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Clinical Investigations: ASTHMA |

Patterns and Predictors of Asthma-Related Emergency Department Use in Harlem* FREE TO VIEW

Jean G. Ford, MD, FCCP; Ilan H. Meyer, PhD; Pamela Sternfels, ScM; Sally E. Findley, PhD; Diane E. McLean, PhD; Joanne K. Fagan, PhD; Lynne Richardson, MD
Author and Funding Information

*From the Harlem Lung Center, Harlem Lung Center and the Joseph L. Mailman School of Public Health at Columbia University, New York, NY.

Correspondence to: Jean G. Ford, MD, FCCP, Harlem Hospital Center, Harlem Lung Center, 506 Lenox Ave, MLK 12–106, New York, NY 10037; e-mail: jf24@columbia.edu



Chest. 2001;120(4):1129-1135. doi:10.1378/chest.120.4.1129
Text Size: A A A
Published online

Study objectives: To assess the roles of poor access to care, psychological risk factors, and asthma severity in frequent emergency department (ED) use.

Design: A cross-sectional survey.

Setting: Harlem Hospital Center ED and outpatient chest clinic.

Participants: Three hundred seventy-five adult residents of Harlem, a predominantly African-American community in New York City.

Measurements: Asthma severity was assessed by self-reported symptoms using National Asthma Education and Prevention Program guidelines, health-care utilization, and psychometric scales.

Results: Respondents with more severe asthma were more likely to have a primary asthma care provider, and to have had more scheduled office visits for asthma in the year prior to the interview (mean number of visits for patients with severe asthma, 3.6 visits; moderate asthma, 2.4 visits; and mild asthma, 1.7 visits). Despite having a regular source of care, 69% of respondents identified the ED as their preferred source of care; 82% visited the ED more than once in the year prior to interview (median, four visits). Persons with moderate or severe asthma were 3.8 times more likely to be frequent ED users compared to those with mild asthma (odds ratio [OR], 3.8; 95% confidence interval [CI], 2.2 to 6.6). This was the strongest predictor of frequent ED use. Other predictors of ED use were number of comorbid disorders (OR, 1.5; 95% CI, 1.1 to 2.1) and self-reported global health in the year prior to the ED visit (OR, 1.8; 95% CI, 1.2 to 2.7). Psychological characteristics were not predictive of frequent ED use when controlling for disease severity.

Conclusions: Frequent ED users present with serious medical conditions. They do not substitute physician care with ED care; they augment it to address serious health needs.

Figures in this Article

African Americans and Hispanics within urban centers have significantly higher rates of both asthma mortality and health-care utilization for asthma than whites.14 A 1996 study5 documented that in the United States, African Americans had a rate of asthma-related mortality that was 2.5 times higher than the national average, a rate of hospital admissions that was more than three times higher than the national average, and a rate of emergency department (ED) visits that was almost five times higher than the national average.

ED visits for asthma usually indicate a failure of available primary care, and most of these visits can be prevented.68 Through improvement of patient asthma management skills, provision of appropriate pharmacotherapy, and avoidance of known triggers of asthma exacerbations, there can be a reduction of symptoms and exacerbations and a return to normal or near-normal lung function.6 Frequent ED use for asthma also is associated with an elevated risk for near-fatal and fatal episodes.910 Nevertheless, ED visits remain the primary if not sole source of care for many low-income people with asthma in urban areas, and are a major source of asthma-related costs.1112

Understanding correlates of asthma-related ED visits is essential before proper interventions can be designed to reduce ED use for asthma. Poverty and lack of access to quality health care may be risk factors for ED visits among both children and adults.1318 However, in urban minority communities such as Harlem where poverty is a condition shared by many persons with asthma, it is not clearly understood what distinguishes the frequent users of the ED from those who use it little or not at all. A range of psychosocial factors may contribute to exacerbations ending in ED visits,6,1923 but little is known about the role of these factors in determining ED use in the context of poverty and poor access to health care. This article presents a study of asthma-related ED use at Harlem Hospital Center, conducted by the Harlem Lung Center. The study was designed to assess criteria used to classify asthma severity and to test the hypotheses that frequent ED use is associated with: (1) poor access to care, (2) psychological risk factors, and (3) asthma severity.

