Value of serial quantification of fungal DNA by a real-time PCR-based technique for early diagnosis of invasive Aspergillosis in patients with febrile neutropenia

Abstract

A study was designed to assess the reliability of the serial detection of Aspergillus sp. DNA to diagnose invasive aspergillosis (IA) in patients with febrile neutropenia. Two blood and two serum samples were taken weekly from 83 patients. A total of 2,244 samples were analyzed by real-time quantitative PCR. Twelve (14.4%) patients were diagnosed with IA. Taking two consecutive positive results as the diagnostic criterion, PCR detected 11 cases, with 4 false positives, giving sensitivity, specificity, positive, and negative predictive values of 91.6%, 94.4%, 73.3%, and 98.5%, respectively. On analyzing in conjunction with high-resolution chest tomography (HRCT) and galactomannan (GM) testing, the combination of serial PCR and GM detected 100% of aspergillosis cases, with a positive predictive value of 75.1%. This diagnostic strategy presented, according to CART analysis, a receiver-operator curve with an area under the curve of 0.97 (95% confidence interval, 0.895 to 1.032; P < 0.01), with a relative risk of IA 6.92 times higher than the control population and with predictive success of 95.2%. As regards early diagnosis, the serial detection of Aspergillus DNA took on average 21 days less than HRCT and 68 days less than GM. The serial detection of Aspergillus DNA using real-time quantitative PCR has great diagnostic applicability, which increases when combined with GM quantification.

FIG. 1.

ROC spaces produced by the results obtained with the PCR-based technique and the GM test. ROC spaces for three or more positive PCR results and GM results were of equal area.

FIG. 2.

Model obtained by means of CART analysis with two or more positive PCR results and GM results.