Background
Methods
Study design and treatment setting
Patients
Data collection and instruments
CaReQoL asthma
Asthma quality of life questionnaire
Asthma control questionnaire
Forced expiratory volume in one second
Statistical analyses
Construct validity
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Physical functioning vs. changes in AQLQ Total score, AQLQ Symptoms, AQLQ Activity limitations, and ACQ;
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Social functioning vs. changes in AQLQ Total score, AQLQ Activity limitations and ACQ;
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Coping with asthma vs. changes in AQLQ Emotional functioning and ACQ;
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Medication vs. changes in AQLQ Symptoms and ACQ;
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Overall quality of life (1 item) vs. changes in AQLQ Total score, AQLQ Symptoms and ACQ;
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Global perceived effect (1 item) vs. changes in AQLQ Total score, AQLQ Symptoms and ACQ.
Criterion validity
Responsiveness
Minimal important change
Results
Descriptives and follow-up scores
Baseline t0 | Follow-up t38 | Follow-up t64 | |
---|---|---|---|
Mean scores: | Mean (95 CI) | Mean (95 CI) | Mean (95 CI)# |
CaReQoL asthma: | |||
Total (1–5) | – | 3.89 (3.73–4.06) (n = 77) | 3.92 (3.68–4.16) (n = 47) |
- Physical functioning (1–5) | – | 3.76 (3.53–3.99) (n = 80) | 3.66 (3.34–3.99) (n = 48) |
- Social functioning (1–5) | – | 3.62 (3.39–3.86) (n = 79) | 3.70 (3.43–3.98) (n = 49) |
- Coping with asthma (1–5) | – | 4.23 (4.07–4.40) (n = 80) | 4.23 (3.96–4.49) (n = 48) |
- Knowledge about asthma (1–5) | – | 4.53 (4.37–4.68) (n = 82) | 4.57 (4.37–4.78) (n = 49) |
- Medication (1–5) | – | 3.36 (3.10–3.63) (n = 81) | 3.41 (3.07–3.74) (n = 49) |
Overall quality of life (1–5) | – | 4.05 (3.82–4.29) (n = 80) | 4.08 (3.76–4.40) (n = 49) |
Global perceived effect (1–7) | – | 5.35 (5.05–5.65) (n = 78) | 5.29 (4.90–5.68) (n = 49) |
AQLQ: | |||
Total | 4.18 (3.96–4.40) (n = 83) | 5.05 (4.78–5.32)Δ (n = 67) | 4.94 (4.65–5.24)* (n = 62) |
- Symptoms | 4.30 (4.07–4.53) (n = 83) | 5.09 (4.80–5.39)Δ (n = 67) | 4.97 (4.67–5.26)* (n = 62) |
- Activity limitations | 3.67 (3.41–3.92) (n = 82) | 4.66 (4.34–4.99)Δ (n = 67) | 4.54 (4.19–4.89)* (n = 62) |
- Emotional functioning | 5.08 (4.80–5.35) (n = 83) | 5.94 (5.71–6.17)Δ (n = 67) | 5.87 (5.57–6.16) (n = 62) |
- Environmental stimuli | 4.12 (3.81–4.44) (n = 83) | 4.88 (4.53–5.23)Δ (n = 67) | 4.82 (4.45–5.19) (n = 62) |
ACQ | 2.78 (2.56–2.99) (n = 81) | 2.06 (1.78–2.34)Δ (n = 66) | 2.18 (1.87–2.49)* (n = 61) |
FEV1 | 85.55 (80.64–90.45) (n = 82) | 88.57 (82.65–94.49)+ (n = 61) | 90.97 (83.85–98.08) (n = 47) |
Missing data
Construct validity
Factor | # items | Factor loadings (range) | Cronbach’s alpha | |
---|---|---|---|---|
Physical functioning | 8 | 0.72–0.90 | 0.95 | |
Social functioning | 4 | 0.85–0.88 | 0.93 | |
Coping with asthma | 5 | 0.65–0.78 | 0.85 | |
