Efficacy of home respiratory culture kits in people with cystic fibrosis

ABSTRACT

Background: Respiratory cultures are an important part of clinical care for people with cystic fibrosis (CF). Telemedicine visits during the COVID-19 pandemic have not allowed for routine collection. To address this, the University of Michigan Adult Cystic Fibrosis Program mailed home culture kits to patients. We hypothesized that results from home sputum samples would be consistent with prior cultures obtained in sputum collected in clinic but that self-collected throat swabs would provide false-negative results. We also sought to determine percentage return rate. Method(s) Adults with CF were sent culture kits containing a specimen cup and a throat swab. Patients had the choice to submit either sample for processing. Medical personnel provided written instructions with the culture kits and, on occasion, instructed patients on proper collection techniques via phone. Samples were then refrigerated for up to 24 hours before a delivery service returned the specimen to a University of Michigan laboratory for analysis. Data collected from December 2020 to December 2021 (N = 77) included percentage return rate, result, source, and presence of microorganisms. Pairwise culture data of samples collected in clinic versus home-collected samples within 1 yearwere included in the analysis. Descriptive statistics and Cohen kappa correlation coefficients were computed for all culture data and subgroups (Table 1A-E). Result(s) Of 77 culture kits returned, 46 had corresponding clinic samples collected using the same method, and the remaining 21 were collected using different methods (throat swab vs sputum sample). Overall, approximately 200 kits were mailed to patients, with a return rate of 38.5%. A similar percentage of positive culture results was obtained with same method of collection sputum and throat samples (Table 1C, D, E), although the discordance rate between cultures collected in clinic and at home ranged from approximately 10% to 30%. Correlation between clinic and home culture data was generally good throughout, except for clinic Table 1 ( 115) Analysis of respiratory culture results for (A) all cultures, (B) different collection, and (C, D, E) same collection method. *p < 0.05. Cohen kappa correlation coefficient between groups poor agreement <0.20;fair agreement = 0.21-0.40;moderate agreement = 0.41-0.60;good agreement = 0.61-0.80;very good agreement = 0.81-1.00. PsA = Pseudomonas aeruginosa;Staph = Staphylococcus aureus.(Table Presented)versus home throat swabs, probably because of a lowevent rate in the small sample size. Conclusion(s) The data suggest that, overall, clinic and home culture kits provide similar positive results, although discordance in specific culture results was common. This may be due to natural fluctuations from culture to culture in people with CF. A limitation of this study is that the cultures being compared in our study were not completed on the same day. Nevertheless, our data also indicate that collection technique may influence results for certain microorganisms. How these differences might influence antibiotic selection and treatment outcomes in the era of telemedicine requires more investigation. The return rate was found to be relatively low, demonstrating the need for interventions to improve patient outreach and compliance.Copyright © 2022, European Cystic Fibrosis Society. All rights reserved