PEDIATRICS Vol. 120 No. 5 November 2007, pp. e1174-e1181 (doi:10.1542/peds.2007-0206)
ARTICLE |
Does Current Asthma Control Predict Future Health Care Use Among Black Preschool-aged Inner-City Children?
a Division of Pediatric Allergy and Immunology, Department of Pediatrics, and Division of Pulmonary and Critical Care Medicine
b Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
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ABSTRACT |
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OBJECTIVES. Factors predictive of future asthma must be identified among young inner-city children, who suffer disproportionately from asthma. We investigated whether current asthma control predicts future asthma-related health care use among inner-city preschool-aged children with asthma.
METHODS. A total of 150 inner-city preschool-aged children with asthma were followed prospectively for 6 months. At baseline, symptom frequency and reliever-medication use were assessed to classify children into National Asthma Education and Prevention Program–derived control categories. Long-term controller-medication use was also assessed, as well as asthma-related health care use at baseline and at 3 and 6 months.
RESULTS. The mean age was 4.4 years, 92% were black, and 39% reported long-term controller use. At baseline, 37% were classified as having mild-intermittent, 17% had mild-persistent, 21% had moderate-persistent, and 25% had severe-persistent asthma control. Significant changes in asthma control were observed over time, including 46% of children originally categorized with mild-intermittent asthma who had worsened asthma control by 3 months. Asthma control significantly predicted future health care use 3 months later but not 6 months later. Multivariate analyses showed that, once control status was known, reported use of long-term controller medication added little additional predictive value.
CONCLUSIONS. Among inner-city preschool-aged children, significant fluctuations in asthma control occur as early as 3 months after assessment. Poor control but not long-term controller-medication use is an independent predictor of future asthma-related health care use at 3 months but is not significantly predictive of 6-month outcomes. Therefore, clinicians caring for inner-city children with asthma should consider reassessing asthma control at least every 3 months to identify those at highest future risk and to provide early interventions.
Key Words: asthma • severity • control • health care use • prediction • risk • children • inner city
Abbreviations: HCU—health care use • GINA—Global Initiative for Asthma • NAEPP—National Asthma Education and Prevention Program • LTC—long-term controller • UD—unscheduled doctor • ED—emergency department • OR—odds ratio
In the United States, asthma is the most common chronic illness of childhood, causing significant levels of preventable morbidity, particularly among inner-city black populations.1 The toll of pediatric asthma is especially reflected in the high rates of asthma-related health care use (HCU) in this high-risk population. One key component of successful prevention of asthma-related HCU is the ability to accurately identify those children at greatest risk of future morbidity. Thereby, children at high-risk may be targeted, and treatment and follow-up plans can be tailored specifically to lower their future risk. However, not enough is known about which clinical factors predict the risk of future asthma-related HCU among children. For example, previous asthma-related HCU is a well-recognized predictor of future HCU among various populations, including children,2–6 but there are undoubtedly other important predictors to be identified, especially in the high-risk black pediatric population.
There is growing interest in the use of asthma control assessment as a predictor of future morbidity.7–11 Asthma control describes the degree to which current disease activity is minimized by treatment. Severity, meanwhile, refers to a patient's inherent disease state, as reflected by the degree of symptoms before starting treatment. Several limitations to the concept of asthma severity exist, including the incomplete ability to describe the dynamic nature of asthma, the unclear value of the baseline assessment after treatment has begun, and lack of consideration of both frequency and intensity of asthma exacerbations.7 Classification by level of control, rather than severity, is, therefore, recommended in the most recent version of the Global Initiative for Asthma (GINA) guidelines.12 Although the development of validated measures of asthma control has progressed well in adults, such validated measures of control for young children are still anticipated. Asthma status among children is most often assessed by the National Asthma Education and Prevention Program (NAEPP) guidelines, which recommend evaluation of symptoms, bronchodilator use, and lung function to determine appropriate therapy.13 In practice, the severity ratings outlined in the NAEPP guidelines are often interpreted as evidence of current control. There is already evidence that classification by the NAEPP guidelines predicts current and future asthma morbidity in adults,14 but studies among children have only been cross-sectional and have not evaluated current control as a predictor of long-term future morbidity.15
Other asthma guidelines have encouraged consideration not only of current asthma symptoms, but also long-term controller (LTC) medication use.16 In these classification schemes, a patient with rare symptoms on high-dose inhaled corticosteroids is considered to have worse asthma than one with the same symptom frequency on low-dose inhaled corticosteroids. The importance of LTC use as an independent predictor of future asthma morbidity is unknown. In addition, it is unclear whether the additional consideration of LTC use in other guidelines enhances our predictive ability beyond symptom status alone.
