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Levels of IgE in serum from normal children and allergic children as measured by an enzyme immunoassay
Levels of IgE in serum from normal children and allergic children as measured by an enzyme immunoassay Roger E. Lindberg, and Chicago,
Ph.D., and Carlos Arroyave,
M.D., Ph.D. North Chicago
Ill.
Serum IgE levels of 346 nonallergic and 301 allergic children were measured by an enzyme immunoassay. The data are presented as the geometric mean t 95% confidence interval for each age from less than I to 12 years of age with those 13 to 16 years of age, pooled. The geometric mean for nonallergic patients increases from 0.9 IUiml at less than I year of age to 45.4 IlJlml at 13 to 16 years of age. By use of an IgE value between confidence intervals of allergic and nonallergic subjects, a cutoff value for each age was established to differentiate allergic from nonallergic children. This value increases from 10 Wlml at less than 1 year to 100 IUlml at 13 to 16 years of age. The diagnostic sensrtivity and speciJicity of the assay, based on the cutoff values, average 83% and 91%, respectively. (J ALLERGY CLIN IMMUNOL 748:614-t?, 1986.)
Elevated levels of IgE are observed in serum of most patients with atopic disorders, such as allergic rhinitis. extrinsic asthma, urticaria, and atopic eczema,‘-s as well as some disorders not related to allergy, including parasitic diseases,6 some cases of bronchiolitis and bronchopulmonary aspergillosis,’ and some immunodeficiency diseases such as WiskottAldrich syndrome ,* DiGeorge’s syndrome,’ and hyper-IgE syndrome.‘” Elevated levels of IgE are also helpful in predicting the subsequent development of allergies in childre:n. “-I3 The definition of what constitutes an elevated level of IgE has been the subject of several articles,‘4-24but most of these articles were studies of European populations or included subjects who were combined in age groups of various sizes. Since age.2.3, II_12genetic background,16, 25-27 and environmental factors2’ have all been demonstrated to be important determinants of IgE levels, the reported normal values of IgE may not be directly applicable to children m the United States. This study reports the use of a new enzyme immunoassay (the Abbott IgE EIA) to compare IgE levels in allergic and nonallergic children to determine levels that may be useful in differentiating allergic from nonallergic individuals.
Abbreviation used CVs:
Coefficients
1.6
of variation
r
I 40
80
120
160
200
IgE (lU/ml) From the Clinical Immunology Group, Abbott Laboratories, and Children’s Memorial Hospital, Chicago, Ill. Received for publication Sept. 25, 1985. Accepted for publication March 18, 1986. Reprint requests: Roger E. Lindberg, Ph.D., Dept. 908, AP 9, Abbott Laboratories. Abbott Park, IL 60064. 614
FIG. 1. A typical standard curve of the enzyme immunoassay for total serum IgE. The five standards used to establish the standard curve include samples containing 0, 10, 40, 7E. and 200 IUiml of IgE from a diluted myeloma specimen.
VOLUME NUMBER
78 4, PART 1
IgE measured
TABLE I. Number of subjects nonallergic children -Age WI
1 2 3 4 5 6 7 8
9 10 11 12 13 to 16
(nonaiergic)
studied,
geometric
Geometric mean (nonallergic)
0 to 6.6 0 to 20 0.1 to 15.8 0 to 29.2 0.3 to 25 0.2 to 17.6 0.2 to 13.1 0.3 to 46.1 1.8 to 60.1 3.6 to 81 8 to 95 1.5 to 99.7 3.9 to 83.5 3.3 to 188
0.9 2.3 3.4 4.2 3.7 5.5 5.1 8.9 11.9 24.4 33.1 33.0 32.0 45.4
MATERIAL AND METHODS IgE measurements SerumIgE levels were determinedby the Abbott IgE EIA (Abbott Laboratories, North Chicago, Ill.) with fresh or recently frozen sera. This test is a sandwich enzyme immunoassay in which samples are incubated with polystyrene beads coated with rabbit antihuman IgE. After a 30-minute
incubation, unbound material is removed by washing, and the beads are incubated for another 30 minutes with goat antihuman IgE conju,gated with horseradish peroxidase. Af-
ter a secondwash, beadsare incubated for 30 minutes with o-phenylenediaminecontaining hydrogenperoxide, and the reaction is stopped by the addition of 1 N H,SO,. IgE levels
are calculated from absorbancevalues at a wavelength of 492 nm automatically by the Abbott Quantum TM spectrophotometer.
