Number and timing of blood samples for culture
Blood samples are often taken at the time of fever, but the importance of this is unclear. Typically, bacteraemia (ie entry of organisms into the bloodstream) occurs about 30 to 60 minutes before the onset of fevers and rigors. Some studies have shown no significant difference in isolation rates for blood drawn either at intervals or taken simultaneously with fever spikesLi, 1994. For bacterial endocarditis, where bacteraemia is generally continuous, the timing of blood samples in relation to fevers appears to be unimportant.
Absence of a fever does not necessarily rule out the possibility of an underlying infection because some patients with bacteraemia do not have a fever.
Advice on the number and timing of blood samples is included for: