Procollagen I carboxy-terminal propeptide: a multi-faceted biomarker.

Procollagen I carboxy-terminal propeptide (PICP) is a cleavage product of procollagen I, the precursor of type I collagen. Type I collagen is the most abundant type of collagen in the human body and plays a central role in maintaining structural integrity across tissues such as skin, bone, vasculature, and connective organs. Procollagen I carboxy-terminal propeptide, released during collagen synthesis, has been associated with fibrotic activity and tissue remodeling in different conditions across organ systems, including the heart, lungs, liver, kidneys, skin, and musculoskeletal system. Although many studies have investigated PICP in individual diseases, ranging from cardiomyopathies to liver cirrhosis and chronic lung disorders, its overall diagnostic and prognostic value remain incompletely defined. Serum PICP is a biomarker of fibrotic activity, with potential to be a valuable screening tool or component of diagnostic risk scores before moving to invasive methods such as biopsy. The ability to monitor fibrotic progression or therapeutic response through a simple blood test presents an opportunity for earlier diagnosis, improved disease stratification, and more efficient treatment monitoring. This literature review aims to provide a comprehensive synthesis of current knowledge on PICP, focusing on its biological role in collagen metabolism and clinical applications. By critically evaluating recent advances in assay methodologies, reference ranges, and interpretation in diverse patient populations, this review highlights both the strengths and limitations of PICP as a diagnostic and prognostic tool to identify future directions for research and clinical practice.