The Journal of Allergy and Clinical Immunology
Volume 120, Issue 1 , Pages 113-120, July 2007

Lack of association between indoor allergen sensitization and asthma morbidity in inner-city adults

  • Juan P. Wisnivesky, MD, MPH

      Affiliations

    • From the Division of General Internal Medicine
    • Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine
    • Corresponding Author InformationReprint requests: Juan P. Wisnivesky, MD, MPH, Division of General Internal Medicine, Mount Sinai School of Medicine, One Gustave L. Levy Place, Box 1087, New York, NY 10029.
    • ,
  • Hugh Sampson, MD

      Affiliations

    • Department of Pediatrics
    • ,
  • Stephen Berns, MD

      Affiliations

    • From the Division of General Internal Medicine
    • ,
  • Meyer Kattan, MD

      Affiliations

    • Department of Pediatrics
    • ,
  • Ethan A. Halm, MD, MPH

      Affiliations

    • From the Division of General Internal Medicine
    • Department of Health Policy, Mount Sinai School of Medicine

Received 20 December 2006; received in revised form 6 March 2007; accepted 27 March 2007. published online 26 May 2007.

New York, NY

Article Outline

Background

Sensitivity and exposure to indoor allergens is associated with increased asthma morbidity in inner-city children. However, it is unknown whether sensitization is associated with worse asthma in adults.

Objective

To evaluate the relationship between sensitization and asthma morbidity in urban adults.

Methods

We prospectively studied 245 adults with persistent asthma recruited from an inner-city clinic. Sensitization to indoor allergens was evaluated by specific IgE antibodies measured at enrollment. Data on asthma control, asthma-related emergency department visits, hospitalizations, and oral steroid use were collected at baseline and at 1-month and 3-month follow-up contacts. Univariate, stratified, and multiple regression analyses were used to compare asthma morbidity in sensitized and nonsensitized patients after controlling for self-reported exposure and other potential confounders.

Results

The study cohort consisted predominantly of low income, minority patients with high rates of resource utilization. The prevalences of sensitization to cockroach, dust mite, cat, mold, and mouse were 60%, 43%, 41%, 21%, and 14%. On univariate analyses, patients sensitized to each allergen did not have worse asthma control or higher resource utilization compared with nonsensitized individuals. Stratified and multivariate analyses also showed no association between sensitization and several measures of asthma morbidity even after controlling for self-reported exposure to indoor allergens and other potential confounders.

Conclusion

Sensitization to indoor allergens does not appear to be associated with increased asthma morbidity in inner-city adults.

Clinical implications

These findings suggest that efforts to improve asthma control among urban populations should focus on other modifiable risk factors for morbidity.

Key words: Asthma, sensitization, inner-city, morbidity, allergy, IgE

Abbreviations used: ACQ, Asthma Control Questionnaire, ED, Emergency department

 

Asthma is a common disease with an overall prevalence in the general population of 6% to 7%.1, 2 Several studies have documented that minority inner-city residents have disproportionately higher rates of asthma and increased morbidity and mortality rates.1, 2, 3, 4 Proposed explanations for the urban asthma problem include higher exposure to allergens, viral infection, air pollution, psychosocial and communication problems, suboptimal self-management, and poor quality and access to care.5, 6, 7, 8, 9, 10, 11

Studies have shown that inner-city residents are often exposed to high levels of indoor allergens.12, 13 The importance of sensitization to these allergens, such as house dust mites, cockroaches, fungi, and cats, as a risk factor for asthma morbidity has been increasingly recognized, particularly in children.13, 14, 15, 16, 17, 18 The National Cooperative Inner City Asthma Study clearly demonstrated higher asthma morbidity among children who are sensitized and exposed to cockroach allergen in their homes.13 More recently, studies have also shown increased asthma morbidity among women19 or elderly patients with asthma sensitized to cockroach allergen.20 However, the role of indoor allergen sensitization in contributing to asthma morbidity among inner-city adults remains unclear.

