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Interrelationships of quantitative asthma-related phenotypes in the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy

Published:November 14, 2006DOI:https://doi.org/10.1016/j.jaci.2006.09.026

      Background

      Delineating asthma subphenotypes is of interest to understand the cause of the disease. Few studies have addressed the interrelationships of quantitative asthma-related traits.

      Objective

      We sought to study the interrelationships of allergy markers and FEV1 in relation to asthma and sex in children and adults.

      Methods

      Total IgE levels, skin prick test (SPT) positivity, eosinophil counts, and FEV1 were assessed in 299 asthmatic cases (children and adults) recruited in chest clinics and 309 nonasthmatic population-based control subjects in the French Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy.

      Results

      Allergy parameters were significantly higher in asthmatic cases than in control subjects for children and adults and for both sexes. Sex and age modified the pattern of concordance of high IgE levels, SPT positivity, and eosinophilia among asthmatic cases, with the greatest overlap in male children (64%) and the lowest in male adults (18%). Patterns of change over the lifespan of IgE levels, eosinophil counts, and FEV1/height2 varied, with the acceleration of FEV1 decrease being particularly evident in asthmatic adults. In adult cases and control subjects, SPT positivity (particularly to indoor allergens) was significantly related to IgE levels but not to eosinophil counts. The association of eosinophil counts with IgE levels was evident only in children. Environmental factors (smoking, pets, and country living) did not alter the patterns observed.

      Conclusions

      Each allergy-related phenotype showed a distinct relation with asthma, with the role for eosinophils being different than that for IgE levels and SPT responses.

      Clinical implications

      Taking age and sex into account is essential for understanding the interrelationships of the various allergy-related phenotypes to asthma status.

      Key words

      Abbreviations used:

      EGEA (Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy), FEV1/H2 (FEV1/height2), IU (International units), SPT (Skin prick test), SPTQ (Skin prick test quantitative score)
      The current debate regarding eosinophils no longer considers whether they are friend or foe
      • Van Dellen R.G.
      The eosinophil: friend or foe?.
      but rather focuses on determining the circumstances in which they act as a foe.
      • Busse W.W.
      The eosinophil—quo vadis?.
      • Miranda C.
      • Busacker A.
      • Balzar S.
      • Trudeau J.
      • Wenzel S.E.
      Distinguishing severe asthma phenotypes: role of age at onset and eosinophilic inflammation.
      Eosinophils were among the first allergy markers studied as potential risk factors for FEV1 decrease in the context of the Dutch hypothesis,
      • Postma D.S.
      • Boezen H.M.
      Rationale for the Dutch hypothesis. Allergy and airway hyperresponsiveness as genetic factors and their interaction with environment in the development of asthma and COPD.
      which postulates that features of asthma are risk factors of chronic obstructive pulmonary disease. Although investigations of skin prick test (SPT) responses and IgE levels support the hypothesis, the relation of various allergy traits to FEV1 decrease varied between studies, suggesting disease heterogeneity.
      • Gottlieb D.J.
      • Sparrow D.
      • O'Connor G.T.
      • Weiss S.T.
      Skin test reactivity to common aeroallergens and decline of lung function. The Normative Aging Study.
      • Frette C.
      • Annesi I.
      • Korobaeff M.
      • Neukirch F.
      • Dore M.F.
      • Kauffmann F.
      Blood eosinophilia and FEV1. Cross-sectional and longitudinal analyses.
      • Lapperre T.S.
      • Snoeck-Stroband J.B.
      • Gosman M.M.
      • Stolk J.
      • Sont J.K.
      • Jansen D.F.
      • et al.
      Dissociation of lung function and airway inflammation in chronic obstructive pulmonary disease.
      Skin test positivity, high serum total IgE levels, and peripheral blood eosinophilia likely represent different expressions of the atopic phenotype,
      • Jansen D.F.
      • Rijcken B.
      • Schouten J.P.
      • Kraan J.
      • Weiss S.T.
      • Timens W.
      • et al.
      The relationship of skin test positivity, high serum total IgE levels, and peripheral blood eosinophilia to symptomatic and asymptomatic airway hyperresponsiveness.
      • Baldacci S.
      • Omenaas E.
      • Oryszczyn M.P.
      Allergy markers in respiratory epidemiology.
      which might explain their varied relation with FEV1. Eosinophils and other allergy markers are strongly related to asthma, but not all asthmatic patients present with allergic traits, and the attributable risk of allergy in asthma has been questioned.
      • Douwes J.
      • Gibson P.
      • Pekkanen J.
      • Pearce N.
      Non eosinophilic asthma: importance and possible mechanisms.
      Furthermore, the interpretation of the role of eosinophils is more nuanced after studies in adults have shown no effect of anti-IL-5 treatment, an eosinophil-specific cytokine,
      • Busse W.W.
      The eosinophil—quo vadis?.
      on airways dysfunction in asthma.
      Each marker of allergy shows a different relation with age, with eosinophil counts decreasing early in infancy, whereas IgE levels increase to early adulthood. Sex-related patterns have also been shown, with higher values of all parameters in male than in female subjects but stronger associations of eosinophils with asthma in women with persistent asthma.
      • Siroux V.
      • Curt F.
      • Oryszczyn M.P.
      • Maccario J.
      • Kauffmann F.
      Role of gender and hormone-related events on IgE, atopy and eosinophils in the Epidemiological study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness and Atopy.
      Different patterns of familial correlation of asthma-related phenotypes have been observed according to the mode of ascertainment of the families (offspring or parents).
      • Bouzigon E.
      • Chaudru V.
      • Carpentier A.S.
      • Dizier M.H.
      • Oryszczyn M.P.
      • Maccario J.
      • et al.
      Familial correlations and inter-relationships of four asthma-associated quantitative phenotypes in 320 French EGEA families ascertained through asthmatic probands.
      In addition, environmental
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Paty E.
      • Maccario J.
      • Kauffmann F.
      Relationships of active and passive smoking to total IgE in adults of the Epidemiological study of the Genetics and Environment of Asthma, bronchial hyperresponsiveness, and atopy (EGEA).
      • Matricardi P.M.
      • Rosmini F.
      • Riondino S.
      • Fortini M.
      • Ferrigno L.
      • Rapicetta M.
      • et al.
      Exposure to foodborne and orofecal microbes versus airborne viruses in relation to atopy and allergic asthma: epidemiological study.
      • Kauffmann F.
      • Oryszczyn M.P.
      • Maccario J.
      The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial hyper-responsivenes and Atopy.
      determinants of eosinophil counts, IgE levels, and skin test responses have been identified.
      Few epidemiologic studies have collected data on the various markers simultaneously in subjects over the lifespan, and no study has assessed their interrelationships at the phenotypic level in relation to age, sex, and asthma status. The aim of the present study is to assess the relationships between total IgE levels, SPT responses, eosinophil counts, and FEV1 in child and adult asthmatic cases and control subjects from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness, and Atopy (EGEA), taking into account asthma and sex. Specific consideration is given to eosinophils and to quantitative assessment of SPT responses, as recently validated.
      • Maccario J.
      • Oryszczyn M.P.
      • Charpin D.
      • Kauffmann F.
      Methodologic aspects of the quantification of skin prick test responses: the EGEA study.

