COPD exacerbation frequency and its association with health care resource utilization and costs

Figures & data

Table 1 Exacerbation definition by severity type

Exacerbation severity	Definition
Level I exacerbation (ambulatory)	A medical claim for an ER or outpatient visit with the following:
	1. COPD diagnosis code (ICD-9-CM code 491.xx, 492.xx, or 496.xx) in the primary position OR
	2. Respiratory failure diagnosis code (ICD-9-CM code 518.81, 518.83, or 518.84) in the primary position accompanied by a COPD diagnosis code in the secondary position OR
	3. Any diagnosis code indicative of an acute exacerbation (ICD-9-CM codes 466–466.19, 480–486, 487.0, 490, 493.12, 493.22, 493.92, 494.1, 506.0–506.3, 511.0–511.1, or 518.82) in the primary position and a COPD diagnosis code in the secondary position
	AND
	1. A prescription claim for any of the antibiotics commonly used for respiratory infections within 7 days of the visit OR
	2. A prescription claim for an oral corticosteroid within 7 days of the visit
Level II exacerbation (requiring hospitalization)	A medical claim for a hospitalization with the following:
	1. COPD diagnosis code in the primary position OR
	2. Any diagnosis code indicative of an acute exacerbation in the primary position and a COPD diagnosis code in the secondary position
	AND
	1. No respiratory failure diagnosis code in secondary position
Level III exacerbation (leading to acute respiratory failure)	A medical claim for a hospitalization with the following:
	1. COPD diagnosis code in the primary position and a respiratory failure diagnosis code in secondary position OR
	2. Any diagnosis code indicative of an acute exacerbation in the primary position and a COPD and a respiratory failure diagnosis code in the secondary position OR
	3. Respiratory failure diagnosis code in the primary position accompanied by a COPD diagnosis code in the secondary position

Abbreviations: ER, emergency room; ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification.

Figure 1 Patient selection.

Notes: ^aCOPD diagnosis: ≥2 medical claims occurring on separate dates within 90 days with a COPD diagnosis code (ICD-9-CM code 491.xx, 492.xx, or 496.xx) in the primary or secondary position; ^b≥1 medical claim with any of the following ICD-9-CM diagnosis codes in any position: 277.0x (cystic fibrosis), 011.x (pulmonary tuberculosis), or 140.xx–172.xx, 174.xx–209.3x, 209.7x (malignant neoplasms); ^cIndex date: the date of first medical claim with a COPD diagnosis during the identification period; ^dPreindex period: a 12-month period prior to index date; ^ePostindex period: a 24-month period after index date.
Abbreviations: ICD-9-CM, International Classification of Diseases, Ninth Revision, Clinical Modification; MAPD, Medicare advantage plan with prescription drug benefits.

Table 2 Exacerbation patterns

Exacerbation patterns for patients in the final study sample (N=52,459)
	n	%
Exacerbation frequency
Zero exacerbations	29,222	55.7
≥one exacerbation	23,237	44.3
One exacerbation	13,797	26.3
Two exacerbations	4,982	9.5
≥three exacerbations	4,458	8.5
Number of exacerbations (mean)	0.79
Number of exacerbations (median)	0
Exacerbation severity
Level I (ambulatory)
n, %	12,568	24.0
Number of exacerbations (mean)	0.52
Number of exacerbations (median)	0
Level II (requiring hospitalizations)
n, %	7,987	15.2
Number of exacerbations (mean)	0.21
Number of exacerbations (median)	0
Level III (leading to respiratory failure)
n, %	2,682	5.1
Number of exacerbations (mean)	0.06
Number of exacerbations (median)	0

