Diagnostics Flashcards
A patient presents with what appears to be bacterial cellulitis
What blood tests would you recommend sending?
Full blood count - assess for neutrophilia seen in bacterial infection
Urea & electrolytes - assess renal function as this can affect dosing of antimicrobials
Liver function tests - assess liver function as this can affect dosing of antimicrobials
CRP - raised in bacterial infection.
Lactate - raised lactate indicates organ hypoperfusion, which is a marker of severe infection/ sepsis
Blood culture - growth of bacteria in blood suggests a disseminated and more severe infection
HIV test - anyone presenting with a severe infection, with no clear cause, should be offered testing
What swabs can be sent for testing?
Bacterial swab - used for culture.
This aims to grow the causative bacteria, and allows antibiotic susceptibility testing.
However, there is a risk that you may grow commensal skin bacteria. Which can lead to some confusion about whether that bacteria is causing an infection or not.
Deeper wound/ tissue swabs are higher quality samples, and will give more reliable results
Virology swab - has antibiotics in the medium, to inhibit any growth of bacteria.
PCR testing is performed, to look for any viruses.
De-roof blisters/ vesicles prior to swabbing
When diagnosing an infection, it is always important to ask:
Why did this patient get an infection?
This is so we can prevent any further infections in the future, and identify if there is another underlying condition which has triggered this.
What are potential reasons why a patient develops an infection?
Old age –immunosenescence
Altered microbiome – antibiotic use
Underlying disease – e.g Diabetes mellitus
Poor vasculature – smoker
Broken barrier – chronic skin ulcers
Immunosuppression – HIV/ chemotherapy
Epidemiology/ travel exposure
