PEDIATRICS Vol. 117 No. 4 April 2006, pp. S71-S77 (doi:10.1542/peds.2005-2000D)
SUPPLEMENT ARTICLE |
National Asthma Education and Prevention Program Severity Classification as a Measure of Disease Burden in Children With Acute Asthma
a Divisions of Emergency Medicine and
b Allergy/Immunology, Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin
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ABSTRACT |
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 TOP ABSTRACT MATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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OBJECTIVE. To examine the association between the National Asthma Education and Prevention Program (NAEPP) severity classification and other measures of burden of disease in children with acute asthma.
METHODS. We performed a cross-sectional study of 750 children <18 years of age with a physician diagnosis of asthma and treated in an emergency department (ED) for acute asthma exacerbation. Subjects were assigned to 1 of 4 levels of severity (mild intermittent, mild persistent, moderate persistent, or severe persistent). Assignments followed 3 methods: the report of symptom frequency alone (standard method); symptom frequency and reported controller-medication use (modified method); or the additive modified method in which the symptom frequency and reported controller-medication use were assigned numeric values and a score was calculated. An asthma-specific quality-of-life score was calculated by using the Integrated Therapeutics Group Child Asthma Short Form (ITG-CASF). The number of ED visits and hospital admissions for asthma over the previous 12 months was collected also. Differences between severity groups were compared with analysis of variance, and the proportion of variance explained (r2) was calculated.
RESULTS. Using the standard classification method, 55% of subjects had mild intermittent asthma, 21% had mild persistent asthma, 14% had moderate persistent asthma, and 10% had severe persistent asthma. Among those classified as having mild intermittent asthma by symptoms alone, 22% were reclassified as having persistent asthma when controller medications were accounted for. With all 3 scoring methods, mean ITG-CASF scores decreased significantly with each increasing level of severity. However, the magnitude of this association was modest. There was a significant but limited association between severity level and mean number of ED visits and hospitalizations.
CONCLUSION. NAEPP severity classification alone provides an incomplete picture of the burden of disease in children with asthma.
Key Words: asthma • severity classification • children • disease burden
Abbreviations: NAEPP—National Asthma Education and Prevention Program • ED—emergency department • QoL—quality of life • MI—mild intermittent asthma • MildP—mild persistent asthma • ModP—moderate persistent asthma • SevP—severe persistent asthma • ITG-CASF—Integrated Therapeutics Group Child Asthma Short Form
Asthma is the most common chronic disease of childhood, with a prevalence approaching 10% in the United States.1,2 In 1991, the National Asthma Education and Prevention Program (NAEPP) of the National Heart, Lung, and Blood Institute developed a chronic asthma severity classification to guide long-term asthma management, including the use of controller medications. Their expert panel report was revised in 1997, and emphasis was placed on controller-medication dosing according to pretreatment severity. An update on selected topics was published in 2002 and recommended initiation of long-term control therapy in infants and children, presented written action plans, and emphasized stepwise treatment based on the NAEPP severity classification system.3,4 This classification system considers activity limitation, daytime symptoms, nighttime symptoms, and peak expiratory flow rate or spirometry (forced expiratory volume in 1 second), when applicable.4 The NAEPP severity classification system has been used for other purposes, including as a marker for burden of illness to adjust for severity differences in clinical trials.5–7 Validation of this classification for use as a risk adjustor is lacking.
The purpose of this study was to assess the validity of the NAEPP classification system by examining the association between the NAEPP chronic asthma severity classification and other measures of burden of disease in children with acute asthma presenting to an emergency department (ED). The secondary objective was to determine if the addition of information on controller medications to the NAEPP severity classification would better describe the overall burden of illness.
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MATERIALS AND METHODS |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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This study was approved by the Children's Hospital of Wisconsin Institutional Review Board. The study was a cross-sectional analysis of subjects from a prospective cohort of children with asthma entered into the ED Allies tracking system, a pediatric ED-based system.8 The cohort for this study comprised subjects from an urban regional children's hospital who ranged in age from 0 to 18 years and who presented to the ED with a history of physician-diagnosed asthma and symptoms related to their asthma. Seventy-seven variables were collected8; items relating to demographics, history of asthma, quality of life (QoL), and ED and hospital utilization were used in this study. Subjects enrolled from July 2002 to March 2003 were eligible if all 4 components of the chronic asthma severity classification were recorded during the pediatric ED visit (Table 1).
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ED standards for asthma care were enhanced before the implementation of the tracking-system study. One enhancement was the addition of the chronic severity classification grid (essentially as shown in Table 1) to the ED chart. Physicians received group and individual education on how to use the grid. Written instructions for use were provided and displayed in the ED. Physicians were instructed to ask the parent(s), "In the last 1 to 2 months, before your child developed the symptoms that brought you to the ED today, how would you rate your child's limitation of daily activities, daytime symptoms, and nighttime symptoms? What medication(s) does your child use each day for asthma?" Daily activities were defined as activities that require physical exertion such as exercising or playing. Parents' responses were matched to the descriptors for each category.