Sample

Adult residents of Central Harlem or West Harlem who visited the Harlem Hospital Center ED for asthma between March 1, 1997, and February 28, 1998, and spoke English were eligible to participate in the Reducing Emergency Asthma Care in Harlem (REACH) study, as approved by the Harlem Hospital Center institutional review board. During the REACH study period, 1,391 adults visited the ED for asthma, 254 patients (18%) could not be screened for eligibility, 411 patients (30%) were ineligible, and 726 patients (52%) were eligible. Eligible respondents were asked to participate in an asthma study at an outpatient chest clinic. Of those eligible, 375 patients (52%) consented to participate and came for their scheduled interview approximately 3 weeks (median, 24 days) following the ED visit. At that time, a structured comprehensive asthma questionnaire was administered in a face-to-face interview lasting approximately 1.5 h. Eligible interviewed respondents did not differ significantly from those not interviewed in age, gender, race, and level of education, but more of those who were interviewed (25%) than those who were not (15%) lacked medical insurance (χ2 = 3.57; p = 0.06).

Measures Collected With the Comprehensive Asthma Questionnaire
Demographic Characteristics:

These were classified based on self-report by respondents. Per capita income was calculated by dividing reported household income by the reported number of household members.

Asthma Severity:

This was determined using the National Asthma Education and Prevention Program (NAEPP) 1997 guidelines. We classified respondents either as mild intermittent/mild persistent or moderate/severe based on self-reported frequencies of daytime symptoms, exacerbation episodes, and sleep disturbances due to asthma symptoms (referred to as “nighttime symptoms”). We also classified respondents by combining all of these categories, classifying the respondent in the most severe category for which he or she qualified. We used classification by nighttime symptoms in analyses of the associations of severity with other variables.

Health-Care Utilization:

This included the number of ED and scheduled office visits in the previous year, any history of admission to a hospital overnight for asthma and to an ICU, and any history of endotracheal intubation. We defined frequent ED use as two or more visits for asthma in the year prior to the interview.

Psychological Measures:

These were measured using standard psychometric questions. Depressive symptoms were assessed using five items from the Center for Epidemiologic Studies depression scale.24 The health locus-of-control scale was used to measure three orientations to control of one’s health: internal, chance, or powerful others.20 Self-esteem was measured using Rosenberg’s scale.25

Asthma Knowledge:

This was measured using an 11-item scale developed as part of the REACH study26; the score of the scale indicates percentage of correct responses, ranging from 0 to 100%.

Measures Collected During the ED Visit by Medical Staff
Medical History:

This was recorded during the ED visit based on self-report to the admitting nurse. It is a count of up to nine prior conditions: hypertension, diabetes, alcohol abuse, drug abuse, depression, heart disease, lung disease, pneumonia, and kidney diseases.

Global Health:

This was recorded from an adopted version of the global health question from the 36-item Short Form.27 Respondents were asked whether their health before getting sick had been excellent, very good, fair, or poor.

Statistical Analysis

We used Pearson’s correlation to assess associations between continuous variables, t tests to assess differences in continuous variables between groups, and χ2 tests to assess associations between categorical variables. We used logistic regression to assess the simultaneous effect of the risk factors on predicting ED use. All analyses were conducted using software (SPSS version 6.1.3; SPSS; Chicago, IL).

Characteristics of ED Users

The study group (n = 375) was a predominantly low-income and minority population. The mean age of the 375 respondents was 40 years (SD, 14 years). Sixty-four percent of participants were female, 93% were black or African American, 9% (of the total) were Latino, and 14% were of Caribbean descent (these categories were asked separately from race). Fifty-nine percent had ≥ 12 years of education. Only 24% of the respondents worked full-time or part-time, and 47% had an annual household income of $9,000 or less. Forty-six percent were current smokers, 15% were past smokers, and 39% never smoked. Twenty-eight percent were classified with comorbid bronchitis, defined as cough and phlegm most days for ≥ 3 months that has lasted at least 2 years.

