COPD exacerbations associated with the modified Medical Research Council scale and COPD assessment test among Humana Medicare members

Figures & data

Figure 1 Patient flow diagram.

Table 1 Baseline demographic and clinical characteristics of survey respondents and non-respondents; completers and non-completers

Measure	Invited for survey participation (n=4,000)			Survey respondents (n=1,159)
	Survey respondents	Survey non-respondents	P-valuea	Survey completers	Survey non-completers	P-valuea
n (%)	1,159 (29.0)	2,841 (71.0)	n/a	765 (66.0)	394 (34.0)	n/a
Age, years (mean [SD])	72.2 (8.5)	72.0 (9.5)	0.640	72.0 (8.3)	72.7 (9.0)	0.180
Age ≥65 years (n [%])	985 (85.0)	2,333 (82.1)	0.029	650 (85.0)	335 (85.0)	0.979
Sex, female (n [%])	630 (54.4)	1,513 (53.3)	0.526	411 (53.7)	219 (55.6)	0.547
Race/ethnicity, white (n [%])	1,035 (89.3)	2,437 (85.8)	0.024	698 (91.2)	337 (85.5)	0.031
Geographic region, south (n [%])	694 (59.9)	1,931 (68.0)	<0.001	443 (57.9)	251 (63.7)	0.043
Qualify for low-income subsidy and dual eligible (n [%])	172 (14.8)	462 (16.3)	0.264	102 (13.3)	70 (17.8)	0.044
RxRisk-V comorbidity index	5.7 (3.7)	6.0 (3.8)	0.014	5.6 (3.8)	6.0 (3.7)	0.033
Deyo–Charlson comorbidity index	2.0 (1.9)	2.1 (1.9)	0.135	1.9 (1.8)	2.0 (1.9)	0.877
Comorbidities (top five)b
Unspecified essential hypertension (ICD-9-CM: 401.9x) n (%)	722 (62.3)	1,851 (65.2)	0.087	465 (60.8)	257 (65.2)	0.139
Other and unspecified hyperlipidemia (ICD-9-CM: 272.4x) n (%)	671 (57.9)	1,639 (57.7)	0.906	453 (59.2)	218 (55.3)	0.204
Essential hypertension, benign (ICD-9-CM: 401.1x) n (%)	425 (36.7)	1,132 (39.9)	0.062	282 (36.9)	143 (36.3)	0.849
Dyspnea and respiratory abnormalities (ICD-9-CM: 786.0x) n (%)	443 (38.2)	1,038 (36.5)	0.316	286 (37.4)	157 (39.9)	0.414
Diabetes mellitus without mention of complication (ICD-9-CM: 250.0x) n (%)	364 (31.4)	1,034 (36.4)	0.003	238 (31.1)	126 (32.0)	0.763
CAT score (mean [SD])	n/a	n/a	n/a	17.6 (9.7)	17.2 (10.6)	0.480

Notes:

a Two-sample t-test used for continuous measures; chi-square test used for categorical measures (all tests are two-sided);

b top five comorbidities based on 4,000 COPD members invited for survey participation, at the four digit ICD-9-CM level.

Abbreviations: CAT, COPD assessment test; ICD-9-CM, International Classification of Diseases-9th edition; SD, standard deviation; n/a, not applicable.

Table 2 Baseline demographic and clinical characteristics of low- and high-symptom patients by mMRC and CAT among survey completers (n=765)

Measure	mMRC			CAT
	Low-symptom patients	High-symptom patients	P-valuea	Low-symptom patients	High-symptom patients	P-valuea
n (%)	416 (54.4)	349 (45.6)	n/a	185 (24.2)	580 (75.8)	n/a
Age (years), mean (SD)	73.3 (7.4)	70.3 (9.0)	<0.001	74.1 (7.1)	71.3 (8.5)	<0.001
Age ≥65 years, n (%)	380 (91.4)	270 (77.4)	<0.001	175 (94.6)	475 (81.9)	<0.001
Sex, female, n (%)	225 (54.1)	186 (53.3)	0.828	101 (54.6)	310 (53.5)	0.800
Race/ethnicity, white, n (%)	380 (91.4)	318 (91.1)	0.903	164 (88.7)	534 (92.1)	0.027
Geographic region, south, n (%)	236 (56.7)	207 (59.3)	0.398	104 (56.2)	339 (58.5)	0.402
Qualify for low-income subsidy and dual eligible, n (%)	38 (9.1)	64 (18.3)	<0.001	18 (9.7)	84 (14.5)	0.107
RxRisk-V comorbidity index	4.7 (3.5)	6.6 (3.9)	<0.001	4.3 (3.3)	6.0 (3.8)	<0.001
Deyo–Charlson comorbidity index	1.7 (1.7)	2.3 (2.0)	<0.001	1.7 (1.8)	2.0 (1.9)	0.014
Comorbidities (top five)b
Unspecified essential hypertension (ICD-9-CM: 401.9x), n (%)	242 (58.2)	223 (63.9)	0.119	109 (58.9)	356 (61.4)	0.604
Other and unspecified hyperlipidemia (ICD-9-CM: 272.4x), n (%)	247 (59.4)	206 (59.0)	0.941	112 (60.5)	341 (58.8)	0.731
Dyspnea and respiratory abnormalities ICD-9-CM: 786.0x), n (%)	133 (32.0)	153 (43.8)	<0.001	51 (27.6)	235 (40.5)	0.002
Essential hypertension, benign (ICD-9-CM: 401.1x), n (%)	149 (35.8)	133 (38.1)	0.547	60 (32.4)	222 (38.3)	0.162
Diabetes mellitus without mention of complication (ICD-9-CM: 250.0x), n (%)	108 (26.0)	130 (37.3)	<0.001	54 (29.2)	184 (31.7)	0.584

Notes:

a Two-sample t-test used for continuous measures; chi-square test used for categorical measures (all tests are two-sided);

b top five comorbidities based on 4,000 COPD members invited for survey participation, at the four-digit ICD-9-CM level.

