Diagnosis of invasive aspergillosis using bronchoalveolar lavage in haematology patients: influence of bronchoalveolar lavage human DNA content on real-time PCR performance
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In order to improve invasive pulmonary aspergillosis (IPA) diagnosis, a real-time polymerase chain reaction (PCR) assay detecting Aspergillus spp. was developed. Its detection limit reached 2–20 conidia. The retrospective evaluation on 64 bronchoalveolar lavage (BAL) fluids from 57 patients at risk for IPA, including 20 probable and five proven IPA patients, revealed a 88% or 38% sensitivity in direct examination (DE)/culture-positive or culture-negative BAL, respectively, whereas galactomannan (GM) sensitivity reached 88% or 58%, respectively. Influence on the Aspergillus-PCR yield of BAL fluid volume, cellular count and DNA content (evaluated by human β-globin quantification) was assessed. Significantly higher β-globin levels were detected in Aspergillus PCR-positive (median 5,112 pg/μl) than negative (median 1,332 pg/μl) BAL fluids, suggesting that the β-globin level could reflect BAL yields and DNA extraction. Using β-globin for the interpretation of fungal PCR could improve the negative predictive value of this test.