The need to identify factors predictive of future asthma risk is especially urgent among inner-city black children, because these children suffer disproportionate asthma morbidity, and disparities have widened over the latter half of the 1990s.17 Therefore, the purpose of this study was to determine which clinical indicators predict future asthma-related HCU in a population of inner-city preschool-aged children with asthma.
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METHODS |
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Study Population and Recruitment Procedures
Recruitment for this study, a part of the Center for Childhood Asthma in the Urban Environment, occurred between September 2001 and December 2003. Participants were recruited from the health systems that provide care to the majority of residents of east Baltimore. Inclusion criteria were (1) age between 2 and 6 years, (2) residence within the catchment area defined by 9 contiguous zip codes, (3) doctor-diagnosed asthma, and (4) symptoms of asthma and/or medication use for asthma in the previous 6 months.
During a screening visit, informed consent was obtained, and an extensive survey was conducted, followed 2 weeks later by administration of the clinical status questionnaire. Participants had 2 additional visits at 3 and 6 months for repeat assessments of asthma status and outcomes. The study was approved by the Johns Hopkins School of Medicine Institutional Review Board.
Clinical Status Questionnaire
During the baseline visit, a questionnaire was administered by trained study personnel to the primary caregiver to assess demographic characteristics, asthma-related HCU in the previous 3 months (unscheduled doctor [UD] visits, emergency department [ED] visits, and hospitalization), LTC use (within the previous 2 weeks), rescue medication use (within the previous 2 weeks), and recent symptoms (within the previous 2 weeks). Use of the following LTC medications was assessed: inhaled corticosteroids, cromolyn and nedocromil, oral leukotriene modifiers, long-acting β-agonists, and oral theophylline. HCU outcomes and LTC-medication use were analyzed as dichotomous variables. Ten close-ended questions assessed frequency of daytime and nighttime symptoms, short-acting β-agonist use, and activity limitation during the previous 2 weeks. Ordered responses to these questions, ranging from 0 to 14 (number of days in the last 2 weeks), were fit to the NAEPP scheme as closely as possible to assign participants to a given asthma control category.18 For example, criteria for mild-intermittent control included wheezing, coughing, or chest tightness 
2 days per week; mild-persistent control included >2 days per week but less than daily; and moderate-persistent control included daily. These symptoms represented control, rather than severity, because they reflected recent disease activity, irrespective of treatment. The follow-up questionnaires administered at 3 and 6 months assessed interval asthma-related health care use (previous 3-month period) and recent symptoms (within the previous 2 weeks).
Statistical Analysis
The relationships between asthma control at the baseline visit and recent asthma-related HCU were analyzed. In addition, relationships between asthma control at the baseline visit and future HCU, assessed at the 3- and 6-month visits, were analyzed. The 
2 test was used to compare proportions between groups, and logistic regression was used to generate odds ratios (ORs). The independent variables of interest were asthma control classification and LTC-medication use. Multivariate logistic regression was used to analyze the relationships between the independent variables and the 3 outcomes of interest: UD visit, ED visit, and hospitalization. In logistic regression models, asthma control was treated as a 4-category ordinal variable. Age, gender, and caregiver educational attainment were not found to be significant confounders and were, therefore, not included in the final models. All of the analyses were performed with Stata SE 8.0 (Stata Corp, College Station, TX). Statistical significance was defined as a P value of <.05.
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RESULTS |
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Baseline Study Population
The baseline cohort of 150 children had more boys (57%) than girls, was predominantly black (92%), and had caregivers mostly with highest educational attainment of high school or less (80%; Table 1). The mean age of the participants was 4.4 years. All 4 of the asthma control categories were well represented at baseline. Although 62% of the children met criteria for persistent asthma, only 39% reported using a LTC medication at baseline. Even among the subjects with severe persistent asthma, only 56% reported LTC-medication use. Of those reporting use of an LTC medication, 86% were taking inhaled corticosteroids, and the remaining 14% were taking oral leukotrienes or cromolyn/nedocromil. Recent outpatient asthma-related HCU was more common (UD visit: 18%; ED visit: 24%) than inpatient HCU (hospitalization 3%).
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Variability in Asthma Control Over Time
Asthma control varied markedly over time (Fig 1). Nearly half (46%) of children originally categorized with mild-intermittent asthma at baseline had worsening in their degree of asthma control by 3 months, which would have required intensification of treatment according to guideline recommendations. Similarly, of those with mild-persistent asthma at baseline (Fig 1B), one third had worse asthma control by 3 months. Changes in the level of control between baseline and 3 months were also observed in more than half of those with moderate-persistent asthma (Fig 1C) and approximately half of those with severe persistent asthma (Fig 1D).
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Even greater shifts were observed between baseline and 6 months among children with persistent symptoms at baseline. More than two thirds of children with persistent asthma experienced a change in their degree of asthma control by 6 months.
