A new real-time polymerase chain reaction (PCR) assay shows promise in the noninvasive diagnosis of aspergillosis and mucormycosis, according to a poster presented at American Society of Microbiology (ASM) Microbe 2019, held June 20 to 24, 2019 in San Francisco, California.

Because of the limitations of currently available diagnostic methods, the diagnosis of invasive aspergillosis and invasive mucormycosis has remained a challenge. The standard tests that are used for diagnosing invasive mucormycosis and invasive aspergillosis include sterile culture, immunohistochemistry, and histopathology. However, real-time PCR assays may provide a noninvasive way to diagnose these invasive infections. Therefore, this study used blood samples from patients with invasive aspergillosis and invasive mucormycosis to evaluate the diagnostic performance of real-time PCR assays.

In total, 16 patients with invasive aspergillosis (10 proven and 6 probable) and 17 patients with proven invasive aspergillosis were enrolled from 2017 to 2018. By comparing results with those of reference standard tests, the diagnostic performance of the real-time PCR assays was assessed.

The real-time PCR assay showed a sensitivity of 70% and a specificity of 94% in patients with proven invasive aspergillosis, and showed a sensitivity of 71% (95% CI, 44%-90%) and a specificity of 80% (95% CI, 44%-97%) in patients with proven invasive mucormycosis. There were 3 (11%) discordant results between the reference standards and the real-time PCR assays among the 27 patients with proven invasive aspergillosis or invasive mucormycosis, which suggested either possible coinfections with invasive aspergillosis or mucormycosis or false-negative PCR tests.

Further, of the 6 patients with probable invasive aspergillosis based on nonsterile culture or galactomannan assay, 3 of those patients were positive for mucormycosis via the real-time PCR assay, which suggested coinfections with invasive aspergillosis or mucormycosis, false-positive PCR results, and/or Mucorales infections.

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Overall, the study authors concluded that, “The newly developed real-time PCR assays using blood samples may be promising, non-invasive tests for diagnosing aspergillosis and mucormycosis, especially when it is difficult to differentiate between [invasive aspergillosis] and [invasive mucormycosis].”

Reference

Kim MC, Kim J, Choi S, Lee SO, Chio SH, Kim Y, Woo J, Kim SH. Diagnostic performance of real-time polymerase chain reaction using blood samples in patients with suspected invasive aspergillosis and mucormycosis. Presented at: ASM Microbe 2019; June 20-24, 2019; San Francisco, California. Poster P550.