Asthma Classification:

Venn diagrams depict the overlap among NAEPP severity classifications for mild intermittent and mild persistent asthma (Fig 1 ) and moderate and severe persistent asthma (Fig 2 ). For mild intermittent and mild persistent asthma, classification by the three criteria (daytime symptoms, nighttime symptoms, and exacerbations) converged for only 25% of the patients, and classification by two of the three criteria converged for 36% of the patients. For moderate and severe persistent asthma, agreement among criteria was somewhat better: all three criteria converged for 38% and two criteria converged for 32% of the patients.

Correlates of Asthma Severity:

Table 1 shows correlates of asthma severity. Severity was unrelated to gender, age, or employment status. Lower levels of education were related to moderate and severe persistent asthma. Current smokers and respondents with bronchitis were more likely to have moderate and severe persistent asthma. Severity was unrelated to access to health insurance. Regardless of severity, most respondents said they “relied primarily” on the ED for their asthma care. Respondents with more severe disease were more likely to have a health-care provider whom they identified as a primary asthma care provider, and to have had more scheduled office visits for asthma in the year prior to the interview (mean number of visits among patients with severe asthma, 3.6 visits; moderate asthma, 2.4 visits; and mild asthma, 1.7 visits). Respondents with severe disease were also more likely to have been hospitalized for asthma in the year prior to the interview.

Patterns and Predictors of ED Use

In the 12 months prior to their interview, 304 patients (82%) visited the ED for asthma two or more times and 68 patients (18%) visited the ED once. People with more than one visit had a mean of 8.5 visits (SD, 14.7) and a median of 4.0 visits. There were no significant differences between one-time and frequent ED users in age, gender, ethnicity, education, employment status, or annual household income (Table 2 ).

Disease Severity:

Disease severity as measured by any of the criteria was related to frequent ED use. Persons with moderate or severe persistent asthma were 3.8 times more likely to be frequent ED users compared to those with mild asthma (odds ratio [OR], 3.8; 95% confidence interval [CI], 2.2 to 6.6). Frequent ED users were also more likely to report more health problems in addition to asthma (OR, 1.5; 95% CI, 1.1 to 2.1), and to be in poorer general health in the year prior to the ED visit (OR, 1.8; 95% CI, 1.2 to 2.7).

Utilization of Health Care:

One-time ED users were as likely as frequent ED users to say that they rely on the ED for their asthma care (70% vs 69%, not significant). They also did not differ in access to health insurance; 31% of one-time users vs 23% of frequent users had no insurance coverage (OR, 0.7; 95% CI, 0.4 to 1.2). However, a history of hospitalization for asthma, ICU use, or intubation were all significantly associated with frequent ED use (OR, 2.5; 95% CI, 1.2 to 5.5; OR, 10.0; 95% CI, 1.3 to 72.7; and OR, 4.4; 95% CI, 1.3 to 14.6, respectively).

People who visited a doctor’s office for asthma and those who reported having an asthma care provider were significantly more likely than people who did not to be frequent ED users (OR, 2.2; 95% CI, 1.3 to 3.8; and OR, 1.8; 95% CI, 1.1 to 3.1, respectively). Because visiting a doctor’s office for asthma and having an asthma care provider may be indicators of severity, we repeated this using regression analysis controlling for asthma severity. In that analysis, having visited a doctor’s office for asthma remained a significant predictor of frequent ED use (OR, 1.8; 95% CI, 1.1 to 3.4), but having an asthma care provider did not (OR, 1.6; 95% CI, 0.9 to 2.9).

Psychological Characteristics:

There is some evidence of a relationship between mental health status and frequent ED use. People with a higher level of depressive symptoms and those who do not perceive themselves to be in charge of their health (low internal locus of control) were more likely to be frequent ED users (OR, 1.5; 95% CI, 1.0 to 2.2; and OR, 1.1; 95% CI, 1.0 to 1.1, respectively). But neither external control orientation (powerful others or chance health locus of control) nor the respondents’ level of self-esteem was associated with frequency of ED use. None of these psychological characteristics remained significant when the analyses were repeated using regression analysis controlling for asthma severity. In addition, there was no association between the respondent’s level of asthma knowledge and ED use.

