Combined BAL Fractions Essential for Optimal Aspergillus and Mucorales PCR Sensitivity
Testing 99 bronchoalveolar lavage specimens from hematology patients, this multicenter study found that combining cell pellet and supernatant fractions before PCR was critical for detecting mold DNA. Using either fraction alone missed Aspergillus in 18-57% of positive cases. The findings have direct implications for how clinical labs should process BAL specimens for fungal molecular diagnostics.
The original study
A Comparison of Aspergillus and Mucorales PCR Testing of Different Bronchoalveolar Lavage Fluid Fractions from Patients with Suspected Invasive Pulmonary Fungal Disease.
- Authors
- Springer J, White PL, Kessel J, Wieters I, Teschner D, Korczynski D, et al.
- Journal
- Journal of clinical microbiology
- Type
- Comparative Study, Journal Article, Multicenter Study, Research Support, Non-U.S. Gov't
- PMID
- 29187564
Original abstract
In patients with hematological malignancies, bronchoalveolar lavage fluid (BALF) specimens are commonly used for the diagnosis of mold infections. However, it is not clear whether the cell pellet (P) or the supernatant fraction (S) of the BALF specimen is optimal for molecular diagnostic testing. Thus, 99 BALF specimens were collected from 96 hematology patients with or without allogeneic hematopoietic stem cell transplant. The cell pellets and supernatants were processed alone and in combination (S/P) for testing by two fungus-specific real-time PCR assays compliant with international recommendations. The results achieved with S/P were revealed to be superior in comparison to those achieved with S and P alone, with the use of each single fraction showing a reduced sensitivity for the detection of Aspergillus DNA (82% and 43% for S and P, respectively). In 57% of the samples, testing of the combination of S and P generated a lower quantification cycle value than testing of S or P alone. Molds would have been missed in 5 and 16 out of 28 samples if only S or P, respectively, was analyzed. No sample was positive by testing of S or P only. Similar results were obtained for the detection of Mucorales DNA in BALF specimens (reduced sensitivity of 67% and 50% for S and P, respectively). Study patients were categorized according to the current European Organization for the Research and Treatment of Cancer/Mycoses Study Group classification for invasive fungal disease (IFD), revealing that 35 patients had proven/probable IFD (36%), 47 patients had possible IFD (49%), and 14 patients had undetermined IFD (15%).