      Methods

       Population

      EGEA is a case-control and family study of adult and childhood asthma. Cases were recruited in chest clinics, as were population-based control subjects. The protocol has been described elsewhere.
      • Kauffmann F.
      • Dizier M.H.
      • Pin I.
      • Paty E.
      • Gormand F.
      • Vervloet D.
      • et al.
      Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness and Atopy (EGEA)—phenotype issues.
      • Kauffmann F.
      • Dizier M.H.
      • Annesi-Maesano I.
      • Bousquet J.
      • Charpin D.
      • Demenais F.
      • et al.
      [Epidemiological study of genetic and environmental factors in asthma, bronchial hyperresponsiveness and atopy. Protocol and potential selection bias].
      All subjects have been extensively characterized regarding phenotypic and environmental characteristics by using standardized questionnaires.
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Paty E.
      • Maccario J.
      • Kauffmann F.
      Relationships of active and passive smoking to total IgE in adults of the Epidemiological study of the Genetics and Environment of Asthma, bronchial hyperresponsiveness, and atopy (EGEA).
      • Kauffmann F.
      • Oryszczyn M.P.
      • Maccario J.
      The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial hyper-responsivenes and Atopy.
      • Kauffmann F.
      • Dizier M.H.
      • Pin I.
      • Paty E.
      • Gormand F.
      • Vervloet D.
      • et al.
      Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness and Atopy (EGEA)—phenotype issues.
      • Kauffmann F.
      • Dizier M.H.
      • Annesi-Maesano I.
      • Bousquet J.
      • Charpin D.
      • Demenais F.
      • et al.
      [Epidemiological study of genetic and environmental factors in asthma, bronchial hyperresponsiveness and atopy. Protocol and potential selection bias].
      The present analysis concerns 299 asthmatic cases and 309 nonasthmatic control subjects with data on IgE levels, SPT responses, eosinophil counts, and FEV1. The proportion of missing data (13.8%) was similar in cases and control subjects and by sex. Adult cases with missing data were older than other subjects (43.3 vs 37.8, P = .03). The study was approved by the appropriate institutional review board, and informed consent was obtained from all subjects (and from parents for the children; see additional Methods information in the Online Repository at www.jacionline.org).

