How do we diagnose Candidaemia? – Part 2

What antifungal stewardship approaches could be used to prevent overuse of antifungals in the ICUs? What diagnostics are available and how should these be used?

β-1-3-D-glucan

• Has good sensitivity for candidaemia in the ICU setting with negative predictive value up to 99%
• Not specific to Candida
• Numerous causes for false positive results making interpretation of single positive results difficult; two consecutive positive results have a reasonable positive predictive value.
• Single negative result can be used to rule infection out if the negative predictive value calculated using local epidemiological figures approaches 100%
• Result available in 1 day

Candida mannan and anti-mannan testing

• Detects Candida mannan (a Candida specific antigen) and antibodies against Candida mannan (IgG and/or IgM)
• Performance and sensitivity are comparable to serum β-1-3-D-glucan
• Sensitivity of mannan detection alone is poor in immunocompetent patients due to phagocyte uptake of the antigen
• Sensitivity of anti-mannan detection alone is poor in immunocompromised patients with weak immune responses
• Result available in 1 day

Candida PCR on Blood

• Various Candida PCR assays are available but their sensitivity is low due to the low concentration of Candida in blood during candidaemia, and the intermittent and transient release of Candida from biofilms
• Specificity is high
• Lack of clinical research to support its use for the diagnosis of candidaemia
• May be useful as an additional tool in deep tissue candidosis, where blood culture sensitivity is much lower
• Result available in 1-2 days

T2 Magnetic Resonance Assay

• A novel rapid method using magnetic resonance analysis of blood samples to detect the five main Candida species
• Performance is similar to PCR testing at laboratory level but limited to the 5 species included
• Increasing evidence to support its use for the diagnosis of candidaemia and superiority to blood culture
• May be useful as an additional tool
• Result available in 1 day