Relationship of Current Asthma Control to Recent Asthma-Related HCU
There was a strong, significant association between poor asthma control and recent HCU, suggesting that asthma control is related to overall recent disease activity. For example, the proportion of children with an asthma-related UD visit in the preceding 3 months increased significantly with worse control (mild-intermittent: 5%; mild-persistent: 8%; moderate-persistent: 23%; severe-persistent: 42%; P < .01 by Cuzick's test for trend; Fig 2A) Similar trends were observed for asthma-related ER visits in the previous 3 months (P < .01) and asthma-related hospitalization, although the latter relationship was not statistically significant (P = .07). In logistic regression models, there was approximately a twofold average increase in the odds of recent asthma-related HCU for each increment of worsening asthma control (Table 2).
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Relationship of Current Asthma Control to Future Asthma-Related HCU
In addition to being associated with recent HCU, baseline asthma control also strongly predicted future asthma-related HCU at 3 months. (Fig 2B) Poorer baseline asthma control was significantly associated with an increasing likelihood of an interval 3-month UD visit (P < .01) or ED visit (P = .02). Similar trends were seen for 3-month hospitalization, although the relationship was not significant (P = .07). Despite being a good predictor at 3 months, asthma control did not predict future asthma-related HCU at 6 months, as shown: UD visit (P = .35), ED visit (P = .09), and hospitalization (P = .33; Fig 2C).
Because baseline control status was a good predictor of future asthma-related HCU during the subsequent 3 months but less so beyond this 3-month interval, additional analyses examined relationships between asthma control status at 3 months and HCU at 6 months. A key additional observation was that the poorer the asthma control at the 3-month visit, the greater the odds of asthma-related HCU at the 6-month visit. For example, there was a 1.7-fold increase in the odds of an ED visit at 6 months for each worse category of asthma control status when assessed at 3 months (OR: 1.7; 95% CI: 1.1–2.8), supporting the notion that control status predicts future HCU up to 3 months after assessment.
Relationship of LTC-Medication Use to Recent and Future HCU
Not surprisingly, baseline LTC-medication use was significantly associated with an approximately threefold average increase in the odds of recent HCU, specifically UD and ED visits (Table 2). However, baseline LTC use was a significant predictor of only 1 future outcome, UD visit at 3 months (OR: 5.5; 95% CI: 2.0–15.5).
Multivariate Model of Asthma Control Status and Reported LTC-Medication Use
After adjusting for baseline asthma control status, LTC-medication use had little additional predictive value for future HCU (Table 2). LTC use was only an independent predictor of UD visit at 3 months (OR: 4.0; 95% CI: 1.4–11.9). On the other hand, adjustment for LTC status had little impact on the associations between control status and future HCU. Independent of LTC use, baseline control predicted future HCU at 3 months. For example, relative to those with mild-intermittent baseline control, children with mild-persistent asthma had an approximately twofold increased odds of an ED visit by 3 months, children with moderate-persistent asthma had an approximately threefold increased odds, and children with severe-persistent asthma had an approximately fourfold increased odds (Fig 3 ). Neither baseline asthma control nor LTC use was associated with asthma-related HCU by 6 months.
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DISCUSSION |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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This study found that current asthma control is a strong predictor of future asthma-related HCU among inner-city black children with asthma. In addition, asthma control status changed substantially in as little as 3 months, suggesting that asthma control should be reassessed frequently so that appropriate changes in treatment can be made with the aim of reducing future HCU.
Other studies have shown that asthma control predicts HCU in adult patients,14,19,20 but this is the first study, to our knowledge, that shows that baseline control predicts future HCU in one of the most vulnerable asthma populations, namely, inner city preschool minority children. Studies in adults have shown that poor asthma control is associated with both current and future ED visits, doctor's visits, and hospitalizations.14,19–22 Although these studies in adult populations are informative, it is unclear whether these findings can be extrapolated to children, particularly inner-city black children who arguably are at highest risk for morbidity. Two cross-sectional studies in pediatric populations found relationships between asthma status and recent HCU, but future HCU was not examined.15,23 Another study found that control as assessed by diary-reported asthma symptoms predicted future HCU among children, but outcomes were assessed only in the short-term, 1 month into the future.24 Our study extends this body of literature in the pediatric population by focusing specifically on a high-risk group, black inner-city children, and by relating current guideline-derived asthma control status to longer-term future asthma-related HCU.
It is striking that current asthma control was found to be a strong predictor of future HCU in the subsequent 3 months but not beyond. The lack of longer-term predictive ability may be because of the inherently labile nature of asthma,25 particularly in the inner city population included in our study. Of particular concern is the fact that nearly half of the children initially classified with mild-intermittent asthma had worse control just 3 months later, crossing a threshold that would have required treatment escalation according to asthma guidelines. Therefore, reassessment, even as soon as 3 months after an initial evaluation, would have already missed an early opportunity for intervention. Taken together, these findings suggest that frequent reassessment of control status may reduce future morbidity in this high-risk population.
