Diagnostic accuracy of Mucorales PCR testing in bronchoalveolar lavage fluid samples: a retrospective analysis of a prospectively collected cohort

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OBJECTIVES: To evaluate the diagnostic performance, particularly specificity, of the MucorGenius® PCR assay for detecting pulmonary mucormycosis in bronchoalveolar lavage fluid (BALF) samples from at-risk patients. METHODS: This is a retrospective diagnostic accuracy study using prospectively collected BALF samples. All consecutive BALF samples obtained from patients who were considered to be at risk for invasive mould infections (IMIs) were prospectively collected. Patients were retrospectively classified according to European Organization for Research and Treatment of Cancer and Mycoses Study Group Education and Research Consortium and adapted Invasive Fungal Diseases in Adult Patients in Intensive Care Unit definitions. All samples were retrospectively tested with the MucorGenius® assay. RESULTS: A total of 1407 BALF samples obtained from 1330 patients had been included and tested for Mucorales DNA. A total of 256 patients (19.6%) fulfilled European Organization for Research and Treatment of Cancer and Mycoses Study Group Education and Research Consortium host factors and 664 (49.9%) Invasive Fungal Diseases in Adult Patients in Intensive Care Unit host factors. Proven or probable pulmonary mucormycosis was routinely diagnosed (without Mucorales PCR) in four patients (0.3%), 26 patients had proven or probable invasive pulmonary aspergillosis (IPA) (2%), and 25 (1.9%) had possible IMI. Overall, 32 positive MucorGenius® results had been observed. Per patient the MucorGenius® assay gave a specificity of 98.6% (95% CI: 97.8-99.2; n = 1251/1269) and a sensitivity of 100% (95% CI: 39.8-100; n = 4/4). Two cases with IPA were routinely diagnosed with mixed Mucorales infection and three additional IPA cases had a positive MucorGenius® PCR. In total, 5 of 26 IPA cases were therefore diagnosed with a mixed mould infection. Six of the 25 possible IMI cases (24%) also turned out positive on MucorGenius® PCR. Nineteen Mucorales PCR-positive samples had been obtained from patients without any routinely diagnosed IMI. CONCLUSIONS: We observed a near-to-perfect specificity of the MucorGenius® assay in BALF, making diagnosis of pulmonary mucormycosis very likely in patients with a positive PCR. In addition, the test was able to identify mucormycosis in a relevant proportion of cases with possible IMI and probable IPA, potentially indicating otherwise missed mixed-mould infections.

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