Investigations

Why?

• Swabbing of any breaks in the skin in patients with cellulitis frequently isolates a pathogen - around 40% are positive. ^c  
• More invasive techniques are not very helpful. ^c and contaminants are common. ^c

Culture techniques are not very sensitive for diagnosing the cause of cellulitis

Diagnostic test	Sensitivity (95% CI)
primary lesion swab c	42% (28% to 56%)
punch biopsy	20% (8.9% to 31%)
needle aspiration	10% (1.7% to 18%)
blood culture	4.0% (0.0% to 9.4%)

Note:

• Identification of an organism may reflect colonisation rather than infection. ^d