13C-methacetin-breath test compared to also noninvasive biochemical blood tests in predicting hepatic fibrosis and cirrhosis in chronic hepatitis C

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.

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.

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

Introduction

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

Methods

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

Results

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

Conclusion

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

(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.

A novel variant of the 13C-methacetin liver function breath test that eliminates the confounding effect of individual differences in systemic CO2 kinetics

The principle of dynamic liver function breath tests is founded on the administration of a ¹³C-labeled drug and subsequent monitoring of ¹³CO₂ in the breath, quantified as time series delta over natural baseline ¹³CO₂ (DOB) liberated from the drug during hepatic CYP-dependent detoxification. One confounding factor limiting the diagnostic value of such tests is that only a fraction of the liberated ¹³CO₂ is immediately exhaled, while another fraction is taken up by body compartments from which it returns with delay to the plasma. The aims of this study were to establish a novel variant of the methacetin-based breath test LiMAx that allows to estimate and to eliminate the confounding effect of systemic ¹³CO₂ distribution on the DOB curve and thus enables a more reliable assessment of the hepatic detoxification capacity compared with the conventional LiMAx test. We designed a new test variant (named "2DOB") consisting of two consecutive phases. Phase 1 is initiated by the intravenous administration of ¹³C-bicarbonate. Phase 2 starts about 30 min later with the intravenous administration of the ¹³C-labelled test drug. Using compartment modelling, the resulting 2-phasic DOB curve yields the rate constants for the irreversible elimination and the reversible exchange of plasma ¹³CO₂ with body compartments (phase 1) and for the detoxification and exchange of the drug with body compartments (phase 2). We carried out the 2DOB test with the test drug ¹³C-methacetin in 16 subjects with chronic liver pathologies and 22 normal subjects, who also underwent the conventional LiMAx test. Individual differences in the systemic CO₂ kinetics can lead to deviations up to a factor of 2 in the maximum of DOB curves (coefficient of variation CV ≈ 0.2) which, in particular, may hamper the discrimination between subjects with normal or mildly impaired detoxification capacities. The novel test revealed that a significant portion of the drug is not immediately metabolized, but transiently taken up into a storage compartment. Intriguingly, not only the hepatic detoxification rate but also the storage capacity of the drug, turned out to be indicative for a normal liver function. We thus used both parameters to define a scoring function which yielded an excellent disease classification (AUC = 0.95) and a high correlation with the MELD score (R_Spearman = 0.92). The novel test variant 2DOB promises a significant improvement in the assessment of impaired hepatic detoxification capacity. The suitability of the test for the reliable characterization of the natural history of chronic liver diseases (fatty liver-fibrosis-cirrhosis) has to be assessed in further studies.

Assessment of Regional Perfusion and Organ Function: Less and Non-invasive Techniques

Sufficient organ perfusion essentially depends on preserved macro- and micro-circulation. The last two decades brought substantial progress in the development of less and non-invasive monitoring of macro-hemodynamics. However, several recent studies suggest a frequent incoherence of macro- and micro-circulation. Therefore, this review reports on interactions of macro- and micro-circulation as well as on specific regional and micro-circulation. Regarding global micro-circulation the last two decades brought advances in a more systematic approach of clinical examination including capillary refill time, a graded assessment of mottling of the skin and accurate measurement of body surface temperatures. As a kind of link between macro- and microcirculation, a number of biochemical markers can easily be obtained. Among those are central-venous oxygen saturation (S_cvO₂), plasma lactate and the difference between central-venous and arterial CO₂ (cv-a-pCO₂-gap). These inexpensive markers have become part of clinical routine and guideline recommendations. While their potential to replace parameters of macro-circulation such as cardiac output (CO) is limited, they facilitate the interpretation of the adequacy of CO and other macro-circulatory markers. Furthermore, they give additional hints on micro-circulatory impairment. In addition, a number of more sophisticated technical approaches to quantify and visualize micro-circulation including video-microscopy, laser flowmetry, near-infrared spectroscopy (NIRS), and partial oxygen pressure measurement have been introduced within the last 20 years. These technologies have been extensively used for scientific purposes. Moreover, they have been successfully used for educational purposes and to visualize micro-circulatory disturbances during sepsis and other causes of shock. Despite several studies demonstrating the association of these techniques and parameters with outcome, their practical application still is limited. However, future improvements in automated and “online” diagnosis will help to make these technologies more applicable in clinical routine. This approach is promising with regard to several studies which demonstrated the potential to guide therapy in different types of shock. Finally several organs have specific patterns of circulation related to their special anatomy (liver) or their auto-regulatory capacities (brain, kidney). Therefore, this review also discusses specific issues of monitoring liver, brain, and kidney circulation and function.