       Allergy markers, lung function, and asthma severity

      Total IgE levels (in international units [IU] per milliliter) were measured by means of RIA.
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Paty E.
      • Maccario J.
      • Kauffmann F.
      Relationships of active and passive smoking to total IgE in adults of the Epidemiological study of the Genetics and Environment of Asthma, bronchial hyperresponsiveness, and atopy (EGEA).
      Specific IgE levels to a mixture of several inhalant allergens were assessed by using the Phadiatop (Pharmacia Diagnostics, AB, Guyancourt, France). The exact composition of the aeroallergens present in the Phadiatop has not been reported by the manufacturer, but information on its constituents is available. The percentage binding of the Phadiatop was classified as positive or negative according to the reference serum value. SPTs were performed to 11 allergens (including molds and indoor and outdoor allergens). A quantitative score (the skin prick test quantitative score [SPTQ]) was constructed as the number of positive test results and validated regarding its biometric properties.
      • Maccario J.
      • Oryszczyn M.P.
      • Charpin D.
      • Kauffmann F.
      Methodologic aspects of the quantification of skin prick test responses: the EGEA study.
      Total and differential white blood cell counts were obtained by using standard methods, and the apparatuses used were those available in each center.
      The maximum FEV1 of 3 maneuvers was used to calculate the FEV1 percent predicted value, correcting for height, age, and sex.
      A score (1-4) was calculated to assess asthma severity, as previously described.
      • Le Moual N.
      • Siroux V.
      • Pin I.
      • Kauffmann F.
      • Kennedy S.
      on behalf of the Epidemiological Study on the genetics and Environment of Asthma (EGEA)
      Asthma severity and exposure to occupational asthmagens.

       Environmental factors

      Smoking,
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Paty E.
      • Maccario J.
      • Kauffmann F.
      Relationships of active and passive smoking to total IgE in adults of the Epidemiological study of the Genetics and Environment of Asthma, bronchial hyperresponsiveness, and atopy (EGEA).
      contact with pets,
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Kauffmann F.
      Allergy markers in adults in relation to the timing of pet exposure in the EGEA study.
      and country living (an indirect marker of contact with livestock),
      • Kauffmann F.
      • Oryszczyn M.P.
      • Maccario J.
      The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial hyper-responsivenes and Atopy.
      previously shown in the EGEA to relate to total IgE levels, SPT positivity (any wheal ≥3 mm), eosinophil counts, or FEV1, were considered in the adult analyses. Active smoking (nonsmokers, exsmokers, and smokers), childhood exposure to cat (≤16 years of age), and ever living in the country were included in models to assess whether the patterns observed between quantitative trait phenotypes were explained by environmental factors.

       Statistical methods

      Dichotomous variables used in analyses were SPT positivity, eosinophilia (>5%), Phadiatop positivity, and high IgE levels (≥100 IU/mL). IgE levels and eosinophil counts were log transformed and expressed as geometric means. Analyses regarding eosinophil counts also used tertiles computed separately for adults and children. Standard statistical tests (linear and logistic regression) were used to assess the interrelations between asthma-associated traits in models, including age, sex, and environmental factors. Analyses on the relationships of eosinophils with FEV1 were adjusted on age, sex, smoking, and inhaled steroid treatment and on age, sex, and smoking for other allergy parameters. SAS (version 9.1; SAS Institute, Inc, Cary, NC) software was used. (See additional Methods information in the Online Repository at www.jacionline.org).

