Intra-individual fasting versus postprandial variation of biochemical markers of liver fibrosis (FibroTest) and activity (ActiTest).

BACKGROUND: Biochemical marker combinations, including alpha2-macroglobulin, haptoglobin, apolipoprotein A1, gamma-glutamyl transpeptidase, and total bilirubin (all part of FibroTest) plus alanine aminotransferase (all part of ActiTest), are being developed as alternatives to liver biopsy in patients with chronic hepatitis C and other various chronic liver diseases. Considering this premise, the primary aim of this study was to assess the impact of meal intake on FibroTest and ActiTest results. Such studies are very important for patients, as many clinical errors have been related to the absence of baseline evidence. RESULTS: Intra-individual variation was assessed for the 6 above components and for FibroTest and ActiTest, by measuring time dependent variations before and one hour after a standard meal in 64 subjects. These consisted of 29 healthy volunteers and 35 patients with chronic liver diseases. Meal intake had no significant impact on any of the six components, or on FibroTest or ActiTest, as assessed by repeated measure variance analyses (ANOVA all p > 0.90); the Spearman correlation coefficient ranged from 0.87 (total bilirubin) to 0.995 (gamma-glutamyl transpeptidase). The coefficients of variation (CV) between fasting and postprandial measurements fluctuated for the six components from 0.09 (apolipoprotein A1) to 0.14 (alpha2-macroglobulin), and from 0.09 for FibroTest to 0.13 for ActiTest. In contrast, meal intake had a significant impact on triglycerides (ANOVA p = 0.01, CV = 0.65) and glucose (ANOVA p = 0.04, CV = 0.31). As for the prediction of liver injury, the concordance between fasting and postprandial predicted histological stages and grades was almost perfect, both for FibroTest (kappa = 0.91, p < 0.001) and ActiTest (kappa = 0.80, p < 0.001). CONCLUSIONS: The intra-individual variation of biochemical markers was low, and it was shown that measurements of FibroTest, ActiTest and their components are not significantly modified by meal intake. This fact makes the screening of patients at risk of chronic liver diseases more convenient.

Intermethod calibration of alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) results: application to Fibrotest and Actitest scores.

Two multi-component scores (Fibrotest and Actitest) have been proposed to evaluate liver fibrosis or necro-inflammatory lesions as an alternative to liver biopsy. This approach requires standardization of alanine aminotransferase (ALT) and gamma-glutamyltransferase (GGT) determinations. For this purpose, ALT and GGT values were assigned to a multi-enzyme material using the appropriate primary reference procedure. This material was used as a common calibrator for sera from 20 patients with viral hepatitis. Measurements were carried out in 11 laboratories, using their own automated routine methods and compared to results obtained using the primary reference procedure. The expression of results in multiples of the upper reference limit worsened the inter-laboratory variation for both enzymes. The multi-enzyme material was commutable for ALT and GGT determination carried out with six analytical systems. Common calibration significantly improved inter-laboratory consistency, which finally reached 1.8% and 3.3% for ALT and GGT, respectively. For each enzyme, it also permitted the retention of a common reference interval for a set of calibrated methods and the improvement of inter-laboratory coherency of Fibrotest and Actitest scores.

A reference material for traceability of aspartate aminotransferase (AST) results.

Standardization of aspartate aminotransferase (AST) determination is highly desirable for inter-laboratory comparison. Serum AST mean values for 20 patients suffering from viral hepatitis showed an inter-laboratory (n = 13) variation of 9.4%. Part of this variation was due to two laboratories using procedures without pyridoxal-5'-phosphate. A traceable AST value was assigned to an enzyme calibrator (EC) through the appropriate International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) primary reference procedure. The EC was commutable for seven routine methods. Common calibration using the EC reduced the inter-laboratory coefficient of variation (CV = 5.9% ) and allowed retention of a common reference interval for a set of routine procedures. Calibration made superfluous the expression of results in multiples of the upper reference limit, which increased inter-laboratory variation (CV = 18.5%). Furthermore, for 92% of patients, calibration with the EC allowed the correction of misclassifications when taking into account the reference interval of the reference procedure. Use of this EC could be proposed to complete the AST reference system.

Intra-laboratory analytical variability of biochemical markers of fibrosis (Fibrotest) and activity (Actitest) and reference ranges in healthy blood donors.

Combinations of tests comprising alpha2-macroglobulin, haptoglobin, apolipoprotein Al, gamma-glutamyltransferase, total bilirubin (Fibrotest) and alanine aminotransferase (Actitest) are being developed as alternatives to liver biopsy in patients with chronic hepatitis C. The aim of this study was to assess in the same laboratory the impact of parameter assay variations on Fibrotest and Actitest results and intra-patient reproducibility of the two tests. The stability of the samples for each test was studied after storage at -80 degrees C and -20 degrees C. Within-run, between-run and total imprecision for each parameter assay, and for Fibrotest and Actitest results, were determined. Transferability of assay results between different analyzers was studied. Intra-patient reproducibility was assessed in 55 hospitalized patients. Fibrotest and Actitest reference ranges were determined in 300 blood donors (reference group). The stability of the parameters was affected by serum storage at -20 degrees C only. The impact of parameter analytical variability on Fibrotest and Actitest results was less than 10% and intra-patient reproducibility was acceptable (p > 0.05). The transferability between different analyzers of results of assays performed under the same standardized and calibration conditions was excellent. Fibrotest and Actitest reference ranges in blood donors were (mean+/-SE) 0.075+/-0.004 and 0.068+/-0.004, respectively. The low intra-laboratory and intra-patient variability in Fibrotest and Actitest results confirm Fibrotest and Actitest reliability.

Prediction of liver histological lesions with biochemical markers in patients with chronic hepatitis B.

BACKGROUND AIMS: Liver biopsy is the gold standard for assessing hepatitis B virus (HBV)-related histology. The aim was to determine the diagnostic utility of noninvasive serum markers in patients with chronic hepatitis B. METHODS: The aminotransferases and indices including alpha(2)-macroglobulin, apolipoprotein A1, haptoglobin, gamma-glutamyl-transpeptidase (GGT), and total bilirubin (Fibrotest), and ALT (Actitest) were compared with liver histology. The primary outcomes were A2-A3 activity and F2-F4 fibrosis (METAVIR). RESULTS: Two hundred and nine patients were included. Forty-one patients (20%) had A2-A3 activity and 61 (29%) had F2-F4 fibrosis. AST and GGT (P<0.001) were independently associated with A2-A3 activity. AST, ALT, and Actitest accurately predicted activity ((areas under receiver operating characteristic (ROC) curves (AUROC), 0.81-0.82+/-0.04)); an AST or ALT< or =30IU/l excluded significant activity with 96% certainty. Fibrotest accurately predicted F2-F4 fibrosis (AUROC, 0.78+/-0.04). Fibrotest scores (range, 0-1.0) < or =0.20 and >0.80 had negative and positive predictive values of 92%, respectively. Restricting biopsy to patients with intermediate scores (>0.20 and < or =0.80) may prevent liver biopsies in 46% of patients while maintaining 92% accuracy. CONCLUSIONS: The aminotransferases and an index including five biochemical markers are accurate noninvasive markers of HBV-related activity and fibrosis, respectively.