Reliance on the ED as the preferred source of care in urban, low-income, and medically underserved communities remains a vexing problem.8,13,27 We analyzed factors associated with frequent ED use for asthma in Harlem, a predominantly African American community in New York City. We found that most study participants utilized the ED as their preferred source of asthma care. While this finding is consistent with previous findings in similar populations, the question remains whether frequent ED use is related to psychosocial or economic factors, or to more severe disease, and to more asthma exacerbations that require ED interventions. We were able to clarify the association by showing the importance of disease severity as a predictor of frequent ED use. We found that psychological characteristics that have been reported to increase ED visits, such as depressive symptoms, health locus-of-control, and level of knowledge about asthma, were not predictive of frequent ED use after we controlled for disease severity. However, indicators of severity, including a history of hospitalization, ICU admission, or endotracheal intubation for asthma, were each associated with frequent ED use. These findings are consistent with other studies8,28 that identified disease severity as a strong predictor of repeated ED use, even in areas such as Ontario, Canada, where universal free health coverage is the standard.14 This suggests that frequent ED users represent a group of patients with more severe, poorly managed asthma.8 Similarly, Farber et al13 found that young children visiting the ED had poorly managed and poorly controlled chronic asthma.

Current guidelines6 recommend that patients contact their providers when home management of an evolving exacerbation is unsuccessful. If the patient has access to a medical care provider at a time of crisis and with the administration of appropriate therapy, most asthma exacerbations should not result in an ED visit. But approximately 70% of our respondents, regardless of disease severity, access to a primary asthma care provider, or health insurance status, relied on the ED as the main source of care. This raises a question whether provider assistance in crisis management is functionally inaccessible for most patients, or whether patients simply prefer to utilize the ED during an exacerbation. In our community, having visited a physician’s office for asthma and having an asthma care provider were related to increased frequency of ED use. A plausible explanation is that a visit to a physician’s office for asthma and having an asthma care provider may be themselves indicators of severity.27 When controlled for disease severity, however, the association between a visit to a physician for asthma (but not to specialty care) remained a significant predictor of frequent ED use. Only specialty care for asthma was protective against frequent ED visits. General medical care alone, even when available, did not prevent repeated ED visits.14

We also found that compared with the one-time users, frequent ED users were more likely to report general health problems in addition to asthma, as indicated by the number of disorders reported in the medical history obtained at the ED and self-reported global health in the year prior to the ED visit. That comorbid conditions are more common among frequent ED users indicates the need for an integrated approach to disease management in this population. Focusing on asthma management alone is insufficient for Harlem and similar communities.

As part of our analysis, we examined application of NAEPP guidelines for asthma classification. Our findings underscore the difficulty of attempting to classify asthma severity based only on a reported history of symptoms. We found that the classifications were not reliable, namely that the classifications resulting from only daytime or only nighttime symptoms usually did not agree. The classification problem is greatest for the persons with mild intermittent and mild persistent asthma, but even for those with moderate or severe asthma, the classifications agreed for only one of three respondents. This finding is consistent with the observations of the NAEPP and demonstrates that classification of asthma severity based on symptoms alone is varied and fluid.

Our study is restricted by the cross-sectional design, which limits our conclusions to correlational observations rather than identification of causal processes. Our study design has the advantage of allowing us to examine a geographically and socioeconomically homogeneous group, thus controlling for some effects of poverty that may mask other differences among frequent ED users. At the same time, because our sample is homogenous, we are limited in describing larger socioeconomic effects or in making generalizations. Our results are also limited in that close to half of those eligible to participate in the study did not participate. Although the interviewed respondents did not differ significantly in most demographic characteristics from those who were not interviewed, we do not know whether their disease was in fact more severe. This may bias our descriptive statistics, but would not affect our conclusions regarding differences between frequent and one-time ED users.

Nevertheless, from our results, a picture emerges of patients with serious medical conditions indicated by comorbid disease and more severe asthma, who do not substitute physician care with ED care, but for whom ED use supplements regular care.8 These results suggest that to be effective, interventions aimed at reducing ED use must address the emergency and urgent care issues facing patients with greater asthma morbidity and comorbid conditions.

