13C-aminopyrine breath test to evaluate severity of disease in patients with chronic hepatitis C virus infection

Mitochondria Matter: Systemic Aspects of Nonalcoholic Fatty Liver Disease (NAFLD) and Diagnostic Assessment of Liver Function by Stable Isotope Dynamic Breath Tests

The liver plays a key role in systemic metabolic processes, which include detoxification, synthesis, storage, and export of carbohydrates, lipids, and proteins. The raising trends of obesity and metabolic disorders worldwide is often associated with the nonalcoholic fatty liver disease (NAFLD), which has become the most frequent type of chronic liver disorder with risk of progression to cirrhosis and hepatocellular carcinoma. Liver mitochondria play a key role in degrading the pathways of carbohydrates, proteins, lipids, and xenobiotics, and to provide energy for the body cells. The morphological and functional integrity of mitochondria guarantee the proper functioning of β-oxidation of free fatty acids and of the tricarboxylic acid cycle. Evaluation of the liver in clinical medicine needs to be accurate in NAFLD patients and includes history, physical exam, imaging, and laboratory assays. Evaluation of mitochondrial function in chronic liver disease and NAFLD is now possible by novel diagnostic tools. "Dynamic" liver function tests include the breath test (BT) based on the use of substrates marked with the non-radioactive, naturally occurring stable isotope 13C. Hepatocellular metabolization of the substrate will generate 13CO2, which is excreted in breath and measured by mass spectrometry or infrared spectroscopy. Breath levels of 13CO2 are biomarkers of specific metabolic processes occurring in the hepatocyte cytosol, microsomes, and mitochondria. 13C-BTs explore distinct chronic liver diseases including simple liver steatosis, non-alcoholic steatohepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug, and alcohol effects. In NAFLD, 13C-BT use substrates such as α-ketoisocaproic acid, methionine, and octanoic acid to assess mitochondrial oxidation capacity which can be impaired at an early stage of disease. 13C-BTs represent an indirect, cost-effective, and easy method to evaluate dynamic liver function. Further applications are expected in clinical medicine. In this review, we discuss the involvement of liver mitochondria in the progression of NAFLD, together with the role of 13C-BT in assessing mitochondrial function and its potential use in the prevention and management of 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.

Non-Alcoholic Steatohepatitis Decreases Microsomal Liver Function in the Absence of Fibrosis

The incidence of non-alcoholic fatty liver disease (NAFLD) is rising across the globe, with the presence of steatohepatitis leading to a more aggressive clinical course. Currently, the diagnosis of non-alcoholic steatohepatitis (NASH) is based on histology, though with the high prevalence of NAFLD, a non-invasive method is needed. The 13C-aminopyrine breath test (ABT) evaluates the microsomal liver function and could be a potential candidate. We aimed to evaluate a potential change in liver function in NASH patients and to evaluate the diagnostic power of ABT to detect NASH. We performed a retrospective analysis on patients suspected of NAFLD who underwent a liver biopsy and ABT. 440 patients were included. ABT did not decrease in patients with isolated liver steatosis but decreased significantly in the presence of NASH without fibrosis and decreased even further with the presence of significant fibrosis. The predictive power of ABT as a single test for NASH was low but improved in combination with ALT and ultrasonographic steatosis. We conclude that microsomal liver function of patients with NASH is significantly decreased, even in the absence of fibrosis. The ABT is thus a valuable tool in assessing the presence of NASH; and could be used as a supplementary diagnostic tool in clinical practice.

Aminopyrine breath test predicts liver-related events and death in HCV-related cirrhosis on SVR after DAA therapy

BACKGROUND & AIMS

In patients with hepatitis C virus (HCV)-related advanced cirrhosis, the effects of sustained virological response (SVR) by direct antiviral agents (DAAs) on decompensation and liver deaths are less clearcut, since up to 30% of patients do not improve, and no predictors of outcome have been identified. We used ¹³ C-aminopyrine breath test (ABT) to assess whether its changes can predict liver-related outcomes after DAA treatment in patients with HCV cirrhosis.

METHODS

Fifty consecutive patients with HCV cirrhosis were enrolled. Patients were included if they had Child A cirrhosis at risk for decompensation - defined as Child A6 (N = 22, 44%) or previous decompensation (N = 7, 14%) - or Child B cirrhosis (N = 21, 42%) eligible for DAA-based antiviral therapy. ABT was performed at baseline and 12 weeks after the end of antiviral therapy. Patients received sofosbuvir-based regimens.

RESULTS

Aminopyrine breath test was available for all 50 patients at baseline. The 120' cumulative dose was directly associated at regression analysis only with albumin levels (P = .001). ABT was available at follow-up week 12 for 41 patients (FUW12), all with SVR, and followed for a median of 25.2 months (range 12.2-32.1 months). Lower Ʌ ABT - defined as changes of 120' cumulative dose from FUW12 to baseline - (HR 0.97, 95% CI 0.94-0.99; P = .02) and FUW12 hepatic encephalopathy (HR 19.0, 95% CI 1.16-310.3; P = .03) were the only independent predictors of liver events/death at multivariate Cox regression analysis. The AUC of Ʌ ABT was good (0.87, 95% CI 0.75-0.97), with a delta ≥0% well discriminating patients at lower vs patients at higher risk of liver-related events/death (P < .001).

CONCLUSIONS

In patients with advanced HCV cirrhosis who achieve SVR with DAA, Ʌ ABT assists in assessing the residual likelihood of liver-related events and deaths after viral cure.

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.

Drug metabolism and liver disease: a drug-gene-environment interaction

Despite the central role of the liver in drug metabolism, surprisingly there is lack of certainty in anticipating the extent of modification of the clearance of a given drug in a given patient. The intent of this review is to provide a conceptual framework in considering the impact of liver disease on drug disposition and reciprocally the impact of drug disposition on liver disease. It is proposed that improved understanding of the situation is gained by considering the issue as a special example of a drug-gene-environment interaction. This requires an integration of knowledge of the drug's properties, knowledge of the gene products involved in its metabolism, and knowledge of the pathophysiology of its disposition. This will enhance the level of predictability of drug disposition and toxicity for a drug of interest in an individual patient. It is our contention that advances in pharmacology, pharmacogenomics, and hepatology, together with concerted interests in the academic, regulatory, and pharmaceutical industry communities provide an ideal immediate environment to move from a qualitative reactive approach to quantitative proactive approach in individualizing patient therapy in liver disease.

Isoprene in the Exhaled Breath is a Novel Biomarker for Advanced Fibrosis in Patients with Chronic Liver Disease: A Pilot Study

Objectives:

Analysis of volatile organic compounds (VOCs) in the exhaled breath can identify markers for alcoholic and nonalcoholic fatty liver disease. The aim of this pilot study was to investigate the utility of breath VOCs measured by mass spectrometry to diagnose advanced fibrosis in patients with chronic liver disease (CLD).