Populations
immunoassay
mean, and range of IgE values for allergic
Range (NJ/ml) (nonallergic)
31 60 23 22 25 24 16 20 23 16 12 12 17 45
by enzyme
studied
The population studied included 647 children who were referred to Children’s Memorial Hospital in Chicago, Ill. The 346 nonatopic children selected for study (192 male and 154 female children of which 74% were white, 16% were Hispanic, and 9% were black) were admitted for plastic or orthopedic surgery, had no evidence of rheumatic diseases, were without tumors or parasitic infections, and had no family history of allergic disease but were not skin tested. The 30 I atopic subjects included in the study (185 male and I16 female subjects of which 68% were white, 19% Hispanic, 12% black, and 1% Oriental) were classified as allergic on the basis of family history, personal history, and
at least one positive skin test. Statistics Measurements of serum IgE were tabulated for age groups less than 1 year and each age 1 to 12 years with those 13 to 16 years, pooled. Since the data are skewed, a
(alle?gicl
27 29 24 20 2s 29 31 21 25 4 14 19 14 16
Range W/ml) (allergic)
IO to 750 7 to 195 0.2 to 700 2 to 540 0.4 to 246 1.7 to 680 2.6 to 1000 0.5 to 2491 3.8 to 630 169 to 900 10 to 895 3.6 to 1273 4.7 to 1046 70 to 793
615
and
Geometric mean (allergic)
41.3 38.9 24.1 78.3 47.9 59.5 101.9 166.3
84.3 432.3 168.2 134.8 94.5 338.7
log tran&rmation was done, and geometric means 4 95% confidence intervals were calculated for each age group according to the method previously described.”
RESULlrS A typical standard curve of the Abbott IgE EIA is presented in Fig. 1. The reproducibility of the assay was evaluated at four clinical sites by use of a panel of 15 serum samples. Results from these sites yielded intrarun percent CVs that ranged from 5.3% to 17.8%, and interrun percent CVs that ranged from 7.3% to 20.2%. The between laboratory percent CVs ranged from 7.8% to 17.4%.“’ Linear regression analysis of 397 sample results obtained by use of the Abbott IgE EIA and the Pharmacia IgE EIA or RIA (PRIST) demonstrated a correlation coefficient of 0.995, a slope of 0.850, and a y-intercept of -4.3. The analytical sensitivity of the assay is defined as the mean absorbance of duplicate values of the zero standard plus 2 SD. The mean absorbance of the zero standard was 0.063, and plus 2 SD yields a value of 0.079 or a theoretical sensitivity of 0.46 IU/ml. Results from three experiments done in replicates of six indicate that accurate IgE values down to 0.5 IU/ml can be reliably achieved in dilution studies.“’ The number of subjects studied, the geometric mean, and the range of IgE values for both allergic and nonallergic subjects at each age from less than 1 to 12 years of age with those 13 to 16 years, pooled, is illustrated in Table I. There was no significant difference in IgE levels between male and female subjects or between the races studied (p > 0.05 by analysis of variance in comparing Hispanics to whites at each age, but there was too small a number of blacks to
616
Lindberg
and Arroyave
100
J. ALLERGY
l
Allergic Patients
n
Nonallergic
CLIN. IMMUNOL. OCTOBER 1986
Patients
L b I I I I I I I I I I I I I <
1
1
2
3
4
5
6
7
8
9
10
11
12
13-16
PATIENT AGE (YRS 1 FIG. 2. The geometric mean k 95% confidence interval of IgE levels from allergic and nonallergic children of various ages is compared. Significant difference:: (p < 0.05) are observed at all age groups except at 11 and 12 years of age.
TABLE II. The diagnostic
sensitivity and specificity of the assay by use of cutoff values that increase with age
Age (yr)
Cutoff (IUlml)
10
15
2 3 4 5 6 I 8 9
15 1.5
10 II
12 13 to 16
15 15 15 15 25 50 75 15 15 loo
Sensitivity*
Specificityt
100 90 63 90 88 72 90 91 88 100
79 79 46 88
100 97 96 91 84 92 100
80 85 81 83 92 94 98
*Percent of allergic patients correctly identified. TPercent of nonallergic subjects correctly identified.