Investigators assigned asthma severity using the following methods. Three distinct overall severity classification methods were used for the data in Table 1. The standard 3-component NAEPP classification was symptom-based and included patient or parent report of activity limitation, daytime symptoms, and nighttime symptoms. The most severe category in which a symptom was noted determined the asthma severity classification of the subject. A modified NAEPP 4-component classification included the standard 3 symptom-based components and also considered controller-medication use (Table 1). Scoring was performed in the same manner for both methods, with the score based on the highest category of a noted single item. An additive, modified 4-component score was devised in which each of the 4 items was assigned a numeric value from 1 to 4, with 1 being the mildest symptom for each category and a value of 4 being severe (Table 1). The score then was calculated from the sum of the numeric values of each of the 4 components. Subjects who received a score of 4 were defined as having mild intermittent asthma (MI), 5 to 8 as having mild persistent asthma (MildP), 9 to 12 as having moderate persistent asthma (ModP), and 13 to 16 as having severe persistent asthma (SevP) (Appendix).
Three outcome measures were used to define the construct of burden of disease in children with asthma at the time of the ED visits: the Integrated Therapeutics Group Child Asthma Short Form (ITG-CASF) for asthma-specific QoL, the number of asthma-related ED visits, and the number of hospital admissions in the previous 12 months, as reported by the parents. The ITG-CASF is a validated 10-item questionnaire that assesses asthma-specific QoL in children.9 A higher score indicates better QoL, with a minimum value of 0 and maximum value of 100. In this study, QoL was assessed for the 2 weeks before the ED visit.
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ANALYSIS |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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The main analysis compared outcomes between severity groups by using analysis of variance. Linear regression was used to determine the association between each outcome and severity level after adjusting for confounders such as age at the time of enrollment, race, gender, and insurance type. An r2 calculation was used as measure of model fit. Partial correlations were calculated to assess the independent contribution of severity to the mode, adjusted for the confounding variables. All analyses were conducted by using SPSS 11.0 (SPSS Inc, Chicago, IL) and Stata 8.2 (Stata Corp, College Station, TX).
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RESULTS |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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Between July 2002 and March 2003, 750 subjects met the inclusion criteria and were included in this study; 62% were male, and the mean age was 5.8 years. The racial/ethnic composition was 55% black, 30% white, and 8% Hispanic. Forty-five percent had private insurance (Table 2). Cohort age, gender, racial/ethnic composition, and insurance status were consistent with those of the general ED asthma population. Of the 750 subjects, 128 (17%) were admitted from the ED to the hospital for additional management of their acute asthma exacerbation. Fifty-four percent of the subjects reported
1 hospital admissions in their lifetime, and 25% were hospitalized for asthma in the previous 12 months. Of these, 50% had a single admission, and the other 50% had 2 to 5 admissions in the previous year. In the previous 12 months, 82% of the subjects had 1 ED visits for asthma, 65% had a minimum of 2 ED visits, and 17% had 5 ED visits. The mean number of ED visits in the previous 12 months for asthma was 2.4.
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Using the standard NAEPP 3-component classification system, 413 (55%) subjects were classified as having MI, 160 (21.3%) as having MildP, 105 (14%) as having ModP, and 72 (9.6%) as having SevP. Within the MI group, 101 (24.5%) were on controller medications. In contrast, the majority of children with persistent asthma were taking
1 controller medications (Table 3).
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Use of the modified NAEPP 4-component classification system resulted in reclassification of 123 (16.4%) subjects (Table 4). Because final categorization was based on the highest value for any of the 4 criteria, a subject could not be placed into a lower severity category with the addition of the fourth component (controller-medication use). In contrast, the assignment of numeric values to each category in the additive modified NAEPP 4-component score produced a change in classification in 174 (23.2%) subjects. Of these subjects, 74 (43%) moved to a lower severity class, although no patient moved from the persistent to intermittent classification.
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In general, the ITG-CASF scores decreased with increasing chronic asthma severity regardless of the method used (Fig 1). The number of ED visits and hospital admissions for asthma in the previous 12 months also increased with increasing severity across all 3 scoring methods (Figs 2 and 3). In all cases, the test for trend was significant at P < .05. However, as shown in the figures, there was substantial overlap in the distribution of outcomes between the severity levels.
