An Electronic Diary Is Shown to Be More Reliable than a Paper Diary: Results from a Randomized Crossover Study in Patients with Persistent Asthma

Objectives. Test–retest reliability of an asthma paper diary versus an electronic diary (e-diary) with an integrated peak flow meter was investigated. The equivalence of the two modes was also evaluated. Methods. Prospective, randomized crossover study design in adolescents (12–17 years) and adults (≥18 years). Key inclusion criteria were persistent asthma, Asthma Control Test (ACT) scores ≥16, use of inhaled corticosteroid with or without long-acting beta-agonist for ≥12 weeks, nocturnal awakenings <2 times in the past week, and activity limitations <1 per week. Participants were randomized to either paper then e-diary or e-diary then paper, to be completed for 14 days each. Results. Forty-seven participants completed all study visits. Weekly percentage of symptom-free days (SFDs) and rescue-free days (RFDs) were calculated. Intraclass correlation coefficients (ICCs) of Week 1 mean SFD and RFD (test) and Week 2 mean SFD and RFD (retest), respectively, were estimated in three groups defined as stable: (i) minimal changes in asthma symptoms, as measured by the global patient reported symptom change question, (ii) less than 15% change (absolute value) in 1 second FEV1 at adjacent study visits, and (iii) changes in ACT scores less than three points for each mode. SFD demonstrated acceptable ICC (≥0.70) using all three definitions of asthma stability for both modes. Conclusion. Acceptable reproducibility of the percentage of RFD (ICC = 0.78) was only observed for the e-diary using the FEV1 stability criterion. The ICCs for SFD and RFD were acceptable, 0.84 and 0.70, respectively, suggesting better reliability for the e-diary.