Abbreviations: CI = confidence interval; ED = emergency department; NAEPP = National Asthma Education and Prevention Program; OR = odds ratio; REACH = Reducing Emergency Asthma Care in Harlem

This research was supported by National Heart, Lung, and Blood Institute grant No. RO1 HL 51492.

Figure Jump LinkFigure 1. Mild asthma. Classification of asthma severity by varying symptom criteria (n = 248).Grahic Jump Location
Figure Jump LinkFigure 2. Moderate and severe asthma. Classification of asthma severity by varying symptom criteria (n = 295).Grahic Jump Location
Table Graphic Jump Location
Table 1. Correlates of Asthma Severity: Demographic Characteristics and Health-Care Utilization*
* 

Classified according to sleep-awakening symptoms in the NAEPP 1997 guidelines.

 

ORs are for moderate/severe as compared with mild asthma.

Table Graphic Jump Location
Table 2. Correlates of Frequent ED Use: Severity, Demographic Characteristics, Health-Care Utilization, and Psychological Characteristics
* 

Classified according to sleep-awakening symptoms in the NAEPP 1997 guidelines.

Mannino, DM, Homa, DM, Pertowski, CA, et al (1998) Surveillance for asthma—United States, 1960–1995.MMWR Morb Mortal Wkly Rep47(SS-1),1-28
 
Carr, W, Zeitel, L, Weiss, K Variations in asthma hospitalizations and deaths in New York City.Am J Public Health1992;82,59-65. [PubMed] [CrossRef]
 
De Palo, VA, Mayo, PH, Friedman, P, et al Demographic influences on asthma hospital admission rates in New York City.Chest1994;106,447-451. [PubMed]
 
Claudio, L, Tulton, L, Doucette, J, et al Socioeconomic factors and asthma hospitalization rates in New York City.J Asthma1999;36,343-350. [PubMed]
 
Burt, CW, Knapp, DE Ambulatory care visits for asthma: United States, 1993–94.Adv Data1996;277,1-19. [PubMed]
 
National Asthma Education and Prevention Program. Expert panel report 2: guidelines for the diagnosis and management of asthma. Bethesda, MD: National Institutes of Health, April 1997; publication No. 97–4051.
 
National Heart, Lung, and Blood Institute. Global initiative for asthma: global strategy for asthma management and prevention NHLBI/WHO workshop report. Bethesda, MD: National Institutes of Health, 1995; publication No. 95–3659.
 
Dales, RE, Schweitzer, I, Kerr, P, et al Risk factors for recurrent emergency visits for asthma.Thorax1995;50,520-524. [PubMed]
 
Turner, MO, Noertjojo, K, Vedal, S, et al Risk factors for near-fatal asthma.Am J Respir Crit Care Med1998;157,1804-1809. [PubMed]
 
Strunk, RC, Nicklas, RA, Milgrom, H, et al Risk factors for fatal asthma. Sheffer, AL eds.Fatal asthma1998,31-41 Marcel Dekker. New York, NY:
 
Weiss, KB, Gergen, PJ, Crain, EF Inner-city asthma: the epidemiology of an emerging US public health concern.Chest1992;101(suppl),362-367
 
Sullivan, S, Elixhauser, A, Buist, AS, et al National Asthma Education and Prevention Program working group report on the cost effectiveness of asthma care.Am J Respir Crit Care Med1996;154(3 pt 2),S84-S95
 
Farber, HJ, Johnson, C, Beckerman, RC Young inner-city children visiting the emergency room (ER) for asthma: risk factors and chronic care behaviors.J Asthma1998;35,547-552. [PubMed]
 
Brown, EM, Goel, V Factors related to emergency department use: results from the Ontario health survey 1990.Ann Emerg Med1994;24,1083-1091. [PubMed]
 
Miller, JE The effects of race/ethnicity and income on early childhood asthma prevalence and health care use.Am J Public Health2000;90,428-430. [PubMed]
 
Targonski, PV, Persky, VW, Orris, P, et al Trends in asthma mortality among African Americans and whites in Chicago, 1968 through 1991.Am J Public Health1994;84,1830-1833. [PubMed]
 
