Ribosomal and mitochondrial DNA target for real-time PCR diagnosis of invasive aspergillosis.

The aim of the present study was to assess the diagnostic efficacy of a combination of two quantitative Aspergillus PCR assays, targeting a mitochondrial and a ribosomal target, in patients with risk factors for invasive aspergillosis (IA) and positive galactomannan (GM) antigen. Forty-four patients with hematological malignancies and risk factors for IA according to revised European Organization for Research on Treatment of Cancer and the Mycoses Study Group criteria (EORTC/MSG) criteria and presenting at least two sequential GM-positive sera were included in the study. Mitochondrial PCR was carried out prospectively on all GM-positive serum samples. Ribosomal PCR was carried out retrospectively on frozen stored sera. The sensitivities of mitochondrial and ribosomal PCRs were 58% and 50%, respectively. The diagnostic test performance was improved by using a combination of both PCR assays and by considering a patient PCR positive when at least two positive results were obtained. The sensitivity, specificity, and positive and negative likelihood ratios were 65%, 94%, and 11.8 and 0.37, respectively. A significant association between fatal outcome at 90 days and positive results of ribosomal PCR assays was observed (adjusted hazard ratio = 8.2; 95% confidence interval [CI] = 1.0 to 65.8; P = 0.048). Our results showed that the combination of two PCR assays targeting mitochondrial and ribosomal Aspergillus DNA improves the sensitivity of PCR in the diagnosis of IA in hematological patients with risk factors and positive GM results. This study also confirms that a positive PCR result is associated with a poor prognosis in these patients and should lead to specific antifungal therapy being introduced immediately.

False-positive Aspergillus real-time PCR assay due to a nutritional supplement in a bone marrow transplant recipient with GVH disease.

PCR screening for circulating DNA, especially when combined with antigen testing, has shown promise for the definitive diagnosis of invasive aspergillosis. False positives for Aspergillus real-time PCR assays have been described in several reports, but no sources of fungal DNA contamination could be clearly identified. We report a false-positive case for both galactomannan (GM) antigenemia and Aspergillus PCR due to nutritional supplement intake in a bone marrow transplant recipient with digestive graft-versus-host disease. Our case report also suggests that fungal DNA can pass into the serum from the intestinal tract in the same way as fungal GM. Clinicians should be aware of this possibility, so that the administration of costly, unnecessary antifungal treatments with potential adverse side-effects can be avoided.