do meaningful comparisons), therefore, data from male and female subjectsof all raceshave beenpooled in establishing statistical values. The geometric mean for nonallergic children increasesfrom 0.9 IU/ml at less than 1 year of ageto 45.4 IU/ml at 13 to 16 years of age. Although the geometric mean for allergic individuals is higher at all ages, there is considerable
overlap in IgE values at all ages except less than 1 year of age. The standarddeviations from the meansare widespreadfor all age groups and do not provide a useful guide to differentiate the allergic and nonallergic group; however, when the geometric mean -+ 95% confidence interval is compared, significant differences between allergic and nonallergic subjects can be observed (Fig. 2). With an IgE value midway betweenthe upperlimit of the 95% confidenceinterval for nonallergic and the lower limit of the 95% confidence interval for allergic subjects, a cutoff value was established, and the diagnostic sensitivity (i.e., percentof allergic individuals correctly identified) and specificity (i .e. , the percent of nonallergic individuals correctly identified) of the assay were determined (Table II). Table III presents a comparison of the geometric meansof IgE values of children from this study with those reported for children from other countries. Although I[gE levels in children less than 1 year of age are sliglntly higher in Mexican than in Swedish or American children, large differences do not appear until children reach 4 years of age, at which time Mexican children have somewhat higher IgE levels (13.6 ILJlml) than either Swedish (8.6 IU/ml) or American (3.7 NJ/ml) children. At 10 years of age, differences between American and Mexican children disappear(33.1 versus32.4 IU/ml), whereasSwedish
VOLUME NUMBER
78 4, PART 1
TABLE III. Comparison Age (W
IgE measured
of normal United
IgE levels among nonallergic States
children
of different
Mexicoz4
Swedenlz
2.0 4.3 5.0 6.2 13.6 14.8 12.4 24.2 26.3
CO.82 3.5 3.0 1.8 8.6
32.4
23.7
0.9 2.3 3.4 4.2 3.7 5.5 5.1 8.9 11.9 24.4 33.1 33.0 32.0 45.4
children have lower IgE levels than either American or Mexican children (23.7 IU/ml). Venezuelan children have much higher IgE levels than Mexican, American, or Swedish children between 7 and 10 years of age, but their IgE levels fall to a point that, when the children reach 12 years of age, they are very similar to American children (28 versus 32 IU/ml, respectively).
DISCUSSION Since total IgE has been demonstrated to be important in predicting the subsequent development of allergies among children,‘*, ** we have limited our study to individuals younger than 17 years of age. No extensive studies of serum IgE in American children have been reported by use of an enzyme immunoassay. We used the Abbott IgE EIA test and found it to be easy to use and reliable for the estimation of serum IgE levels. The assay is reproducible and sensitive down to 0.5 IU/ml, making it particularly useful for the analysis of pediatric specimens in which low levels of IgE are expected. There was no significant difference in IgE levels between male and female subjects, which agrees with previous studies.‘. .“. 32 Although comparisons between geometric means are helpful in comparing IgE levels among individuals from different ethnic backgrounds and geographical locations, a more useful statistic for predicting the likelihood of an allergy based on a single IgE determination is the diagnostic sensitivity and specificity of a particular assay with regard to the population studied. We used a value midway between the upper limit of the 95% confidence limit of nonallergic subjects and the lower limit for allergic subjects to establish a cutoff value that could be used to determine
by enzyme
12.9
immunoassay
617
nationalities Venezuela=
51 53 74 52 38 28
20.1
the diagnostic sensitivity and specificity of the assay (Table II). With 100 IU/ml as the cutoff between allergic and nonallergic subjects, the diagnostic sensitivity and specificity of the assay for subjects 13 to 16 years, of age (pooled) were 88% and 98%, respectively. Wittig et a1.3also found that a cutoff value of 100 is a.cceptable for all age groups except infants, but no mention was made of cutoff values for younger age groups. Our study indicates that for younger age groups, a lower cutoff provides a better combination of diagnostic sensitivity and specificity. For example, a cutoff of 10 IU/ml for children less than 1 year of age provided 100% specificity and sensitivity in the 27 allergic and 3 1 nonallergic children that we studied. A