In this study, we prospectively evaluated the relationship between sensitization to common indoor allergens and several measures of asthma morbidity in a cohort of inner-city adults with persistent asthma.

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Methods 

Patient population 

Our study population was composed of a cohort of adult patients with asthma who receive care at a large hospital-based general internal medicine clinic located in East Harlem, New York City. Study participants were enrolled over a 19-month period from July 2004 to January 2006. Potential participants were identified by daily screening the clinic's computerized registration system listing all adults with a physician diagnosis of asthma. Patients were deemed eligible if they were ≥18 years of age, spoke English or Spanish, and had mild persistent, moderate persistent, or severe asthma.21, 22, 23, 24, 25 Individuals with a smoking history of ≥10 pack-years, a diagnosis of chronic obstructive lung disease or emphysema, restrictive lung disease, or other chronic respiratory illnesses were excluded from the study. The study protocol was approved by the Institutional Review Board.

Data collection and measurements 

Standardized questionnaires were used to obtain information at baseline and at 1 month and 3 months after enrollment. Domains of interest included the following: sociodemographic characteristics, access to care, asthma history, asthma treatment, medication adherence, comorbidities, and smoking habits. Trained bilingual research staff conducted interviewer-administered surveys in English or Spanish.

Data on home environmental exposure were ascertained using questions from the National Inner-City Asthma Study, the 1978 American Thoracic Society Division of Lung Disease Respiratory Symptoms questionnaire, and the questionnaire used by Health and Welfare–Canada for a community-based study of children's health.12, 26, 27, 28, 29, 30 These questions have adequate reproducibility, were administered to a large number of residents as part of previous epidemiologic studies, and have been validated against findings from home inspections.12, 30, 31 Items measured included type of dwelling, presence of visible mold, cockroaches, rodents, dampness, leaks or water damage, cats, indoor tobacco exposure, and flooring surface in various rooms. In addition, study subjects reported whether they had wall-to-wall carpeting, humidifiers, air conditioning in their bedrooms, and plastic covers on mattresses.

Allergic sensitization assessment 

At the baseline intake evaluation, a sample of peripheral blood was obtained from all study subjects for quantization of serum IgE levels to cockroaches (Blatella germanica and Periplaneta americana), house dust mites (Dermatophagoides farinae and Dermatophagoides pteronyssinus), cats (cat epithelium and dander), mouse (mouse epithelium), and molds (Alternaria alternata and Aspergillus fumigatus). Serum IgE levels were determined with the UniCap System (Phadia, Uppsala, Sweden) using methods provided by the manufacturer. Allergen-specific serum IgE levels >0.35 kU/L were considered indicative of sensitization.32, 33, 34 In addition, secondary analyses were performed by using a more stringent definition of sensitization—that is, IgE levels ≥0.7 kU/L as a cutoff for sensitization.

Outcome measures 

We collected information on several measures of asthma morbidity at baseline and during each of the follow-up surveys. The level of asthma control was measured with the Asthma Control Questionnaire (ACQ),35 a validated instrument that includes items about wheezing, shortness of breath, waking up at night, limitation of daily activities, severity of morning symptoms, and bronchodilator use. All questions were scored on a 7-point Likert scale with higher scores indicating worse asthma control. This instrument has been shown to have good responsiveness, reliability, and validity and is one of the most commonly used scales to evaluate asthma control.36, 37, 38 Additional measures of asthma control included the number of oral steroid courses in the year before enrollment and during the 3-month follow-up period.

Health care resource utilization was also used to assess the degree of asthma morbidity. Measures of health care services use at baseline included the frequency of emergency department (ED) visits, hospitalizations for asthma during the previous year, and history of endotracheal intubation. Information regarding ED visits and hospitalizations for asthma since enrollment was also collected at the 3-month follow-up interview.

