Molecular detection of invasive aspergillosis in hematologic malignancies

Aspergillus species are the most frequent causes of invasive mold infections in immunocompromised patients, particularly those who underwent chemotherapy for hematologic malignancies. The aim of this study was to determine the incidence and efficiency of the PCR-enzyme linked immunosorbent assay method (PCR-ELISA) for early detection of Aspergillus species in patients with hematologic malignancies.

From 2004 to 2006, 194 patients with hematologic malignancies (who received chemotherapy) were evaluated for invasive aspergillosis (IA) in Shiraz, southern Iran. Ethylenediaminetetraacetic acid anticoagulant whole blood samples were collected prospectively once a week and stored at -20 degrees C until examination. All collected blood samples were assayed for the presence of the bands on ethidium bromide stained gel and for hybridization.

The female-to-male ratio was 61:133, the mean age of patients was 33.7 years, and mean of hospitalization period was 21.2 days. PCR-ELISA was positive in 14 (7.2%) patients who exhibited clinical and radiologic signs of IA. The etiologic agents were Aspergillus flavus (11 cases) and Aspergillus fumigatus (three cases). The mean time of positivity of PCR-ELISA in the blood before the appearance of clinical signs was 12.6 days. PCR was found to be the earliest indicator of IA preceding nonspecific clinical and radiologic findings. The sensitivity, specificity, positive, and negative predictive values of PCR-ELISA to detect DNA-specific for Aspergillus species in patients with proven and probable IA were 66%, 96%, 62.5%, and 97%, respectively. In case patients were treated with antifungal drugs, and the treatment was successful, fungal PCR assay became negative after 14 days and if the treatment failed, assay was positive until death.

We demonstrated, in the present study, the incidence of IA in leukemic patients and the usefulness of molecular assay for early diagnosis and monitoring of the treatment of IA.