cutoff of 15 IU/ml for children 1 to 7 years of age provided 83% sensitivity and 92% specificity (179 allergic and 190 nonallergic children). The cutoff increases fivefold between 7 and 10 years of age, increasing from 15 IU/ml to 75 IU/ml. The cutoff values suggested include patient material that has not been selected on the basis of a follow-up and may include “nonatopic” children with pathologic IgE levels that may be present before the appearance of symptoms.33 A comparison of normal IgE values from this study and those reported by other investigators is presented in Table III. Other studies have also been done but have been excluded from this comparison because they have pooled data from allergic and nonallergic individua;ls’* or have pooled data from children of different ages.3 Variations in the assays used and differences in the number of individuals studied at each age make direct comparisons difficult; however, it appears that children of different nationalities reach peak IgE levels at different ages, i.e., Japanese children at age 2 years,” Venezuelan children at age 9 years,” Swedish children at age 10 years,‘* Mexican children
618
Lindberg
and Arroyave
at age 10 year,s or later,24 and American children at age 13 to 16 years. Whether this difference is due primarily to environmental factors or genetic factors is unknown. REFERENCES I Johansson SGO: In vitro diagnosis of reagin-mediated allergic diseases. Allergy 33:292, 1978 2. Berg T. Johansson X0: IgE concentrations in children with atopic diseases. Int Arch Allergy 36:219, 1969 3. Wittig HJ, Belloit J, DeFillippi I, Royal G: Age-related serum immunoglobulin E levels in healthy subjects and in patients with allergic disease. J ALLERGYCLIN IMMUNOL66:305, 1985 4. Johansson SGO: Raised levels of a new immunoglobulin class (IgND) in asthma. Lancet 2:951, 1967 5. Juhlin L, Johansson SGO. Bennich H: Immunoglobulin E in dermatoses. Arch Dermatol 100:12, 1969 6. Savant T, Thammapalerd N, Jaroonvesma N, Bunnag D: Total serum IgE levels in patients with amoebic liver abscess and other parasitic infections. Southeast Asian .I Trap Med Public Health 8: 149, 1977 7. Patterson R, Fink JN, Pruzansky JJ, Reed C, Roberts M, Slavin R, Zeiss CR: Serum immunoglobulin E in pulmonary allergic aspcrgillosi\. J ALLERGYCLIN IMMUNOL 49:98, 1972 8. Waldmann IA, Polrnar SH, Balestra ST, Jost MC, Bruce RM, Terry WD: Irnmunoglobulin E in immunologic deficiency diseases. II. Serum IgE concentration of patients with acquired hypogammaglobulinemia, myotonic dystrophy, intestinal lymphangiectasia, and Wiskott-Aldrich syndrome. J Immunol 109:304, 1972 9. Kikkawa ‘L , Kamimura K, Hamajima T, Sekiguchi T, Kawai T, Takenaka M, Tada T: Thymic alymphoplasia with hyperIgE globuhncmia. Pediatrics 51:690, 1973 IO. Donabedian H, Ailing DW, Gallin JL: Levamisole is inferior to placebo in the hyper-immunoglobulin E recurrent-infection (Job’s) syndrome. N Engl J Med 307:290, 1982 I I. Hamburger RN, Lenoir M, Groshong TE, Miller JR, Wallace W. Orgel HA: Development of IgE and allergy during the tirst year of life preliminary data J ALLERGYCLIN IMMUNOL53:94, 1074 12. Kjellman NIM: Predictive value of high IgE levels in children. Acta Paediatr Stand 65:465, 1976 13. Danaeus A, Johansson SGO, Foucard T: Clinical and immunological aspects of food allergy in childhood. Acta Paediatr Stand 67:497. 1978 14. Johansson SGO: Serum IgND levels in healthy children and adults. Int Arch Allergy 34: 1, 1968 15. Kjellman NIM, Johansson SGO, Roth A: Serum IgE levels in healthy children quantified by a sandwich technique (PRIST). Clin Allergy 6:5 1. 1976 16. Gerrxd JW., Ko CG. Geddes CA, Reggin PL, Gerrard CD, Home S: Serum IgE levels in white and Metis communities in Saskatchewan. Ann Allergy 37:91, 1976
J. ALLERGY
CLIN. IMMUNOL. OCTOBER 1986
17 Csorba S,, Jezemiczky J, Byes I, Nagy B, Dvoracsek E, Szabo 9: Immtnoglobulin E in the sera of infants and children. Acta Paediatr Sci Hung 17:207, 1976 18 Gamo T Serum IgE levels in Japanese children. Acta Pdediatr Jpn 16:32, 1974 IY Nye L, Merrett TG, Landon J, White RJ: A detailed investigation of circulating IgE levels in a normal population. Clin Allergy 1:13, 1975 20 Brown ‘NG, Halonen MJ, Kaltenborn WT. Barbee RA: The relationship of respiratory allergy, skin-test reactivity, and serum IgE in a community population sample. J ALLERGYCLIN IMMUNOL 63:328, 1979 21 Orgel HA, Hamburger BN, Bazaral M. Gorrin H, Troshong T, Lenon M, Miller JR, Wallace W: Development of IgE and allergy In infancy. J ALLERGYCLIN IMMUNOL 56:296, 1975 22 Gleich GJ, Averbeck AK, Swedlund HA: Measurement of IgE in normal and allergic serum by radioimmunoassay. J Lab Clin Med 77:690, 1971 23 Ponce PP, Anderson 0, Ilja R, Monzon A, Bianco NE: Total serum IgE levels in Venezuelan schoolchildren. Clin Allergy 13:521, 1983 24 Arroya\e CM, Canseco C. Lopez-Lizarraga DN, Mora A, Trevino-Hemandez M, Carrera ME: Valores sericos normales de la inmunoglobulina E (IgE) en una poblacion pediatrica Mexicana. Bol Med Hasp Infant Mex 42:605. 