Wissow, LS, Gittelsohn, AM, Szklo, M, et al Poverty, race, and hospitalization for childhood asthma.Am J Public Health1988;78,777-782. [PubMed]
 
Lang, DM, Polansky, M Patterns of asthma mortality in Philadelphia from 1969 to 1991.N Engl J Med1994;331,1542-1546. [PubMed]
 
Campbell, DA, Yellowlees, PM, McLennan, G, et al Psychiatric and medical features of near fatal asthma.Thorax1995;50,254-259. [PubMed]
 
Wallston, KA, Wallston, BS Who is responsible for your health? The construct of health locus of control. Sanders, GS Suls, J eds.Social psychology of health and illness1982,65-95 Lawrence Erlbaum Associates. Hillsdale, NJ:
 
Creer, T, Bender, B Asthma. Gatchel, R Blanchard, E eds.Psycho-physiological disorders research and clinical applications1994,151-203 American Psychological Association. Washington, DC:
 
Nouwen, A, Freeston, MH, Labbe, R, et al Psychological factors associated with emergency room visits among asthmatic patients.Behav Modif1999;23,217-233. [PubMed]
 
Vamos, M, Kolbe, J Psychological factors in severe chronic asthma.Aust N Z J Psychiatry1999;33,538-544. [PubMed]
 
Radloff, LS The CES-D scale: a self-report depression scale for research in the general population.Appl Psychol Measurement1977;1,385-401
 
Rosenberg, M. Society and the adolescent self-image. 1965; Princeton University Press. Princeton, NJ:.
 
Meyer, IH, Sternfels, P, Fagan, JK, et al Characteristics and correlates of asthma knowledge among emergency department users in Harlem.J Asthma2001;38,531-539. [PubMed]
 
Stewart, AL, Hays, RD, Ware, JE, Jr The MOS short-form general health survey: reliability and validity in a patient populationMed Care1988;26,724-735. [PubMed]
 
Wakefield, M, Staugas, R, Ruffin, R, et al Risk factors for repeat attendance at hospital emergency departments among adults and children with asthma.Aust N Z J Med1997;27,277-284. [PubMed]
 

Figures

Figure Jump LinkFigure 1. Mild asthma. Classification of asthma severity by varying symptom criteria (n = 248).Grahic Jump Location
Figure Jump LinkFigure 2. Moderate and severe asthma. Classification of asthma severity by varying symptom criteria (n = 295).Grahic Jump Location

Tables

Table Graphic Jump Location
Table 1. Correlates of Asthma Severity: Demographic Characteristics and Health-Care Utilization*
* 

Classified according to sleep-awakening symptoms in the NAEPP 1997 guidelines.

 

ORs are for moderate/severe as compared with mild asthma.

Table Graphic Jump Location
Table 2. Correlates of Frequent ED Use: Severity, Demographic Characteristics, Health-Care Utilization, and Psychological Characteristics
* 

Classified according to sleep-awakening symptoms in the NAEPP 1997 guidelines.

References

Mannino, DM, Homa, DM, Pertowski, CA, et al (1998) Surveillance for asthma—United States, 1960–1995.MMWR Morb Mortal Wkly Rep47(SS-1),1-28
 
Carr, W, Zeitel, L, Weiss, K Variations in asthma hospitalizations and deaths in New York City.Am J Public Health1992;82,59-65. [PubMed] [CrossRef]
 
De Palo, VA, Mayo, PH, Friedman, P, et al Demographic influences on asthma hospital admission rates in New York City.Chest1994;106,447-451. [PubMed]
 
Claudio, L, Tulton, L, Doucette, J, et al Socioeconomic factors and asthma hospitalization rates in New York City.J Asthma1999;36,343-350. [PubMed]
 
Burt, CW, Knapp, DE Ambulatory care visits for asthma: United States, 1993–94.Adv Data1996;277,1-19. [PubMed]
 
National Asthma Education and Prevention Program. Expert panel report 2: guidelines for the diagnosis and management of asthma. Bethesda, MD: National Institutes of Health, April 1997; publication No. 97–4051.
 
