Blood cultures – two sets drawn before administration of antimicrobials provided it will not lead to significant delays in therapy (positive in 30–50% and then associated with a worse outcome)

If a vascular catheter is suspected as the source then either:

1. Take paired cultures from peripheral stab and from each lumen of the catheter (this technique may be associated with a high rate of contamination) or
2. Remove the catheter and request MC&S on the tip – this latter is recommended if the patient is in septic shock and deteriorating.

Mid-stream urine for urinalysis and MC&S

Invasive sampling/drainage of fluid collections in otherwise sterile spaces, for example joint aspiration if suspected septic arthritis (P. 701), pleural or ascitic fluid aspiration for microscopy and culture (P. 679 and 688), lumbar picture for CSF examination if suspected meningitis (P. 696)

Stool MC&S, CDT (if diarrhoea or recent foreign travel)

Bacterial swabs of any inflamed or discharging soft tissue areas or wounds

Molecular or antigen based tests, for example urinary antigens for legionella, pneumococcus, nasopharyngeal swabs for respiratory viral panel

Malarial film if appropriate travel history (P. 211)

HIV test