1985 25 Levine BB. Stember RH, Fotino M: Ragweed hay fever: genetic control and linkage to HL-A haplotypes. Science 178:1201. 1972 26 Gerrard JW. Home S, Vickers P, Mackeney JWA, Goluboff N, Gar;on JZ, Maning CS: Serum IgE level>, in parents and children. J Pediatr 85:660, 1974 27 Fumer KJ, Rosman DL, O’Mahony J: Prevalence and familial associalion of atopic disease and its relationship to setum IgE levels in 1061 school children and their families. Int Arch Allergy Appl lmmunol 47:650, 1974 28 Businco L, Marchetti F, Pellegrini G, Perlin R: Predictive value of core blood IgE levels in “at risk” newborn babies and influence of type of feeding. Clin Allergy 13:503. 1983 29 Sokal RR, Rohlf FJ: In Biometry. ed I. San Francisco, 1969, WH Freeman & Co, pp 145-9 30 Fairbanks TR. Leman GC, Anawis MA, Lindberg RE: Clinical evaluation of the Abbott IgE enzyme immunoassay (EIA). Eighty-fifth Annual Meeting of American Society of Microbiology, 1985 (abst) 31 Berg ‘I, Johansson SGO: lmmunoglobulin levels during childhood, ‘with special regard to IgE. Acta Paediatr Stand 58:513, 1969 32 Grundhacher FJ: Causes of variations in serum IgE levels in normal populations. J ALLERGYCLIN IMMUNOL 56:104, 1975 33 Boucard T: A follow-up study of children with asthmatoid bronchitis. I. Skin test reactions and IgE antibodies to common allergens. Acta Paediatr Stand 62633. 1973
Ph.D., and Carlos Arroyave,
M.D., Ph.D. North Chicago
Ill.
Serum IgE levels of 346 nonallergic and 301 allergic children were measured by an enzyme immunoassay. The data are presented as the geometric mean t 95% confidence interval for each age from less than I to 12 years of age with those 13 to 16 years of age, pooled. The geometric mean for nonallergic patients increases from 0.9 IUiml at less than I year of age to 45.4 IlJlml at 13 to 16 years of age. By use of an IgE value between confidence intervals of allergic and nonallergic subjects, a cutoff value for each age was established to differentiate allergic from nonallergic children. This value increases from 10 Wlml at less than 1 year to 100 IUlml at 13 to 16 years of age. The diagnostic sensrtivity and speciJicity of the assay, based on the cutoff values, average 83% and 91%, respectively. (J ALLERGY CLIN IMMUNOL 748:614-t?, 1986.)
Elevated levels of IgE are observed in serum of most patients with atopic disorders, such as allergic rhinitis. extrinsic asthma, urticaria, and atopic eczema,‘-s as well as some disorders not related to allergy, including parasitic diseases,6 some cases of bronchiolitis and bronchopulmonary aspergillosis,’ and some immunodeficiency diseases such as WiskottAldrich syndrome ,* DiGeorge’s syndrome,’ and hyper-IgE syndrome.‘” Elevated levels of IgE are also helpful in predicting the subsequent development of allergies in childre:n. “-I3 The definition of what constitutes an elevated level of IgE has been the subject of several articles,‘4-24but most of these articles were studies of European populations or included subjects who were combined in age groups of various sizes. Since age.2.3, II_12genetic background,16, 25-27 and environmental factors2’ have all been demonstrated to be important determinants of IgE levels, the reported normal values of IgE may not be directly applicable to children m the United States. This study reports the use of a new enzyme immunoassay (the Abbott IgE EIA) to compare IgE levels in allergic and nonallergic children to determine levels that may be useful in differentiating allergic from nonallergic individuals.
Abbreviation used CVs:
Coefficients
1.6
of variation
r
I 40
80
120
160
200
IgE (lU/ml) From the Clinical Immunology Group, Abbott Laboratories, and Children’s Memorial Hospital, Chicago, Ill. Received for publication Sept. 25, 1985. Accepted for publication March 18, 1986. Reprint requests: Roger E. Lindberg, Ph.D., Dept. 908, AP 9, Abbott Laboratories. Abbott Park, IL 60064. 614
FIG. 1. A typical standard curve of the enzyme immunoassay for total serum IgE. The five standards used to establish the standard curve include samples containing 0, 10, 40, 7E. and 200 IUiml of IgE from a diluted myeloma specimen.
