Reconcilable Differences: CLDSI
This sample was well distributed across all levels of asthma severity (Table 2). All three severity scores were normally distributed across the entire range of the score, with the Ng Score encompassing its entire range, while the CLDSI and ASS ranged from 5 and 6 to 28, respectively. Table 2 also illustrates the construct validity of each severity score. According to the Canadian Asthma Guidelines, patients with moderate and severe asthma were significantly more likely to have used a greater amounts of SA P-agonists, whereas those with higher asthma severity scores (ie, less severe disease) were less likely to have used greater amounts of SA P-agonist. Furthermore, as postulated, having visited an emergency department or been hospitalized were also positively associated with SA P-agonist use, and the better one’s pulmonary function, the less likely they were to use greater amounts of SA P-agonist.
There was no significant association between age, gender, or genotype and the amount of a SA P-agonist used. Corticosteroid use, all indexes and dimensions of asthma severity, except having been hospitalized for asthma in the previous year, and all proximate and contextual measures of SES were significantly associated with SA P-agonist use.
Independent of the method used for adjusting for asthma severity, lower SES was associated with using greater amounts of a SA P-agonist. Patients receiving social assistance were at least 2.5 times more likely to have received greater amounts of SA P-agonist (Fig 1). Adjusting for asthma severity using the Canadian Asthma Guidelines, measuring SES using the receipt of social assistance or annual household income accounted for only 22% and 24% of the variance in the magnitude of SA (3-agonist use, respectively. Conversely, using any of the asthma severity scores to adjust for asthma severity, and any metric of SES explained between 33 to 37% of the variance of SA (3-agonist use. Adding genotype to each final model did not affect the parameter estimates for any variables and reduced the adjusted R2 of each model, and therefore was not included in the final models.
Figure 1. Association between receipt of social assistance and the use of greater amounts of SA P-agonist, adjusted for asthma severity. ORs are for those individuals receiving social assistance relative to those not receiving social assistance. *Adjusted for emergency department visit in previous year. tAdjusted for emergency department visit in previous year, daily ICS use (yes/no), daily ICS dose. jModel includes emergency department visit in previous year, daily ICS use, frequency of daytime symptoms, and AQLQ(S) symptom score. §The distance between the ORs of 0 to 1 is not equal to the distance for 1-U increase in the ORs > 1 because while a decreased risk can only be represented by a value between 0 and 1, an increased risk can be any value between 1 and
Table 2—Univariate Analysis of the Associations Between Asthma Severity Scores and Dimensions and the Use of Greater Amounts of SA fi-Agonist
Factors |
Mean ± SD or Frequency (%) |
OR (95% CI) |
Adjusted R2 |
Severity score Canadian asthma guidelines Mild |
42 (21) |
Reference |
|
Moderate |
55 (27) |
3.0 (1.3-6.9) |
0.13 |
Severe |
105 (51) |
6.0 (2.8-12.9) |
|
CLDSI (range 4-28)t |
16.5 (4.9) |
0.88 (0.82-0.92) |
0.12 |
ASS (range 4-28)t |
17.6 (5.0) |
0.87 (0.83-0.92) |
0.12 |
Ng Score (range 3-10)t |
7.0(2.0) |
0.72 (0.62-0.83) |
0.12 |
Severity-related factors Emergency department visit No |
168 (83) |
1.0 |
0.06 |
Yes |
34 (17) |
3.2 (1.6-6.4) |
|
Hospitalization No |
194 (96) |
1.0 |
< 0.01 |
Yes |
8 (4) |
1.5 (0.4-5.4) |
|
FEVj, % predicted! |
85 (20) |
0.98 (0.97-0.99)| |
0.04 |
Peak expiratory flow rate, % predicted! |
102 (26) |
0.98 (0.97-0.99)| |
0.03 |