Rapid diagnosis of invasive candidiasis: ready for prime-time?

We review the performance of culture-independent diagnostic tests (CIDTs), including β-D-glucan (BDG), polymerase chain reaction (PCR) and T2Candida, in diagnosing invasive candidiasis, their potential roles in patient management, and unintended consequences of testing.

In a recent multicenter trial, T2Candida was 90% sensitive and 98% specific for diagnosing candidemia. A new study provided the first data for T2Candida in diagnosing deep-seated candidiasis, demonstrating sensitivity/specificity of 45%/96%. Two studies showed that ongoing T2Candida-positivity is associated with poor prognosis. In several studies, serum BDG and T2Candida, targeted to patients at-risk for invasive candidiasis, were useful in guiding treatment decisions and antifungal stewardship. A randomized, multicenter trial of BDG-guided empiric antifungal treatment is underway among critically ill patients. PCR performance was highly variable for candidemia and deep-seated candidiasis in recent studies. CIDT results may overstate bloodstream infections, according to current National Healthcare Safety Network (NHSN) definitions.

BDG and T2Candida are nearing prime-time status in the clinic. To be useful, testing must be directed to carefully chosen patients and specific clinical questions. Candida PCR is limited by a need for standardized methodologies and commercial assays. NHSN definitions of bloodstream infections must be revised in the era of CIDTs.