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

Combinations of tests comprising alpha(2)-macroglobulin, haptoglobin, apolipoprotein A1, 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 intrapatient reproducibility of the two tests. The stability of the samples for each test was studied after storage at -80degreesC and -20degreesC. Withinrun, betweenrun 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 -20degreesC only. The impact of parameter analytical variability on Fibrotest and Actitest results was less than 10% and intrapatient 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 intralaboratory and intrapatient variability in Fibrotest and Actitest results confirm Fibrotest and Actitest reliability.