Statistical analysis 

We used the t test to compare ACQ scores of sensitized and nonsensitized patients at baseline and at the 1-month and 3-month follow-up contacts. The χ2 test was used to assess the relationship between allergic sensitization to use of oral steroids, ED visits, asthma-related hospitalizations, and history of intubation.

To evaluate the effect of sensitization on asthma morbidity according to self-reported exposure status, patients were classified in 4 groups with respect to each allergen tested: those who were not allergic and were not exposed, those who were not allergic but were exposed, those who were allergic but were not exposed, and those who were allergic and exposed to the allergen. Evidence of association between each allergen and ACQ scores was assessed by using the likelihood ratio test comparing a linear regression model that contained dummy variables representing the different sensitization/exposure groups and a null model (containing only an intercept).39 The potential relationship of the resource utilization measures was similarly evaluated by using logistic regression models.

Multiple linear regression models were fitted to assess whether sensitization to each indoor allergen was associated with higher ACQ scores after adjusting for age, sex, race/ethnicity, socioeconomic status, age of asthma onset, asthma medication regimen, self-reported asthma medication adherence, comorbidities, and whether the patient was exposed to the allergen being tested. Similarly, logistic regression models were used to assess the relationship between sensitization to each allergen and resource utilization measures (oral corticosteroids, ED visits, hospitalizations, and history of intubation) after adjusting for potential confounders. Multivariate models were built manually, using a forward strategy. The final models were evaluated to assess the goodness of fit and to identify outliers and influential observations.

Power calculations showed that a total of approximately 240 patients were required for the study to have 80% power to detect a difference ≥0.5 units (a difference considered clinically significant)37 in the ACQ score among patients sensitized and not sensitized to each indoor allergen. Similar numbers of patients were required for the study to be powered to identify whether allergic sensitization is associated with ≥2.5 increased odds of steroid use, ED visits, or hospitalizations. All analyses used 2-tailed significance levels of P < .05 and were conducted with SAS statistical software (SAS Institute, Cary, NC).

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Results 

Between June 2004 and January 2006, 952 patients were identified from the primary care's computerized appointment schedule system and assessed for potential study eligibility. Of these, 654 were excluded for the following reasons: (1) no history of asthma (175 patients, 27%); (2) mild intermittent asthma (163 patients, 25%); (3) history of smoking >10 pack-years (111 patients, 17%); (4) other chronic lung disease (88 patients, 13%); (5) cognitive impairment (26 patients, 4%); and (6) other reasons (91 patients, 14%). Of the remaining 298 eligible patients, 245 (82%) were enrolled in the study. Of these, 213 (87%) completed the 1-month survey and 176 (72%) completed the 3-month survey.

The characteristics of the cohort are described in Table I. The mean age of patients was 47.7 ± 13.1 years. Consistent with the epidemiology of urban asthma, the cohort was composed predominantly of women (85%). Approximately 60% of patients were of Hispanic ethnicity (88% of Puerto Rican origin), 30% were African American, and 5% were white. Overall, patients reported high rates of oral steroid use (49% during the year before enrollment) and asthma-related resource utilization (53% reported ED visit and 24% hospitalization during the previous year). In terms of severity, 34% were classified as having mild persistent asthma, 27% as having moderate persistent asthma, and 39% as having severe persistent asthma. Most patients were insured by Medicaid, but 12% of patients reported having no insurance during the previous year. Approximately 68% of patients had an annual income <$15,000 per year. Almost 2/3 of patients (63%) reported living in public housing. The prevalence of home environmental exposure to cats, cockroach, dampness/molds, or rodents was 20%, 50%, 39%, and 40%, respectively.

