Disclosed are methods and apparatus for diagnosis, detection of host response, monitoring, treatment or management of sepsis, infection-negative systemic inflammatory response syndrome (SIRS) and post-surgical inflammation in mammals. More particularly, the present invention discloses marker genes and their splice variant transcripts as well as their expression products, which are useful for distinguishing between sepsis and infection-negative SIRS, including post-surgical inflammation, and to the use of these markers in grading, monitoring, treatment and management of these conditions.