13C Methacetin Breath Test for Assessment of Microsomal Liver Function: Methodology and Clinical Application

Assessment of the liver function, and the need of constant monitoring of the organ's capacity, concerns not only patients with primary liver diseases, but also those at risk of hepatopathies secondary to other chronic diseases. Most commonly, the diagnostics is based on measurements of static biochemical parameters, which allow us to draw conclusions only indirectly about the function and the degree of damage of the organ. On the other hand, liver biopsy is an invasive procedure and therefore it is associated with a considerable risk of complications. Dynamic tests enable us to assess quantitatively the organ's functional reserve by analyzing the kinetics of the metabolization of the substrate by the liver. In practice applied are breath tests using substances such as aminopyrine, caffeine, methacetin, erythromycin (for assessment of the microsomal function); phenylalanine, galactose (for assessment of the cytosolic function); methionine, octanoate, ketoisocaproic acid (for assessment of the mitochondrial function). The test with ¹³C methacetin belongs to the best described and most widely applied methods in noninvasive liver function assessment. Due to the rising availability of this method, knowledge concerning its limitations and controversies regarding the methodology, as well as its usefulness in chosen groups of patients, seems to be vital.

Cost-effectiveness of non-invasive methods for assessment and monitoring of liver fibrosis and cirrhosis in patients with chronic liver disease: systematic review and economic evaluation

BACKGROUND

Liver biopsy is the reference standard for diagnosing the extent of fibrosis in chronic liver disease; however, it is invasive, with the potential for serious complications. Alternatives to biopsy include non-invasive liver tests (NILTs); however, the cost-effectiveness of these needs to be established.

OBJECTIVE

To assess the diagnostic accuracy and cost-effectiveness of NILTs in patients with chronic liver disease.

DATA SOURCES

We searched various databases from 1998 to April 2012, recent conference proceedings and reference lists.

METHODS

We included studies that assessed the diagnostic accuracy of NILTs using liver biopsy as the reference standard. Diagnostic studies were assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Meta-analysis was conducted using the bivariate random-effects model with correlation between sensitivity and specificity (whenever possible). Decision models were used to evaluate the cost-effectiveness of the NILTs. Expected costs were estimated using a NHS perspective and health outcomes were measured as quality-adjusted life-years (QALYs). Markov models were developed to estimate long-term costs and QALYs following testing, and antiviral treatment where indicated, for chronic hepatitis B (HBV) and chronic hepatitis C (HCV). NILTs were compared with each other, sequential testing strategies, biopsy and strategies including no testing. For alcoholic liver disease (ALD), we assessed the cost-effectiveness of NILTs in the context of potentially increasing abstinence from alcohol. Owing to a lack of data and treatments specifically for fibrosis in patients with non-alcoholic fatty liver disease (NAFLD), the analysis was limited to an incremental cost per correct diagnosis. An analysis of NILTs to identify patients with cirrhosis for increased monitoring was also conducted.

RESULTS

Given a cost-effectiveness threshold of £20,000 per QALY, treating everyone with HCV without prior testing was cost-effective with an incremental cost-effectiveness ratio (ICER) of £9204. This was robust in most sensitivity analyses but sensitive to the extent of treatment benefit for patients with mild fibrosis. For HBV [hepatitis B e antigen (HBeAg)-negative)] this strategy had an ICER of £28,137, which was cost-effective only if the upper bound of the standard UK cost-effectiveness threshold range (£30,000) is acceptable. For HBeAg-positive disease, two NILTs applied sequentially (hyaluronic acid and magnetic resonance elastography) were cost-effective at a £20,000 threshold (ICER: £19,612); however, the results were highly uncertain, with several test strategies having similar expected outcomes and costs. For patients with ALD, liver biopsy was the cost-effective strategy, with an ICER of £822.

