Journal of Patient-Reported Outcomes (Aug 2025)

Patient-reported outcomes and home-based self-swabs for influenza-like illness events - lessons learned from the 2023/2024 DANFLU-2 Homeswab PRO substudy

  • Filip Soeskov Davidovski,
  • Kristoffer Grundtvig Skaarup,
  • Niklas Dyrby Johansen,
  • Daniel Modin,
  • Nabila Shaikh,
  • Jose Bartelt-Hofer,
  • Matthew M. Loiacono,
  • Rebecca C. Harris,
  • Carsten Schade Larsen,
  • Lykke Larsen,
  • Lothar Wiese,
  • Michael Dalager-Pedersen,
  • Randi Jessen,
  • Nina Steenhard,
  • Brian L. Claggett,
  • Scott D. Solomon,
  • Lars Køber,
  • Pradeesh Sivapalan,
  • Jens Ulrik Staehr Jensen,
  • Cyril Jean-Marie Martel,
  • Tor Biering-Sørensen

DOI
https://doi.org/10.1186/s41687-025-00936-8
Journal volume & issue
Vol. 9, no. 1
pp. 1 – 8

Abstract

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Abstract Background Self-swabs and digital patient-reported outcomes (PROs) offer innovative tools for decentralized monitoring of infectious diseases. The DANFLU-2 HomeSwab PRO substudy evaluated the feasibility of using these methods for tracking influenza-like illness (ILI) within a large-scale, pragmatic, randomized trial. Methods During the 2023/2024 influenza season, adults aged ≥ 65 years were recruited from the DANFLU-2 trial, which evaluates the relative effectiveness of high-dose influenza vaccine compared to standard-dose. Participants were instructed to self-swab at home upon ILI symptom onset and complete the Respiratory Infection Intensity and Impact Questionnaire (RiiQ™) for 14 days. Swabs were registered via QR code in a webapp and mailed for centralized PCR testing. Compliance was defined as completing all 14 days of RiiQ™ reporting. Results Among 1,976 enrolled participants, 208 (10.5%) completed at least one RiiQ™, and 171 (82.2%) met the ILI case definition. Most participants found self-swabbing easy (66.1%) and more practical than visiting a clinic (78.6%). Compliance with daily RiiQ™ symptom tracking was 85.7%. Among those with ILI, 89.4% performed a self-swab within 1 day [IQR: 0; 3] of symptom onset; 65.8% of swabs were correctly registered in the webapp, and 96.5% were RNaseP-positive. Thirty-six participants (1.8%) withdrew, mainly due to weekly reminders; allowing reduced reminder frequency improved retention. Conclusion The study confirmed the feasibility of using home-based self-swabs for remote disease diagnosis and digital PRO tracking for symptoms during ILI events in a large-scale, pragmatic randomized trial. While the approach proved viable, the findings also highlighted areas for improvement in participant engagement and data collection efficiency. Clinicaltrials.gov ID NCT05517174.

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