Comparative analysis of galactomannan lateral flow assay, galactomannan enzyme immunoassay and BAL culture for diagnosis of COVID-19-associated pulmonary aspergillosis

Abstract

Background: Galactomannan Enzyme Immunoassay (GM-EIA) is proved to be a cornerstone in the diagnosis of COVID-19-associated pulmonary aspergillosis (CAPA), its use is limited in middle and low-income countries, where the application of simple and rapid test, including Galactomannan Lateral Flow Assay (GM-LFA), is highly appreciated. Despite such merits, limited studies directly compared GM-LFA with GM-EIA. Herein we compared the diagnostic features of GM-LFA, GM-EIA and bronchoalveolar lavage (BAL) culture for CAPA diagnosis in Iran, a developing country.

Materials/methods: Diagnostic performances of GM-LFA and GM-EIA in BAL (GM indexes ≥1) and serum (GM indexes >0.5), i.e. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) and areas under the curve (AUC), were evaluated using BAL (n = 105) and serum (n = 101) samples from mechanically ventilated COVID-19 patients in intensive care units. Patients were classified based on the presence of host factors, radiological findings and mycological evidences according to 2020 ECMM/ISHAM consensus criteria for CAPA diagnosis.

Results: The Aspergillus GM-LFA for serum and BAL samples showed a sensitivity of 56.3% and 60.6%, specificity of 94.2% and 88.9%, PPV of 81.8% and 71.4%, NPV of 82.3% and 83.1%, when compared with BAL culture, respectively. GM-EIA showed sensitivities of 46.9% and 54.5%, specificities of 100% and 91.7%, PPVs of 100% and 75%, NPVs of 80.2% and 81.5% for serum and BAL samples, respectively.

Conclusion: Our study found GM-LFA as a reliable simple and rapid diagnostic tool, which could circumvent the shortcomings of culture and GM-EIA and be pivotal in timely initiation of antifungal treatment.

Keywords: COVID-19-associated pulmonary aspergillosis; culture; galactomannan enzyme immunoassay; galactomannan lateral flow assay.

FIGURE 1

The frequency of positivity of galactomannan lateral flow assay (GM‐LFA) and galactomannan enzyme immunoassay (GM‐EIA) in bronchoalveolar lavage (BAL) (n = 33) and serum (n = 32) samples from COVID‐19‐associated pulmonary aspergillosis.

FIGURE 2

The receiver operating characteristic curves of serum and BAL galactomannan in diagnosing COVID‐19‐associated pulmonary aspergillosis.

FIGURE 3

The receiver operating characteristic curves of serum and BAL galactomannan in diagnosing COVID‐19‐associated pulmonary aspergillosis (cases with culture positive CAPA compared with other cases).