LIMITATIONS

A substantial number of tests had only one study from which diagnostic accuracy was derived; therefore, there is a high risk of bias. Most NILTs did not have validated cut-offs for diagnosis of specific fibrosis stages. The findings of the ALD model were dependent on assuptions about abstinence rates assumptions and the modelling approach for NAFLD was hindered by the lack of evidence on clinically effective treatments.

CONCLUSIONS

Treating everyone without NILTs is cost-effective for patients with HCV, but only for HBeAg-negative if the higher cost-effectiveness threshold is appropriate. For HBeAg-positive, two NILTs applied sequentially were cost-effective but highly uncertain. Further evidence for treatment effectiveness is required for ALD and NAFLD.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42011001561.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

(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.

Prevalence of minimal hepatic encephalopathy and quality of life in patients with decompensated cirrhosis

AIM

Minimal hepatic encephalopathy (MHE) affects more than 30% of patients with cirrhosis, and it has been suggested that despite no recognizable clinical symptoms of neurological abnormalities, it may affect health-related quality of life (HRQL); however, this fact remains controversial. The aim of our study was to evaluate the prevalence of MHE and HRQL in patients diagnosed with decompensated cirrhosis.

METHODS

Patients with liver cirrhosis were selected independent of the etiology of the disease. All patients underwent a complete clinical history, and only patients with decompensated hepatic cirrhosis were included. Psychometric tests were applied to evaluate the presence of MHE along with the Chronic Liver Disease Questionnaire. Appetite was measured by verbal and visual analog scales.

RESULTS

One hundred and twenty-five patients were included with a median age of 56.0 years. They were classified according to the Child-Pugh index as A, (n = 56), B, (n = 51) and C (n = 18). Prevalence of MHE was 44.0% (n = 55). In patients with MHE, a significant reduction was observed in domains of activity (3.3 [2.0] vs 4.8 [2.8]), fatigue (3.2 [2.0] vs 3.9 [2.3]), systemic symptoms (3.8 [2.0] vs 4.8 [1.7]), emotional function (3.6 [1.9] vs 4.0 [1.9]) and global scoring (3.7 [1.7] vs 4.3 [1.8]) when compared with non-MHE patients (n = 70). Twenty-two percent of the patients with MHE reported little appetite compared with 11% in the non-MHE group.

CONCLUSION

The results suggest that MHE and a reduction in appetite are associated with deterioration in HRQL in patients with decompensated cirrhosis.

Noninvasive Biomarkers of Liver Fibrosis: An Overview

Chronic liver diseases of differing etiologies are among the leading causes of mortality and morbidity worldwide. Establishing accurate staging of liver disease is very important for enabling both therapeutic decisions and prognostic evaluations. A liver biopsy is considered the gold standard for assessing the stage of hepatic fibrosis, but it has many limitations. During the last decade, several noninvasive markers for assessing the stage of hepatic fibrosis have been developed. Some have been well validated and are comparable to liver biopsy. This paper will focus on the various noninvasive biochemical markers used to stage liver fibrosis.

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.

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.

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.

Phenacetin O-deethylation is a useful tool for evaluation of hepatic functional reserve in rats with CCl(4)-induced chronic liver injury

BACKGROUND

Mortality of liver resection is as high as 3.1% to 25% in patients with chronic liver disease. Evaluation of hepatic functional reserve is critical for the prediction of risk of postoperation death. Phenacetin O-deethylation is a marker reaction of cytochrome P4501A2 (CYP1A2) activity. In this study, our aim is to investigate whether phenacetin O-deethylation is a useful tool for the evaluation of hepatic functional reserve in rats with chronic liver injury.

