National Validation and Sensitivity to Change of the SAQ
Research type
Research Study
Full title
National Validation and Sensitivity to Change of a scale to measure quality of life in patients with severe asthma
IRAS ID
250167
Contact name
Matthew Masoli
Contact email
Sponsor organisation
University Hospitals Plymouth HNS Trusy Research and Development Department
Duration of Study in the UK
1 years, 6 months, 27 days
Research summary
Research Summary:
“Is the Severe Asthma Questionnaire a better measure of quality of life in patients with severe asthma compared to established scales?” Unlike mild/moderate asthma which can usually be controlled using inhaled medication, patients with severe asthma often require oral corticosteroids (OCS) to keep their asthma symptoms under control. OCS use is associated with side effects. Of major concern to patients are changes in facial and body appearance, weight gain, gastro-oesophageal reflux, mood changes and sleep disruption. For patients with severe asthma, the impact of OCS can to be far greater than the impact of other asthma treatments, and therefore, severe patients, i.e. those exposed to high doses of OCS, are likely to have a greater treatment burden than other patients. Despite experiencing very different health related quality of life burdens compared to patients with mil/moderate asthma, patients with severe asthma are still asked to complete the same quality of life questionnaires. \n\nA new questionnaire, the Severe Asthma questionnaire was drafted with the aim of capturing the experience of patients with severe asthma including their asthma symptoms and medication side effects. This experiential information was gained from 23 semi-structured interviews with patients with severe asthma. The wording and concepts in this draft were amending based on the feedback from 16 patients across 4 focus groups. The SAQ was then field tested in 160 patients and compared to other questionnaires. This further study is to provide additional validating data from multiple centres around the UK for the Severe Asthma Questionnaire as the prior study was in a relatively small dataset (160) and in one geographical location. Data to determine the Minimum Clinically Important Difference (MCID) of the SAQ will also be collected. The MCID of the SAQ is required if the questionnaire is to be useful in clinical practice and trials. For patients with severe asthma, the impact of OCS can to be far greater than the impact of other asthma treatments, and therefore, severe patients, i.e. those exposed to high doses of OCS, are likely to have a greater treatment burden than other patients. Despite experiencing very different health related quality of life burdens compared to patients with mil/moderate asthma, patients with severe asthma are still asked to complete the same quality of life questionnaires. A new questionnaire, the Severe Asthma questionnaire was drafted with the aim of capturing the experience of patients with severe asthma including their asthma symptoms and medication side effects. This experiential information was gained from 23 semi-structured interviews with patients with severe asthma. The wording and concepts in this draft were amending based on the feedback from 16 patients across 4 focus groups. The SAQ was then field tested in 160 patients and compared to other questionnaires. This further study is to provide additional validating data from multiple centres around the UK for the Severe Asthma Questionnaire as the prior study was in a relatively small dataset (160) and in one geographical location. Data to determine the Minimum Clinically Important Difference (MCID) of the SAQ will also be collected. The MCID of the SAQ is required if the questionnaire is to be useful in clinical practice and trials.Summary of Results:
The Severe Asthma Questionnaire (SAQ) is a new severe asthma specific Health Related Quality of Life (HRQoL) Questionnaire. In 2018 we published validation data collected from a single site in Plymouth. These data supported the statistical properties of the SAQ including construct validity, internal and test re-test reliability (1). To overcome this issue, the next two studies were conducted as multi-site studies with six severe asthma specialist hospitals contributing data for analysis. However, there was insufficient data to determine its factor structure, and the study had not been designed to allow longitudinal data collection needed to conduct sensitivity to change analysis. To overcome this issue, the next two studies were conducted as multi-site studies with six severe asthma specialist hospitals contributing data for analysis.Subscales of the SAQ
Patients with severe asthma were recruited from five additional severe asthma specialist hospitals, bringing the number of recruiting sites to six. New SAQ data from 300 patients were added to the SAQ data collected from 160 patients previously. Factor analysis was carried out to determine the factor structure of the questionnaire (2). Principle axis factoring with oblimin rotation was used.
All 16 items loaded > 0.64 on the first unrotated factor of a principal axis factor analysis. The factor correlations were: factors 1 and 2 r = 0.70, factors 1 and 3 r = 0.73, factors 2 and 3 r = 0.67. The three resulting subscales were labelled ‘My Life’ assesses the impact of severe asthma on different life activities, ‘My Mind’ assesses the perceived emotional impact and ‘My Body’ the impact of extra-pulmonary symptoms and side effects.
Fifteen of the 16 items loaded on only one of the three factors with item grouping consistent with the content derived domains. Item 14 (night disturbance) loaded on two factors: factor 1 and factor 3. To explore potential reasons for this cross-loading factor analysis was run again and split as a function of sex. For males item 14 loaded only on factor 1 (0.67) but not on factor 3 (0.29) or 2 (− 0.10), whereas for females item 14 loaded on factor 1 (0.41) and on factor 3 (0.41) but not on factor 2 (0.57). These results indicate that males and females interpret item 14 differently. For males, night disturbance loads on the My Life factor and just misses significance on the My Body factor, indicating that for males the meaning of night disturbance is primarily, but not exclusively, in terms of limitation to daily activities. For females, the night disturbance item loads equally on the My Life and My Body factors, showing that for females, night disturbance limits daily activity as well as adversely affecting bodily perceptions (e.g., fatigue and appearance). The night disturbance item (item 14) is scored to contribute to both the My Life and My Body subscales, consistent with the data from the total sample.