Methods:

Patients undergoing liver biopsy were recruited. Fibrosis was determined by an experienced pathologist (F0–4) and advanced fibrosis was defined as F3–4. Exhaled breath and plasma samples were collected on the same day of the biopsy. Selective ion flow tube mass spectrometry (SIFT-MS) was used to analyze breath samples. Bonferroni correction was applied to decrease the false discovery rate.

Results:

In all, 61 patients were included with a mean age of 50.7±9.9 years and 57% were male. Twenty patients (33%) had advanced fibrosis (F3–4), 44% had chronic hepatitis C, 30% had nonalcoholic fatty liver disease, and 26% had other CLD. SIFT-MS analysis of exhaled breath revealed that patients with advanced fibrosis had significantly lower values of six compounds compared with those without advanced fibrosis, P value <0.002 for all. Isoprene was found to have the highest accuracy for the prediction of advanced fibrosis with an area under the receiver operating characteristics curve of 0.855 (95% confidence interval: 0.762, 0.948). The median breath isoprene level in patients with F3–4 was 13.5[8.7, 24.7] p.p.b. compared with 40.4[26.2, 54.1] for those with F0–2, P value <0.001. Isoprene is an endogenous VOC that is a byproduct of cholesterol biosynthesis.

Conclusions:

Isoprene is a potential biomarker for advanced fibrosis that deserves further validation.

(13)CO2 breath tests in non-invasive hepatological diagnosis

In liver diagnostics, a simple, non-invasive test with high sensitivity and specificity is permanently being sought in order to assess the degree of liver damage. In addition to liver biopsy, algorithms using blood parameters or elastometry are used in clinical practice. However, these methods do not provide information about the true liver reserve, so the liver breath test seem to be a promising diagnostic tool. The basis of this test depends on the ability of particular hepatocyte enzyme systems to metabolise a tested substance labelled with a stable carbon isotope. The kinetics of ¹³CO₂ elimination with expiratory air then permits quantitative assessment of the functional liver reserve and the degree of organ damage. In this paper the most commonly used tests, grouped according to the main metabolic pathways, are described. The usefulness of liver breath tests in specific clinical situations, both as a diagnostic and prognostic tool, is presented.

Dynamic carbon 13 breath tests for the study of liver function and gastric emptying

In gastroenterological practice, breath tests (BTs) are diagnostic tools used for indirect, non-invasive assessment of several pathophysiological metabolic processes, by monitoring the appearance in breath of a metabolite of a specific substrate. Labelled substrates originally employed radioactive carbon 14 (¹⁴C) and, more recently, the stable carbon 13 isotope (¹³C) has been introduced to label specific substrates. The ingested ¹³C-substrate is metabolized, and exhaled ¹³CO₂ is measured by mass spectrometry or infrared spectroscopy. Some ¹³C-BTs evaluate specific (microsomal, cytosolic, and mitochondrial) hepatic metabolic pathways and can be employed in liver diseases (i.e. simple liver steatosis, non-alcoholic steato-hepatitis, liver fibrosis, cirrhosis, hepatocellular carcinoma, drug and alcohol effects).

Another field of clinical application for ¹³C-BTs is the assessment of gastric emptying kinetics in response to liquids (¹³C-acetate) or solids (¹³C-octanoic acid in egg yolk or in a pre-packed muffin or the ¹³C-Spirulina platensis given with a meal or a biscuit). Studies have shown that ¹³C-BTs, used for gastric emptying studies, yield results that are comparable to scintigraphy and can be useful in detecting either delayed- (gastroparesis) or accelerated gastric emptying or changes of gastric kinetics due to pharmacological effects. Thus, ¹³C-BTs represent an indirect, cost-effective and easy method of evaluating dynamic liver function and gastric kinetics in health and disease, and several other potential applications are being studied.

Sorafenib metabolism is significantly altered in the liver tumor tissue of hepatocellular carcinoma patient

Background

Sorafenib, the drug used as first line treatment for hepatocellular carcinoma (HCC), is metabolized by cytochrome P450 (CYP) 3A4-mediated oxidation and uridine diphosphate glucuronosyl transferase (UGT) 1A9-mediated glucuronidation. Liver diseases are associated with reduced CYP and UGT activities, which can considerably affect drug metabolism, leading to drug toxicity. Thus, understanding the metabolism of therapeutic compounds in patients with liver diseases is necessary. However, the metabolism characteristic of sorafenib has not been systematically determined in HCC patients.

Methods

Sorafenib metabolism was tested in the pooled and individual tumor hepatic microsomes (THLMs) and adjacent normal hepatic microsomes (NHLMs) of HCC patients (n = 18). Commercial hepatic microsomes (CHLMs) were used as a control. In addition, CYP3A4 and UGT1A9 protein expression in different tissues were measured by Western blotting.

Results

The mean rates of oxidation and glucuronidation of sorafenib were significantly decreased in the pooled THLMs compared with those in NHLMs and CHLMs. The maximal velocity (V_max) of sorafenib oxidation and glucuronidation were approximately 25-fold and 2-fold decreased in the pooled THLMs, respectively, with unchanged K_m values. The oxidation of sorafenib in individual THLMs sample was significantly decreased (ranging from 7 to 67-fold) than that in corresponding NHLMs sample. The reduction of glucuronidation in THLMs was observed in 15 out of 18 patients’ samples. Additionally, the level of CYP3A4 and UGT1A9 expression were both notably decreased in the pooled THLMs.

Conclusions

Sorafenib metabolism was remarkably decreased in THLMs. This result was associated with the down regulation of the protein expression of CYP3A4 and UGT1A9.

Critical appraisal of 13C breath tests for microsomal liver function: aminopyrine revisited

As liver diseases are a major health problem and especially the incidence of metabolic liver diseases like non-alcoholic fatty liver disease (NAFLD) is rising, the demand for non-invasive tests is growing to replace liver biopsy. Non-invasive tests such as carbon-labelled breath tests can provide a valuable contribution to the evaluation of metabolic liver function. This review aims to critically appraise the value of the (13) C-labelled microsomal breath tests for the evaluation of metabolic liver function, and to discuss the role of cytochrome P450 enzymes in the metabolism of the different probe drugs, especially of aminopyrine. Although a number of different probe drugs have been used in breath tests, the perfect drug to assess the functional metabolic capacity of the liver has not been found. Data suggest that both the (13) C(2) -aminopyrine and the (13) C-methacetin breath test can play a role in assessing the capacity of the microsomal liver function and may be useful in the follow-up of patients with chronic liver diseases. Furthermore, CYP2C19 seems to be an important enzyme in the N-demethylation of aminopyrine, and polymorphisms in this gene may influence breath test values, which should be kept in mind when performing the (13) C(2) -aminopyrine breath test in clinical practice.