MATERIALS AND METHODS

Rat model for chronic liver injury was established by subcutaneous administration of 50% CCl(4), 1 mL/kg twice per week for 12 wk. Hepatic CYP1A2 activity, content, and mRNA expression were determined (n = 10). Effects of 15%, 30%, and 45% hepatectomy on phenacetin O-deethylation were evaluated in the rats (n = 5 in each group). Additionally, the correlation of risk of death after 70% hepatectomy with phenacetin O-deethylation was studied in 27 rats with chronic liver injury.

RESULTS

Compared with normal controls, CYP1A2 activity, content, and mRNA expression decreased 33%, 60%, and 50% in the rats with chronic liver injury (P < 0.05), respectively. Following the increasing of liver-resected size, CYP1A2 activity decreased proportionally (r(s) = -0.877, P < 0.05). Six of 27 rats with chronic liver injury died within 7 d after 70% hepatectomy. Phenacetin metabolism was impaired more severely in 6 rats that died than in 21 living rats (P < 0.05).

CONCLUSIONS

Phenacetin O-deethylation is a useful tool for the evaluation of hepatic functional reserve in the rats with CCl(4)-induced chronic liver injury.

Diagnostic value of the C methacetin breath test in various stages of chronic liver disease

The accuracy of the ¹³C-methacetin breath test (¹³C-MBT) in differentiating between various stages of liver disease is not clear. A cross-sectional study of Asian patients was conducted to examine the predictive value of the ¹³C-MBT in various stages of chronic liver diseases. Diagnostic accuracy of the breath test was determined by sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve analysis. Seventy-seven patients (47 men/30 women, mean age 50 ± 16 years) were recruited. Forty-seven patients had liver cirrhosis (Child Pugh A = 11, Child Pugh B = 15, and Child Pugh C = 21), 21 had fibrosis, and 9 had chronic inflammation. The sensitivity and positive predictive value for liver fibrosis, cirrhosis (all stages), Child-Pugh A, Child-Pugh B, and Child-Pugh C were 65% and 56%, 89% and 89%, 67% and 42%, 40% and 40%, and 50% and 77%, respectively. Area under curve values for fibrosis was 0.62 (0.39–0.86), whilst that for cirrhosis (all stages) was 0.95 (0.91–0.99). The ¹³C-methacetin breath test has a poor predictive value for liver fibrosis but accurately determines advanced cirrhosis.

Performance of the aspartate aminotransferase-to-platelet ratio index for the staging of hepatitis C-related fibrosis: an updated meta-analysis

The aspartate aminotransferase-to-platelet ratio index (APRI), a tool with limited expense and widespread availability, is a promising noninvasive alternative to liver biopsy for detecting hepatic fibrosis. The objective of this study was to update the 2007 meta-analysis to systematically assess the accuracy of APRI in predicting significant fibrosis, severe fibrosis, and cirrhosis stage in hepatitis C virus (HCV) monoinfected and HCV / human immunodeficiency virus (HIV) coinfected individuals. Studies comparing APRI versus biopsy in HCV patients were identified via a thorough literature search. Areas under summary receiver operating characteristic curves (AUROC), sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were used to examine the APRI accuracy for the diagnosis of significant fibrosis, severe fibrosis, and cirrhosis. Heterogeneity was explored using meta-regression. Twenty-one additional studies were eligible for the update and, in total, 40 studies were included in this review (n = 8,739). The summary AUROC of the APRI for the diagnosis of significant fibrosis, severe fibrosis, and cirrhosis were 0.77, 0.80, and 0.83, respectively. For significant fibrosis, an APRI threshold of 0.7 was 77% sensitive and 72% specific. For severe fibrosis, a threshold of 1.0 was 61% sensitive and 64% specific. For cirrhosis, a threshold of 1.0 was 76% sensitive and 72% specific. Moreover, we found that the APRI was less accurate for the identification of significant fibrosis, severe fibrosis, and cirrhosis in HIV/HCV coinfected patients.

CONCLUSION

Our large meta-analysis suggests that APRI can identify hepatitis C-related fibrosis with a moderate degree of accuracy. Application of this index may decrease the need for staging liver biopsy specimens among chronic hepatitis C patients.