Knowledge about asthma | 3 | 0.71–0.91 | 0.83 | |
Medication | 3 | 0.72–0.78 | 0.82 |
CaReQoL domain (scores at t38 or t64) | Comparison instruments: change scores (∆ t0–t38 or ∆ t0–t64) | Expected correlation strength# (direction) | Construct validity and responsiveness (t38) | Respon-siveness (t64) | Explanation/hypothesis |
---|---|---|---|---|---|
Physical functioning (8 items) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.40–0.59 (+) 0.40–0.59 (+) 0.40–0.59 (+) 0.00–0.39 (+) 0.00–0.39 (+) | 0.48*** 0.53*** 0.39** 0.15 (n.s.) 0.29* | 0.45** 0.44** 0.44** 0.30 (n.s.) 0.32* | Physical functioning is likely to be moderately related with changes in Total, Activity limitations and Symptoms scores, but not to other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.52*** | − 0.55*** | Physical functioning is likely to be moderately related to a change in ACQ | |
Δ FEV1 | 0.00–0.39 (+) | 0.25 (n.s.) | 0.15 (n.s.) | Physical functioning is expected to be weakly related to a change in FEV1 | |
Social functioning (4 items) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.40–0.59 (+) 0.00–0.39 (+) 0.40–0.59 (+) 0.00–0.39 (+) 0.00–0.39 (+) | 0.49*** 0.48*** 0.45*** 0.10 (n.s.) 0.42*** | 0.45** 0.40** 0.49** 0.14 (n.s.) 0.38* | Social functioning is likely to be moderately related to changes in the Total score and Activity limitations, but not to other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.53*** | − 0.43** | Social functioning is likely to be moderately related to a change in ACQ | |
Δ FEV1 | 0.00–0.39 (+) | 0.19 (n.s.) | 0.07 (n.s.) | Social functioning is expected to be weakly related to a change in FEV1 | |
Coping with asthma (5 items) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.00–0.39 (+) 0.00–0.39 (+) 0.00–0.39 (+) 0.40–0.59 (+) 0.00–0.39 (+) | 0.16 (n.s.) 0.20 (n.s.) 0.09 (n.s.) 0.18 (n.s.) 0.06 (n.s.) | 0.32* 0.24 (n.s.) 0.37* 0.07 (n.s.) 0.38* | Coping is likely to be moderately related to changes in Emotional function, but not to other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.14 (n.s.) | − 0.46** | Coping is expected to be moderately related to a change in ACQ | |
Δ FEV1 | 0.00–0.39 (+) | 0.17 (n.s.) | 0.01 (n.s.) | Coping is expected to be weakly related to a change in FEV1 | |
Knowledge about asthma (3 items) | Δ AQLQ: Total score Δ ACQ Δ FEV1 | 0.00–0.39 (+) 0.00–0.39 (−) 0.00–0.39 (+) | 0.17 (n.s.) − 0.15 (n.s.) 0.14 (n.s.) | 0.36* − 0.23 (n.s.) 0.10 (n.s.) | Since there are no similar items on Knowledge about asthma in all other measures, correlations are expected to be very weak |
Medication (3 items) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.00–0.39 (+) 0.40–0.59 (+) 0.00–0.39 (+) 0.00–0.39 (+) 0.00–0.39 (+) | 0.38** 0.48*** 0.29* 0.02 (n.s.) 0.27* | 0.23 (n.s.) 0.19 (n.s.) 0.28 (n.s.) -0.04 (n.s.) 0.28 (n.s.) | Medication is likely to be moderately related to changes in Symptoms, but not to other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.47*** | − 0.35* | Since 1 item of the ACQ concerns the use of medicine, a moderate correlation is expected | |