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To identify whether 1 of the 3 classification methods demonstrated greater association with the 3 clinical outcomes, we compared mean QoL score, number of ED visits, and hospital admissions among the 4 severity categories by using analysis of variance. Table 5 shows the analysis-of-variance results when severity was categorized by using each of the 3 classification methods. Regardless of the method chosen, there were significant differences in the clinical outcomes among the 4 severity levels. However, the proportion of variation in the outcomes explained by differences in severity category (indicated by the value for r2) was relatively low and was similar for each of the scoring methods, indicating that little of the variation among patients in the 3 clinical outcomes is explained by the chronic severity level assigned regardless of the method used to categorize severity. The r2 values for the QoL score were higher than those for the number of ED visits and hospital admissions, indicating a stronger association between the QoL score and the chronic asthma severity score. These results were unchanged when controlling for race/ethnicity, gender, insurance type, or age. Younger children may be more prone to wheezing that occurs only with viral respiratory infections, with few symptoms between exacerbations. We therefore performed a subgroup analysis in subjects >5 years of age and obtained similar results.
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Because the number of admissions was relatively low, with little variance, we categorized patients as having any asthma-related hospital admission in the previous 12 months versus no admissions. Using logistic regression with any admission as the outcome, we obtained similar results, with pseudo-r2 values of 0.04 to 0.05.
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DISCUSSION/CONCLUSIONS |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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The NAEPP chronic asthma severity classification was designed to classify chronic asthma severity and guide the management of chronic asthma. This classification was intended to measure asthma severity before the initiation of controller medications. The use of this classification, however, has expanded beyond the original intended use. Clinicians in outpatient settings, including the ED, utilize this score to assess the degree of asthma burden in patients they manage. The classification has also been used to adjust for differences in asthma severity in clinical trials. Interestingly, this classification has never been validated for use as a guide to manage chronic asthma or as a tool for risk adjustment.
Although patients with increasingly severe classifications of asthma tended to have greater morbidity, we found a statistically significant but clinically limited association between the standard NAEPP asthma severity classification and other measures of asthma burden (ITG-CASF score, number of ED visits, and number of hospitalizations for asthma) as shown by the low r2 values. This finding suggests that in addition to the clinical symptoms assessed, other unmeasured factors contribute to the QoL score and number of ED visits and hospitalizations. Our results are consistent with those of Bisgaard et al,10 who similarly found heterogeneous morbidity among patients considered to have MildP. In chronic management of children with asthma, the chronic severity classification should be one of the several factors to consider, because there is only a modest association with the "traditional" measures for assessing severity or determining treatment (ED visits and hospitalizations). This classification only weakly describes the likelihood of ED visits or hospitalization. Moreover, the chronic severity classification correlates better with the ITG-CASF QoL score, which reflects the patient's overall well-being in the previous 2 weeks. This correlation suggests that the NAEPP severity level is substantially influenced by recent disease activity. Therefore, this score, as a single measure, has limited value in describing the overall burden of asthma in children; however, when this score is combined with additional information, such as the QoL score, it can provide a more accurate picture of this burden.
We examined whether the addition of information about controller medications to the NAEPP severity classification better describes the burden of disease in children with acute asthma. The additional information on controller medications, as well as use of other scoring methods, did not better describe the overall burden of disease in children with acute asthma. This finding again suggests the limitation of using the NAEPP asthma severity classification as a shorthand global indicator for assessing the burden of illness in children with asthma.
This study also demonstrated that the number of controller medications used by most subjects with ModP and SevP was lower than that recommended. That fact may contribute to the unchanged r2 values noted when using the modified NAEPP 4-component classification method, which considers the use of controller medication. It is important to emphasize that the NAEPP recommendation is to use the chronic asthma severity classification as one measure to determine the need for controller medications in patients with chronic asthma.
Despite the limitations of the NAEPP severity classification system, it outlines important information to obtain in outpatient settings. In the ED setting, this classification helps to both characterize the overall control of asthma symptoms and identify an individual patient's compliance with current recommendations for controller medications. It enables ED physicians to partner with primary care physicians in identifying patients who may benefit from changes in asthma management using the NAEPP recommended stepwise approach. When used as a factor in determining management, the traditional 3-component classification is sufficient, because the addition of information on controller medication does not effectively improve our ability to characterize asthma burden.
Several limitations of the study merit discussion. The outcome measures studied (ITG-CASF score, number of ED visits and hospitalizations) are surrogate measures of burden of illness in children with acute asthma. The ITG-CASF scores reflect the subjects' symptoms in the 2 weeks before the ED visit (in other words, the subjects' short-term asthma severity). However, we believe that the 2-week time frame is sufficiently long to minimize any bias caused by patient or parent overemphasis of very recent symptoms, and the validity and responsiveness of this time frame has been established previously. Also, the other outcome measure used (the number of ED visits and hospitalizations for asthma) may not directly reflect asthma severity; other factors, including inadequate health care delivery, may affect these numbers. Because the number of hospital admissions is relatively low, this may be an insensitive marker of morbidity. However, the finding of generally weak association between NAEPP severity class and previous admissions was similar to that for other, more robust measures of disease burden. Finally, we acknowledge that our study included only patients treated in an ED for acute asthma, and the findings may not be generalizable to the asthma population at large.
