New (1-3)-β-D-Glucan assay for Pneumocystis pneumonia evaluated
February 09 2018
In adults without respiratory samples, the diagnosis of Pneumocystis jirovecii pneumonia (PCP) can be made by measuring (1-3)-β-D-Glucan (BDG) in serum. Lewis White and colleagues from Cardiff evaluated the performance of the Dynamiker® Fungus BDG assay for the diagnosis of PCP in a retrospective study across 2 UK centres. The assay has recently become available in Europe and allows for frequent, cost-effective testing.
The diagnosis of PCP was considered: (i) proven if a respiratory specimen was positive by Grocott’s stain, (ii) probable if the patient was immunosuppressed, had clinical/radiographic signs consistent with PCP and positive Pneumocystis PCR and/or Fungitell assay, (iii) possible in symptomatic cases with nonspecific radiographic findings but positive PCR or Fungitell.
A total of 73 samples were included (41 cases of PCP, 5 other forms of fungal disease, 27 patients without invasive fungal disease). The positivity threshold for the Dynamiker® Fungus BDG assay was 95 pg/ml. Among proven/probable cases, sensitivity was 87% and specificity 70%. The negative likelihood ratio was 0.19. All control patients were HIV negative. Hence, a specificity value for the HIV-positive population could not be calculated.
In a previously published meta-analysis of 12 studies on PCP, the pooled sensitivity of BDG assays was 96% and sensitivity 84% (Onishi et al., 2012). The diagnostic accuracy was not significantly different between HIV-positive and HIV-negative patients. The performance of the Dynamiker® Fungus BDG assay may reflect differences in the assay itself, the study population, geographic factors or other parameters. The results will need to be validated in a larger prospective study.
Read the papers:
- White et al. (2017) An evaluation of the performance of the Dynamiker® Fungus (1-3)-β-D-Glucan Assay to assist in the diagnosis of Pneumocystis pneumonia. Med Mycol myx097.
- Onishi A et al. (2012) Diagnostic accuracy of serum 1,3-β-D-glucan for Pneumocystis jiroveci pneumonia, invasive candidiasis, and invasive aspergillosis: systematic review and meta-analysis. J Clin Microbiol. 50(1):7-15.