Risk assessment of readmissions following an initial COPD-related hospitalization

Figures & data

Figure 1 Patient flow diagram.

Abbreviation: COPD, chronic obstructive pulmonary disease.

Figure 2 Percentage of study sample readmitted by time to first readmission since the index hospitalization and readmission type (n = 6,095).

Abbreviation: COPD, chronic obstructive pulmonary disease.

Figure 3 Time to first hospital readmission (months) since the index hospitalization for all readmitted patients (n = 2,527).

Table 1 Baseline demographic characteristics (% patients)

Variable	All readmissionsa (n = 2,527)	COPD-related readmissionsb (n = 1,681)	Not readmitted (n = 3,568)
Gender
Male	40.80	40.21	41.28
Female	59.20	59.79	58.72
Age group, years*
40–44	1.98	1.55	2.30
45–49	6.57	5.95	7.06
50–54	16.70	15.11	16.87
55–59	28.21	29.33	29.32
60–65	45.94	48.07	44.45
Residence
Urban	76.61	77.10	75.25
Rural	23.39	22.90	24.75
US geographic region
South	44.76	43.43	47.06
North central	36.09	36.29	33.21
West	9.85	10.59	10.34
Northeast	9.22	9.58	9.22
Unknownc	0.08	0.12	0.17
Insurance plan type
PPO	57.18	57.53	57.96
HMO	14.13	15.53	13.65
Comprehensive	11.91	12.43	10.96
POS	10.37	8.51	10.01
Other	6.41	6.01	7.43

Notes:

a Defined as all readmissions that occurred during the follow-up period, regardless of diagnosis

b defined as a subset of all readmissions, which includes only readmissions where COPD was listed as a primary or secondary diagnosis

c treated as missing in logistic regression.

* P = 0.0301 COPD-related readmissions versus not readmitted.

Abbreviations: COPD, chronic obstructive pulmonary disease; PPO, preferred provider organization; HMO, health maintenance organization; POS, noncapitated point-of-service.

Table 2 Pre-index Deyo–CCI and respiratory medications (% patients)

Variable	All readmissionsa (n = 2,527)	COPD-related readmissionsb (n = 1,681)	Not readmitted (n = 3,568)
Deyo-CCI comorbidities
Chronic pulmonary disease	86.43**	91.55**	79.18
Diabetes	30.71**	27.66**	21.92
Congestive heart failure	23.23**	20.70**	11.46
Cerebrovascular disease	11.40**	10.23**	7.09
Malignancy	11.12**	10.59**	6.75
Peripheral vascular disease	7.84**	6.96*	5.16
Renal disease	7.64**	6.25**	3.34
Myocardial infarction	7.32**	7.50**	3.81
Diabetes with chronic complications	6.61**	5.77**	3.31
Rheumatologic disease	4.59*	3.57	3.11
Metastatic solid tumor	2.14*	1.84*	0.98
Peptic ulcer disease	1.94	1.73	1.46
Mild liver disease	1.62*	1.49*	0.70
Moderate or severe liver disease	0.87*	0.71*	0.25
Hemiplegia or paraplegia	0.67	0.48	0.34
AIDS	0.24	0.24	0.08
Dementia	0.12	0.00	0.08
Respiratory medicationsc
Short-acting bronchodilator	46.42**	49.79**	39.97
Systemic corticosteroid	39.14**	40.81**	31.33
Long-acting bronchodilator	35.22**	40.04**	27.72
Oxygen therapy	32.49**	35.51**	19.14
Inhaled corticosteroid	11.00	10.71	10.06
Leukotriene modifier	9.81*	10.05*	7.34
Mast cell stabilizer	0.04	0.06	0.03

Notes:

a Defined as all readmissions that occurred during the follow-up period, regardless of diagnosis

b defined as a subset of all readmissions, which includes only readmissions where COPD was listed as a primary or secondary diagnosis

c within 90-day period before index hospitalization.

* P < 0.05 versus not readmitted

** P < 0.0001 versus not readmitted.

Abbreviations: AIDS, acquired autoimmune deficiency syndrome; CCI, Charlson comorbidity index; COPD, chronic obstructive pulmonary disease.

Table 3 Pre-index health care utilization for COPD (% patients)

Variable	All readmissionsa (n = 2,527)	COPD-related readmissionsb (n = 1,681)	Not readmitted (n = 3,568)
Inpatient hospitalizations**,c
0	73.05	68.41	89.41
1	17.85	20.23	8.80
≥2	9.10	11.36	1.79
Emergency department visits**,c
0	28.49	25.76	32.48
1	40.09	38.19	47.03
≥2	31.42	36.05	20.49
Outpatient visits**,c
0	17.10	11.30	22.65
1	9.62	7.56	12.22
≥2	73.29	81.14	65.13

Notes:

a Defined as all readmissions that occurred during the follow-up period, regardless of diagnosis

b defined as a subset of all readmissions, which includes only readmissions where COPD was listed as a primary or secondary diagnosis

c required COPD diagnosis in any primary or secondary position.

** P < 0.0001 versus not readmitted for both readmission types.

Abbreviations: COPD, chronic obstructive pulmonary disease.