Correlations between subscale scores and clinically relevant data were used to assess the construct validity of the subscales. The correlation between FEV1% predicted and My Life was significantly different (p = 0.016) from the correlations between FEV1% predicted and either My Mind or My Body. The correlation between Anxiety/depression and My Mind was significantly different (p < 0.001) from the correlations between anxiety/depression and either My Life or My Body.
The three subscales provide a more nuanced picture of quality of life deficits that can be obtained from an overall score. The understanding provided by this more nuanced picture should help facilitate better communication between patient and healthcare workers and allow more detailed assessment regarding response to different treatments and management strategies, for example, whether an intervention reduces lifestyle limitations, improves mood, or reduces side effects—or does all three.Sensitivity to Change and Minimum Clinically important Difference (MCID) Patients commencing a biologic treatment for their severe asthma were recruited to this study, and asked to complete the SAQ at baseline, 4, 8 12 and 16 weeks. Data collection was curtailed from 23rd March 2020 due to Covid-19 and a UK national lockdown. This prevented all enrolled participants from completing all 16 weeks of questionnaire data. In total, 110 participants provided SAQ data at one or more of the four follow up time points, with 107 completing one or more questionnaires at 4 weeks, 74 participants at 8 weeks, 30 participants at 12 weeks, and 48 participants at 16 weeks.
In addition to the SAQ, patients were asked to complete an 11-point Global Rating of Change (GRoC) scale which assesses perception of response to treatment. The scale included the following response options: no change, a little better, somewhat better, moderately better, a good deal better and a great deal better, with deterioration represented by the same quantifiers but using the word ‘worse’ (3). The mean change in participant’s SAQ and SAQ-global scores for those scoring “a little better” provided the smallest possible values perceived as meaningful improvement. The MCID of the SAQ was 0.5 and for the SAQ-global 11.00.
This method for determining MCID is referred to as the anchor method (4) as it relies on an independent criterion or “anchor”. Is the case of this study, the anchor used was a score of “a little better” on the GRoC. We chose this method over alternatives for two main reasons. Firstly, the MCID is defined in terms of the patient’s perception of treatment, and the patient’s perception of their treatment is recognised as being an important outcome for clinical decision making (4). This means that patients with severe asthma directly contributed to the determination of the MCID of the SAQ, which is consistent with our approach of involving patients in the development of the questionnaire. Secondly, the authors of the AQLQ also used the anchor method which means a precedent had already been set (5).
The anchor method can be contrasted to a purely statistical method for calculating MCID. Distribution methods define the MCID in terms of the relationship between the distributions of scores and mean change score and uses the formula for Standard Error of Measurement (SEM) (6). This produces an MCID of 0.5 for the SAQ and 6.0 for the SAQ-global based on data reported elsewhere (1).
This study provided evidence for the SAQ’s sensitivity to change and that clinically significant improvement was detected within four weeks of starting biologic therapy. The MCID and multiples of the MCID provided a way of assessing clinical significance of change in contrast to the statistical significance of a treatment. The MCID of the SAQ is 0.5 and of the SAQ-global is 11. Further studies are required to assess longer term HRQoL benefits in different populations and whether there is a differential HRQoL response or rate of response between biologic treatments.References
1. Hyland ME, Jones RC, Lanario JW, Masoli M. The construction and validation of the Severe Asthma Questionnaire. Eur Respir J. 2018;52(1).
2. Lanario JW, Hyland ME, Menzies-Gow A, Mansur AH, Dodd JW, Fowler SJ, et al. Validation of subscales of the Severe Asthma Questionnaire (SAQ) using exploratory factor analysis (EFA). Health and Quality of Life Outcomes. 2020;18(1):1-10.
3. Kamper SJ, Maher CG, Mackay G. Global rating of change scales: a review of strengths and weaknesses and considerations for design. Journal of Manual & Manipulative Therapy. 2009;17(3):163-70.
4. Revicki D, Hays RD, Cella D, Sloan J. Recommended methods for determining responsiveness and minimally important differences for patient-reported outcomes. Journal of clinical epidemiology. 2008;61(2):102-9.
5. Juniper EF, Guyatt GH, Willan A, Griffith LE. Determining a minimal important change in a disease-specific quality of life questionnaire. Journal of clinical epidemiology. 1994;47(1):81-7.
6. Wyrwich KW, Wolinsky FD. Identifying meaningful intra‐individual change standards for health‐related quality of life measures. Journal of evaluation in clinical practice. 2000;6(1):39-49.REC name
Wales REC 3
REC reference
19/WA/0011
Date of REC Opinion
24 Jan 2019
REC opinion
Further Information Favourable Opinion