Table 3 Baseline patient characteristics

Characteristic	Zero exacerbations (n=29,222)	One exacerbation (n=13,797)	Two exacerbations (n=4,982)	≥Three exacerbations (n=4,458)	Total (n=52,459)	P-valuea
Age, mean (SD)	71.29 (9.4)	71.10 (9.2)	70.78 (9.0)	70.22 (8.9)	71.10 (9.3)	<0.001
Age category, years, n (%)						<0.001
40–49	737 (2.5)	334 (2.4)	113 (2.3)	93 (2.1)	1,277 (2.4)
50–59	2,523 (8.6)	1,196 (8.7)	443 (8.9)	420 (9.4)	4,582 (8.7)
60–69	8,716 (29.8)	4,281 (31.0)	1,607 (32.3)	1,517 (34.0)	16,121 (30.7)
70–79	11,372 (38.9)	5,370 (38.9)	1,954 (39.2)	1,749 (39.2)	20,445 (39.0)
80–89	5,874 (20.1)	2,616 (19.0)	865 (17.4)	679 (15.2)	10,034 (19.1)
Female, n (%)	15,622 (53.5)	7,748 (56.2)	2,938 (59.0)	2,484 (55.7)	28,792 (54.9)	<0.001
Race/ethnicity, n (%)						<0.001
White	25,099 (85.9)	12,138 (88.0)	4,471 (89.7)	3,991 (89.5)	45,699 (87.1)
Black	2,868 (9.8)	1,099 (8.0)	327 (6.6)	305 (6.8)	4,599 (8.8)
Hispanic	594 (2.0)	240 (1.7)	67 (1.3)	68 (1.5)	969 (1.8)
Other	604 (2.1)	283 (2.1)	102 (2.0)	81 (1.8)	1,070 (2.0)
Unknown	57 (0.2)	37 (0.3)	15 (0.3)	13 (0.3)	122 (0.2)
Geographic region, n (%)						<0.001
Northeast	518 (1.8)	254 (1.8)	83 (1.7)	71 (1.6)	926 (1.8)
Midwest	6,080 (20.8)	3,185 (23.1)	1,163 (23.3)	1,096 (24.6)	11,524 (22.0)
South	20,231 (69.2)	9,282 (67.3)	3,368 (67.6)	2,985 (67.0)	35,866 (68.4)
West	2,393 (8.2)	1,076 (7.8)	368 (7.4)	306 (6.9)	4,143 (7.9)
Plan characteristics, n (%)
LIS status	5,763 (19.7)	2,845 (20.6)	1,013 (20.3)	809 (18.1)	10,430 (19.9)	0.003
Dual eligibility	3,977 (13.6)	1,898 (13.8)	661 (13.3)	440 (9.9)	6,976 (13.3)	<0.001
Oxygen therapy, n (%)	3,227 (11.0)	1,713 (12.4)	966 (19.4)	1,425 (32.0)	7,331 (14.0)	<0.001
Exacerbations in the preindex period
n (%)	1,835 (6.3)	1,573 (11.4)	1,051 (21.1)	1,824 (40.9)	6,283 (12.0)	<0.001
Mean (SD)	0.07 (0.3)	0.14 (0.4)	0.30 (0.7)	0.74 (1.1)	0.17 (0.5)	<0.001
DCCI, mean (SD)	1.62 (1.8)	1.61 (1.8)	1.68 (1.7)	1.84 (1.7)	1.64 (1.8)	<0.001
Airflow testingb, n (%)	11,558 (39.6)	6,536 (47.4)	2,763 (55.5)	2,899 (65.0)	23,756 (45.3)	<0.001

Notes:

a Univariate statistical comparisons were made among the four cohorts (zero, one, two, and ≥three exacerbations) using analysis of variance for continuous variables and chi-square tests for categorical variables;

b measured during the preindex period and postindex period.

Abbreviations: COPD, chronic obstructive pulmonary disease; DCCI, Deyo–Charlson comorbidity index; ER, emergency room; LIS, low-income subsidy; SD, standard deviation.