Relationship between 13C-aminopyrine breath test and the MELD score and its long-term prognostic use in patients with cirrhosis

BACKGROUND

(13)C-Aminopyrine breath test ((13)C-ABT) is a non-invasive, dynamic, quantitative liver function test, and the model for end-stage liver disease (MELD) is a recognised biochemical score used to predict survival in patients with cirrhosis.

AIMS

The purpose of this study was to evaluate the relationship between the (13)C-ABT and MELD score in a cohort of cirrhotic patients and, moreover, to assess the prognostic value of (13)C-ABT results in the same group of patients.

PATIENTS AND METHODS

Forty-six patients with cirrhosis and without hepatocellular carcinoma who underwent (13)C-ABT and who had at least 1-year follow-up were prospectively included in this study. MELD score was calculated at entry into the study in all patients. End-points of the study were 1-year liver-related death or liver transplantation.

RESULTS

(13)C-ABT %dose/h at 30 min (%dose/h30) results showed significant, inverse correlation with MELD scores (r = -0.414, P = 0.004). During 1-year follow-up nine patients died (19.6 %) and two were transplanted (4.3 %). Median (13)C-ABT %dose/h30 results (3.2 vs. 1.8) were significantly higher in patients who survived as compared to those who died or underwent transplantation (P = 0.04). Receiver operating characteristics curves showed that a (13)C-ABT %dose/h30 cut-off of 2.0 had the best accuracy (c-index = 0.717) in assessing 1-year prognosis.

CONCLUSIONS

We observed a correlation between a flow-independent quantitative liver function test and the MELD score, and found that the (13)C-ABT may accurately provide long-term prognostic information in cirrhotic patients.

A phase II study of sunitinib in advanced hepatocellular carcinoma

BACKGROUND

In 2007, sorafenib was the first drug able to improve overall survival in patients with advanced hepatocellular carcinoma.

AIM

In 2005 we designed a phase II study to assess safety and efficacy of sunitinib.

METHODS

This is a single arm, open-label, single-centre phase II trial. Eligibility criteria were advanced hepatocellular carcinoma; no prior chemotherapy, performance status 0-1; and Child≤B8. The treatment schedule was 50mg each day orally, 4 weeks on, 2 weeks off.

RESULTS

Between 10/2007 and 10/2010, 34 patients were enrolled. A significant worsening of liver functional reserve after sunitinib was observed. Grade 3/4 adverse effects occurred in 80% of patients and included fatigue (47%), nausea (15%), liver failure (15%), encephalopathy (12%) and upper gastrointestinal bleeding (12%). Six patients (18%) died within 60 days of enrolment. A partial response was observed in 4 patients (12%). Median time to tumour progression was 2.8 months and median overall survival was 5.8 months.

CONCLUSION

A dose of 50mg/d induces a high rate of severe adverse events. Toxicity remains a key concern also at the dose of 37.5mg/d. However, sunitinib is able to induce a prolonged response in some patients. Positron Emission Tomography/Computed Tomography scans may select good responders.

13C-aminopyrine demethylation is decreased in cirrhotic patients with normal biochemical markers

This study determined the rates of (13)C-aminopyrine metabolism in patients with varying degrees of liver cirrhosis as defined by clinical scores. Twenty-five cirrhotic patients and 18 healthy subjects underwent a (13)C-aminopyrine breath test. The cumulative per cent dose recovery (cPDR) of (13)C on breath expressed as a percentage of the administered dose at 2 h was significantly lower in cirrhotic patients than in healthy subjects (median: 1.7% versus 9.0%; p<.0001). Significant inverse associations between cPDR at 2 h and the model for end-stage liver disease score, Child-Pugh score, international normalised ratio and bilirubin (all p<.05), but not alanine aminotransferase or alkaline phosphatase were observed in the cirrhotic patients. Taking each biochemical marker independently, cirrhotic patients with normal biochemistry had a significantly lower cPDR at 2 h than healthy subjects (all p<.05). Differences in (13)C-aminopyrine metabolism were evident in cirrhotic patients with less severe disease and may mark hepatic dysfunction when conventional biochemical markers appear unchanged.

Staging of liver disease: which option is right for my patient?

It is important to assess the stage of liver fibrosis in chronic hepatitis C to guide treatment decisions. Liver biopsy has limitations in staging fibrosis. Several blood tests, algorithms, and imaging tests have been studied as noninvasive markers to stage fibrosis in hepatitis C. In patients without suspicion for cirrhosis, 2 noninvasive methods can be used to predict presence of absence of significant liver fibrosis; however, liver biopsy remains the gold standard. It is imperative not to miss the diagnosis of cirrhosis, because this has further implications for screening of hepatocellular carcinoma and varices.

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.

13C-aminopyrine breath test accurately predicts long-term outcome of chronic hepatitis C

BACKGROUND & AIMS

Although numerous non-invasive tests are currently available to explore liver function and disease activity in patients with HCV-related chronic diseases, none of these indicate the likelihood of disease progression in the individual patient. We aimed at assessing the prognostic ability of (13)C(2)-aminopyrine breath test ((13)C-ABT) in the prediction of liver fibrosis progression in patients with HCV chronic hepatitis who prospectively entered a long-term follow-up.

METHODS

Fifty patients with HCV-related chronic disease who underwent paired liver biopsy (at baseline and after a mean period of 86 months) were included in the study. (13)C-ABT was carried out at baseline and every 3 years. Histological progression was defined as increase of at least 2 fibrosis units according to Ishak score.

RESULTS

Fourteen patients progressed of at least 2 fibrosis units during the follow-up. These patients were more frequently infected with a HCV-1b genotype and had, at baseline, a significantly older age, higher BMI, AST levels, and AST to platelet ratio index (APRI). (13)C-ABT was altered in 57% of cases at baseline and in 100% of the cases at 3-year follow-up. In the univariate analysis, age (p=0.005), BMI (p=0.006), platelet count (p=0.03), AST (p=0.012) and ALT (p=0.04) levels, APRI (p=0.03), and baseline (13)C-ABT results (p<0.0001) were all independently associated with progression of liver fibrosis. By Cox's multiple regression analysis, the (13)C-ABT was the only covariate that significantly predicted liver fibrosis progression (HR 6.7; 95% CI 2.3-20.1; p<0.001).

CONCLUSIONS

(13)C-ABT accurately predicts the risk of disease progression in patients with HCV-related chronic hepatitis.

