Interlaboratory and interstudy reproducibility of a novel lateral-flow device and influence of antifungal therapy on detection of invasive pulmonary aspergillosis

Abstract

Interest in lateral-flow devices (LFDs) as potential point-of-care assays for the diagnosis of infectious diseases has increased. Our objective was to evaluate the interlaboratory and interstudy reproducibility and the effects of antifungal therapy on an LFD developed for invasive pulmonary aspergillosis (IPA) detection. An established neutropenic guinea pig model of IPA caused by Aspergillus fumigatus was used. At predetermined time points (1 h and 3, 5, and 7 days postinoculation), blood and bronchoalveolar lavage (BAL) fluid were collected from infected and uninfected animals. In a separate experiment, guinea pigs were treated with posaconazole (10 mg/kg of body weight orally [p.o.] twice a day [BID]), voriconazole (10 mg/kg p.o. BID), liposomal amphotericin B (10 mg/kg intraperitoneally [i.p.] once a day [QD]), or caspofungin (2 mg/kg i.p. QD), and samples were collected on days 7 and 11. Each laboratory independently evaluated the IgG monoclonal antibody-based LFD. Galactomannan and (1 → 3)-β-D-glucan were also measured using commercially available kits. Good interlaboratory agreement was observed with the LFD, as the results for 97% (32/33) of the serum and 78.8% (26/33) of the BAL fluid samples from infected animals were in agreement. Good interstudy agreement was also observed. The serum sensitivity of each surrogate-marker assay was reduced in animals treated with antifungals. In contrast, these markers remained elevated within the BAL fluids of treated animals, which was consistent with the fungal burden and histopathology results. These results demonstrate that the LFD assay is reproducible between different laboratories and studies. However, the sensitivity of this assay and other markers of IPA may be reduced with serum in the presence of antifungal therapy.

Fig 1

(1→3)-β-d-Glucan, galactomannan, and LFD results using serum and BAL fluid from guinea pigs with invasive aspergillosis that were exposed to antifungal agents. Antifungal therapy with posaconazole (PSC; 10 mg/kg p.o. BID), voriconazole (VRC; 10 mg/kg p.o. BID), liposomal amphotericin B (LAMB; 10 mg/kg i.p. QD), or caspofungin (CFG; 2 mg/kg i.p. QD) began 1 day after aerosol inoculation and continued through day 8. Serum samples were collected on day 7 and day 11 from animals that survived to the study endpoint, and BAL fluid samples were collected on day 11. Uninf., uninfected.

Fig 2

Pulmonary fungal burden (A) and representative histopathology sections (B) for guinea pigs that received antifungal therapy. Antifungal therapy with posaconazole (PSC; 10 mg/kg p.o. BID), voriconazole (VRC; 10 mg/kg p.o. BID), liposomal amphotericin B (LAMB; 10 mg/kg i.p. QD), or caspofungin (CFG; 2 mg/kg i.p. QD) began 1 day after aerosol inoculation and continued through day 8. Lungs were collected on day 11 or when the animals succumbed to infection, and the lines depict the median log₁₀ numbers of CFU/g. For histopathology, lung sections were stained with GMS and viewed at ×200 magnification by light microscopy.