Objective: Blood tests are usually designed to identify significant fibrosis. We evaluated their diagnostic accuracy, and how to increase it, for the clinically important targets of severe fibrosis and cirrhosis.
Methods: The accuracy for severe fibrosis or cirrhosis of four blood tests was evaluated based on Metavir staging in 1056 patients with chronic hepatitis C recruited in five independent hospitals.
Results: Using original scores, an original diagnostic target (significant fibrosis) and best diagnostic cutoff, the correct classification rates in severe fibrosis and cirrhosis stages were, respectively: FibroMeter: 90.1, 100%, Fibrotest: 78.2, 95.1%, Hepascore: 73.8, 94.9%, aspartate aminotransferase to platelet ratio index (APRI): 71.4, 88.0% (P<0.003, P=0.004, respectively, between tests). The corresponding area under the receiver operating characteristics were FibroMeter: 0.885, 0.907, Fibrotest: 0.837, 0.882, Hepascore: 0.834, 0.896, APRI: 0.822, 0.841 (P<0.003, respectively). Observed 100% negative predictive values for severe fibrosis and cirrhosis were, respectively, FibroMeter: 15.4, 47.5%, Fibrotest: 3.6, 31.9%, Hepascore: 0.3, 24.6%, APRI: 1.4, 5.3% of patients (P<0.003, respectively, between tests). By calculating a specific test for cirrhosis, including the FibroMeter markers, the correct classification (93.0%) was significantly higher for the cirrhosis diagnosis compared with the original FibroMeter (90.9%, P=0.005). This specific test provided a 100% positive predictive value for cirrhosis diagnosis versus 88% for original FibroMeter.
Conclusion: Using the most accurate original test, cirrhosis can be excluded in 47.5% of patients and is correctly diagnosed, as significant fibrosis, in 100% of patients. A specific test for cirrhosis provides a significant gain in diagnostic accuracy to 93% and in positive predictive value to 100% compared with the original test.