A comparison of the reproducibility of the parameters of the ¹³C-aminopyrine breath test for the assessment of hepatic function

This study determined the within-subject and between-subject variability of different ways of expressing the results of the (13)C-aminopyrine breath test ((13)C-ABT) and the effect of shortening the test duration. The (13)C-ABT was conducted on three separate occasions in 10 healthy volunteers and on a single occasion in 22 patients with established liver cirrhosis. The within-subject variability of cumulative percentage dose recovered (cPDR), using measured CO(2) production rate (VCO(2)), in the reference group over three trials was 15% over 120 min. Higher within-subject variability in cPDR would have been evident if the test was terminated at either 30 or 60 min. Substitution of predicted VCO(2) to calculate cPDR yielded comparable values at all time points. Significant differences between cirrhotics and reference group were evident after just 10 min using PDR/h, cPDR or enrichment (all P<0.05). The ABT demonstrates clinically acceptable reproducibility. Shortening of the duration may make the test more acceptable clinically, but it is associated with increasing imprecision.

Influence of different proton pump inhibitors on activity of cytochrome P450 assessed by [(13)C]-aminopyrine breath test

Aminopyrine is metabolized by cytochrome P450 (CYP) in the liver. The investigators evaluated influences of different PPIs on CYP activity as assessed by the [(13)C]-aminopyrine breath test ([(13)C]-ABT). Subjects were 15 healthy volunteers with different CYP2C19 status (5 rapid metabolizers [RMs], 5 intermediate metabolizers [IMs], and 5 poor metabolizers [PMs]). Breath samples were collected before and every 15 to 30 minutes for 3 hours after oral ingestion of [(13)C]-aminopyrine 100 mg on day 8 of each of the following regimens: control; omeprazole 20 mg and 80 mg, lansoprazole 30 mg, and rabeprazole 20 mg. Changes in carbon isotope ratios in carbon dioxide ((13)CO(2)/(12)CO(2)) in breath samples were measured by infrared spectrometry and expressed as delta-over-baseline (DOB) ratios (‰). Mean areas under the curve of DOB from 0 to 3 h (AUC(0-3h) of DOB) were significantly decreased by omeprazole 20 mg and lansoprazole 30 mg but not by rabeprazole 20 mg. Conversely, higher PPI dose (ie, omeprazole 80 mg) seemed to further decrease AUC(0-3h) of DOB in RMs but increased it in PMs. Omeprazole and lansoprazole at the standard doses inhibit CYP activity but rabeprazole does not, whereas high-dose omeprazole seems to induce CYPs.

Noninvasive diagnosis and prognosis of liver cirrhosis: a comparison of biological scores, elastometry, and metabolic liver function tests

BACKGROUND

Recently, noninvasive methods for the diagnosis of liver cirrhosis have been extensively developed. We assessed the accuracy of liver stiffness measurement, aspartate aminotransferase-to-platelet ratio index (APRI) score, 13C-aminopyrine breath test, and indocyanine green plasma clearance for the diagnosis of cirrhosis in patients with chronic liver disease and for the prediction of severe complications in cirrhotic patients.

METHODS

A total of 296 consecutive patients with chronic liver diseases of various causes were studied. Diagnostic accuracy was assessed by receiver operating characteristic curve analysis.

RESULTS

Areas under the receiver operating characteristic curve for the diagnosis of cirrhosis were (95% confidence interval) 0.93 (0.90-0.96) for liver stiffness measurement, 0.82 (0.77-0.87) for 13C-aminopyrine breath test, and 0.81 (0.76-0.86) for APRI score. Using cutoff values of 14.1 kPa for liver stiffness, 4.15% dose/h for 13C-aminopyrine breath test, and 1 for APRI score, the positive predictive value was approximately 90% for the diagnosis of cirrhosis. Using cutoff values of 65.2 kPa for liver stiffness, 1.17% dose/h for 13C-aminopyrine breath test, 2.82 for APRI score, and 51.1% for indocyanine green plasma clearance, the positive predictive value was approximately 80% for the occurrence of severe complications among cirrhotic patients.

CONCLUSION

Liver stiffness measurement, 13C-aminopyrine breath test, indocyanine green plasma clearance, and APRI score are reliable noninvasive methods for the diagnosis of cirrhosis in patients with chronic liver diseases of various causes, and are also prognostic indicators for the occurrence of severe complications in cirrhotic patients.

Effect of alcohol consumption on the liver detoxication capacity as measured by [13C2]aminopyrine and L-[1-13C]phenylalanine breath tests

The aim of this study was to investigate the hepatic microsomal and cytosolic functions by using the 13CO2 breath test in healthy subjects either before or after consumption of red wine. Twelve adults received [13C2]aminopyrine and L-[1-13C]phenylalanine together with a standardised dinner. Expired air samples were taken over 6 h. After a wash-out period, the subjects consumed 0.4 ml ethanol per kg per day together with dinner over a 7.5-day period on average. Thereafter, 13C-tracer administration was repeated under identical conditions. The 13CO2 enrichments were measured by isotope ratio mass spectrometry. The mean cumulative percentage 13C-dose recovery after administration of [13C2]aminopyrine and L-[1-13C]phenylalanine either without or with red wine consumption amounted to 17.0+/-4.4 vs. 14.7+/-3.1% (p=0.170) and 14.0+/-2.8 vs. 11.5+/-3.9% (p=0.084), respectively. Moderate alcohol consumption does not induce significant short-term changes of the microsomal and the cytosolic function of the human liver in healthy subjects.

Methods and functions: Breath tests

Breath tests provide a valuable non-invasive diagnostic strategy to in vivo assess a variety of enzyme activities, organ functions or transport processes. Both the hydrogen breath tests and the (13)C-breath tests using the stable isotope (13)C as tracer are non-radioactive and safe, also in children and pregnancy. Hydrogen breath tests are widely used in clinical practice to explore gastrointestinal disorders. They are applied for diagnosing carbohydrate malassimilation, small intestinal bacterial overgrowth and for measuring the orocecal transit time. (13)C-breath tests non-invasively monitor the metabolisation of a (13)C-labelled substrate. Depending on the choice of the substrate they enable the assessment of gastric bacterial Helicobacter pylori infection, gastric emptying, liver and pancreatic function as well as measurements of many other enzyme activities. The knowledge of potential pitfalls and influencing factors are important for correct interpretation of breath test results before drawing clinical conclusions.

Utility of a 13C-methacetin breath test in evaluating hepatic injury in rats

BACKGROUND AND AIM

Methacetin is thought to be a good substrate for the evaluation of different cytochrome P450 enzymatic systems of liver microsomes because of its rapid metabolism and lack of toxicity in small doses. Recent studies indicate that a methacetin breath test may be a non-invasive alternative for the evaluation of liver function since it correlates well with the severity of liver damage. It may also discriminate between different stages of liver cirrhosis and correlates with the Child-Pugh score. The application of this test in experimental liver damage in animal models has not yet been examined. This study aimed to evaluate the efficacy of the (13)C-methacetin breath test in assessing the extent of hepatic injury in models of acute liver failure, liver cirrhosis, and fatty liver in rats.