      Results

      Total IgE levels, Phadiatop positivity, SPT responses, and eosinophil counts considered either dichotomously or quantitatively were significantly higher for cases versus control subjects among both children and adults of both sexes (Table I). Both SPT positivity and high IgE levels were evident in about 90% of the child cases. The greatest difference between cases and control subjects in SPT responses was observed for indoor allergens, in particular for Dermatophagoides pteronyssinus, for which 75.6% versus 21.2% in pediatric cases and control subjects and 46.2% versus 15.3% in adult cases and control subjects had positive results. For outdoor allergens, timothy grass positivity was the most common (38.2% vs 18.2% in children and 27.3% vs 16.1% in adults, respectively). FEV1 was significantly lower in cases than in control subjects, especially in adults.
      Table ICharacteristics of the population
      Female subjectsMale subjects
      ChildrenAdultsChildrenAdults
      Cases (n = 39)Control subjects (n = 45)Cases (n = 87)Control subjects (n = 111)Cases (n = 84)Control subjects (n = 41)Cases (n = 89)Control subjects (n = 112)
      Age (y; mean ± SD)11.1 ± 2.012.1 ± 2.235.4 ± 13.340.0 ± 12.011.3 ± 2.112.2 ± 2.340.1 ± 15.043.6 ± 13.2†
      Total IgE (IU/mL)
       GM (95% CI)312 (36-2688)36 (1-937)‡161 (7-3874)28 (1-542)‡454 (49-4198)68 (4-1551)‡228 (20-2620)36 (2-647)‡
       IgE ≥100 IU/mL (%)87.224.4‡62.119.8‡94.034.1‡80.920.5‡
      Specific IgE, Phadiatop positivity (%)94.922.2‡66.719.8‡92.936.6‡78.722.3‡
      SPTs
       SPT positivity, any (%)84.642.2‡67.827.0‡94.046.3‡77.534.8‡
       SPT positivity, indoor (%)79.524.4‡60.921.6‡88.124.4‡61.820.5‡
       SPT positivity, outdoor (%)51.318.2§36.817.142.926.8†46.118.8‡
       SPT positivity, molds (%)18.422.220.77.2§23.817.524.710.7§
       SPTQ, mean ± SD1.9 ± 1.20.7 ± 0.9‡1.7 ± 1.80.6 ± 1.3‡2.2 ± 1.30.9 ± 1.2‡2.0 ± 1.90.7 ± 1.1‡
      Eosinophils (no./mm3)
       GM (95% CI)376 (94-1509)168 (48-588)‡260 (50-1342)102 (19-557)‡474 (136-1652)212 (56-804)‡207 (39-1096)124 (32-475)‡
       Eosinophils >5% (%)56.413.3‡40.27.2‡67.922.0‡24.77.1
      FEV1 % predicted, mean ± SD90.5 ± 9.895.4 ± 12.189.9 ± 19.9105.0 ± 13.1‡92.1 ± 13.199.2 ± 10.4‡85.5 ± 21.9103.7 ± 15.0‡
      FEV1 % predicted <80% (%)15.48.927.60.9‡16.72.436.03.6‡
      Comparison of cases and control subjects: P ≤ .05; †P ≤ .10; ‡P ≤ .001; §P ≤ 0.01.
      GM, Geometric mean.
      Among cases, nearly all were in the active phase. More precisely, 111 (90.2%) children and 163 (92.6%) adults reported attacks in the last 12 months, and among those without attacks in that period, 5 children and 12 adults were using inhaled steroids. Among pediatric cases, 23%, 33%, 17%, and 27% were in each asthma severity category from mild to severe, with comparable proportions being 7%, 30%, 21%, and 42% in adults.

       Sex and age

      Among asthmatic cases, there was a greater overlap of the 3 allergy markers among children than among adults for both sexes (Fig 1). A substantial proportion (18.4%) of women with asthma had no marker of allergy, whereas 2.3% of male asthmatic cases lacked any marker of allergy (P = .001). Stratifying the sample according to smoking, country living, or pet exposure did not change the pattern.
      Figure thumbnail gr1
      Fig 1Concordance of SPT positivity, high IgE levels, and eosinophilia in asthmatic cases according to age and sex (Venn diagrams).
      The pattern of change with age of all quantitative parameters was studied cross-sectionally on the basis of asthma status. FEV1/height2 (FEV1/H2) was used to adjust for the dimensional aspect of growth. Quadratic models gave the best fit for eosinophil counts and lung function with age, capturing the marked decrease of eosinophil counts during childhood and the pattern of lung growth during childhood followed by decrease in lung function in adulthood (Fig 2). The best fit for log IgE values was a linear decrease over the age range studied. For SPTQ scores, a nonsignificant decrease was observed after 35 years of age in both cases and control subjects. For all parameters, curves for allergic markers were higher but roughly parallel along the lifespan between cases and control subjects. For FEV1/H2, the curve of cases started at less than that of control subjects, remained parallel until midadulthood, and then showed an acceleration of decrease with age (Fig 2). A similar pattern was observed when considering FEV1 expressed in liters or FEV1 percent predicted (according to external reference values) instead of FEV1/H2 (data not shown). Separate models for male and female subjects were represented (see Fig E1 in the Online Repository at www.jacionline.org).
      Figure thumbnail gr2
      Fig 2Associations of total IgE levels, eosinophil counts, and FEV1/H2 by age in cases and control subjects over the lifespan. Control subjects (n = 309) and patients (n = 299) are represented by open circles/thin curves and solid circles/thick curves, respectively. Cases and control subjects differed significantly for all parameters (P < .001). FEV1/H2 decrease with age among adults was significantly steeper in cases than in control subjects (P < .001).
      Among asthmatic cases, analyses taking the age of onset into account showed that adults with an early age of onset (<4 years) had higher SPTQ scores than those with an age of onset of 4 years or more and were younger at the time of the study. SPTQ scores were 1.96 versus 1.57 (P = .002) in women and 2.67 versus 2.03 (not significant) in men, respectively. The associations were similar after adjustment for age at assessment (or for age and smoking).

