Clinical validation of a multiplex real-time PCR assay for detection of invasive candidiasis in intensive care unit patients

BACKGROUND: New techniques, such as those based on multiplex quantitative real-time PCR (MRT-PCR), can improve the detection of invasive candidiasis (IC).

METHODS: We prospectively studied 63 intensive care unit patients with suspected IC and 40 healthy controls. Blood cultures and MRT-PCR were performed at day 0 and +2, +7, +14 and +21 days in all patients. In addition, β-d-glucan (BDG) and Candida albicans germ tube antibody (CAGTA) were quantified.

RESULTS: IC was confirmed in 27 patients. Colonization was significantly higher in patients with IC (96% versus 64%, P = 0.002). The sensitivity, specificity, positive predictive value and negative predictive value of MRT-PCR for the diagnosis of IC were 96.3%, 97.3%, 92.8% and 98.7%, respectively. The positive predictive value and specificity were significantly higher for MRT-PCR than for BDG and CATGA. MRT-PCR performed very well, especially in deep-seated IC (sensitivity 90.9% versus 45.4% for blood culture; P = 0.06). As regards the most appropriate clinical sample for DNA amplification, in this study whole blood and serum presented similar results.

CONCLUSIONS: MRT-PCR appears to be a useful test for confirming a diagnosis of IC in critically ill patients, especially in those with deep-seated disease. Its high sensitivity and positive predictive value make it a much more efficient tool for the management of IC than other diagnostic procedures and clinical scores.