Number and timing of blood samples for adults and adolescents 16 years or older

For most adults and adolescents 16 years or older, 2 sets of blood samples for culture are recommended (with each set consisting of one aerobic and one anaerobic bottle). A third set taken from a different site increases yield and enables recognition of contamination.

In most conditions other than endocarditis, bacteraemia is intermittent. In particular, for the investigation of the specific condition of ‘pyrexia of unknown origin (PUO)’¹ – which does not include unstable or deteriorating patients with sepsis or patients with septic shock – in adults and adolescents 16 years or older, 6 sets of blood samples, taken over a number of days, is generally recommended since it increases the likelihood of identifying intermittent bacteraemia.