Table 5.

Logistic regression of factors associated with post-index exacerbations (≥1/0)^a

Variable	Analysis of maximum likelihood ratio estimates			Odds ratio estimates
	Estimate	Standard error	P-value	Odds ratio estimate	95% Wald confidence limits
Symptoms and exacerbation history as separate variablesb
RxRisk-V comorbidity index score	0.08	0.03	0.002	1.08	1.03–1.14
Pre-index exacerbations (0 as reference)
1	1.12	0.20	<0.001	3.06	2.06–4.56
2	1.52	0.31	<0.001	4.55	2.46–8.42
≥3	2.79	0.49	<0.001	16.28	6.22–42.56
Symptom by CAT (low as reference)	0.92	0.22	<0.001	2.51	1.62–3.89
Symptoms and exacerbation history combined into GOLD classifications A–Dc
RxRisk-V comorbidity index score	0.09	0.02	<0.001	1.09	1.04–1.15
GOLD classification by CATd
A. Low risk/low symptom as reference
B. Low-risk/high-risk symptom	1.12	0.24	<0.001	3.07	1.93–4.89
C. High-risk/low-risk symptom	1.82	0.55	<0.001	6.15	2.10–18.07
D. High-risk/high-risk symptom	2.62	0.35	<0.001	13.67	6.94–26.93

Notes:

^aUsing stepwise logistic regression, the earlier variables were selected based on parameter estimates P≤0.05 from the following: age, sex, race, region, dual eligibility, LIS status, RxRisk-V comorbidity index score, Deyo–Charlson comorbidity index score, number of pre-index exacerbations, symptoms by CAT, and symptoms by mMRC;

^bHosmer and Lemeshow Goodness-of-Fit chi-square =7.5 (degrees of freedom =8, P=0.48), c statistic =0.76;

^cHosmer and Lemeshow Goodness-of-Fit chi-square =18.9 (degrees of freedom =8, P=0.02), c statistic =0.72;

^dlow-symptom CAT score <10; high-symptom CAT score ≥10.

Abbreviations: CAT, COPD assessment test; GOLD, Global initiative for chronic Obstructive Lung Disease; mMRC, modified Medical Research Council; LIS, low income subsidy.