       Relationships between total IgE levels, specific IgE levels, and SPT responses

      Total IgE levels were significantly associated with SPT positivity in adult and child control subjects (73 versus 22 and 86 versus 31 IU/mL, respectively) and in adult cases (248 versus 96 IU/mL; all P < .004). In asthmatic children nearly all of whom had positive SPT responses, the association of IgE levels to SPT positivity and SPTQ scores did not reach statistical significance (see Table E1 in the Online Repository at www.jacionline.org), even after adjustment for age and sex. Among child control subjects, the association between SPT responses and IgE levels was strongest for outdoor allergens and remained significant after adjustment for age and sex. Among adult cases and control subjects, the association between SPT responses and IgE levels were strongest for indoor allergens. Associations between total IgE levels and SPT positivity were not modified by adjustment for potential confounders (age, sex, smoking, and country living; see Table E1 in the Online Repository at www.jacionline.org).
      The concordance of Phadiatop with SPT positivity was high, with overall κ coefficients being 0.49 and 0.44 for cases and control subjects among children and 0.68 and 0.54 for cases and control subjects among adults, respectively. Excluding Aspergillus and Blattella species from the definition of SPT positivity led to a slight increase in the κ statistic. Considering all subjects together, the positive and negative predictive values of Phadiatop for any of the 11 allergens were 90% and 78%, respectively.

       Relationships of FEV1 and asthma severity with IgE levels and SPT responses

      In children FEV1 was unrelated to IgE levels, SPT positivity, or SPTQ scores in cases and control subjects. In adult cases a significant positive association of FEV1 percent predicted with SPT positivity was observed. However, nonatopic adult cases were 10 years older than atopic cases (46.9 versus 34.4 years), and the association of SPT positivity with FEV1 disappeared after adjustment for age (84.2% vs 89.0%). No association was observed for FEV1 with SPTQ score. Among asthmatic cases, associations of allergy markers with asthma severity scores showed that there was no clear pattern of IgE in relation to asthma severity, even after taking into account age, sex, and smoking in the analyses (see Table E2 in the Online Repository at www.jacionline.org).

       Relationships between eosinophil counts with other allergy markers, FEV1, and asthma severity

      Because of the marked association of eosinophil counts with age, analyses of the relation with other allergy markers were conducted by using age-specific (children and adults) eosinophil tertiles (Fig 3). In children IgE levels increased significantly with eosinophil tertiles both in cases and in control subjects. For SPTQ scores, the pattern was complex: eosinophils were significantly inversely related to SPTQ scores in cases, whereas a significant positive association among control subjects was observed. Child cases in the lowest eosinophil tertile were more often receiving inhaled steroids than in the other tertiles (78.9%, 53.5%, and 55.9%, respectively). Eosinophils were unrelated to atopy, except among child control subjects, for whom the prevalence of atopy increased by eosinophil tertile (36.7%, 44.4%, and 80.0% of SPT positivity for the first, second, and third tertiles, respectively). For FEV1, there was a nonsignificant inverse relation with eosinophils for both cases and control subjects; in adults there was no clear pattern. None of the associations of eosinophil tertiles with the other parameters were modified by taking environmental factors into account. Among asthmatic cases, no particular pattern was evidenced regarding the association of asthma severity scores and eosinophils (see Table E2 in the Online Repository at www.jacionline.org). Results were similar when inhaled steroid treatment was excluded from construction of the severity variable (data not shown).
      Figure thumbnail gr3
      Fig 3Associations of total IgE levels, SPTQ scores, and FEV1 with eosinophil tertiles according to asthma in children and adults. Numbers of subjects in each group are shown below the bars. P ≤ .01; ‡P ≤ .05.

