recovery in breath air.

Effects of ergot alkaloids on liver function of piglets can be detected by the [(13)C]methacetin breath test irrespective of oral or intramuscular route of tracer administration

Ergot alkaloids (sum=total alkaloids, TA) originate from the phyto-pathogenic fungus Claviceps purpurea and might exert feed intake depressing and hepatotoxic effects on animals. The aim of the study was to evaluate TA effects on performance and liver function of piglets with the [(13)C]methacetin breath test and two routes of tracer administration (orally, p.o.; intramuscularly, i.m.). Two ergot batches were mixed into piglet diets resulting in 21 and 17 mg TA kg(-1) (Ergot-5 and -12, respectively) and compared with an ergot-free control diet. Feed intake was significantly depressed after feeding the ergot containing diets (p=<0.001). The time at maximum (13)CO(2) exhalation (t (max)) and the half-life (t (0.5)) were not influenced by treatments and varied between 25 and 68 min after the p.o., and 28 and 62 min after the i.m. administration of [(13)C]methacetin, respectively. The cumulative (13)C recovery (cPDR(30)) was significantly lower due to feeding the diet Ergot-5 (6.6 %) compared with the Ergot-12 (8.8 %) and the control diet (9.7 %) irrespective of the route of tracer administration (p=0.044). As a discrimination of the diet effects through both tracer administration routes is possible, the i.m. application should be preferred in piglets as this causes less stress than the oral forced administration.

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.

Dumping syndrome following nissen fundoplication in an adult patient diagnosed by continuous online 13C/12C monitoring of ¹³C-Octanoic acid breath test "a case report"

BACKGROUND

Nissen Fundoplication is a common surgical procedure performed in treating gastroesophageal reflux disease (GERD). Complications include dysphagia, gastric hypersensitivity, abnormal gastric motility, gas bloat syndrome and GERD relapse. Dumping syndrome may occur when a large volume of gastric content is delivered to the duodenum or jejunum, resulting in both gastrointestinal and vasomotor symptoms. Occasionally, dumping syndrome may be a complication in patients that have undergone nissen Fundoplication, especially in adults. The BreathID® continuous online 13C-Octanoicoctanoic acid breath test detects variations of less than 1/100,000 in the 13CO2/12CO2 ratio in exhaled air.

CASE PRESENTATION

We report a case of a 38 year old male who was admitted and diagnosed with dumping syndrome following nissen Fundoplication, who was diagnosed using the BreathID® continuous online 13C-Octanoic acid breath test.

CONCLUSIONS

Early performance of a gastric emptying rate breath test in symptomatic patients, following upper GI tract surgery may help in the prediction or diagnosis of nissen Fundoplication complications such as dumping syndrome.

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.

Assessment and management of methotrexate hepatotoxicity in psoriasis patients: report from a consensus conference to evaluate current practice and identify key questions toward optimizing methotrexate use in the clinic

Experts in psoriasis, hepatology, pharmacokinetics and pharmacogenetics convened to discuss the safety and monitoring of methotrexate with respect to hepatotoxicity when used in the treatment of psoriasis. Methotrexate is an efficacious and cost-effective treatment for psoriasis, but is associated with significant safety issues, particularly relating to hepatotoxicity. Current British, Dutch, German, EU and US guidelines for baseline evaluations, monitoring and prevention of hepatotoxicity in patients with psoriasis receiving methotrexate were evaluated. Liver safety monitoring is currently reliant upon multiple methods, including biopsy, serological tests for biomarkers such as type III procollagen amino terminal propeptide (PIIINP), and liver function tests based on liver enzymes. Monitoring of patients receiving long-term therapy is expected to be improved by the utilization of serum biomarkers currently in development such as the Enhanced Liver Fibrosis (ELF) panel and other non-invasive tests of hepatic architecture, such as fibroelastography, microbubbles and magnetic resonance imaging. Appropriate studies to determine optimal dosing to maximize efficacy and minimize toxicity, potentially utilizing pharmacogenetic principles, are clearly needed. Key questions for future research are identified including needs for optimal screening and monitoring, identification of appropriate biomarkers, assessment of relationships between dosing and safety, utility of liver biopsy, optimal dosing regimens (including route of administration), methods to measure methotrexate levels in blood, and use of methotrexate as a standardized active comparator in trials of experimental drugs used to treat psoriasis.