Currently, the NAEPP asthma severity classification grid is the standard tool to assess chronic asthma severity. Although not perfect, it is simple to use and provides clinicians a method to assess chronic asthma severity. Clinicians should continue to use the standard 3-component NAEPP asthma severity classification, because the additional information on controller medications does not better describe chronic asthma severity. However, clinical researchers must be cautious when using the standard NAEPP asthma severity classification as a risk adjustor in their studies. Our study suggests that, in addition to the chronic severity classification, other factors are associated with the health-related QoL scores, number of ED visits, and hospital admission rate. Additional studies are needed to identify other factors that may contribute to the overall burden of illness in children with asthma.
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APPENDIX: AN EXAMPLE OF CATEGORIZING SUBJECTS USING THE 3 SCORING METHODS |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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A subject reports having activity limitation rarely, daytime symptoms >2 times per week, and nighttime symptoms >2 times per month. He is on 2 controller medications. Using the standard 3-component NAEPP classification, which determines the asthma severity classification based on the most severe category in which a symptom was noted, this subject is classified as having MildP. Using the modified NAEPP 4-component classification, which considers the use of controller medication, this subject would be classified as having ModP. Finally, using the additive modified 4-component score, this subject would receive a score of 8 (1 + 2 + 2 + 3) and be classified as having MildP.
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ACKNOWLEDGMENTS |
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Project support was provided by the Robert Wood Johnson Foundation, an Emergency Department Demonstration Project grant, and the American Academy of Asthma, Allergy, and Immunology (principal investigator: Kevin J Kelly, MD).
Technical assistance was provided by the National Program Office (director, Gary Rachelefsky, MD, Allergy Research Foundation Inc; deputy director, Amy Stone, American Academy of Allergy, Asthma and Immunology; and research associate, Suzanne Kennedy, PhD, American Academy of Allergy, Asthma and Immunology).
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FOOTNOTES |
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Accepted Dec 6, 2005.
Address correspondence to Kevin J. Kelly, MD, Children’s Mercy Hospital, 2401 Gillham Rd, Kansas City, MO 64108. E-mail: kjkelly{at}chm.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
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REFERENCES |
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TOPABSTRACTMATERIALS AND METHODSANALYSISRESULTSDISCUSSION/CONCLUSIONSAPPENDIX: AN EXAMPLE OF...REFERENCES |
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- President's Task Force on Environmental Health Risks and Safety Risks to Children. Asthma and the environment: a strategy to protect children. May 2000. Available at http://yosemite.epa.gov/ochp/ochpweb.nsf/content/fin.htm/$file/fin.pdf. Accessed February 28, 2006
- US Department of Health and Human Services. Tracking Healthy People 2010: respiratory diseases. November 2000. Available at www.healthypeople.gov/Document/HTML/tracking/OD24.htm. Accessed February 28, 2006
- National Asthma Education and Prevention Program. Expert panel report: guidelines for the diagnosis and management of asthma update on selected topics—2002 [published correction appears in J Allergy Clin Immunol. 2003;111:466]. J Allergy Clin Immunol. 2002;110(5 suppl) :S141 –S219
- National Heart, Blood, and Lung Institute; National Asthma Education and Prevention Program. Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma. Bethesda, MD: National Institutes of Health; 1997. NIH publication No. 97-4051
- Bukstein DA, McGrath MM, Buchner DA, Landgraf J, Goss TF. Evaluation of a short form for measuring health-related quality of life among pediatric asthma patients. J Allergy Clin Immunol. 2000;105 :245 –251[CrossRef][Web of Science][Medline]
- Ng TP. Validity of symptom and clinical measures of asthma severity for primary outpatient assessment of adult asthma. Br J Gen Pract. 2000;50 :7 –12[Web of Science][Medline]
- Graham DM, Blaiss MS, Bayliss MS, Espindle DM, Ware JE Jr. Impact of changes in asthma severity on health-related quality of life in pediatric and adult asthma patients: results from the asthma outcomes monitoring system. Allergy Asthma Proc. 2000;21 :151 –158[Medline]
- Kelly KJ, Walsh-Kelly CM, Christenson P, et al. Emergency Department Allies: a web-based multihospital pediatric asthma tracking system. Pediatrics. 2006;117(4 suppl) :S63 –S70
- Gorelick MH, Brousseau DC, Stevens MW. Validity and responsiveness of a brief, asthma-specific quality-of-life instrument in children with acute asthma. Ann Allergy Asthma Immunol. 2004;92 :47 –51[Web of Science][Medline]
- Bisgaard H, Szefler SJ. Understanding mild persistent asthma in children: the next frontier. J Allergy Clin Immunol. 2005;115 :708 –713[Medline]
PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics
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