METHODS

Absorption of methacetin given per os or intraperitoneally in normal rats was evaluated. The association between liver mass and (13)C-methacetin breath test results was assessed in a 70% hepatectomy rat model. Fulminant hepatic failure was induced by three consecutive intraperitoneal injections of thioacetamide, 300 mg/kg, at 24 h intervals. For induction of liver cirrhosis, rats were given intraperitoneal injections of thioacetamide, 200 mg/kg, twice a week for 12 weeks. A methionine-choline deficient diet was used for the induction of fatty liver. Rats were analyzed for (13)C-methacetin by BreathID (MBID) using molecular correlation spectrometry. BreathID continuously sampled the animal's breath for 60 min and displayed the results on the BreathID screen in real-time.

RESULTS

Methacetin was absorbed well irrespective of the administration method in normal rats. Liver mass was associated with peak amplitude, complete percent dose recovery (CPDR) at 30 and 60 min and MBID peak time. A high degree of association was also demonstrated with MBID results in acute hepatitis (peak amplitude, 19.6 +/- 3.4 vs 6.3 +/- 1.63.4; CPDR30, 6.0 +/- 3.3 vs 1.2 +/- 0.5; CPDR60, 13.3 +/- 4.5 vs 3.2 +/- 1.4; and peak time, 31.0 +/- 14.9 vs 46.9 +/- 10.8 min) and liver cirrhosis (peak amplitude, 24.4 +/- 2.3 vs 15.6 +/- 6.4; CPDR30, 7.9 +/- 1.2 vs 2.7 +/- 1.0; CPDR60, 17.8 +/- 2.6 vs 8.8 +/- 2.1; and peak time, 30.2 +/- 1.5 vs 59.6 +/- 14.5 min), but not with grade of liver steatosis.

CONCLUSIONS

Methacetin is well absorbed and exclusively metabolized in the liver. MBID is a sensitive test and may be a useful tool for the evaluation of functional liver mass in animal models of acute liver failure and cirrhosis. However, MBID could not distinguish between fatty liver and normal liver in rats.

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.

Monitoring cytochrome P-450 activity during rabeprazole treatment in patients with gastresophageal reflux disease

Proton pump inhibitors (PPIs) are the cornerstone in the treatment of gastresophageal reflux disease (GORD). PPIs are metabolized by the hepatic cytochrome P-450 enzymes (CYP-450). Rabeprazole is a PPI whose metabolism shows fewer interactions compared to other PPIs. In this study we evaluated the influence of rabeprazole administration on hepatic CYP-450 activity as measured by the (13)C-aminopyrine breath test ((13)C-ABT) in a group of patients with GORD. (13)C-ABT was performed on five GORD patients both before and after 1 week of rabeprazole administration (20 mg, b.i.d.). Pretreatment (13)C-ABT results were compared to posttreatment results. Pre- and posttreatment (13)C-ABT results for patients were compared to those obtained in five controls who did the test twice, with a 1-week interval in between. Before treatment, the (13)C-ABT results for the GORD patients did not significantly differ from those of healthy subjects. After treatment, we observed no significant modification of the (13)C-ABT in GORD patients compared to pretreatment values ((13)C-ABT %dose/hr, 10.56+/-1.31 versus 11.17+/-0.88; (13)C-ABT %cumulative dose, 8.08+/-1.11 versus 8.34+/-0.56). Posttreatment (13)C-ABT results were not significantly different from those obtained in controls at weekly repetition of the test. In patients with GORD, 1-week, full-dose rabeprazole does not display any significant interactions with CYP-450 activity.

Noninvasive ratio indexes to evaluate fibrosis staging in chronic hepatitis C: role of platelet count/spleen diameter ratio index

OBJECTIVES

Noninvasive evaluation of fibrosis is an on-going effort in the management of chronic hepatitis C. This study was planned to noninvasively evaluate fibrosis staging.

DESIGN

We evaluated the biochemical, functional [aminopyrine breath test (ABT)] and ultrasonographic variables of 75 chronic hepatitis C patients.

RESULTS

Clinical [body mass index (BMI)], biochemical [aspartate aminotransferase (AST), alanine aminotransferase (ALT) and platelets (PLT)] and ratio indexes, together with the ABT, showed a higher relationship with fibrosis: initial (score<or=2) versus evident (score>2) fibrosis: BMI (24+/-2 vs. 26+/-2, P=0.0007), AST (56+/-36 vs. 88+/-65, P=0.0159), ALT (92+/-54 vs. 139+/-108, P=0.0290), PLT (220+/-64 vs. 173+/-61, P=0.0007), PLT/spleen diameter ratio (PLT/SPD) (2133+/-786 vs. 1540+/-681, P=0.0003), AST/platelet count ratio index (APRI) (0.80+/-0.87 vs. 1.51+/-1.47, P=0.0010), ABT%d/h30 min (10.8+/-4.5 vs. 7.6+/-3.8, P=0.0007), ABT%d/cum120 min (8.9+/-3.3 vs. 6.5+/-3.1, P=0.0007). Considering the differences between fibrosis score 2 and 3 patients, BMI, ABT and PLT/SPD ratio proved to be statistically significant. Multivariate stepwise analysis (with and without BMI) identified two models for distinguishing between initial and evident fibrosis: Model 1: -0.569+(BMIx0.107)+(APRIx0.169)-(PLT/SPDx0.304), and Model 2: 2.376+( APRIx0.152)-(ABTd/h30x0.043)-(PLT/SPDx0.249). These models showed concordance in identifying or ruling out evident fibrosis in 76% and 78.7% of the patients respectively. The PLT/SPD ratio also showed 78.7% concordance with the histological score.

CONCLUSION

These results suggest that noninvasive evaluation of fibrosis in chronic hepatitis C may be considered an effective tool thanks to the use of an inexpensive, reproducible ratio index.

Hyaluronic acid and aspartate aminotransferase levels normalized by liver function can reflect sinusoidal impairment in chronic liver disease

BACKGROUND/AIM

To evaluate the relationship between hyaluronic acid/aminopyrine breath test (HA/ABT) ratio and fibrosis score in chronic hepatitis, and between HA/ABT and clinical staging (child-turcotte-pugh'score, CTP; and model for end stage liver disease, MELD) in cirrhosis, as well as to evaluate the aspartate aminotransferase (AST)/ABT in relation to the HA/ABT.

METHODS

We studied 48 patients with histologically proven chronic hepatitis C (CHC) and 35 patients with compensated cirrhosis (CIR).

RESULTS

HA/ABT and AST/ABT showed a more significant correlation with the fibrosis score than HA or ABT or AST alone in the 48 CHC patients: r=0.568 (P<0.0001), r=0.610 (P<0.0001), r=0.450 (P=0.0021), r=-0.449 (P=0.0021), and r=0.472(P=0.0012), respectively. Progressive liver damage (fibrosis 1-2 vs fibrosis 3-6 vs cirrhosis) was significantly (P<0.05) reflected by both HA/ABT (mean+/-SEM: 4.0+/-0.9 vs 18.1+/-4.2 vs 149.9+/-33.1) and AST/ABT (6.3+/-1.8 vs 12.7+/-1.6 vs 42.1+/-14.6). A strong relationship was found between HA/ABT and AST/ABT (r=0.755 P<0.0001). In cirrhotic patients, the most significant relationship was observed between HA/ABT and CTP r=0.483 and P=0.0049, and MELD r=0.523 and P=0.0023.