A fourth dimension in decision making in hepatology

Today, the assessment of liver function in patients suffering from acute or chronic liver disease is based on liver biopsy and blood tests including synthetic function, liver enzymes and viral load, most of which provide only circumstantial evidence as to the degree of hepatic impairment. Most of these tests lack the degree of sensitivity to be useful for follow-up of these patients at the frequency that is needed for decision making in clinical hepatology. Accurate assessment of liver function is essential to determine both short- and long-term prognosis, and for making decisions about liver and non-liver surgery, TIPS, chemoembolization or radiofrequency ablation in patients with chronic liver disease. Liver function tests can serve as the basis for accurate decision-making regarding the need for liver transplantation in the setting of acute failure or in patients with chronic liver disease. The liver metabolic breath test relies on measuring exhaled (13) C tagged methacetin, which is metabolized only by the liver. Measuring this liver-specific substrate by means of molecular correlation spectroscopy is a rapid, non-invasive method for assessing liver function at the point-of-care. The (13) C methacetin breath test (MBT) is a powerful tool to aid clinical hepatologists in bedside decision-making. Our recent findings regarding the ability of point-of-care (13) C MBT to assess the hepatic functional reserve in patients with acute and chronic liver disease are reviewed along with suggested treatment algorithms for common liver disorders.

Assessment of insulin resistance by a 13C glucose breath test: a new tool for early diagnosis and follow-up of high-risk patients

Background/Aims

Insulin resistance (IR) plays an important role in the pathogenesis of diabetes and non-alcoholic fatty liver disease (NAFLD). Current methods for insulin resistance detection are cumbersome, or not sensitive enough for early detection and follow-up. The BreathID^® system can continuously analyse breath samples in real-time at the point-of-care. Here we determined the efficacy of the BreathID^® using the ¹³C-Glucose breath test (GBT) for evaluation of insulin resistance.

Methods

Twenty healthy volunteers were orally administered 75 mg of ¹³C-glucose 1-¹³C. An oral glucose tolerance test (OGTT) was performed immediately; followed by serum glucose and insulin level determinations using GBT. GBT and OGTT were repeated following exercise, which alters insulin resistance levels.

Results

Within-subject correlations of GBT parameters with serum glucose and serum insulin levels were high. Before and after exercise, between-subjects correlations were high between the relative insulin levels and the % dose recoveries at 90 min (PDR 90), and the cumulative PDRs at 60 min (CPDR 60). Pairwise correlations were identified between pre-exercise Homeostasis Model Assessment (HOMA) IR at 90 min and PDR 90; HOMA B (for beta cell function) 120 and CPDR 30; HOMA IR 60 and peak time post-exercise; and HOMA B 150 with PDR 150.

Conclusions

The non-invasive real-time BreathID^® GBT reliably assesses changes in liver glucose metabolism, and the degree of insulin resistance. It may serve as a non-invasive tool for early diagnosis and follow up of patients in high-risk groups.

Assessment of liver function in acute or chronic liver disease by the methacetin breath test: a tool for decision making in clinical hepatology

Patients suffering from acute or chronic liver disease require on-going assessment of disease progression in terms of the degree of hepatic fibrosis and overall liver impairment. This assessment is pivotal for determining the prognosis and for making decisions about medical treatment and liver transplantation. Currently available methods are either invasive, lack diagnostic accuracy or are limited by technical difficulties such as obesity or biochemical confounders. The metabolic breath test relies on the measurement of tagged metabolites of an organ-specific substrate in the exhaled breath. (13)C-methacetin is metabolized uniquely by the liver, and (13)CO(2) is measured continuously in the exhaled breath. Measuring this liver-specific substrate using molecular correlation spectroscopy provides a rapid, point-of-care, non-invasive method to assess liver function. The use of the (13)C-methacetin breath test (MBT) may provide a powerful tool for clinical hepatologists in decision making at the bedside. This paper reviews recent findings regarding the ability of the point-of-care (13)C-MBT to assess fibrosis, cirrhosis and hepatic functional reserve in patients with acute and chronic liver disease.

