Diagnostic performance of MucorGenius® real-time polymerase chain reaction assay on tissue samples for the diagnosis of mucormycosis

ABSTRACT

Poster session 3, September 23, 2022, 1230 PM - 130 PM   Objectives: To assess the diagnostic utility of MucorGenius® real-time PCR in tissue samples for the diagnosis of mucormycosis in patients suspected of having invasive mucormycosis (IM) during the second wave of the COVID-19 pandemic. Methods: A total of 193 clinically suspected cases of IM presenting at our tertiary care center from May to July 2021 were included and defined as proven, probable, possible, or negative for invasive fungal disease (IFD) according to EORTC/MSGERC guidelines. One sample from each patient (nasal/sinus biopsy, nasal crust, or orbital tissue) was subjected to conventional methods for diagnosis of IM and MucorGenius® real-time PCR (hereafter called ‘the assay’). Results: A total of 5 (1.92%), 124 (47.6%), and 44 (16.9%) cases respectively were classified as having proven, probable, and possible IM. The remaining 20 (7.69%) were classified as not having invasive fungal infections and were used as controls to calculate the specificity of the test. The majority of cases were classified as ‘probable’ because specimens received included biopsy from the nasal or sinus cavity.According to radiological findings, sino-nasal involvement was seen in 26/173 (15.02%), sino-orbital involvement in 122/173 (70.5%), and additional intracranial extension in 25/173 (14.4%) of the 173 cases of IM.Among 129 proven and probable cases, direct microscopy of samples showed only aseptate hyphae in 70 cases, and both aseptate and septate hyphae in 36 cases;the assay was positive in 53 and 13 of these cases respectively. In the remaining 23 cases, direct microscopy of samples showed only septate hyphae and the assay was negative.Additionally, the assay was able to detect the presence of Mucorales among 44 possible cases of IM in which direct microscopy of samples showed no fungal elements, but the patients displayed clinical and radiological features of IM and improved with antifungal therapy.The overall sensitivity and specificity of the assay were 63.21% and 90.48% respectively.The sensitivity of the assay in proven and probable cases of IM was 60% and 66.7% respectively, while specificity was 90% for both, using the presence of aseptate hyphae in direct microscopy as a gold standard. Sensitivity and specificity in possible cases were 27.27% and 90% respectively, using the presence of clinical and radiological features of IM and response to antifungal treatment as a reference.When sensitivity and specificity were determined independently in cases of mucormycosis and mixed infection (mucormycosis + aspergillosis), they increased to 75.71% and 90.48% respectively in the former, and both decreased to 38% in the latter. Conclusion: The MucorGenius® real-time PCR performs well in detecting IM as a single infection, especially in cases of possible IM which are not detected by conventional methods. However, it is inefficient in detecting co-infections of invasive mucormycosis and aspergillosis, possibly because Aspergillus can suppress the growth of Mucorales. With further studies using the results to guide clinical intervention and measuring the impact on the outcome, it can be a useful tool to make an early diagnosis of mucormycosis in patients with a high index of clinical suspicion.