CONCLUSION

Considering that HA levels in chronic hepatitis depend on the progressive impairment of sinusoidal endothelial cells (SEC), related to progressive fibrosis, HA/ABT ratio would seem to be the most specific reflection of progressive impairment of the SEC. AST/ABT could be used as a possible surrogate of HA in identifying SEC impairment in chronic hepatitis.

PATIENT AGE IS A STRONG INDEPENDENT PREDICTOR OF 13C-AMINOPYRINE BREATH TEST RESULTS: A COMPARATIVE STUDY WITH HISTOLOGY, DUPLEX-DOPPLER AND A LABORATORY INDEX IN PATIENTS WITH CHRONIC HEPATITIS C VIRUS INFECTION

1. Noninvasive tests for the staging of chronic hepatitis C virus (HCV) infection would be an attractive alternative to liver biopsy. The 13C-aminopyrine breath test (ABT) has been proposed for the noninvasive assessment of hepatic function and partly correlates with fibrosis. We aimed to investigate causes for the lack of discriminatory power for different degrees of hepatic fibrosis. 2. Eighty-three patients (median age 49 years (28-78 years)) with chronic HCV infection underwent the ABT after an oral load of 75 mg N,N-dimethyl-13C-aminopyrine. Portal vein flow was assessed by duplex-Doppler and a laboratory index (aspartate aminotransferase to platelet ratio index or APRI) was calculated. Parameters were compared with liver histology. 3. The cumulative 13C-recovery differed significantly between patients without relevant fibrosis (fibrosis score 0-2) and cirrhosis (5-6), beginning after 30 min of sampling (P < 0.05). The ABT did not discriminate patients with fibrosis scores 3-4 from the remaining two patient groups. Sensitivity and specificity for the prediction of cirrhosis was 73.4-82.8% and 63.2-68.4%, depending on the sampling time. Compared with the fibrosis score (P = 0.04), patient age was a highly significant independent predictor for the 13C-recovery (P < 0.0001). Aspartate aminotransferase to platelet ratio index and duplex-Doppler predicted cirrhosis with 76.6%vs. 87.5% sensitivity and 63.2%vs. 68.4% specificity. 4. Our data suggest an age-dependent decrease of cytochrome P450 activity which probably accounts for the large overlap of ABT results that preclude clear differentiation. This is also consistent with former pharmacodynamic trials. Age-adapted reference ranges could improve ABT results.

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.

Improvement of quantitative testing of liver function in patients with chronic hepatitis C after installment of antiviral therapy

AIM: To investigate if and to what extent antiviral therapy influenced a broad panel of quantitative testing of liver function (QTLF).

METHODS: Fifty patients with chronic hepatitis C were either treated with interferon (n = 8), interferon/ribavirin (n = 19) or peg-interferon/ribavirin (n = 23). Quantitative testing of liver function, including aminopyrine breath test (ABT), galactose elimination capacity (GEC), sorbitol clearance (SCl) and indocyanine green clearance (ICG) was performed before and 3 mo after initiation of antiviral therapy.

RESULTS: After 3 mo of antiviral treatment, 36 patients showed normal transaminases and were negative for HCV-RNA, 14 patients did not respond to therapy. ABT and GEC as parameters of microsomal and cytosolic liver function were reduced in all patients before therapy initiation and returned to normal values in the 36 therapy responders after 3 mo. Parameters of liver perfusion (SCl and ICG) were not affected by antiviral therapy. In the 14 non-responders, no changes in QTLF values were observed during the treatment period.

CONCLUSION: ICG and SCl remained unaffected in patients with chronic hepatitis C, while ABT and GEC were significantly compromised. ABT and GEC normalized in responders to antiviral therapy. Early determination of ABT and GEC may differentiate responders from non-responders to antiviral treatment in hepatitis C.

Influence of 1-week Helicobacter pylori eradication therapy with rabeprazole, clarithromycin, and metronidazole on 13C-aminopyrine breath test

Helicobacter pylori eradication therapy is commonly prescribed in the general population. Treatment consists of drugs that are mainly metabolized by the liver cytochrome P-450 (CYP) enzymatic pool. Most H. pylori-infected patients often take drugs for comorbid illnesses, therefore increasing the potential for drug-drug interactions. We aimed to evaluate the interactions of rabeprazole, clarithromycin, and metronidazole 1-week H. pylori eradication therapy with CYP-dependent liver metabolic function in clinical practice. Ten patients referred to our unit for H. pylori infection underwent 1-week eradication therapy with rabeprazole (20 mg, b.i.d.), clarithromycin (500 mg, b.i.d.), and metronidazole (500 mg, b.i.d.). We chose the 13C-aminopyrine breath test (13C-ABT) to evaluate CYP-dependent liver function since it is noninvasive and nonharmful. All patients underwent 13C-ABT at three time points: before therapy (to), at the end of therapy (t8), and after 1 month of follow-up (t38). Mean 13C-ABT dose/hr (t0 = 14.0 +/- 5.4, t8 = 13.5 +/- 4.0, t38 = 16.1 +/- 5.6) as well as 13C-ABT cumulative dose (t0 = 2.4 +/- 1.1, t8 = 2.4 +/- 0.8, t38 = 2.6 +/- 1.0) were not statistically different at the three time points of the study. These results did not seem to be influenced by drugs being administered concomitantly. In everyday clinical practice rabeprazole-based H. pylori eradication therapy does not seem to display any significant interactions with CYP-dependent liver function, even in patients on multiple drugs.

Validity of 13C-phenylalanine breath test to evaluate functional capacity of hepatocyte in patients with liver cirrhosis and acute hepatitis

BACKGROUND

No definitive method for quantitative evaluation of hepatic function has as yet been established.

AIM

To investigate whether the (13)C-phenylalanine breath test would be useful for the evaluation of hepatic function in patients with liver cirrhosis and acute hepatitis.

METHODS

L-[1-(13)C]-phenylalanine was administered orally in a dose of 100 mg to 25 patients with liver cirrhosis, 22 patients with acute hepatitis and 10 healthy subjects. The relationships of the cumulative excretion with the (13)C-%dose/h, blood biochemical parameters and asialoscintigraphy were investigated.