Table I. Baseline patient characteristics and prevalence of indoor allergen sensitization
CharacteristicValue
Age (y), mean ± SD47.7 ± 13.1
Female (%)85
Race/ethnicity (%)
Hispanic61
Black29
White5
Other5
Insurance status (%)
Medicaid67
Medicare20
Commercial12
Uninsured1
No insurance during the past year (%)12
Income <$15,000 per year (%)68
Asthma history
Age of onset (y), mean ± SD21.8 ± 17.7
Ever intubated (%)11
ED visits in the past year (%)53
Hospitalized in the past year (%)24
Required steroids in the past year (%)49
Asthma severity (%)
Mild persistent34
Moderate persistent27
Severe persistent39
Asthma regimen (%)
Inhaled corticosteroid or leukotriene inhibitor prescribed87
Comorbid conditions (%)
Eczema18
Hay fever26
Chronic sinusitis19
Gastroesophageal reflux36
Diabetes24
Home environment exposure (%)
Second-hand smoking29
Cat exposure20
Cockroach exposure50
Dampness/mold exposure39
Rodent exposure40
Indoor allergen sensitization (%)∗
Cockroaches60
Dust mites43
Cat41
Molds21
Mouse14

∗Patients were classified as sensitized if serum IgE titers were > 0.35 kU/L.

Overall, 152 (62%) of patients were sensitized to at least 1 of the indoor allergens assessed in the study. The frequency of sensitization was 60% for cockroaches (B germanica and/or P americana), 43% for dust mites (D farinae, and/or D pteronyssinus), 41% for cat, 21% for molds (Alternaria and/or Aspergillus), and 14% for mouse.

Asthma control and resource utilization in relation to allergen sensitization status: univariate and stratified analyses 

Univariate analyses showed that ACQ scores at baseline, 1-month, and 3-month follow-up surveys were not significantly worse among patients sensitized to each of the indoor allergens measured in the study (Table II). Similarly, sensitization to most allergens was not associated with increased risk of oral steroid use, ED visits, hospitalizations, or history of intubation during the year before enrollment or during the 3-month follow-up period. However, cockroach and dust mite sensitization appear to be associated with increased use of oral steroids in the year before enrollment but not during the 3-month follow-up period. In addition, sensitivity to mouse allergens appears to be associated with an increased number of hospitalizations during the previous year, and patients sensitized to cat allergens showed a trend toward a decreased number of ED visits during the 3-month follow-up. The results of the analyses stratified according to sensitization and self-reported home exposure status also showed a lack of association between allergic sensitization and asthma control or acute asthma-related resource utilization (Table III).

Table II. Asthma control and resource utilization in relation to allergen sensitization status∗
Allergic sensitization
CockroachesDust mitesCatMouseMolds
VariableYesNoP valueYesNoP valueYesNoP valueYesNoP valueYesNoP value
ACQ score (mean)
Baseline3.113.13.903.023.19.283.123.10.923.333.08.353.203.10.59
1-Month follow-up2.893.03.382.853.02.292.783.06.103.132.92.373.032.93.59
3-Month follow-up3.053.10.822.953.17.262.903.18.173.403.02.193.143.06.74
Oral steroid use (%)
During the year before enrollment5836.0015942.0075446.265349.645348.55
During the 3-month follow-up period2623.692624.832027.301825.471727.24
Resource utilization at baseline (%)
ED visits in the past year5453.835752.465950.176552.175953.43
Hospitalized in the past year2326.482523.682722.343822.033122.18
Ever intubated1211.911112.971111.981511.481012.71
Resource utilization at the 3-month follow-up (%)
ED visits1918.911918.891122.062218.631420.42
Hospitalized55.9355.9964.5505.2665.88

∗Higher ACQ scores indicate worse control.

