Conclusion: Despite reproducibility of Fibro-and Actitest results among the six laboratories, large scale investigation (n=64) displayed increasing variability of the results depending on interlaboratory differences that were still in a quality controlled, analytically acceptable range. Furthermore, calculated scores coincided with histological findings only in less than 25% of all cases. Thus, the diagnostic accuracy of these tests seems low, if histology is accepted as gold standard. Background: Current knowledge attributes connective tissue growth factor (CTGF/CCN2) a crucial role in enhancing TGF-actions during hepatic fibrogenesis. Recently, we demonstrated that caffeine leads to an upregulation of PPAR in hepatocytes, thus sensitizing these cells to the well known inhibitory effect of 15-deoxy-12,14 -prostaglandin J2 (15-d-PGJ2) on CTGF expression. However, upregulation of the receptor alone is not sufficient per se, its physiological ligand 15-d-PGJ2 is required for exerting its inhibitory effect on CTGF synthesis. Aim and Methods: This study compares serum concentrations of 15-d-PGJ2 in Caucasian patients with fibrotic liver diseases (n=289), Caucasian controls (n=136) and Caucasian non-liver disease sick (n=307), as well as of Chinese patients with hepatocellular carcinoma (n= 43) and Chinese healthy controls (n=63) in order to characterize their suitability for therapeutic approaches with PPAR inducing (i.e. CTGF inhibitory) drugs such as caffeine.