Clinical value of IRIS 13C-methacetin breath test in assessing liver function in patients with cirrhosis

AIM: To investigate the clinical value of ¹³C-methacetin breath test in the assessment of liver function by comparing with Child-Pugh classification and measurement of liver and spleen volume by CT in patients with cirrhosis.

METHODS: Seventy-one patients with liver cirrhosis, 17 patients with hepatitis, and 10 healthy controls were included in this study. Patients with cirrhosis were divided into three groups according to Child-Pugh classification: patients with Child-Pugh A liver function, those with Child-Pugh B, and those with C. All patients received ¹³C-methacetin breath test to compare the breath test parameters with liver function parameters and liver and spleen volume.

RESULTS: Depending on the severity of liver damage, the parameters MVmax40, CUM40, and CUM120 were obviously reduced. There is a significant correlation between ¹³C-methacetin breath test classification and Child-Pugh classification (κ = 0.57, P < 0. 05). In cirrhotic patients, the above three parameters were negatively correlated with TBIL, Child-Pugh score, and spleen volume (all P < 0.005), positively with PTA and DALB (both P < 0.05), but not with ALB, ALT, and liver volume (all P > 0.05).

CONCLUSION: ¹³C-methacetin breath test is a helpful tool for measurement of hepatocyte injury and liver functional reserve in patients with cirrhosis.

Noninvasive tools to assess liver disease

PURPOSE OF REVIEW

Improved understanding of the pathophysiology of fibrosis and recent technological advances have resulted in the development of several serum biomarkers and imaging tools as noninvasive alternatives to biopsy. This review highlights some of the recent advances and potential application of these tools in clinical practice.

RECENT FINDINGS

Several newer approaches have been used to improve the semiquantitative histological assessment of fibrosis in relation to biomarker development. These include statistical considerations, smooth muscle actin morphometry, and emerging microscopy techniques to quantify fibrillar collagen. Serum marker panels, initially developed for determining disease stage in chronic hepatitis C infection, have now been adapted for use in nonalcoholic fatty liver disease. Genetic markers of disease progression have been validated, and newer proteomic technologies are increasingly being applied towards biomarker discovery. A sequential approach or the combination of serum markers and transient elastography is able to significantly reduce the need for biopsy for the diagnosis of cirrhosis. Serum markers also appear to provide useful prognostic information in end-stage liver disease. Newer imaging methods and breath tests require further validation, but appear promising adjunctive techniques for prediction of advanced stage fibrosis and providing functional assessment.

SUMMARY

Current noninvasive tools have potential diagnostic and prognostic utility for end-stage liver disease. Adapting these methods into clinical practice remains a challenge.

Systematic review: non-invasive methods of fibrosis analysis in chronic hepatitis C

BACKGROUND

Accurate determination of the presence and degree of liver fibrosis is essential for prognosis and for planning treatment of patients with chronic hepatitis C virus (HCV). Non-invasive methods of assessing fibrosis have been developed to reduce the need for biopsy.

AIM

To perform a review of these non-invasive measures and their ability to replace biopsy for assessing hepatic fibrosis in patients with chronic HCV.

METHODS

A systematic review of PUBMED and EMBASE was performed through 2008 using the following search terms: HCV, liver, elastography, hepatitis, Fibroscan, SPECT, noninvasive liver fibrosis, ultrasonography, Doppler, MRI, Fibrotest, Fibrosure, Actitest, APRI, Forns and breath tests, alone or in combination.

RESULTS

We identified 151 studies: 87 using biochemical, 57 imaging and seven breath tests either alone or in combination.

CONCLUSIONS

Great strides are being made in the development of accurate non-invasive methods for determination of fibrosis. Although no single non-invasive test or model developed to date can match that information obtained from actual histology (i.e. inflammation, fibrosis, steatosis), combinations of two modalities of non-invasive methods can reliably differentiate between minimal and significant fibrosis, and thereby avoid liver biopsy in a significant percentage of patients.

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.