VOLUME NUMBER
78 4, PART 1
IgE measured
TABLE I. Number of subjects nonallergic children -Age WI
1 2 3 4 5 6 7 8
9 10 11 12 13 to 16
(nonaiergic)
studied,
geometric
Geometric mean (nonallergic)
0 to 6.6 0 to 20 0.1 to 15.8 0 to 29.2 0.3 to 25 0.2 to 17.6 0.2 to 13.1 0.3 to 46.1 1.8 to 60.1 3.6 to 81 8 to 95 1.5 to 99.7 3.9 to 83.5 3.3 to 188
0.9 2.3 3.4 4.2 3.7 5.5 5.1 8.9 11.9 24.4 33.1 33.0 32.0 45.4
MATERIAL AND METHODS IgE measurements SerumIgE levels were determinedby the Abbott IgE EIA (Abbott Laboratories, North Chicago, Ill.) with fresh or recently frozen sera. This test is a sandwich enzyme immunoassay in which samples are incubated with polystyrene beads coated with rabbit antihuman IgE. After a 30-minute
incubation, unbound material is removed by washing, and the beads are incubated for another 30 minutes with goat antihuman IgE conju,gated with horseradish peroxidase. Af-
ter a secondwash, beadsare incubated for 30 minutes with o-phenylenediaminecontaining hydrogenperoxide, and the reaction is stopped by the addition of 1 N H,SO,. IgE levels
are calculated from absorbancevalues at a wavelength of 492 nm automatically by the Abbott Quantum TM spectrophotometer.
Populations
immunoassay
mean, and range of IgE values for allergic
Range (NJ/ml) (nonallergic)
31 60 23 22 25 24 16 20 23 16 12 12 17 45
by enzyme
studied
The population studied included 647 children who were referred to Children’s Memorial Hospital in Chicago, Ill. The 346 nonatopic children selected for study (192 male and 154 female children of which 74% were white, 16% were Hispanic, and 9% were black) were admitted for plastic or orthopedic surgery, had no evidence of rheumatic diseases, were without tumors or parasitic infections, and had no family history of allergic disease but were not skin tested. The 30 I atopic subjects included in the study (185 male and I16 female subjects of which 68% were white, 19% Hispanic, 12% black, and 1% Oriental) were classified as allergic on the basis of family history, personal history, and
at least one positive skin test. Statistics Measurements of serum IgE were tabulated for age groups less than 1 year and each age 1 to 12 years with those 13 to 16 years, pooled. Since the data are skewed, a
(alle?gicl
27 29 24 20 2s 29 31 21 25 4 14 19 14 16
Range W/ml) (allergic)
IO to 750 7 to 195 0.2 to 700 2 to 540 0.4 to 246 1.7 to 680 2.6 to 1000 0.5 to 2491 3.8 to 630 169 to 900 10 to 895 3.6 to 1273 4.7 to 1046 70 to 793
615
and
Geometric mean (allergic)
41.3 38.9 24.1 78.3 47.9 59.5 101.9 166.3
84.3 432.3 168.2 134.8 94.5 338.7
log tran&rmation was done, and geometric means 4 95% confidence intervals were calculated for each age group according to the method previously described.”
RESULlrS A typical standard curve of the Abbott IgE EIA is presented in Fig. 1. The reproducibility of the assay was evaluated at four clinical sites by use of a panel of 15 serum samples. Results from these sites yielded intrarun percent CVs that ranged from 5.3% to 17.8%, and interrun percent CVs that ranged from 7.3% to 20.2%. The between laboratory percent CVs ranged from 7.8% to 17.4%.“’ Linear regression analysis of 397 sample results obtained by use of the Abbott IgE EIA and the Pharmacia IgE EIA or RIA (PRIST) demonstrated a correlation coefficient of 0.995, a slope of 0.850, and a y-intercept of -4.3. The analytical sensitivity of the assay is defined as the mean absorbance of duplicate values of the zero standard plus 2 SD. The mean absorbance of the zero standard was 0.063, and plus 2 SD yields a value of 0.079 or a theoretical sensitivity of 0.46 IU/ml. Results from three experiments done in replicates of six indicate that accurate IgE values down to 0.5 IU/ml can be reliably achieved in dilution studies.“’ The number of subjects studied, the geometric mean, and the range of IgE values for both allergic and nonallergic subjects at each age from less than 1 to 12 years of age with those 13 to 16 years, pooled, is illustrated in Table I. There was no significant difference in IgE levels between male and female subjects or between the races studied (p > 0.05 by analysis of variance in comparing Hispanics to whites at each age, but there was too small a number of blacks to
616
Lindberg
and Arroyave
100
J. ALLERGY
l
Allergic Patients
n
Nonallergic
CLIN. IMMUNOL. OCTOBER 1986
Patients
L b I I I I I I I I I I I I I <
1
1
2
3
4
5
6
7
8
9
10
11
12
13-16
PATIENT AGE (YRS 1 FIG. 2. The geometric mean k 95% confidence interval of IgE levels from allergic and nonallergic children of various ages is compared. Significant difference:: (p < 0.05) are observed at all age groups except at 11 and 12 years of age.
