Clinical characteristics and psychological factors among the three groups of adults with CF
| Low adherence <50% n=46 | Moderate adherence 50%–79.9% n=8 | High adherence ≥80% n=7 | P values* | |
| % Normative adherence, median (IQR) | 15.8 (4.5–35.4) | 65.5 (56.0–75.8) | 91.5 (80.2–96.7) | |
| Clinical characteristics | ||||
| Age in years, median (IQR) | 27.4 (21.7–37.1) | 23.7 (18.4–32.0) | 26.1 (21.2–37.5) | 0.616 |
| Female, n (%) | 22 (47.8) | 5 (62.5) | 1 (14.3) | 0.164 |
| Baseline %FEV1, median (IQR) | 49.5 (43.1–66.4) | 83.5 (43.1–66.4) | 79.7 (52.7–89.1) | 0.068 |
| Prior-year IV days, median (IQR) | 28 (13–47) | 15 (4–53) | 0 (0–10) | 0.012 |
| IV days during trial, median (IQR) | 14 (0–23) | 15 (0–30) | 0 (0–0) | 0.160 |
| Quality of life (CFQ-R), median (IQR) | 50 (28–78) | 64 (34– 88) | 67 (44–78) | 0.306 |
| Psychological factors | ||||
| Anxiety (GAD) score, median (IQR) | 4 (1–7) | 1 (1–4) | 0 (0–5) | 0.186 |
| Depression (PHQ-8) score, median (IQR) | 6 (3–11) | 6 (3–13) | 4 (2–4) | 0.389 |
| Intention (COM-B) score, median (IQR) | 7 (5–7) | 7 (7–7) | 7 (5–7) | 0.256 |
| Necessity (BMQ) score, median (IQR) | 3.1 (2.7–3.8) | 3.3 (2.8–3.9) | 3.4 (2.7–4.6) | 0.496 |
| Concerns (BMQ) score,† median (IQR) | 2.3 (1.9–2.6) | 1.9 (1.5–2.3) | 1.6 (1.3–1.7) | 0.030 |
| Habit (SRBAI) scores,† median (IQR) | 9.0 (4.8–12.0) | 14.5 (11.3–18.3) | 18.0 (14.0–20.0) | <0.001 |
The values in bold indicates results that are statistically significant.
*All p values were calculated using Kruskal-Wallis H test, except the p value for gender which was calculated using Fisher’s exact test.
†Since concerns and habit scores were associated with adherence, both scores were included as covariates in a multiple ordinal regression model with adherence category as the dependent variable. In this model, only habit strength was independently associated with adherence:
Pseudo-r2 of model=0.408 (Nagelkerke); model χ2 (2)=22.9, p<0.001.
Adjusted OR for concerns score=0.344 (95% CI 0.103 to 1.152, p=0.083).
Adjusted OR for habit score=1.313 (95% CI 1.123 to 1.536, p=0.001).
BMQ, Beliefs about Medicines Questionnaire; CF, cystic fibrosis; CFQ-R, Cystic Fibrosis Questionnaire-Revised respiratory domain; COM-B, capability, opportunity, motivation and behaviour; GAD, General Anxiety Disorder 7-item anxiety scale; PHQ-8, Patient Health Questionnaire depression scal; SRBAI, Self-Report Behavioural Automaticity Index.