Risk factors for respiratory hospitalizations in a population of patients with a clinical diagnosis of COPD

Figures & data

Table 1 Baseline characteristics: classical COPD versus nonobstructed group

Variable (n=210)	Classical COPD (n=157)	Nonobstructed (n=53)	Level of significance (p<0.05)
Age in years (mean ± SD)	68±10	64±11	p=0.028**
Active smoking	85/157 (54%)	28/53 (53%)	p=0.869*
Male gender	76/157 (48%)	15/53 (28%)	p=0.011*
African American	135/157 (86%)	46/53 (87%)	p=0.883*
Body surface area (mean ± SD)	1.91±0.29	2.04±0.29	p=0.007**
Body mass index (mean ± SD)	28.5±8.25	34.9±9.87	p<0.001**
History of cardiac disease	78/157 (50%)	21/53 (40%)	p=0.205*
History of asthma	23/157 (15%)	5/53 (9%)	p=0.334*
History of CKD	39/157 (25%)	7/53 (13%)	p=0.077*
Chronic steroid use	3/157 (2%)	2/53 (4%)	p=0.442*
LAMA	109/157 (69%)	22/53 (42%)	p<0.001*
SAMA	82/157 (52%)	24/53 (45%)	p=0.382*
SABA	132/157 (84%)	41/53 (77%)	p=0.267*
LABA	10/157 (6%)	1/53 (2%)	p=0.205*
SABA + SAMA	61/157 (39%)	23/53 (43%)	p=0.559*
LABA + ICS	112/157 (71%)	27/53 (51%)	p=0.007*
ICS	34/157 (22%)	13/53 (25%)	p=0.664*
Leukotriene receptor antagonist	7/157 (4%)	2/53 (4%)	p=0.831*
Macrolide	69/157 (44%)	24/53 (45%)	p=0.866*
Phosphodiesterase inhibitor	3/157 (2%)	0/53 (0%)	p=0.311*
Methylxanthines	8/157 (5%)	0/53 (0%)	p=0.094*
FVC % predicted (mean ± SD)	77.9±19.5	72.9±19.0	p=0.105**
FEV1 % predicted (mean ± SD)	52.3±18.4	71.0±17.9	p<0.001**
FEV1/FVC (mean ± SD)	51.4±12.8	76±4.9	p<0.001**
TLC % predicted (mean ± SD)a	105±19.3	76.4±18.7	p<0.001**
DLCO % predicted (mean ± SD)b	51.7±19.6	61.4±16.2	p=0.003**
MENT ≥0.5 K/µLc	72.9±19.0	72.9±19.0	p=0.357*
MEP (%)c	4.66±4.46	5.16±5.79	p=0.550**
MEN (K/µL)c	0.325±0.373	0.411±0.438	p=0.198**
≥1 respiratory hospitalization	56/157 (36%)	16/53 (30%)	p=0.467*
≥2 respiratory hospitalization	32/157 (20%)	8/53 (15%)	p=0.397*

Notes:

* χ² analysis;

** Student’s t-test analysis;

a n=25 in obstructed group and n=17 in nonobstructed group;

b n=126 in obstructed group and n=46 in nonobstructed group;

c n=143 in obstructed group and n=45 in nonobstructed group. Bold text indicates p<0.05.

Abbreviations: CKD, chronic kidney disease; DLCO, diffusing capacity of the lungs for carbon monoxide; FVC, forced vital capacity; FEV₁, forced expiratory volume in the first second; ICS, inhaled corticosteroid; LABA, long-acting beta-agonist; LAMA, long-acting muscarinic agent; MEN, maximum eosinophil number; MENT, maximum eosinophil number threshold; MEP, maximum eosinophil percentage; SABA, short-acting beta-agonist; SAMA, short-acting muscarinic agent; TLC, total lung capacity.

Table 2 GOLD⁸ classification and the rate of hospital admission for respiratory illness

GOLD classification of obstruction	Number of patients	At least one admission (number of patients)	At least one admission, % of group*	At least two admissions (number of patients)	At least two admissions, % of group*
None	53	15	28	8	15
Mild	14	4	29	2	7
Moderate	71	22	31	13	15
Severe	55	23	42	11	18
Very severe	17	7	41	6	24

Note:

* Differences among groups were not significant.

Abbreviation: GOLD, Global Initiative for Chronic Obstructive Lung Disease.