      Discussion

      The EGEA, with its well-characterized asthmatic cases and population-based control subjects, provides an opportunity to assess the interrelationships of various quantitative asthma-related phenotypes. In this study conducted both in children and adults, the interrelationships of asthma-related quantitative phenotypes depend not only on asthma but also on age and sex. These variables modified the pattern of association between IgE levels, SPT positivity, and eosinophilia among asthmatic cases, with the greatest overlap occurring in male children and the least in male adults. Eosinophils were significantly related to IgE levels and SPTQ scores in children only. Importantly, environmental factors, deleterious or protective, previously shown to relate to allergy markers did not explain the patterns observed.
      We previously reported that eosinophilia was more strongly related to childhood-onset asthma among female subjects.
      • Siroux V.
      • Curt F.
      • Oryszczyn M.P.
      • Maccario J.
      • Kauffmann F.
      Role of gender and hormone-related events on IgE, atopy and eosinophils in the Epidemiological study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness and Atopy.
      Here we show that sex had a marked influence not only on the level of allergy markers but also on their interrelationships. Among asthmatic cases, significantly more women than men did not have high IgE levels, atopy, and eosinophilia; this group has been little studied. Immunologic mechanisms specific to female subjects might be relevant, and preliminary results in the EGEA have shown a higher level of IgG4 specific to cat both in female cases and control subjects.

      Oryszczyn MP, Van Ree R, Maccario J, Kauffmann F. Relationships between current and past exposure to cat and specific IgE, IgG4 and atopy in 364 adults of the EGEA study. Proc Am Thorac Soc 2006;3:A473.

