(549) A pilot study examining the feasibility of home sputum collection for Aspergillus fumigatus detection in cystic fibrosis

Background: Although Aspergillus fumigatus (Af) is the most common filamentous fungus isolated from people with cystic fibrosis (CF), a standardized microbiology laboratory protocol for fungus culture of CF sputum remains to be developed. Sputum expectoration and collection in clinic, necessary for fungus culture, has decreased due to the widespread use of clinical telemedicine visits and real-world clinical effectiveness of elexacaftor/tezacaftor/ivacaftor (ETI). We aimed to test the feasibility of home sputum collection and transport to a centralized laboratory in adults with CF and determine if sputum processing, microaerophilic conditions, and a nitrate-containing culture medium enhance the cultivation of Af in CF.

Methods: We enrolled adults with CF age 18 years and older with a history of one or more Aspergillus species positive cultures into a decentralized prospective cohort study from October 2021 to present. Individuals with history of solid organ transplantation were excluded. Home sputum collection kits and pre-paid mailers were distributed to each participant with instructions to send in one sample per week for four occasions via FedEx. Subjects completed electronic questionnaires for each shipped sample. Sputum specimens were tested for various conditions including mucolysis, ultrasonication, 1% oxygen (O2), 5% carbon dioxide (CO2), culture media (Inhibitory mold agar, Sabouraud agar with gentamicin, and Czapek Dox agar), and incubation temperature (30ºCelsius [C] versus 37ºC). Primary outcomes were percentage of successful sample collections and Af prevalence. Clinical data and questionnaire results were described. Proportion of Af recovery was compared between conditions.

Results: In this interim analysis, twenty adults were enrolled; 60% female. Median age 35 [30,46] years. Median FEV1 percent predicted 75 [54,90]. Sixteen (80%) were on ETI. The participants sent 78 sputum samples and 75 samples were received by the laboratory. Mean transport time was 1.4 (±1.2) days. Success rate (proportion of participants with 3 or more samples) was 95%. 88% samples were produced during stable health. Among 78 samples, 42 (54%) were spontaneously produced; whereas about 25% required Vest/PEP device with or without mucolytics. Most participants felt it was easy or somewhat easy to cough up a sample (66%). Af prevalence was 19 (95%) in our cohort. Of the 70 samples analyzed, the proportion of Af positive cultures was 56 (80%). Af recovery was highest for sputa that underwent ultrasonication and incubation in 37ºC and 1% O2. Differences in Af isolation between inhibitory mold agar, Sabouraud agar with gentamicin, or nitrate-containing Czapek Dox agar were not observed.

Conclusions: Sputum collection and transport directly from the home to the laboratory is feasible. These preliminary data suggest ultrasonication and incubation at 37° C and 1% O2 may facilitate Af growth in CF sputa. Further data collection and analyses will be conducted to better elucidate these findings.

Acknowledgements: This work was supported by the Cystic Fibrosis Foundation (HONG21A0-1).

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