TABLE II. The diagnostic
sensitivity and specificity of the assay by use of cutoff values that increase with age
Age (yr)
Cutoff (IUlml)
10
15
2 3 4 5 6 I 8 9
15 1.5
10 II
12 13 to 16
15 15 15 15 25 50 75 15 15 loo
Sensitivity*
Specificityt
100 90 63 90 88 72 90 91 88 100
79 79 46 88
100 97 96 91 84 92 100
80 85 81 83 92 94 98
*Percent of allergic patients correctly identified. TPercent of nonallergic subjects correctly identified.
do meaningful comparisons), therefore, data from male and female subjectsof all raceshave beenpooled in establishing statistical values. The geometric mean for nonallergic children increasesfrom 0.9 IU/ml at less than 1 year of ageto 45.4 IU/ml at 13 to 16 years of age. Although the geometric mean for allergic individuals is higher at all ages, there is considerable
overlap in IgE values at all ages except less than 1 year of age. The standarddeviations from the meansare widespreadfor all age groups and do not provide a useful guide to differentiate the allergic and nonallergic group; however, when the geometric mean -+ 95% confidence interval is compared, significant differences between allergic and nonallergic subjects can be observed (Fig. 2). With an IgE value midway betweenthe upperlimit of the 95% confidenceinterval for nonallergic and the lower limit of the 95% confidence interval for allergic subjects, a cutoff value was established, and the diagnostic sensitivity (i.e., percentof allergic individuals correctly identified) and specificity (i .e. , the percent of nonallergic individuals correctly identified) of the assay were determined (Table II). Table III presents a comparison of the geometric meansof IgE values of children from this study with those reported for children from other countries. Although I[gE levels in children less than 1 year of age are sliglntly higher in Mexican than in Swedish or American children, large differences do not appear until children reach 4 years of age, at which time Mexican children have somewhat higher IgE levels (13.6 ILJlml) than either Swedish (8.6 IU/ml) or American (3.7 NJ/ml) children. At 10 years of age, differences between American and Mexican children disappear(33.1 versus32.4 IU/ml), whereasSwedish
VOLUME NUMBER
78 4, PART 1
TABLE III. Comparison Age (W
IgE measured
of normal United
IgE levels among nonallergic States
children
of different
Mexicoz4
Swedenlz
2.0 4.3 5.0 6.2 13.6 14.8 12.4 24.2 26.3
CO.82 3.5 3.0 1.8 8.6
32.4
23.7
0.9 2.3 3.4 4.2 3.7 5.5 5.1 8.9 11.9 24.4 33.1 33.0 32.0 45.4
children have lower IgE levels than either American or Mexican children (23.7 IU/ml). Venezuelan children have much higher IgE levels than Mexican, American, or Swedish children between 7 and 10 years of age, but their IgE levels fall to a point that, when the children reach 12 years of age, they are very similar to American children (28 versus 32 IU/ml, respectively).