The stable isotope ketoisocaproic acid breath test as a measure of hepatic decarboxylation capacity: a quantitative analysis in normal subjects after oral and intravenous administration

BACKGROUND AND AIMS

There is no generally accepted kinetic evaluation method for the stable isotope [(13)C]ketoisocaproic acid (KIC) breath test. Differences found in the results between women and men are contradictory.

METHODS

Oral and intravenous breath tests using 1 mg/kg stable isotope-labelled KIC were performed in healthy male and female volunteers. A power exponential function was fitted to the mass spectrometric data of breath (13)CO(2) enrichment, allowing mathematical analysis of time-to-peak-excretion, half-excretion time, percent label recovery and parameters describing the shape of the curve. Body composition was determined using bioelectrical impedance analysis.

RESULTS

After oral administration, total label recovery after 3 h was about 22% and was not different between men (n=7) and women (n=8). The time to maximal label excretion was 0.67 +/- 0.12 h in men and 0.9 +/- 0.32 h in women (P=0.028) and the excretion curve showed an initially slower rise in women compared with men. Adjusting for lean body mass or body water abrogated the sex differences. Total label recovery after intravenous administration was about 9%, suggesting that the substrate was rapidly catabolized in the muscle compartment after intravenous administration.

CONCLUSIONS

The modified power exponential function described allows standardized estimates of the KIC breath test results. When corrected for body composition, there are no differences in breath test results between men and women. The comparison between oral and intravenous results provides robust evidence that the KIC breath test measures predominantly hepatic and not muscle decarboxylation and is thus a highly specific liver function test.

Point-of-care continuous 13C-methacetin breath test improves decision making in acute liver disease: Results of a pilot clinical trial

AIM: To assess the role of the ¹³C-methacetin breath test (MBT) in patients with acute liver disease.

METHODS: Fifteen patients with severe acute liver disease from diverse etiologies were followed-up with ¹³C-MBT during the acute phase of their illnesses (range 3-116 d after treatment). Patients fasted for 8 h and ingested 75 mg of methacetin prior to the MBT. We compared results from standard clinical assessment, serum liver enzymes, synthetic function, and breath test scores.

RESULTS: Thirteen patients recovered and two patients died. In patients that recovered, MBT parameters improved in parallel with improvements in lab results. Evidence of consistent improvement began on day 3 for MBT parameters and between days 7 and 9 for blood tests. Later convergence to normality occurred at an average of 9 d for MBT parameters and from 13 to 28 d for blood tests. In both patients that died, MBT parameters remained low despite fluctuating laboratory values.

CONCLUSION: The ¹³C-MBT provides a rapid, non-invasive assessment of liver function in acute severe liver disease of diverse etiologies. The results of this pilot clinical trial suggest that the MBT may offer greater sensitivity than standard clinical tests for managing patients with severe acute liver disease.

Critical management decisions in patients with acute liver failure

Few admissions to the ICU present a greater clinical challenge than the patient with acute liver failure (ALF), the syndrome of abrupt loss of liver function in a previously unaffected individual. Although advances in the intensive care management of patients with ALF have improved survival, the prognosis of ALF remains poor, with a 33% mortality rate and a 25% liver transplant rate in the United States. ALF adversely affects nearly every organ system, with most deaths occurring from sepsis and subsequent multiorgan system failure, and cerebral edema, resulting in intracranial hypertension (ICH) and brainstem herniation. Unfortunately, the optimal management of ALF remains poorly defined, and practices are often based on local experience and case reports rather than on randomized, controlled clinical trials. The paramount question in any patient presenting with ALF remains defining an etiology, since specific antidotes can save lives and spare the liver. This article will consider recent advances in the assignment of an etiology, the administration of etiology-specific treatment to abate the liver injury, and the management of complications (eg, infection, cerebral edema, and the bleeding diathesis) in patients with ALF. New data on the administration of N-acetylcysteine to patients with non-acetaminophen ALF, the treatment of ICH, and assessment of the need for liver transplantation will also be presented.

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.