Abstract: The invention provides methods for characterizing the condition or status of a tissue or organ in a multicellular organism, e.g., an animal, by combining a plurality of clinical measures are combined into a composite clinical score (CCS) and using such a CCS to represent the condition or status of the tissue or organ. The invention provides methods for predicting the condition or status of a tissue or organ in a multicellular organism, e.g., an animal, based on measurements of a set of cellular constituent markers, e.g., measured expression levels of a set of marker genes. The invention also provides methods for selecting the set of marker genes whose expression levels can be used in determining the CCS.