High variability in assays of blood markers of collagen turnover in cardiovascular disease: Implications for research and clinical practice.

Aims: Fibrosis is a common feature of many chronic diseases, including heart failure, which can have deleterious effects on cardiac structure and function that are associated with adverse outcomes. By-products of collagen synthesis and degradation, such as carboxy- and amino-terminal pro- or telo-peptides of collagen type I and III (PICP, PINP, PIIINP, and CITP) have been extensively investigated as markers of fibrosis. Although the majority of studies report on the reproducibility of their assay results, there is no a comparison of biomarker assays across studies.