Aspergillus-Specific Lateral-Flow Device and Real-Time PCR Testing of Bronchoalveolar Lavage Fluid: a Combination Biomarker Approach for Clinical Diagnosis of Invasive Pulmonary Aspergillosis

Abstract

Objectives. Clinical experience of the impact of serum biomarkers for invasive fungal disease (IFD) varies markedly in haemato-oncology. Invasive pulmonary aspergillosis (IPA) is the commonest manifestation, so we evaluated biomarkers in broncho-alveolar lavage fluid (BAL). Methods. Aspergillus-specific lateral flow device (LFD), qPCR and galactomannan (GM) tests were used with 32 BAL fluid samples from 32 patients at risk of IPA. Eight patients had proven, 3 probable, 6 possible and 15 patients no IPA by EORTC/MSG criteria. Diagnostic accuracies of the tests were evaluated and pair-wise agreement between biomarkers was calculated. The diagnostic performance of the EORTC/MSG criteria was evaluated against the test(s) identified as most useful in IPA diagnosis. Results. Using EORTC/MSG criteria, sensitivities of qPCR and LFD were 100%, GM was 87.5% (cut-off, GM > 0.8), with specificities between 66.7 and 86.7%. The agreement between the qPCR and LFD was almost perfect (Cohen's kappa = 0.93, 95% CI: 0.81 – 1.00). Combined LFD+qPCR had a sensitivity of 100% and specificity of 85.7%. Calcofluor staining and culture of all BAL samples was negative for fungal infection. The median time from starting mould-active antifungal therapy to obtaining BAL was 6 days. Reversing roles, and using LFD+qPCR dual testing to classify cases, the EORTC/MSG criteria had a sensitivity of 83.3%. Conclusions. All three tests are useful for diagnosis of IPA in BAL samples. Despite the significant delays between starting antifungal therapy and bronchoscopy, unlike microscopy and culture, the biomarkers remain informative. In particular, the combination of LFD+qPCR allows sensitive and specific detection of IPA.