National Heart, Lung, and Blood Institute. Global initiative for asthma: global strategy for asthma management and prevention NHLBI/WHO workshop report. Bethesda, MD: National Institutes of Health, 1995; publication No. 95–3659.
 
Dales, RE, Schweitzer, I, Kerr, P, et al Risk factors for recurrent emergency visits for asthma.Thorax1995;50,520-524. [PubMed]
 
Turner, MO, Noertjojo, K, Vedal, S, et al Risk factors for near-fatal asthma.Am J Respir Crit Care Med1998;157,1804-1809. [PubMed]
 
Strunk, RC, Nicklas, RA, Milgrom, H, et al Risk factors for fatal asthma. Sheffer, AL eds.Fatal asthma1998,31-41 Marcel Dekker. New York, NY:
 
Weiss, KB, Gergen, PJ, Crain, EF Inner-city asthma: the epidemiology of an emerging US public health concern.Chest1992;101(suppl),362-367
 
Sullivan, S, Elixhauser, A, Buist, AS, et al National Asthma Education and Prevention Program working group report on the cost effectiveness of asthma care.Am J Respir Crit Care Med1996;154(3 pt 2),S84-S95
 
Farber, HJ, Johnson, C, Beckerman, RC Young inner-city children visiting the emergency room (ER) for asthma: risk factors and chronic care behaviors.J Asthma1998;35,547-552. [PubMed]
 
Brown, EM, Goel, V Factors related to emergency department use: results from the Ontario health survey 1990.Ann Emerg Med1994;24,1083-1091. [PubMed]
 
Miller, JE The effects of race/ethnicity and income on early childhood asthma prevalence and health care use.Am J Public Health2000;90,428-430. [PubMed]
 
Targonski, PV, Persky, VW, Orris, P, et al Trends in asthma mortality among African Americans and whites in Chicago, 1968 through 1991.Am J Public Health1994;84,1830-1833. [PubMed]
 
Wissow, LS, Gittelsohn, AM, Szklo, M, et al Poverty, race, and hospitalization for childhood asthma.Am J Public Health1988;78,777-782. [PubMed]
 
Lang, DM, Polansky, M Patterns of asthma mortality in Philadelphia from 1969 to 1991.N Engl J Med1994;331,1542-1546. [PubMed]
 
Campbell, DA, Yellowlees, PM, McLennan, G, et al Psychiatric and medical features of near fatal asthma.Thorax1995;50,254-259. [PubMed]
 
Wallston, KA, Wallston, BS Who is responsible for your health? The construct of health locus of control. Sanders, GS Suls, J eds.Social psychology of health and illness1982,65-95 Lawrence Erlbaum Associates. Hillsdale, NJ:
 
Creer, T, Bender, B Asthma. Gatchel, R Blanchard, E eds.Psycho-physiological disorders research and clinical applications1994,151-203 American Psychological Association. Washington, DC:
 
Nouwen, A, Freeston, MH, Labbe, R, et al Psychological factors associated with emergency room visits among asthmatic patients.Behav Modif1999;23,217-233. [PubMed]
 
Vamos, M, Kolbe, J Psychological factors in severe chronic asthma.Aust N Z J Psychiatry1999;33,538-544. [PubMed]
 
Radloff, LS The CES-D scale: a self-report depression scale for research in the general population.Appl Psychol Measurement1977;1,385-401
 
Rosenberg, M. Society and the adolescent self-image. 1965; Princeton University Press. Princeton, NJ:.
 
Meyer, IH, Sternfels, P, Fagan, JK, et al Characteristics and correlates of asthma knowledge among emergency department users in Harlem.J Asthma2001;38,531-539. [PubMed]
 
Stewart, AL, Hays, RD, Ware, JE, Jr The MOS short-form general health survey: reliability and validity in a patient populationMed Care1988;26,724-735. [PubMed]
 
Wakefield, M, Staugas, R, Ruffin, R, et al Risk factors for repeat attendance at hospital emergency departments among adults and children with asthma.Aust N Z J Med1997;27,277-284. [PubMed]
 
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