Implementation of an in-house real-time PCR assay as a diagnostic tool for Invasive Aspergillosis in haematology...

Invasive aspergillosis (IA) is an important cause of mortality in haemato-oncology patients. Polymerase chain reaction (PCR) and galactomannan (GM) enzyme immunoassays are two key laboratory tests in the diagnosis of IA.

An in-house qualitative real-time PCR (Aspergillus PCR) for the detection of IA, and galactomannan assay were performed on serum samples collected from haemato-oncology patients at-risk of Invasive Aspergillosis. Patients were categorized into proven or probable or possible IA according to the revised EORTC/MSGERC (2020) definitions.

The in-house Aspergillus PCR had a sensitivity, specificity, PPV, and NPV of 82.00%, 56.76%, 71.93%, and 70.00% respectively when compared with a galactomannan assay. Among the study participants, two patients had proven, 37 had probable and 48 had possible IA. When the Aspergillus PCR was evaluated against those with proven/probable IA (as per the EORTC/MSGERC 2020 definition), the test showed sensitivity, specificity, PPV, and NPV of 69.23%, 52.08%, 54.00%, and 67.57% respectively. When combined positive results of either PCR or galactomannan were compared against proven/probable IA as per the EORTC 2020 definition, sensitivity, specificity, PPV and NPV were 97.44%, 37.50%, 55.88%, and 94.74% respectively.

Aspergillus PCR from single serum sample as a standalone screening test in those at-risk patients for IA has moderate sensitivity and specificity. Combining molecular testing with serological testing for antigen detection has good diagnostic sensitivity and hence IA PCR needs to be included as part of the screening tests.