Table III. Relationship between sensitization to indoor allergens and asthma morbidity according to exposure level
Allergic sensitization
CockroachesDust mitesCatMouseMolds
VariableScore difference∗P valueScore differenceP valueScore differenceP valueScore differenceP valueScore differenceP value
ACQ score
Baseline0.36.07−0.36.360.24.400.37.690.07.94
1-Month follow-up0.07.36−0.24.74−0.47.170.24.84−0.06.73
3-Month follow-up0.24.28−0.36.67−0.48.450.44.470.34.58

ORPORPORPORPORP
Oral steroid use
During the year before enrollment3.42.0021.46.021.14.651.47.931.15.94
During the 3-month follow-up period1.21.980.93.950.26.241.50.340.75.57
Resource utilization at baseline
ED visits in the past year1.22.910.72.321.72.541.86.591.21.81
Hospitalized in the past year1.29.090.44.100.87.600.18.261.18.30
Ever intubated1.10.831.34.890.24.232.86.571.46.54
Resource utilization at the 3-month follow-up
ED visits1.19.900.60.840.15.082.26.730.61.69
Hospitalized0.50.771.63.990.41.410.99.673.30.44

∗Represents the difference in mean ACQ score between patients sensitized and exposed to the specific indoor allergen compared with those who are neither exposed nor sensitized. The differences in scores for the groups sensitized and not exposed and exposed but not sensitized were omitted for simplicity. Odds ratios (ORs) represent the odds of the outcome among patients sensitized and exposed to the allergen compared with the odds among unsensitized patients who were not exposed. All the P values correspond to the likelihood ratio test comparing a model with 3 terms corresponding to the different sensitization/exposure categories compared with the null model (containing only an intercept).

Asthma control and resource utilization in relation to allergen sensitization status: adjusted analyses 

Multiple regression analyses also demonstrated lack of association between allergic sensitization to cockroach, dust mites, cat, mouse, or molds and ACQ scores (baseline, 1-month, and 3-month surveys) after adjusting for age, sex, race/ethnicity, socioeconomic status, age of asthma onset, asthma regimen, mediation adherence, comorbidities, and home environmental exposure (Table IV). We also found no association between sensitization and increased resource utilization (oral steroid use, ED visits, hospitalization, and history of intubation) at baseline and at 3-months after enrollment in logistic regression models that adjusted for the same variables. However, mouse sensitization was associated with higher ACQ scores at the 3-month follow-up, and sensitization to cat allergens was associated with a lower risk of ED visits at 3 months but not at baseline.

Table IV. Adjusted relationship between allergen sensitization and asthma outcomes
Allergic sensitization
CockroachesDust mitesCatMouseMolds
VariableScore difference∗P valueScore differenceP valueScore differenceP valueScore differenceP valueScore differenceP value
ACQ score
Baseline−0.08.68−0.16.400.04.830.24.350.02.92
1-Month follow-up−0.24.26−0.06.78−0.17.440.43.130.23.35
3-Month follow-up0.14.58−0.26.32−0.17.530.94.0060.33.24

ORPORPORPORPORP
Oral steroid use
During the year before enrollment1.41.301.75.101.01.990.89.791.00.99
During the 3-month follow-up period1.36.501.14.780.59.310.79.720.50.23
Resource utilization at baseline
ED visits in the past year0.79.481.01.971.14.701.18.721.05.90
Hospitalized in the past year0.52.101.01.971.28.571.75.241.72.21
Ever intubated1.15.781.06.900.87.801.64.440.55.34
Resource utilization at the 3-month follow-up
ED visits1.48.431.45.480.20.0082.01.280.81.72
Hospitalized1.64.630.55.541.72.63—†—0.53.59

∗Represents the difference in mean ACQ score between patients sensitized to the specific indoor allergen compared with those who are not sensitized. All models were adjusted for age, sex, race/ethnicity, socioeconomic status, age of asthma onset, asthma regimen, self-reported asthma medication adherence, comorbidities, and whether the patient was exposed to the allergen being tested.

†Because of the problem of quasi-complete separation of data, mouse sensitization was not included in the model predicting whether a patient was hospitalized within 3 months of enrollment in the study.

Secondary analyses using IgE level >0.70 kU/L as indicative of sensitization, log-transformed IgE levels to specific allergens, or whether the patient was sensitized to at least 1 allergen also failed to reveal an association between sensitization and increased asthma morbidity. Similarly, no association was found when the analyses were restricted to younger adults (age < 55 years).