Table 3 Univariate association of nontreatment risk factors with at least two respiratory hospitalizations

Variable	Patients with ≥2 hospitalizations (n=40)	Patients with ≤1 hospitalization (n=170)	Level of significance (p<0.05)
Age in years (mean ± SD)	66±9.6	67±11	p=0.492**
Active smoking	23/40 (58%)	90/170 (53%)	p=0.603*
Male gender	23/40 (58%)	68/170 (40%)	p=0.044*
African American	36/40 (90%)	145/170 (85%)	p=0.438*
Body surface area (mean ± SD)	1.93±0.319	1.95±0.291	p=0.657**
Body mass index (mean ± SD)	29.6±11.1	30.2±8.60	p=0.714**
History of cardiac disease	23/40 (58%)	76/170 (45%)	p=0.145*
History of asthma	3/40 (8%)	25/170 (15%)	p=0.228*
History of CKD	9/40 (23%)	37/170 (22%)	p=0.919*
FVC % predicted (mean ± SD)	73.0±2.8	77.5±18.6	p=0.188**
FEV1 % predicted (mean ± SD)	50.8±9.7	58.5±19.8	p=0.028**
FEV1/FVC (mean ± SD)	55.3±17.0	58.1±15.3	p=0.290***
FEV1/FVC <70%	32/40 (80%)	125/170 (74%)	p=0.397*
TLC % predicted (mean ± SD)a	90.3±35.1	94.7±19.6	p=0.614**
DLCO % predicted (mean ± SD)b	51.7±23.9	54.9±17.9	p=0.385**
MENT ≥0.5 K/µLc	15/40 (38%)	22/148 (15%)	p=0.001*
MEP (%)c	6.30±6.182	4.37±4.281	p=0.024**
MEN (K/µL)c	0.477±0.539	0.310±0.334	p=0.020***

Notes:

* χ² analysis;

** Student’s t-test analysis;

*** Mann–Whitney U test;

a n=10 with ≥2 hospitalizations and n=32 with ≥1 hospitalization;

b n=33 with ≥2 hospitalizations and n=139 with ≥1 hospitalization;

c n=40 with ≥2 hospitalizations and n=148 with ≥1 hospitalization. Bold text indicates p<0.05.

Abbreviations: CKD, chronic kidney disease; DLCO, diffusing capacity of the lungs for carbon monoxide; FVC, forced vital capacity; FEV₁, forced expiratory volume in the first second; MEN, maximum eosinophil number; MENT, maximum eosinophil number threshold; MEP, maximum eosinophil percentage; TLC, total lung capacity.

Table 4 Univariate association of treatment risk factors with at least two respiratory hospitalizations

Variable	Patients with ≥2 hospitalizations	Patients with ≤1 hospitalization	Level of significance (p-value)
Chronic steroid use	1/40 (3%)	4/170 (2%)	0.956*
LAMA	32/40 (80%)	99/170 (58%)	0.011*
SAMA	37/40 (93%)	69/170 (41%)	<0.001*
SABA	35/40 (88%)	138/170 (81%)	0.345*
LABA	6/40 (15%)	5/170 (3%)	0.002*
SABA + SAMA	35/40 (88%)	49/170 (29%)	<0.001*
LABA + ICS	34/40 (85%)	105/170 (62%)	0.005*
ICS	16/40 (40%)	31/170 (18%)	0.003*
Leukotriene receptor antagonist	4/40 (10%)	5/170 (3%)	0.047*
Macrolide	28/40 (70%)	65/170 (38%)	<0.001*
Phosphodiesterase inhibitor	2/40 (5%)	1/170 (1%)	0.034*
Methylxanthines	2/40 (5%)	6/170 (4%)	0.662*

Notes:

* χ² analysis. Bold text indicates p<0.05.

Abbreviations: ICS, inhaled corticosteroid; LABA, long-acting beta-agonist; LAMA, long-acting muscarinic agent; SABA, short-acting beta-agonist; SAMA, short-acting muscarinic agent.

Table 5 Univariate association of nontreatment risk factors with at least one respiratory hospitalization in patients without obstruction by spirometry

Variable	Patients with ≥1 hospitalization (n=16)	Patients with no hospitalization (n=37)	Level of significance (p<0.05)
Age in years (mean ± SD)	65±12	63±11	p=0.503**
Active smoking	10/16 (63%)	18/37 (49%)	p=0.354*
Male gender	6/16 (38%)	9/37 (24%)	p=0.328*
African American	15/16 (94%)	31/37 (84%)	p=0.325*
Body surface area (mean ± SD)	2.01±0.338	2.05±0.274	p=0.639**
Body mass index (mean ± SD)	34.8±13.3	34.9±8.17	p=0.965**
History of cardiac disease	7/16 (44%)	17/37 (46%)	p=0.883*
History of asthma	1/16 (6%)	7/37 (19%)	p=0.237*
History of CKD	1/16 (6%)	8/37 (22%)	p=0.171*
FVC % predicted (mean ± SD)	65.7±21.6	76.0±17.2	p=0.069**
FEV1 % predicted (mean ± SD)	64.3±19.3	74.0±16.6	p=0.068**
FEV1/FVC (mean ± SD)	76.3±5.33	75.9±4.69	p=0.824***
TLC % predicted (mean ± SD)a	66.7±20.5	81.6±16.3	p=0.118**
DLCO % predicted (mean ± SD)b	61.9±16.5	61.2±16.3	p=0.889**
MENT ≥0.5 K/µLc	7/16 (44%)	4/29 (14%)	p=0.025*
MEP (%)c	5.94±4.155	4.72±6.546	p=0.507**
MEN (K/µL)c	0.532±0.4223	0.344±0.440	p=0.054**

Notes:

* χ² analysis;

** Student’s t-test analysis;

*** Mann–Whitney U test;

a n=6 with ≥1 hospitalization and n=11 with no hospitalization;

b n=12 with ≥1 hospitalization and n=34 with no hospitalization;

c n=16 with ≥1 hospitalization and n=29 with no hospitalization. Bold text indicates p<0.05.

