You will be given a definition of a task first, then some input of the task.
Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: The occurrence of fever during various blood purification methods was evaluated in a retrospective study. It could be demonstrated, that patients treated chronically by conventional hemodialysis experience six times more febrile episodes than patients on chronic hemofiltration (4.84% versus 0.81%). Since many of the increased temperatures could not be explained by conventional means, it has to be assumed that the treatment itself caused the fever, possibly activating the monocyte hormone interleukin 1. It is of further note that there was no difference in the magnitude of the temperature due to septicaemia or to no obvious cause. This finding necessitates in our opinion an early antibiotic therapy in those cases where fever develops without clear explanation.
Output:
Blood