      This finding suggests that sensitization, tolerance, and other mechanisms might depend on sex, possibly being hormone dependent. We previously showed that asthma severity increases with body mass index in women with early menarche only,
      • Varraso R.
      • Siroux V.
      • Maccario J.
      • Pin I.
      • Kauffmann F.
      on behalf of the Epidemiological Study on the genetics and Environment of Asthma (EGEA)
      Asthma severity is associated with body mass index and early menarche in women.
      but early menarche did not modify the present findings. These results add to the evidence that both the phenotypic presentation of asthma (here allergy) and the risk factors for asthma differ for female and male subjects,
      • Becklake M.R.
      • Kauffmann F.
      Gender differences in airway behaviours over the human life span.
      • Wright A.L.
      • Stern D.A.
      • Kauffmann F.
      • Martinez F.D.
      Factors influencing gender differences in the diagnosis and treatment of asthma in childhood: the Tucson Children's Respiratory Study.
      particularly in adulthood.
      At any age, prevalence of high IgE levels, SPT responses, SPTQ scores, and eosinophilia was greater for cases than control subjects, indicating that these markers represent asthma-related quantitative phenotypes. However, it cannot be inferred from these associations that these markers are indeed true intermediate phenotypes (ie, on the causal pathway) as opposed to being associated traits.
      • Douwes J.
      • Gibson P.
      • Pekkanen J.
      • Pearce N.
      Non eosinophilic asthma: importance and possible mechanisms.
      Nevertheless, the strength of the association is a major argument to search genetic factors of these parameters, along with those of asthma. Indeed, genetic studies have increasingly focused on the quantitative traits associated with asthma because relations with these more specific phenotypes are likely to help disentangle the genetic determinants of this complex disease.
      In our population the increase of IgE levels from early childhood to adulthood was not evident, as in Barbee et al,
      • Barbee R.A.
      • Halonen M.
      • Lebowitz M.
      • Burrows B.
      Distribution of IgE in a community population sample: correlations with age, sex, and allergen skin test reactivity.
      likely because of the small number of control subjects in this age range and the bias introduced by recruiting of asthmatic cases through chest clinics. Whereas SPT responses, considered either dichotomously or quantitatively, were strongly related to IgE levels, eosinophil counts had markedly weaker associations with the other allergy parameters. Responsiveness at the skin level by using SPTs and an index of polysensitization (SPTQ and Phadiatop), showed that because of very strong association, Phadiatop does not bring additional information not already captured in SPTs. Furthermore, it must be emphasized that positivity to this test is not specific for single sensitization. Among children, IgE levels were most strongly associated with SPT responses to outdoor allergens, whereas among adults, the indoor allergens showed the strongest relation with IgE levels. Interestingly, adults with an early age of onset had higher SPTQ scores, confirming that not only childhood onset but also early-life onset is an interesting subphenotype of asthma to be considered in further studies. The lack of association of polysensitization with asthma severity in adults confirms previous observations from the EGEA.
      • Siroux V.
      • Oryszczyn M.P.
      • Paty E.
      • Kauffmann F.
      • Pison C.
      • Vervloet D.
      • et al.
      Relationships of allergic sensitisation, total IgE and blood eosinophils to asthma severity in children of the EGEA Study.
      In children only eosinophil counts were significantly related to IgE levels. Although we observed the expected relationship between atopy and eosinophil counts among child control subjects, it was not the case in asthmatic children because this relation appeared to be masked by medication use in the asthmatic children. The strength of the association of IgE levels with SPT responses was difficult to assess because nearly all asthmatic children had positive SPT responses. These findings add to the epidemiologic evidence that eosinophilia in childhood, which has been little studied, might represent a different inflammatory state than it does in adulthood and might be etiologically linked to the development of asthma in childhood. This observation is of potential clinical importance because studies questioning the efficacy of anti-IL-5 treatment have been conducted in adults only and thus cannot be directly extrapolated from adults to children.
      • Heaton T.
      • Rowe J.
      • Turner S.
      • Aalberse R.C.
      • de Klerk N.
      • Suriyaarachchi D.
      • et al.
      An immunoepidemiological approach to asthma: identification of in-vitro T-cell response patterns associated with different wheezing phenotypes in children.
      Clearly more research is needed to understand the role of these cells in asthma.
      • Busse W.W.
      The eosinophil—quo vadis?.
      • Jansen D.F.
      • Rijcken B.
      • Schouten J.P.
      • Kraan J.
      • Weiss S.T.
      • Timens W.
      • et al.
      The relationship of skin test positivity, high serum total IgE levels, and peripheral blood eosinophilia to symptomatic and asymptomatic airway hyperresponsiveness.
      • Lewis S.A.
      • Pavord I.D.
      • Stringer J.R.
      • Knox A.J.
      • Weiss S.T.
      • Britton J.R.
      The relation between peripheral blood leukocyte counts and respiratory symptoms, atopy, lung function, and airway responsiveness in adults.
      • Williams T.J.
      The eosinophil enigma.
      • Wills-Karp M.
      • Karp C.L.
      Eosinophils in asthma: remodeling a tangled tale.
      The lack of association of eosinophils with asthma severity observed here likely pertains to the observational nature of the population and the recruitment of asthmatic cases in chest clinics and thus does not conflict with the effect of inhaled steroids on eosinophils observed in clinical trials.
      • Giembycz M.A.
      • Lindsay M.A.
      Pharmacology of the eosinophil.
      The difference in FEV1 between cases and control subjects, although apparent in childhood, was more noticeable in adulthood, which supports the speculation that remodeling-related events are dependent on the duration of asthma.
      • Pascual R.M.
      • Peters S.P.
      Airway remodeling contributes to the progressive loss of lung function in asthma: an overview.
      In children parameters other than lung function characterize asthma severity,
      • Strunk R.C.
      • Szefler S.J.
      • Phillips B.R.
      • Zeiger R.S.
      • Chinchilli V.M.
      • Larsen G.
      • et al.
      Relationship of exhaled nitric oxide to clinical and inflammatory markers of persistent asthma in children.
      • Siroux V.
      • Kauffmann F.
      • Pison C.
      • Pin I.
      [Multidimensional character of asthma severity in the EGEA study.].
      and it would be of interest to assess whether the level of eosinophilia in asthmatic children predicts the persistence of severity of asthma into adulthood. Future epidemiologic studies should be undertaken to determine genetic and environmental determinants of eosinophilic inflammation and its role in allergy and asthma in each sex over the lifespan.
      A major limitation of our analysis is the cross-sectional nature of the data, but no longitudinal study could easily provide data from 7 to 70 years. Because cohort effects likely modify the patterns, both cross-sectional and longitudinal studies are necessary to comprehensively approach lifespan patterns. A follow-up study currently in progress will help to assess whether factors related to low FEV1 cross-sectionally, such as atopy, influence FEV1 decrease over 10 years. A second limitation of our study was the difficulty of analyzing the pattern in control subjects, who appear more atopic than expected but who rarely present with eosinophilia. Although the recruitment of cases from chest clinics provided probands with a definitive diagnosis,
      • Kauffmann F.
      • Dizier M.H.
      • Pin I.
      • Paty E.
      • Gormand F.
      • Vervloet D.
      • et al.
      Epidemiological Study on the Genetics and Environment of Asthma, Bronchial Hyperresponsiveness and Atopy (EGEA)—phenotype issues.
      it precludes the generalization of the findings to asthma in general. Studies in larger populations would be useful to assess the relationships between the various markers in nonasthmatic subjects.
      Environmental factors undoubtedly play a key role in the increase of asthma incidence in the last decades, and substantial research is being directed to understanding the role of environmental factors on allergy-related phenotypes.
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Paty E.
      • Maccario J.
      • Kauffmann F.
      Relationships of active and passive smoking to total IgE in adults of the Epidemiological study of the Genetics and Environment of Asthma, bronchial hyperresponsiveness, and atopy (EGEA).
      • Matricardi P.M.
      • Rosmini F.
      • Riondino S.
      • Fortini M.
      • Ferrigno L.
      • Rapicetta M.
      • et al.
      Exposure to foodborne and orofecal microbes versus airborne viruses in relation to atopy and allergic asthma: epidemiological study.
      • Kauffmann F.
      • Oryszczyn M.P.
      • Maccario J.
      The protective role of country living on skin prick tests, immunoglobulin E and asthma in adults from the Epidemiological Study on the Genetics and Environment of Asthma, Bronchial hyper-responsivenes and Atopy.

