Full blood count and differential white count

Blood films and rapid diagnostic tests for malarial parasites if travel to or through an endemic area; the intensity of the parasitaemia is variable in malaria. If the diagnosis is suspected but the film and RDT are negative, repeat blood films three times over 24–48 hours.

Blood culture × 2

C-reactive protein

Blood glucose

Sodium, potassium, urea and creatinine

Liver function tests

Throat swab

Urine stick test, microscopy and culture

Stool microscopy and culture

Serology as appropriate, for example for suspected viral hepatitis, Legionella pneumonia, typhoid, amoebic liver abscess, leptospirosis (save serum initially if diagnosis uncertain)

Chest X-ray and ultrasound liver if clinical suspicion

Lumbar puncture if neck stiffness present (preceded by CT only if indicated) (Chapter 68)