Retrospective comparison of nucleic acid sequence-based amplification, real-time PCR, and galactomannan test for diagnosis of invasive aspergillosis.

Invasive aspergillosis is a life-threatening infection in immunocompromised patients, and treating these infections at an early stage is often crucial for a favorable outcome. Early diagnosis, however, remains challenging. We performed a retrospective comparison of three methods: real-time quantitative PCR (qPCR), nucleic acid sequence-based amplification (NASBA), and galactomannan enzyme-linked immunosorbent assay (GM-ELISA); these detect circulating Aspergillus DNA, RNA, and galactomannan, respectively. Blood samples from 80 patients at high risk for invasive aspergillosis were tested by each assay. The sensitivity of NASBA, qPCR, and GM-ELISA was 76.47% (95% CI, 58.4-88.6%), 67.65% (95% CI, 49.4-82.0%), and 52.94% (95% CI, 35.4-69.8%), respectively, and the specificity was 80.43% (95% CI, 65.6-90.1%), 89.13% (95% CI, 75.6-95.9%), and 80.43 % (95% CI, 65.6-90.1%), respectively. We also evaluated the efficiency of the three tests in various combinations. Perfect specificity (100%; 95% CI, 90.4-100%) and perfect positive predictive value (100%; 95% CI, 77.1-100%) were achieved by combining NASBA and qPCR testing in series. Testing with both NASBA and qPCR in parallel was the most sensitive and had the highest Youden index. Our data support the great potential of NASBA and qPCR, singly or in combination, for diagnosis of invasive aspergillosis in high-risk populations.