Table 4 Significant predictors of readmission within 30 days of index hospitalization

Risk factor	OR	95% CI	P
All readmissionsa
Moderate or severe liver disease	3.09	1.36–7.02	0.0070
Metastatic solid tumor	2.44	1.35–4.44	0.0034
Number of IP hospitalizations in pre-index period (≥2 versus 0)c	2.25	1.61–3.14	<0.0001
Congestive heart failure	1.41	1.11–1.78	0.0045
Diabetes	1.35	1.10–1.66	0.0046
Number of ICU days in index hospitalization	1.04	1.00–1.09	0.0479
Year of index hospitalization (2009 versus 2008)	0.77	0.61–0.97	0.0238
COPD-related readmissionsb
Number of IP hospitalizations in pre-index (≥2 versus 0)c	3.20	2.24–4.58	<0.0001
Chronic pulmonary disease	2.52	1.56–4.05	0.0001
Metastatic solid tumor	2.26	1.21–4.25	0.0109
Number of IP hospitalizations in pre-index (1 versus 0)c	1.39	1.02–1.90	0.0357
Number of ICU days in index hospitalization	1.05	1.00–1.10	0.0356
Year of index hospitalization (2009 versus 2008)	0.76	0.58–0.99	0.0455

Notes:

a Defined as all readmissions that occurred during the follow-up period, regardless of diagnosis

b defined as a subset of all readmissions, which includes only readmissions where COPD was listed as a primary or secondary diagnosis

c required COPD diagnosis in any primary or secondary position. Statistically significant odds ratios are reported when the corresponding two-sided P-values are ≤0.05 from multivariable stepwise logistic regression analyses.

Abbreviations: IP, inpatient; ICU, intensive care unit; CI, confidence interval; OR, odds ratio.

Table 5 Significant predictors for readmissions within 90 days of index hospitalization

Risk factor	OR	95% CI	P
All readmissionsa
Moderate or severe liver disease	3.10	1.47–6.54	0.0029
Number of IP hospitalizations in pre-index (≥2 versus 0)c	2.90	2.21–3.80	<0.0001
Metastatic solid tumor	1.69	1.01–2.81	0.0447
Congestive heart failure	1.50	1.25–1.79	<0.0001
Plan type (HMO versus comprehensive)	1.46	1.11–1.92	0.0072
Renal disease	1.43	1.09–1.89	0.0102
Number of IP hospitalizations in pre-index (1 versus 0)c	1.39	1.14–1.69	0.0013
Myocardial infarction	1.31	1.00–1.72	0.0481
Malignancy	1.29	1.01–1.65	0.0394
Number of ED visits in pre-index (≥2 versus 0)c	1.27	1.05–1.53	0.0149
Systemic corticosteroidsd	1.22	1.06–1.41	0.0072
Diabetes	1.20	1.03–1.41	0.0199
Number of ICU days in index hospitalization	1.04	1.00–1.07	0.0413
COPD-related readmissionsb
Number of IP hospitalizations in pre-index (≥2 versus 0)c	3.92	2.95–5.20	<0.0001
Moderate or severe liver disease	2.79	1.23–6.34	0.0143
Metastatic solid tumor	1.82	1.08–3.10	0.0258
Plan type (HMO versus comprehensive)	1.62	1.17–2.23	0.0034
Number of OP visits in pre-index (≥2 versus 0)c	1.61	1.29–2.01	<0.0001
Number of IP hospitalizations in pre-index (1 versus 0)c	1.61	1.14–2.26	0.0064
Long-acting bronchodilator treatmentd	1.21	1.02–1.45	0.0313
Number of ICU days in index hospitalization	1.04	1.00–1.08	0.0348

Notes:

a Defined as all readmissions that occurred during the follow-up period, regardless of diagnosis

b defined as a subset of all readmissions, which includes only readmissions where COPD was listed as a primary or secondary diagnosis

c required COPD diagnosis in any primary or secondary position

d within 90-day period before index hospitalization. Statistically significant odds ratios are reported when corresponding two-sided P-values are ≤0.05 from multivariable stepwise logistic regression analyses.

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; ED, emergency department; HMO, health maintenance organization; ICU, intensive care unit; IP, inpatient; OP, outpatient; OR, odds ratio.

Table S1 Comorbidity categories used in the Deyo-Charlson comorbidity index algorithm

Conditions	ICD-9 codes
Acquired autoimmune deficiency syndrome	042–044.9
Any malignancy, including lymphoma and leukemia	140–172.9, 174–195.8, 200–208.9
Cerebrovascular disease	430–438.xx
Chronic pulmonary disease	490–496, 500–505, 506.4
Congestive heart failure	428–428.9
Connective tissue disease	710.0, 710.1, 710.4, 714.0–714.2, 714.81, 725
Dementia	290–290.9
Diabetes mellitus	250–250.3, 250.7
Diabetes with end organ disease	250.4–250.6
Hemiplegia or paraplegia	344.1, 342–342.9
Metastatic solid tumor	196–199.1
Mild liver disease	571.2, 571.5, 571.6, 571.4–571.49
Moderate or severe liver disease	572.2–572.8, 456.0–456.21
Moderate or severe renal disease	582–582.9, 583–583.7, 585.xx, 586, 588–588.9
Myocardial infarction	412, 410–410.9
Peripheral vascular disease	441–441.9, 443.9, 785.4, V43.4
Ulcer	531–534.9