Diagnosis of invasive aspergillosis by a commercial real-time PCR assay for Aspergillus DNA in bronchoalveolar lavage fluid samples from high-risk patients compared to a galactomannan enzyme immunoassay.

Culture-independent molecular techniques such as real-time PCRs offer the potential for early diagnosis of invasive aspergillosis (IA), thereby reducing the disease-associated mortality rate. PCR-based testing is presently excluded from disease-defining consensus criteria due to lack of standardization and clinical validation. A single-center prospective study was conducted to investigate the performance of the commercially available MycAssay Aspergillus test for detecting Aspergillus DNA in patients with suspicion of IA. To this end, a total of 158 bronchoalveolar lavage (BAL) fluid specimens that were consecutively collected from hematology (n = 68) and intensive care unit (n = 90) patients were examined. Sixteen of 17 (94.1%) specimens from patients with proven/probable IA were MycAssay positive, and 15 of these 16 patients were also positive by an "in-house" PCR assay. A total of 139 of 141 (98.6%) specimens from patients without proven/probable IA were MycAssay negative. Fifteen of 16 (94.1%) MycAssay-positive patients were also positive for BAL fluid galactomannan (GM) at an index cutoff of ≥1.0 (index range, 1.1 to 8.3), as were 3 patients without IA but with pulmonary fusariosis. Interestingly, in seven of the PCR-positive BAL specimens that tested culture positive for Aspergillus species, cycle threshold values were earlier than those of specimens with a culture-negative result. In conclusion, the MycAssay Aspergillus PCR appears to be a sensitive and specific molecular test for the diagnosis of IA, and its performance is comparable to that of the GM assay. However, more large studies are necessary to firmly establish its clinical utility in high-risk settings.

Multicenter, prospective clinical evaluation of respiratory samples from subjects at risk for Pneumocystis jirovecii infection by use of a commercial real-time PCR assay.

Pneumocystis jirovecii pneumonia (PCP) is a common opportunistic infection. Microscopic diagnosis, including diagnosis using the Merifluor-Pneumocystis direct fluorescent antigen (MP-DFA) test, has limitations. Real-time PCR may assist in diagnosis, but no commercially validated real-time PCR assay has been available to date. MycAssay Pneumocystis is a commercial assay that targets the P. jirovecii mitochondrial large subunit (analytical detection limit, ≤ 3.5 copies/µl of sample). A multicenter trial recruited 110 subjects: 54 with transplants (40 with lung transplants), 32 with nonmalignant conditions, 13 with leukemia, and 11 with solid tumors; 9 were HIV positive. A total of 110 respiratory samples (92% of which were bronchoalveolar lavage [BAL] specimens) were analyzed by PCR. Performance was characterized relative to investigator-determined clinical diagnosis of PCP (including local diagnostic tests), and PCR results were compared with MP-DFA test results for 83 subjects. Thirteen of 14 subjects with PCP and 9/96 without PCP (including 5 undergoing BAL surveillance after lung transplantation) had positive PCR results; sensitivity, specificity, and positive and negative predictive values (PPV and NPV, respectively) were 93%, 91%, 59%, and 99%, respectively. Fourteen of 83 subjects for whom PCR and MP-DFA test results were available had PCP; PCR sensitivity, specificity, PPV, and NPV were 93%, 90%, 65%, and 98%, respectively, and MP-DFA test sensitivity, specificity, PPV, and NPV were 93%, 100%, 100%, and 98%. Of the 9 PCR-positive subjects without PCP, 1 later developed PCP. The PCR diagnostic assay compares well with clinical diagnosis using nonmolecular methods. Additional positive results compared with the MP-DFA test may reflect low-level infection or colonization.