Other asthma guidelines, such as the 1995 GINA guidelines,16 have proposed examining not only symptom frequency but also LTC-medication use in the determination of asthma status. However, our study found that assessment of LTC-medication use, although essential for planning appropriate asthma management, offered little additional value to predicting future HCU once control status was already known. This finding is consistent with the most recent version of the GINA guidelines, which reflects a growing awareness that classification of asthma by level of control may be more useful in identifying high-risk patients than classification by underlying severity, which takes LTC use into account.12 Another question of interest would be whether the predictive ability of LTC use differs by type of LTC. However, given that almost all (86%) of the participants reporting LTC use were taking inhaled corticosteroids, we were unable to investigate that question.
It is notable that the most recent GINA guidelines recommend a dichotomized classification scheme for control (ie, poorly controlled versus controlled), which may be more simple to consider. However, our study's findings suggest that there is value in considering asthma control status for 
4 levels of control, because the risk of future HCU, at least for the next 3 months, varies significantly from one control category to the next. Thus, oversimplification of control status may result in a loss of important clinical information.
Although LTC-medication use would be expected to be an indicator of underlying asthma severity and, consequently, risk of morbidity, this concept may not hold in a "real-world" setting. Outside of a controlled setting, such as a clinical trial, reported use of an LTC medication is likely a marker of overall quality of asthma care rather than disease severity. For example, reported LTC-medication use may reflect access to care, effective provider-patient communication, the health care provider's clinical judgment, and ability to pay for the prescription, among many other factors. It is not surprising, then, that in our inner-city observational study, 62% of children had persistent asthma symptoms, but only 39% were on an LTC medicine. This finding highlights a strength of our study in its ability to look at actual use of LTC medication, a concept distinctly different from need for such medication. Reported LTC-medication use was only weakly related to clinical indications for such medication and, therefore, was a poor predictor of future HCU.
Recently, there has been significant attention focused on asthma control, rather than severity, assessment. This attention to control stems in part from limitations to the operational concept of asthma severity26–28 and the underuse of severity guidelines in clinical practice.29–32 Several well-validated measures of asthma control have been developed, some of which have been found to predict future HCU among adults.19,20,33–36 These measures classify control based on symptom frequency, similar to our study, so that these other measures may also prove to be useful predictors of future HCU. In addition, other indicators of asthma control may predict future HCU, such as lung function, sputum eosinophilia, and exhaled nitric oxide.9,11,37 Future studies should focus on the joint assessment of symptom frequency, lung function, inflammatory markers, and other patient characteristics, which may enhance our ability to predict future asthma risk.
There are some limitations to this study to consider. All of the data regarding symptoms, medication use, and HCU were collected by caregiver report. Therefore, our findings regarding LTC use apply only to reported LTC use, which may differ from verified use, because medication compliance was not assessed. However, reported use may be of greater relevance, because provider determination of LTC use is often reliant on patient report. In addition, HCU as reported by caregivers may have been subject to limitations of recall. However, Juniper et al38 found questionnaires to be more reliable and responsive than daily symptom diaries, and the time frame of 3 months, used in our study for HCU recall, has been shown to be more precise than recall windows of longer duration.39 Finally, our findings may not be generalizable to other populations, such as nonblacks and those outside the urban setting. However, the findings have direct implications to inner-city black children, who bear much of the asthma burden in the United States.
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CONCLUSIONS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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We found that asthma control status but not reported LTC-medication use is a strong predictor of future asthma-related HCU among inner-city black preschool-aged children. Findings from this study underscore the labile nature of asthma, because marked fluctuations in the degree of asthma control were observed within only 3 months. Our findings emphasize that asthma control is valuable to assess in young inner-city children and suggest that such assessments should be repeated at least every 3 months to take advantage of opportunities to prevent future morbidity.
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ACKNOWLEDGMENTS |
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This work was supported by US Environmental Protection Agency grant R82672401, National Institute on Environmental Health Sciences grant ES09606, National Heart, Lung, and Blood Institute grants HL04266 and HL67850, and National Institute of Allergy and Infectious Diseases grant K060955. This research has been supported by a grant from the US Environmental Protection Agency Science to Achieve Results program. Additional funding and support was provided by Johns Hopkins Center for Urban Environmental Health grant NIEHS P30 ES 03819.
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FOOTNOTES |
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Accepted Apr 17, 2007.
Address correspondence to Gregory B. Diette, MD, MHS, 1830 E Monument St, 5th Floor, Baltimore, MD 21205. E-mail: gdiette{at}jhmi.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
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PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
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