RESULTS

In liver cirrhosis patients, the cumulative excretion showed correlations with hepatic function tests, asialoscintigraphy, clinical stage and portal hypertension. In acute hepatitis patients, the cumulative excretion showed correlations with hepatic function tests. There were positive correlations between the cumulative excretion and the (13)C-%dose/h at 20 min (Phe20) and (13)C-%dose/h at 30 min (Phe30) in liver cirrhosis and acute hepatitis patients. Multiple regression analysis demonstrated that total bilirubin, total cholesterol and absence of varices were independent determinants of cumulative excretion in liver cirrhosis patients and prothrombin time in acute hepatitis patients.

CONCLUSION

The (13)C-phenylalanine breath test may allow hepatic function to be evaluated non-invasively in liver cirrhosis and acute hepatitis patients, and the Phe20 and Phe30 may be useful for determination of function at a single time-point.

Comparison of clinical value of IRIS 13C-methacetin breath test and ICG test in assessment of liver function in cirrhosis

AIM: To compare the clinical value of ¹³C-methacetin breath test and ICG test in the assessment of liver function in patients with cirrhosis.

METHODS: Fifty-nine patients with liver cirrhosis received ¹³C-methacetin breath test after an overnight fast. Breath samples were taken before and at different time within 120 min after administration. ¹³CO₂ enrichment was measured by infrared isotope spectrometry (IRIS). The ¹³CO₂ maximum excretive rate before 40 min (mv_max40), ¹³CO₂ cumulative excretion at 40 min (cum₄₀) and ¹³CO₂ cumulative excretion at 120 min (cum₁₂₀) were determined. Plasma retention rate of indocyanine green at 15 min (R_{15 ICG}) was also measured.

RESULTS: ¹³C mv_max40, cum₄₀ and cum₁₂₀ were significantly different between the cirrhosis patients with different Child-Pugh grades (A, B, C). (mv_max40 A-B, B-C and A-C: 2.80, 4.82 and 10.38; cum₄₀ A-B, B-C and A-C: 3.85, 3.39 and 8.64; cum₁₂₀ A-B, B-C and A-C: 4.52, 3.75 and 12.36, P<0.01). The differences of R_{15 ICG} of patients with different Child-Pugh grades were also significant (A-B and B-C: -4.72,-1.27, P<0.01) except between Child-Pugh B and C group (A-C: -5.85, P>0.05).¹³C mv_max40, cum₄₀, cum₁₂₀ and R_{15 ICG} significantly correlated with Child-Pugh classification score (r = -0.562, -0.614, -0.716 and 0.555, P<0.001). For the evaluation of liver function in patients with cirrhosis, the consistence of 13C-methacetin breath test with Child-Pugh classification (Kappa: 0.69, P<0.05) was better than that of ICG test (Kappa: 0.47, P<0.05).

CONCLUSION: ICG test is a good quantitative method for the evaluation of the liver function in cirrhosis. ¹³C-methacetin breath test can be used to measure immediate hepatocyte injure and liver functional reserve. It is more sensitive than ICG test in the evaluation of liver function in cirrhosis, especially in uncompensated patients.

13C-methacetin breath test as liver function test in patients with chronic hepatitis C virus infection

BACKGROUND

The 13C-methacetin breath test enables the quantitative evaluation of the cytochrome P450-dependent liver function.

AIM

To find out whether this breath test is sensitive in noncirrhotic patients also with chronic hepatitis C in early stages of fibrosis.

METHODS

Sixty-one healthy controls and 81 patients with chronic hepatitis C underwent a 13C-methacetin breath test. In all patients, a liver biopsy was performed. The liver histology was classified according to the histology activity index-Knodell score.

RESULTS

Delta over baseline values of the patients at 15 min significantly differed from controls (19.2 +/- 9.2 per thousand vs. 24.1 +/- 5.7 per thousand; P < 0.003). The cumulative recovery after 30 min in patients was 11.4 +/- 4.8% and in healthy controls 13.8 +/- 2.8% (P < 0.002). However, patients with early fibrosis (histology activity index IVB) did not differ in delta over baseline values of the patients at 15 min (23.2 +/- 7.9 per thousand vs. 22.6 +/- 7.2 per thousand; P = 0.61) or cumulative recovery (13.6 +/- 3.7% vs. 13.2 +/- 3.8%; P = 0.45) from patients with more advanced fibrosis (histology activity index IVC). Patients with clinically nonsymptomatic cirrhosis (histology activity index IVD; Child A) metabolized 13C-methacetin to a significantly lesser extent (delta over baseline values of the patients at 15 min: 8.3 +/- 4.9 per thousand; P < 0.005 and cumulative recovery after 30 min: 5.6 +/- 3.2%; P < 0.003). The 13C-methacetin breath test identified cirrhotic patients with 95.0% sensitivity and 96.7% specificity.

CONCLUSION

The non-invasive 13C-methacetin breath test reliably distinguishes between early cirrhotic (Child A) and noncirrhotic patients, but fails to detect early stages of fibrosis in patients with chronic hepatitis C.

13C- mithacetin breath test for assessment of liver functional capacity

AIM: To investigate the clinical significance of ¹³C-mithacetin breath tests for assessment and the classification of liver functional capacity.

METHODS: Twelve healthy volunteers served as a control group. Patients (test group) with different kinds of liver diseases were divided into 4 sub-groups: compensatory period (n = 4), Child-Pugh classification A, B, C (n = 12, 12, 16, respectively). Patients in both groups were examined for liver function by a biochemical test after orally taking ¹³C-mithacetin (75 mg). Gas breathed out was collected at 9 different time within 120 min. The samples were analyzed with mass spectrograph to obtain DOB, MV and CUM curves and CUM120 value.

RESULTS: Biochemical index such as ALB and pre-albumin (PA) in patients of test group (Child-Pugh A, B and C) were significantly decreased as compared with those in patients of control group (ALB: 33.1 ± 3.1, 29.3 ± 6.5, 27.9 ± 5.0 vs 36.6 ± 4.7; PA: 119.7 ± 51.0, 104.3 ± 21.1, 77.4 ± 32.9 vs 176.4 ± 68.2; P < 0.05). The classifications of liver capacity significantly related to the values of ALB and PA (P < 0.05). Peak values of DOB and MV curves negatively related to the peak time in the test group (DOB: r = -0.48, P < 0.01; MV: r = -0.57, P < 0.01). Peak values of DOB, MV and CUM decreased with the development of liver dysfunction. Significant difference existed between the test group (Child-Pugh A, B, and C respectively) and control group (DOB: 10.4 ± 3.39, 6.71 ± 3.58, 4.00 ± 1.40 vs 20.93 ± 7.56; MV: 13.12 ± 9.51, 11.61 ± 8.02, 10.20 ± 4.99 vs 29.53; CUM: 18.09 ± 18.09, 16.60 ± 16.60, 15.82 ± 15.82 vs 30.67 ± 2.85; P < 0.05 repectively). CUM120 values in patients of the test group (Child-Pugh A, B, and C) significantly decreased as compared with those in patients of control group (63.61 ± 36.67, 59.32 ± 24.73, 52.62 ± 23.92 vs 109.45 ± 10.26; P < 0.05), but no significant decrease appeared among sub-groups.