      Oryszczyn MP, Van Ree R, Maccario J, Kauffmann F. Relationships between current and past exposure to cat and specific IgE, IgG4 and atopy in 364 adults of the EGEA study. Proc Am Thorac Soc 2006;3:A473.

      • Arshad S.H.
      Primary prevention of asthma and allergy.
      • Frew A.J.
      Advances in environmental and occupational diseases 2004.
      • von Mutius E.
      Influences in allergy: epidemiology and the environment.
      However, environmental factors associated specifically with eosinophilia are not yet known. None of the environmental factors previously associated with allergy markers
      • Maccario J.
      • Oryszczyn M.P.
      • Charpin D.
      • Kauffmann F.
      Methodologic aspects of the quantification of skin prick test responses: the EGEA study.
      • Oryszczyn M.P.
      • Annesi-Maesano I.
      • Charpin D.
      • Kauffmann F.
      Allergy markers in adults in relation to the timing of pet exposure in the EGEA study.
      in the EGEA (active and passive smoking, country living, and early exposure to cat) modified, even slightly, the pattern of relationships between allergy markers or between allergy markers and FEV1. This is an important unexpected result that suggests that genetic factors and, more likely, gene-environment interactions might play a major role in the phenotypic expression of asthma-related traits.
      Overall, these results support the hypothesis that genetic factors control subphenotypes according to sex and age and that failure to address that complexity will hamper the unraveling of the cause of asthma and related phenotypes. At the clinical and biologic level, phenotypic heterogeneity might be explained by gene-environment interactions according to windows of exposure.
      • Hoffjan S.
      • Nicolae D.
      • Ostrovnaya I.
      • Roberg K.
      • Evans M.
      • Mirel D.B.
      • et al.
      Gene-environment interaction effects on the development of immune responses in the 1st year of life.
      • Martinez F.D.
      Gene-environment interactions in asthma and allergies: a new paradigm to understand disease causation.
      • Ober C.
      • Thompson E.E.
      Rethinking genetic models of asthma: the role of environmental modifiers.
      In any case these results demonstrate that careful characterization of subphenotypes in allergy and asthma might improve our understanding of the cause of asthma and ultimately assist in the management of this complex disease.

      Appendix. EGEA Cooperative Group

      Coordination: F. Kauffmann; F. Demenais (genetics); I. Pin (clinical aspects).
      Respiratory epidemiology: INSERM U578, Grenoble: V. Siroux; INSERM U700, Paris: M. Korobaeff (EGEA1), F. Neukirch (EGEA1); INSERM U707, Paris: I. Annesi-Maesano; INSERM U780, Villejuif: F. Kauffmann, N. Le Moual, R. Nadif, M. P. Oryszczyn.
      Genetics: INSERM U393, Paris: J. Feingold; INSERM U535, Villejuif: M. H. Dizier; INSERM U794, Evry: E. Bouzigon, F. Demenais; CNG, Evry: I. Gut, M. Lathrop.
      Clinical centers: Grenoble: I. Pin, C. Pison; Lyon: D. Ecochard (EGEA1), F. Gormand, Y. Pacheco; Marseille: D. Charpin (EGEA1), D. Vervloet; Montpellier: J. Bousquet; Paris-Cochin: A Lockhart (EGEA1), R. Matran (now in Lille); Paris-Necker: E. Paty, P. Scheinmann; Paris-Trousseau: A. Grimfeld, J. Just.
      Data and quality management: INSERM ex-U155 (EGEA1): J. Hochez; INSERM U780, Villejuif: N. Le Moual, C. Ravault; INSERM U794: N. Chateigner; Grenoble: J. Ferran.

      Appendix. Supplementary data

      Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.jaci.2006.09.026

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