Abbreviations: CAT, COPD assessment test; ICD-9-CM, International Classification of Diseases-9^th edition; mMRC, modified Medical Research Council; SD, standard deviation; n/a, not applicable.

Table 3 GOLD classification by symptom as captured by mMRC and CAT

Kappa statistic (95% CI) =0.331 (0.27–39); Spearman correlation coefficient =63 (P<0.001)
	CAT
mMRC	High symptoms (CAT score ≥10)	Low symptoms (CAT score <10)
High symptoms (mMRC score ≥2) n (%)a	266 (42.2)	14 (2.2)
Low symptoms (mMRC score <2) n (%)a	209 (33.1)	142 (22.5)

Note:

a n (%) are based on final sample size of 631 after 365 days of post-survey follow-up.

Abbreviations: CAT, COPD assessment test; CI, confidence interval; GOLD, Global initiative for chronic Obstructive Lung Disease; mMRC, modified Medical Research Council.

Table 4 GOLD classifications by symptom and exacerbation history

Patient category	Number of exacerbations in earlier year	Symptoms		Sample size, n (%)a
		mMRC	CAT	mMRC	CAT
A	0–1	0–1	<10	309 (49.0)	138 (21.9)
B	0–1	≥2	≥10	208 (33.0)	379 (60.1)
C	≥2	0–1	<10	42 (6.7)	18 (2.9)
D	≥2	≥2	≥10	72 (11.4)	96 (15.2)

Note:

a n (%) are based on final sample size of 631 after 365 days of post-survey follow-up.

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

Figure 2 Exacerbations during follow-up by risk and symptoms.

Notes: (A) In each box plot the mean (standard deviation) is reported and is represented by the cross symbol. (a) Low risk – low mMRC symptom; (b) low risk – high mMRC symptom; (c) high risk – low mMRC symptom; (d) high risk – high mMRC symptom. Low risk – history of <2 exacerbations; high risk – history of ≥2 exacerbations. Low-symptom mMRC score <2; high-symptom mMRC score ≥2. (B) In each box plot the mean (standard deviation) is reported and is represented by the cross symbol. (a) Low risk – low CAT symptom; (b) low risk – high CAT symptom; (c) High risk – low CAT symptom; (d) High risk – high CAT symptom. Low risk – history of <2 exacerbations; high risk – history of ≥2 exacerbations. Low-symptom CAT score <10; high-symptom CAT score ≥10.
Abbreviations: CAT, COPD assessment test; mMRC, modified Medical Research Council.

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:

a Using 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;

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

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

d low-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.

Table 6 Generalized linear model for exacerbation-related costs (log link and Gamma distribution)a

Analysis of maximum likelihood parameter estimates
Parameter	Estimate	Exponentiated estimate	Standard error	Wald 95% confidence limits	P-value
Age in years (<65 as reference)
65–<70	−0.84	0.43	0.36	−1.55, −0.14	0.019
70–<75	0.21	1.23	0.39	−0.55, 0.97	0.594
75–<80	−0.65	0.52	0.40	−1.44, 0.13	0.104
80+	−0.37	0.69	0.40	−1.16, 0.42	0.362
Sex (Male as reference)	−0.52	0.60	0.23	−0.97, −0.06	0.026
Race (white as reference)
Black	−0.65	0.52	0.52	−1.67, 0.37	0.214
Hispanic	−4.98	0.01	1.11	−7.16, −2.80	<0.001
Other	1.32	3.75	0.94	−0.51, 3.16	0.158
Region (South as reference)
Northeast	−2.49	0.08	0.78	−4.02, −0.97	0.001
Midwest	0.88	2.42	0.28	0.33, 1.44	0.002
West	0.58	1.78	0.41	−0.23, 1.39	0.161
Dual eligibility only	0.29	1.34	0.49	−0.66, 1.25	0.550
LIS status only	−0.40	0.67	0.39	−1.15, 0.36	0.304
RxRisk-V comorbidity index score	0.06	1.06	0.03	−0.01, 0.13	0.075
Deyo–Charlson comorbidity index score	0.20	1.23	0.06	0.08, 0.33	0.002
Number of pre-index exacerbations	0.55	1.73	0.13	0.30, 0.80	<0.001
Symptoms by CATb (low as reference)	1.42	4.14	0.27	0.89, 1.95	<0.001
Symptoms by mMRCc (low as reference)	0.22	1.24	0.24	−0.25, 0.68	0.358

Notes:

a The scale parameter was estimated by the maximum likelihood method;

b low symptom: CAT score <10; high symptom: CAT score ≥10;

c low symptom: mMRC score <2; high symptom: mMRC score ≥2.

Abbreviations: CAT, COPD assessment test; mMRC, modified Medical Research Council; LIS, low income subsidy.