Abstract: An assay method is provided for determining the status of the health of a tissue within the body of a subject, wherein the tissue comprises an abundance of at least a first target protein, wherein assay comprises analysis of a liquid biopsy sample obtained from the subject, and wherein the liquid biopsy sample comprises at least a first cell free mRNA (cf-mRNA) that encodes the at least a first target protein. The assays and methods are useful in the diagnosis and treatment of liver health in a subject. In particular, methods and systems are provided for the diagnosis and treatment of fatty liver; non-alcoholic steatohepatitis (NASH); cirrhosis; liver disease; hepatitis; and liver cancer.

Abstract: Processes are provided for establishing a virtual physiologically based pharmacokinetic (PBPK) model in a population comprised of a plurality of individual subjects that has been or may be exposed to a xenobiotic molecule. The processes are derived from the identification of an abundance of a protein that is involved in absorption; distribution; localization; biotransformation; and excretion of the xenobiotic molecule from a liquid biopsy of corresponding cell free RNA. Personalised PBPK models for precision dosing, as well as methods of treatment are also provided.

Abstract: Methods, systems and apparatus are provided for quantifying the amount of at least a first cell free RNA (cfRNA) present in a liquid biopsy obtained from an individual subject. The first cfRNA may encode a protein that functions in the clearance of xenobiotic compounds from the body of the subject. Quantification of the amount of the first cfRNA is normalised to the individual and permits the construction of more accurate virtual models that facilitate improved personalised medicine, dosage regimens and clinical trials.