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Discussion 

In this prospective study of high-risk inner-city adults with asthma, we found no evidence of increased asthma morbidity among patients sensitized to several common indoor allergens. The study was powered to detect clinically meaningful differences in asthma control and assessed several morbidity outcomes highly prevalent in this population, thus suggesting that these are not false-negative results. These data suggest that allergic sensitization may be a less important determinant of asthma morbidity among inner-city adults compared with the role played in urban children with asthma.

Allergic sensitization has been postulated as one of the reasons for the disproportionately high rates of asthma morbidity among inner-city populations.5 Studies have clearly demonstrated that inner-city children sensitized and exposed to allergens are more likely to be hospitalized, have more unscheduled medical visits, and have more time off from school compared with nonsensitized patients with asthma.13 In particular, exposure to cockroach allergens has been shown to be associated with increased asthma morbidity among sensitized urban children,13 and home-based environmental interventions to decrease exposure to indoor allergen results in improved asthma control.40

Epidemiologic evidence for allergen sensitization as a cause of morbidity in inner-city adults with asthma is inconclusive.16, 19, 20 A study of 140 women with asthma, 33 of whom were sensitized to cockroach antigens, showed an association between exposure to cockroach and cat allergens and some measures of asthma morbidity.19 However, the relationship between cockroach sensitization and asthma morbidity disappeared when the analyses were controlled for socioeconomic status. In a case-controlled study of 28 subjects with severe asthma and 28 age-matched and sex-matched controls with mild asthma, Tunnicliffe et al16 showed higher rates of sensitization and exposure to dust mite, dog, and cat allergen among patients with severe asthma. A study of 45 urban patients with asthma age ≥60 years found that cockroach allergen sensitization was associated with increased airway obstruction and hyperinflation.20 Conversely, other studies have shown no association between sensitization and asthma morbidity or lung function among adult patients with asthma.41, 42, 43, 44 Similarly, our study did not demonstrate a significant relationship between indoor allergen sensitization and several measures of asthma morbidity among inner-city adult patients with asthma. The prevalence of atopy and the importance of allergic sensitization as a risk factor for diseases such as asthma, rhinitis, and eczema have traditionally been considered to diminish with age.45, 46 In addition, it has been reported that long-standing asthma is less influenced by allergen sensitization.47 These factors may explain our results showing that allergies may be a weaker contributor to asthma morbidity in adults compared with children. Another possible explanation for the observed lack of association may be related to the fact that adults spend less time exposed to the home indoor environment in comparison with children.

We found potential associations between allergic sensitization to cockroach, dust mites, and cat allergens and some of the outcomes assessed in the study. These relationships, however, were not consistently observed over time or among the different outcomes compared and in general disappeared in the adjusted analyses. Because we evaluated the potential association between sensitization to 5 indoor allergens and multiple different outcomes, it was not surprising to find some statistically significant associations simply by chance alone. The validity of these isolated findings should be further explored in future studies.

The patients in our study sample represent a population of inner-city adults with moderate to severe asthma. Our data confirm previous reports that a large proportion of urban patients with asthma are minorities of low socioeconomic status who have high rates of resource utilization, as demonstrated by >50% rates of ED visits and >20% prevalence of hospitalizations during the year before enrollment. The distributions of sensitization to dust mite, mold, cat, rodent, and cockroach allergens were also similar to those found in previous studies conducted in urban areas.19, 26, 48 Thus, it is unlikely that our negative findings are a result of a low prevalence of sensitized individuals or a limited number of patients who experienced the morbidity outcomes evaluated in the study. Almost 2/3 of the study cohort was composed of Hispanic patients (mostly of Puerto Rican origin). Previous research suggest that the prevalence of allergen sensitization varies among Hispanic subgroups, with Puerto Ricans living in the United States mainland having an increased risk of sensitization to indoor and outdoor allergens similar to that of African Americans.49, 50 Consequently, our results may not be directly generalizable to other inner-city areas in the United States where individuals from different Hispanic groups (such as Mexicans and other Central American countries) represent the majority of the Latino population. However, the high levels of allergy sensitization and asthma morbidity in our study population should strengthen the likelihood that our largely null findings are true negative results.