CONCLUSION: ¹³C-mithacetin breath test is a safe, effective method in assessment and classification of liver capacity. Mean peak values of DOB, MV and CUM curves and CUM120 value decrease with the development of liver dysfunctions. Peak values are more clinically significant than peak time.

Evaluation of hepatic function with 13C-methacetin breath test in patients with liver cirrhosis

AIM: To investigate the characteristics of the ¹³C-methacetin breath test (¹³C-MBT) as a tool to monitor hepatic function of patients with liver cirrhosis.

METHODS: Forty-two patients with liver cirrhosis and thirty-one age- and sex-matched healthy controls underwent ¹³C-MBT.¹³C-methacetin (75 mg) was given orally, and the levels of ¹³CO₂ delta over baseline (DOB), metabolisation velocity (MV) and cumulative percentage doses (CD) before and 10, 20, 30, 40, 50, 60, 80, 100 and 120 min after substrate administration breath samples was determined and compared, by non-dispersive infrared spectrometry.

RESULTS: The ¹³CO₂ peak percent doses of healthy controls, Child class A and Child class B patients were 20.3 ±3.5%, 7.5±1.8% or 6.5±3.3% and 4.5±1.3%, and occurred at 20 min, 20 or 80 min and 40 min, respectively. The differences of¹³CO₂ peak percent doses among healthy controls, Child class A and Child class B patients were obvious (P <0.05). No ¹³CO₂peak percent doses occurred in Child class C patients. The differences of ¹³CO₂ peak metabolic velocity were obvious (P <0.05) between healthy controls (28.8±5.3%) and Child class A patients (9.4±2.4%). No ¹³CO₂ peak metabolic velocity occurred in Child class B and Child class C patients. The ¹³CO₂ cumulative percentage doses of healthy controls, Child class A , Child class B and Child class C patients at 120 min after substrate administration were 31.2±4.5%, 13.8±3.7%, 8.2±2.2% and 2.4±0.8% (P <0.05), respectively.

CONCLUSION: The severity of liver damage can be directly and effectively evaluated by ¹³C-MBT in patients with cirrhosis.

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Relationship between thrombopoietin serum levels and liver function in patients with chronic liver disease related to hepatitis C virus infection

OBJECTIVES

Thrombopoietin (Tpo) is an important regulator of megakaryocyte maturation and platelet production, and is mainly produced by the liver. A decrease in Tpo production is partly responsible for the thrombocytopenia observed in patients with chronic liver disease (CLD). The aim of this study was to evaluate the relationship between Tpo serum levels and liver function in patients with CLD related to hepatitis C virus (HCV) infection.

METHODS

We studied 37 patients with various degrees of HCV-related CLD. Of the patients, 17 had chronic hepatitis and 20 liver cirrhosis. Liver function was evaluated in all patients by the following hepatic blood flow dependent and independent tests that explore various hepatic metabolic functions: carbon-13 (13C)-aminopyrine breath test (13C-ABT), 13C-galactose breath test (13C-GBT), and monoethylglycinexylidide (MEGX) test. Liver function tests results were correlated with Tpo serum levels.

RESULTS

Tpo serum levels were significantly lower in patients with liver cirrhosis (88 +/- 23 pg/ml) as compared to those in patients with chronic hepatitis (128 +/- 55 pg/ml, p=0.0031). However, they did not correlate with serum albumin, bilirubin, or prothrombin activity. Tpo serum levels showed a significant positive correlation with 13C-ABT results (hourly dose at 30 min, rs=0.489, p=0.002; cumulative dose at 120 min, rs=0.425, p=0.008). Moreover, they showed a fair, positive correlation with 13C-GBT hourly dose at 30 min (rs=0.366, p=0.028), and a trend toward a positive correlation with the various MEGX test sampling times (MEGX15, rs=0.314, p=0.059; MEGX30, rs=0.284, p=0.088; and MEGX60, rs=0.320, p=0.059).

CONCLUSIONS

In this study we have shown that a progressive decline in liver function in patients with HCV-related CLD is paralleled by a decrease in Tpo production. The different correlations observed between Tpo and the various liver function tests suggests that this finding is mainly the result of a decrease in hepatic functional mass rather than dependent on alteration in splanchnic hemodynamic.

Review article: breath testing for human liver function assessment

Carbon-labelled breath tests were proposed as tools for the evaluation of human liver function 30 years ago, but have never become part of clinical routine. One reason for this is the complex role of the liver in metabolic regulation, making it difficult to provide essential information for the management of patients with liver disease with a single test and to satisfy the hepatology community. As a result, a battery of breath tests have been developed. Depending on the test compound administered, different metabolic pathways (microsomal, cytosolic, mitochondrial) can be examined. Most available data come from microsomal function tests, whilst information about cytosolic and mitochondrial liver function is more limited. However, breath tests have shown promise in some studies, in particular to predict the outcome of patients with chronic liver disease or to monitor hepatic function after treatment. Whilst we await new substrates that can be used to measure liver function in a more valid manner, and large prospective studies to assess the usefulness of available test compounds, the aim of this review is to describe how far we have come in this controversial and unresolved issue.

Serum thrombopoietin levels are linked to liver function in untreated patients with hepatitis C virus-related chronic hepatitis

BACKGROUND

Thrombocytopenia can be found in patients with chronic hepatitis related to hepatitis C virus (HCV). Both hypersplenism and decreased liver production of thrombopoietin (TPO) have been hypothesized as mechanisms responsible for thrombocytopenia.

AIMS

To assess the presence of relationships among platelet count, spleen size, TPO serum levels, liver histology, and liver function in a group of patients with HCV-related chronic hepatitis.

METHODS

Platelet count, TPO serum levels, and spleen size were assessed in 25 untreated HCV positive chronic hepatitis patients undergoing liver biopsy. These parameters were correlated to liver histology and liver function as evaluated by means of [(13)C]aminopyrine breath test (ABT).

RESULTS

Both platelet counts (146 +/- 48 vs. 202 +/- 56 x 10(9)/1, P < 0.03) and TPO serum levels (103 +/- 24 vs. 158 +/- 7 1 pg/ml, P < 0.02) were lower among patients with high fibrosis scores as compared to patients with low fibrosis scores. Patients with thrombocytopenia as well as patients with high fibrosis scores had lower ABT results as compared to patients with normal platelet counts and patients with no or mild fibrosis, respectively. TPO serum levels were correlated to platelet count (r(s) = 0.493, P = 0.016), and negatively correlated to fibrosis stage (r(s) = -0.545, P = 0.008). Lastly, low TPO serum levels were associated to a decrease in liver function.

CONCLUSIONS

Our study showed that in patients with chronic hepatitis related to HCV infection serum TPO levels are correlated to liver functional impairment and to the degree of liver fibrosis.