Obtaining routine blood cultures during interleukin-2-containing therapy is unnecessary

To evaluate the usefulness of routine blood cultures in patients who develop temperatures of 38.5 degrees C or higher while treated with interleukin-2 (IL-2).

Retrospective chart review study. Charts of patients treated with high-dose IL-2 or biochemotherapy for metastatic melanoma were reviewed at the University of Louisville from 2005 to 2007. The study objective was to estimate the frequency of true and false positive blood cultures.

A total of 205 blood cultures in 46 patients (27 male, 19 female) were reviewed. The average age was 53 years (25-71 years). The patients had an average of 3 cycles of therapy. The mean temperature of the febrile episodes was 38.7 degrees C. The mean absolute neutrophil count was 5.1 K/microL. Of these 205 febrile episodes, only 1 blood culture was true positive. The patient had methicillin sensitive staphylococcus aureus bacteremia. There were 5 false positive blood cultures. Four hundred thirty-four further febrile episodes were documented without blood cultures drawn. None of these patients were found to be infected. The yield of true positive blood cultures in this setting was 0.5% (0%-3%, CI). There was, however, a higher number of false positive blood cultures, 2.4% (0.5%-4.5%, CI).

Blood cultures during IL-2 containing therapy are very inefficient to differentiate between infections versus IL-2-related fever.