Although we did objectively measure sensitization to indoor allergens, the study was not designed to ascertain allergen exposure directly by collection of home dust samples. As a consequence, we could not use objective measures to assess whether individuals who are both sensitized and exposed to indoor allergens have poorer asthma control. However, we did collect information on home environmental characteristics and self-reported indoor exposure using validated questionnaires.27, 29, 30 Data from the National Inner-City Asthma Study show that self-reported rates of indoor exposure appear to be fairly accurate for cats and rodents, although they may underestimate by 15% the frequency of exposure to cockroaches and by up to 25% the number of homes with dampness or water leaks.12 Using these data, we did not find an association between sensitization and asthma morbidity even after stratifying our analyses by self-reported exposure status. Because studies have shown a high prevalence of detectable levels of indoor allergens among inner-city patients with asthma (as high as 85% for cockroaches, 50% for dust mite, 62% for cat, and 95% for mouse allergen), we suspect that a high proportion of the study subjects was exposed to these allergens at home.13, 48, 51, 52 Although we did not objectively assess exposure levels, home dust samples are also considered an imperfect measure because samples are commonly obtained from a single room at enrollment and allergen levels may be distributed differently across the home and change over time. In addition, patients with asthma may be in contact with other important environmental sources of allergen exposure outside their home. Finally, we focus our findings on current levels of exposure to indoor allergens, and thus we could not assess the potential influence of past exposure to these allergens.

The study cohort consisted of individuals recruited from a single institution, thus limiting the generalizability of our findings. Our institution, however, is the largest provider of care to the East Harlem, New York, population, one of the most severely affected communities by the current asthma epidemic.53, 54 We limited our study to patients with a physician diagnosis of asthma and no significant smoking history to exclude patients with chronic obstructive lung disease as well as other chronic lung diseases. However, there is a small possibility of misclassification of subjects with asthma, which could partially explain our negative findings. In addition, all of our outcome measures were self-reported. However, the ACQ is a validated measure of asthma control that has been used in multiple epidemiologic asthma studies. Because patients may visit an ED or be admitted to different hospitals, patient reports were considered the best source for these data. Patient reports of acute resource utilization are considered to be reliable55 and have been used in several similar studies.6, 13, 19, 56, 57 Finally, our sample was modest, so we had limited statistical power to detect relatively weak associations between sensitization to indoor allergens and asthma morbidity.

In summary, our study suggests that the association between sensitization and asthma morbidity may not be operative in inner-city adults or, if present, is considerably weaker than that observed among children. If confirmed in further studies, these findings suggest that efforts to improve asthma control among high-risk inner-city populations should focus on other modifiable risk factors for asthma morbidity.

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We thank Nicky O'Connor, Amy Carney, Jessica Segni, Julian Baez, Jessica Lorenzo, and Michelle Mishoe, whose help was invaluable to this study. We are indebted to Dr Paula Busse for her input regarding allergy sensitization measures. Last, we thank Phadia for providing the reagents used in this study.

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 Supported by the Agency for Healthcare Research and Quality (K08 HS013312, J.P.W.), the National Center for Research Resources (MO1 RR00071), and the National Institute of Aging (RO1 HS09973). Phadia (Uppsala, Sweden) provided the reagents used in this study.Disclosure of potential conflict of interest: H. Sampson has consulting arrangements with Allertein LLC and Dupont-Pioneer and has received grant support from Phadia. M. Kattan is on the speakers' bureau for AstraZeneca. The rest of the authors have declared that they have no conflict of interest.

PII: S0091-6749(07)00643-4

doi:10.1016/j.jaci.2007.03.044

The Journal of Allergy and Clinical Immunology
Volume 120, Issue 1 , Pages 113-120, July 2007

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