Abbreviations: CKD, chronic kidney disease; DLCO, diffusing capacity of the lungs for carbon monoxide; FVC, forced vital capacity; FEV₁, forced expiratory volume in the first second; MEN, maximum eosinophil number; MENT, maximum eosinophil number threshold; MEP, maximum eosinophil percentage; TLC, total lung capacity.

Table 6 Univariate association of treatment risk factors with ≥1 respiratory hospitalization in patients without obstructive by spirometry

Variable	Patients with ≥1 hospitalization (n=16)	Patients with no hospitalization (n=37)	Level of significance (p<0.05)
Chronic steroid use	1/16 (6%)	1/37 (3%)	p=0.534*
LAMA	10/16 (63%)	12/37 (32%)	p=0.041*
SAMA	13/16 (81%)	11/37 (30%)	p<0.001*
SABA	13/16 (81%)	28/37 (76%)	p=0.656*
LABA	1/16 (6%)	1/37 (3%)	p=0.125*
SABA + SAMA	14/16 (88%)	9/37 (24%)	p<0.001*
LABA + ICS	12/16 (75%)	15/37 (41%)	p=0.021*
ICS	5/16 (31%)	8/37 (22%)	p=0.455*
Leukotriene receptor antagonist	1/16 (6%)	1/37 (3%)	p=0.534*
Macrolide	10/16 (63%)	14/37 (38%)	p=0.098*
Phosphodiesterase inhibitor	0/16 (0%)	0/37 (0%)	N/A
Methylxanthines	0/16 (0%)	0/37 (0%)	N/A

Notes:

* χ² analysis. Bold text indicates p<0.05.

Abbreviations: ICS, inhaled corticosteroid; LABA, long-acting beta-agonist; LAMA, long-acting muscarinic agent; SABA, short-acting beta-agonist; SAMA, short-acting muscarinic agent; N/A, no comparison.

Figure S1 Selection algorithm.

Abbreviations: COPD, chronic obstructive pulmonary disease; IM Clinic, Internal Medicine Clinic; PFT, pulmonary function test.

Table S1 ICD-9 codes with description used to determine COPD diagnosis within Internal Medicine Clinic

ICD-9	Description
491.2	Obstructive chronic bronchitis
492	Emphysema
496	Chronic airway obstruction, not elsewhere classified

Abbreviation: ICD-9, International Classification of Diseases, Ninth Revision.

Table S2 ICD-9 & DRG codes with description used to determine RH

ICD-9/DRG	Description
415.19	Other pulmonary embolism and infarction
465.9	Acute upper respiratory infection or unspecified site
466	Acute bronchitis
482.1	Pneumonia due to pseudomonas
482.9	Bacterial pneumonia, unspecified
486	Pneumonia, organism unspecified
487.1	Influenza with pneumonia
487	Influenza with other respiratory manifestations
491.21	Obstructive chronic bronchitis with acute exacerbation
492.8	Other emphysema
493.22	Chronic obstructive asthma with acute exacerbation
493.9	Asthma unspecified
493.92	Asthma, unspecified with acute exacerbation
494.1	Bronchiectasis with acute exacerbation
496	Chronic airway obstruction, not elsewhere classified
507	Pneumonitis due to inhalation of food or vomitus
511.89	Other specified forms of effusion, except tuberculosis
511.9	Unspecified pleural effusion
512	Pneumothorax
518.81	Acute respiratory failure
518.84	Acute and chronic respiratory failure
799.02	Hypoxemia
A31.0	Pulmonary mycobacterial infection
J18.9	Pneumonia, unspecified organism
J40	Bronchitis, not specified as acute or chronic
J44.1	COPD with (acute) exacerbation
J96.21	Acute and chronic respiratory failure with hypoxia
J96.22	Acute and chronic respiratory failure with hypercapnia
J98.01	Acute bronchospasm

Abbreviations: DRG, diagnosis-related group; ICD-9, the International Classification of Diseases, Ninth Revision; RH, respiratory hospitalization.

Global Strategy for the Diagnosis, Management and Prevention of COPD, Global Initiative for Chronic Obstructive Lung Disease (GOLD)2017 Available from: http://goldcopd.orgAccessed July 26, 2017

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