Acute-phase proteins (APPs) are particularly useful for health monitoring compared to cytokines because they remain stable in circulation for 48 hours or longer after a single stimulus, whereas cytokine levels are cleared within a few hours.Determining APP levels can aid in monitoring the health of individual subjects, especially when multiple acute-phase variables are combined into an index. Thoughtfully selected combinations of variables, which may vary across species, can yield a nutritional and acute-phase indicator (NAPI). Incorporating the acute-phase reaction intofuture health assessment systems for animals and human patients offers a biologically relevant mechanism for evaluating health status.