Validity of Combined Serodiagnostic Assays; Galactomannan, Mannan Antigens and Panfungal PCR in Diagnosis of Invasive Fungal Infection

Background: The development of reliable and rapid techniques for accurate diagnosis of invasive fungal infection (IFI) is an important goal that could help in effective treatment. Among the new promising methods used in diagnosis of IFI, pan-fungal PCR for detection of fungal DNA and measurement of serum Mannan and Galactomannan antigens.

Objectives: Our aim was to assess the performance of combined seroassays in diagnosis of IFI; Mannan plus Galactomannan antigens assays and the pan-fungal PCR with Galactomannan antigen tests compared to the culture based method.

Methodology: This study included 76 patients with suspected IFIs, (50 liver transplant recipients and 26 haematologic malignancy patients). Selected cases were subjected to complete diagnostic work-up (complete history, clinical, laboratory and radiological assessment). Blood samples were collected from all 76 cases, were divided into 2 parts; first part was inoculated into blood culture bottle for fungal isolation, serum was separated from the second part. Serum Mannan and Galactomannan antigens were measured by enzyme immunoassay (EIAs). Pan- fungal PCR technique was performed for molecular diagnosis.

Results: Among 76 of IFI patients, pure fungal growth was encountered in 16 cases (21.1%), which were 7 Aspergillus spp. and 9 Candida spp. Pan fungal PCR could diagnose 27/76 (35.5%) IFI cases; whereas, 29/76 (38.2%) cases were positive by combined GM (13.2%) plus MN (25%) EIAs. Sensitivity of combined antigen tests (100%) was higher than Pan- PCR (87.5%) assay alone and was the same as combined GM and PCR, while specificity was the same (78.3%). Blood culture method was considered as the gold standard. Sixteen (21%) patients were confirmed as proven IFI, ten (13.2%) were probable, 19 (25%) were possible and 31 (40.8%) were non-IFI. Unfavorable outcome was encountered in 9/76 (11.8%) patients (5 proven, 2 probable and 2 no-IFI), all of them were PCR positive.

Conclusion: Combinations of GM plus MN or PCR plus GM assays had high diagnostic performance in IFI patients. Both provided 100% sensitivity and NPV and 78.3% specificity. Consequently, these combinations will limit the time for deciding effective treatment strategies or empirical antifungal therapy.