Δ FEV1 | 0.00–0.39 (+) | 0.08 (n.s.) | 0.00 (n.s.) | Medication is expected to be weakly related to a change in the FEV1 | |
Overall quality of life (QoL) (1 item) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.40–0.59 (+) 0.40–0.59 (+) 0.00–0.39 (+) 0.00–0.39 (+) 0.00–0.39 (+) | 0.40** 0.41*** 0.30* 0.24 (n.s.) 0.37** | 0.34* 0.27 (n.s.) 0.40* 0.05 (n.s.) 0.37* | The perceived effect on QoL is likely to be moderately related to changes in the Total and Symptoms scores, and weakly related to other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.34** | − 0.45** | The overall quality of life is likely to be moderately related to a change in ACQ | |
Δ FEV1 | 0.00-0.39 ( +) | 0.15 (n.s.) | 0.14 (n.s.) | The effect on QoL is expected to be weakly related to a change in the predicted FEV1 | |
Global perceived effect (GPE) (1 item) | Δ AQLQ: Total score Symptoms Activity limitations Emotional functioning Environmental stimuli | 0.40–0.59 (+) 0.40–0.59 (+) 0.00–0.39 (+) 0.00–0.39 (+) 0.00–0.39 (+) | 0.46*** 0.47*** 0.43*** 0.09 (n.s.) 0.33** | 0.46** 0.40** 0.51*** 0.18 (n.s.) 0.38* | This criterion variable GPE is expected to be moderately related to changes in the Total and Symptoms scores, and weakly related to changes in other AQLQ scores |
Δ ACQ | 0.40–0.59 (−) | − 0.53*** | − 0.50** | The GPE is expected to be moderately related to a change in ACQ | |
Δ FEV1 | 0.00–0.39 ( +) | 0.18 (n.s.) | 0.20 (n.s.) | The GPE is expected to be weakly related to the FEV1 |
Responsiveness
Criterion validity
Mean scores (t38) | Global perceived effect (t38): | ||
---|---|---|---|
Improvement# | No or little improvement | Deterioration^ | |
CaReQoL asthma | (n = 45) | (n = 25) | (n = 8) |
Total score** | 4.35*** | 3.51** | 2.93*** |
- Physical functioning | 4.37*** | 3.28** | 2.46*** |
- Social functioning | 4.24*** | 3.14** | 2.07*** |
- Coping with asthma | 4.47 | 4.12 | 3.66* |
- Knowledge about asthma | 4.66 | 4.42 | 4.46 |
- Medication | 3.98*** | 2.64 | 2.38*** |
Overall QoL | 4.56** | 3.67* | 2.40*** |
Mean change scores (∆ t0–t38): | |||
∆ AQLQ: | (n = 38) | (n = 18) | (n = 6) |
Total score | 1.12** | 0.39 | 0.02* |
- Symptoms | 1.15** | 0.21 | − 0.10* |
- Activity limitations | 1.26* | 0.49 | − 0.15* |
- Emotional functioning | 0.90 | 0.55 | 0.70 |
- Environmental stimuli | 0.92 | 0.50 | 0.00 |
∆ ACQ | − 1.06** (n = 37) | − 0.11 (n = 17) | 0.30* (n = 5) |
∆ FEV1 | 4.59 (n = 34) | 3.55 (n = 17) | − 2.22 (n = 5) |
Minimal important change
CaReQoL Asthma: mean scores at t38 | ||||||
---|---|---|---|---|---|---|
Physical functioning | Social functioning | Coping with asthma | Knowledge about asthma | Medication | Total | |
Global perceived effect (t38): | ||||||
Much or very much improvement (n = 45) | 4.37 | 4.24 | 4.47 | 4.66 | 3.98 | 4.35 |
No or little improvement (n = 25) | 3.28 | 3.14 | 4.12 | 4.42 | 2.64 | 3.51 |
Minimal important change (MIC)* | 1.09 | 1.10 | 0.35 | 0.24 | 1.34 | 0.84 |