DISCUSSION Since total IgE has been demonstrated to be important in predicting the subsequent development of allergies among children,‘*, ** we have limited our study to individuals younger than 17 years of age. No extensive studies of serum IgE in American children have been reported by use of an enzyme immunoassay. We used the Abbott IgE EIA test and found it to be easy to use and reliable for the estimation of serum IgE levels. The assay is reproducible and sensitive down to 0.5 IU/ml, making it particularly useful for the analysis of pediatric specimens in which low levels of IgE are expected. There was no significant difference in IgE levels between male and female subjects, which agrees with previous studies.‘. .“. 32 Although comparisons between geometric means are helpful in comparing IgE levels among individuals from different ethnic backgrounds and geographical locations, a more useful statistic for predicting the likelihood of an allergy based on a single IgE determination is the diagnostic sensitivity and specificity of a particular assay with regard to the population studied. We used a value midway between the upper limit of the 95% confidence limit of nonallergic subjects and the lower limit for allergic subjects to establish a cutoff value that could be used to determine
by enzyme
12.9
immunoassay
617
nationalities Venezuela=
51 53 74 52 38 28
20.1
the diagnostic sensitivity and specificity of the assay (Table II). With 100 IU/ml as the cutoff between allergic and nonallergic subjects, the diagnostic sensitivity and specificity of the assay for subjects 13 to 16 years, of age (pooled) were 88% and 98%, respectively. Wittig et a1.3also found that a cutoff value of 100 is a.cceptable for all age groups except infants, but no mention was made of cutoff values for younger age groups. Our study indicates that for younger age groups, a lower cutoff provides a better combination of diagnostic sensitivity and specificity. For example, a cutoff of 10 IU/ml for children less than 1 year of age provided 100% specificity and sensitivity in the 27 allergic and 3 1 nonallergic children that we studied. A cutoff of 15 IU/ml for children 1 to 7 years of age provided 83% sensitivity and 92% specificity (179 allergic and 190 nonallergic children). The cutoff increases fivefold between 7 and 10 years of age, increasing from 15 IU/ml to 75 IU/ml. The cutoff values suggested include patient material that has not been selected on the basis of a follow-up and may include “nonatopic” children with pathologic IgE levels that may be present before the appearance of symptoms.33 A comparison of normal IgE values from this study and those reported by other investigators is presented in Table III. Other studies have also been done but have been excluded from this comparison because they have pooled data from allergic and nonallergic individua;ls’* or have pooled data from children of different ages.3 Variations in the assays used and differences in the number of individuals studied at each age make direct comparisons difficult; however, it appears that children of different nationalities reach peak IgE levels at different ages, i.e., Japanese children at age 2 years,” Venezuelan children at age 9 years,” Swedish children at age 10 years,‘* Mexican children
618
Lindberg
and Arroyave
at age 10 year,s or later,24 and American children at age 13 to 16 years. Whether this difference is due primarily to environmental factors or genetic factors is unknown. REFERENCES I Johansson SGO: In vitro diagnosis of reagin-mediated allergic diseases. Allergy 33:292, 1978 2. Berg T. Johansson X0: IgE concentrations in children with atopic diseases. Int Arch Allergy 36:219, 1969 3. Wittig HJ, Belloit J, DeFillippi I, Royal G: Age-related serum immunoglobulin E levels in healthy subjects and in patients with allergic disease. J ALLERGYCLIN IMMUNOL66:305, 1985 4. Johansson SGO: Raised levels of a new immunoglobulin class (IgND) in asthma. Lancet 2:951, 1967 5. Juhlin L, Johansson SGO. Bennich H: Immunoglobulin E in dermatoses. Arch Dermatol 100:12, 1969 6. Savant T, Thammapalerd N, Jaroonvesma N, Bunnag D: Total serum IgE levels in patients with amoebic liver abscess and other parasitic infections. Southeast Asian .I Trap Med Public Health 8: 149, 1977 7. Patterson R, Fink JN, Pruzansky JJ, Reed C, Roberts M, Slavin R, Zeiss CR: Serum immunoglobulin E in pulmonary allergic aspcrgillosi\. J ALLERGYCLIN IMMUNOL 49:98, 1972 8. Waldmann IA, Polrnar SH, Balestra ST, Jost MC, Bruce RM, Terry WD: Irnmunoglobulin E in immunologic deficiency diseases. II. Serum IgE concentration of patients with acquired hypogammaglobulinemia, myotonic dystrophy, intestinal lymphangiectasia, and Wiskott-Aldrich syndrome. J Immunol 109:304, 1972 9. Kikkawa ‘L , Kamimura K, Hamajima T, Sekiguchi T, Kawai T, Takenaka M, Tada T: Thymic alymphoplasia with hyperIgE globuhncmia. Pediatrics 51:690, 1973 IO. Donabedian H, Ailing DW, Gallin JL: Levamisole is inferior to placebo in the hyper-immunoglobulin E recurrent-infection (Job’s) syndrome. N Engl J Med 307:290, 1982 I I. Hamburger RN, Lenoir M, Groshong TE, Miller JR, Wallace W. Orgel HA: Development of IgE and allergy during the tirst year of life preliminary data J ALLERGYCLIN IMMUNOL53:94, 1074 12. Kjellman NIM: Predictive value of high IgE levels in children. Acta Paediatr Stand 65:465, 1976 13. Danaeus A, Johansson SGO, Foucard T: Clinical and immunological aspects of food allergy in childhood. Acta Paediatr Stand 67:497. 1978 14. Johansson SGO: Serum IgND levels in healthy children and adults. Int Arch Allergy 34: 1, 1968 15. Kjellman NIM, Johansson SGO, Roth A: Serum IgE levels in healthy children quantified by a sandwich technique (PRIST). Clin Allergy 6:5 1. 1976 16. Gerrxd JW., Ko CG. Geddes CA, Reggin PL, Gerrard CD, Home S: Serum IgE levels in white and Metis communities in Saskatchewan. Ann Allergy 37:91, 1976
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