Finding the "missing 50%" of invasive candidiasis: how nonculture diagnostics will improve understanding of disease spectrum and transform patient care.

Blood cultures are limited for diagnosing invasive candidiasis by poor sensitivity and slow turn-around time. New diagnostics are needed to complement cultures, in particular to identify the "missing 50%" of patients who are blood culture-negative. Mannan/anti-mannan immunoglobulin G, β-D-glucan (BDG) and polymerase chain reaction (PCR) assays can diagnose candidemia before blood cultures and show promising sensitivity/specificity, but they are not widely investigated in blood culture-negative, deep-seated candidiasis. In a recent study, BDG and PCR were superior to blood cultures in deep-seated candidiasis, suggesting they may identify currently undiagnosed patients and expand our understanding of disease spectrum. Positive predictive values of nonculture tests are limited by the low prevalence of invasive candidiasis, which mandates that results be interpreted judiciously. When used as biomarkers that assess a patient's risk of having invasive candidiasis, tests will facilitate preemptive antifungal strategies. Because negative predictive values are excellent, tests will also be useful for ruling out invasive candidiasis and discontinuing unnecessary antifungal therapy.