Table 4 Health care resource utilization by exacerbation frequency

Outcome	Zero exacerbation (n=29,222)	One exacerbation (n=13,797)	Two exacerbations (n=4,982)	≥Three exacerbations (n=4,458)	Total (n=52,459)	P-valuea
All-cause HCRU
All-cause ER visits
Patients with one or more visits, n (%)	11,923 (40.8)	6,449 (46.7)	2,674 (53.7)	2,634 (59.1)	23,680 (45.1)	<0.001
Number of visits per patient, mean (SD)	1.09 (2.6)	1.28 (2.6)	1.62 (3.0)	2.15 (4.5)	1.28 (2.9)	<0.001
All-cause hospitalizations
Patients with one or more visits, n (%)	14,519 (49.7)	9,161 (66.4)	3,472 (69.7)	3,469 (77.8)	30,621 (58.4)	<0.001
Number of HOSP per patient, mean (SD)	1.13 (2.1)	1.65 (2.4)	2.08 (3.0)	2.96 (4.0)	1.51 (2.6)	<0.001
All-cause 30-day rehospitalizations
Patients with one or more visits, n (%)	3,495 (12.0)	2,604 (18.9)	1,096 (22.0)	1,376 (30.9)	8,571 (16.3)	<0.001
Number of HOSP per patient, mean (SD)	0.25 (1.1)	0.40 (1.4)	0.52 (1.8)	0.85 (2.7)	0.36 (1.5)	<0.001
All-cause outpatient visits
Patients with one or more visits, n (%)	29,162 (99.8)	13,779 (99.9)	4,982 (100.0)	4,457 (100.0)	52,380 (99.8)	<0.001
Number of visits per patient, mean (SD)	49.24 (34.0)	52.59 (34.8)	57.17 (37.2)	62.40 (39.0)	51.99 (35.2)	<0.001
COPD-related HCRU
COPD-related ER visits
Patients with one or more visits, n (%)	120 (0.4)	442 (3.2)	345 (6.9)	536 (12.0)	1,443 (2.8)	<0.001
Number of visits per patient, mean (SD)	0.01 (0.1)	0.04 (0.3)	0.09 (0.4)	0.18 (0.6)	0.04 (0.3)	<0.001
COPD-related hospitalizations
Patients with one or more visits, n (%)	0	5,575 (40.4)	2,396 (48.1)	2,698 (60.5)	10,669 (20.3)	<0.001
Number of HOSP per patient, mean (SD)	0.00 (0.0)	0.42 (0.5)	0.71 (0.9)	1.38 (1.7)	0.30 (0.8)	<0.001
COPD-related 30-day rehospitalizations
Patients with one or more visits, n (%)	0	233 (1.7)	218 (4.4)	500 (11.2)	951 (1.8)	<0.001
Number of HOSP per patient, mean (SD)	0.00 (0.0)	0.02 (0.2)	0.05 (0.3)	0.17 (0.7)	0.03 (0.2)	<0.001
COPD-related outpatient visits
Patients with one or more visits, n (%)	16,303 (55.8)	11,019 (79.9)	4,685 (94.0)	4,384 (98.3)	36,391 (69.4)	<0.001
Number of visits per patient, mean (SD)	1.69 (2.5)	3.17 (3.5)	5.30 (4.3)	9.78 (6.8)	3.11 (4.2)	<0.001
Respiratory antibiotics use
Patients with one or more Rx, n (%)	19,458 (66.6)	12,298 (89.1)	4,795 (96.2)	4,382 (98.3)	40,933 (78.0)	<0.001
Number of Rxs per patient, mean (SD)	2.26 (3.1)	3.66 (4.8)	5.36 (4.5)	8.48 (6.4)	3.45 (4.5)	<0.001
Oral corticosteroid use
Patients with one or more Rx, n (%)	13,068 (44.7)	9,078 (65.8)	4,192 (84.1)	4,177 (93.7)	30,515 (58.2)	<0.001
Number of Rxs per patient, mean (SD)	1.44 (3.1)	2.46 (3.9)	4.21 (5.4)	8.38 (7.7)	2.56 (4.6)	<0.001

Note:

a Univariate statistical comparisons were made among the four cohorts (zero, one, two, and ≥three exacerbations) using analysis of variance for continuous variables and chi-square tests for categorical variables.

Abbreviations: COPD, chronic obstructive pulmonary disease; HCRU, health care resource utilization; HOSP, hospitalizations; Rx, prescription claim; SD, standard deviation; ER, emergency room.

Figure 2 COPD-related health care costs by exacerbation frequency.

Note: *Statistically significant (P<0.001) trend.

Abbreviation: USD, United States dollar.

Figure 3 All-cause health care costs by exacerbation frequency.

Note: *Statistically significant (P<001) trend.
Abbreviation: USD, United States dollar.