Predictive value of food sensitization and filaggrin mutations in children with eczema

Article Outline

• Abstract
• Methods
  • Study populations and phenotyping
    • German Infant Nutritional Intervention birth cohort
    • Influence of Lifestyle-related Factors on the Immune System and the Development of Allergies in Childhood birth cohort
    • Clinical case series
  • Genotyping
  • Statistical analysis
• Results
  • Characteristics of the study population
  • Prediction of asthma
  • Risk for persistent eczema
  • Sensitization patterns
• Discussion
• Appendix 1
• References
• Copyright

Background

It was reported that in infants with eczema and food sensitization, the presence of a filaggrin (FLG) null mutation predicts future asthma with a specificity and positive predictive value of 100%.

Objectives

We sought to evaluate the predictive value of food sensitization and food allergy, FLG haploinsufficiency, and their combination in infants with early-onset eczema for persistent eczema and childhood asthma.

Methods

The German Infant Nutritional Intervention (GINI) and Influence of Lifestyle-related Factors on the Immune System and the Development of Allergies in Childhood (LISA) birth cohorts, as well as a collection of 65 cases of early-onset eczema with and without food allergy were investigated.

Results

The risk for asthma was significantly increased by food sensitization (positive diagnostic likelihood ratios [PLRs] of 1.9 [95% CI, 1.1-3.4] in the GINI cohort and 5.5 [95% CI, 2.8-10.8] in the LISA cohort) and the presence of an FLG mutation (PLRs of 2.9 [95% CI, 1.2-6.6] in the GINI cohort and 2.8 [95% CI, 1.0-7.9] in the LISA cohort) with a rather high specificity (79.1% and 92.9% in the GINI cohort and 89.0% and 91.7% in the LISA cohort, respectively) but low sensitivity (40.0% and 39.3% in the GINI cohort and 31.6% and 23.5% in the LISA cohort, respectively). Likewise, the risk for persistent eczema was increased. In the clinical cases neither food allergy nor FLG mutations had a significant effect. The combination of both parameters did not improve prediction and reached positive predictive values of 52.3% (GINI cohort), 66.9% (LISA cohort), and 30.6% (clinical cases), assuming an asthma prevalence in children with early eczema of 30%.

Conclusion

Early food sensitization and the presence of an FLG mutation in infants with early eczema increase the risk for later asthma, but the combination of the 2 factors does not represent a clinically useful approach to reliably identify children at risk.

Key words: Eczema, atopic dermatitis, asthma, food sensitization, food allergy, filaggrin, prediction

Abbreviations used: DBPCFC, Double-blind, placebo-controlled food challenge, FLG, Filaggrin, GINI, German Infant Nutritional Intervention, LISA, Influence of Lifestyle-related Factors on the Immune System and the Development of Allergies in Childhood, MAS, Multicenter Allergy Study, NPV, Negative predictive value, PLR, Positive diagnostic likelihood ratio, PPV, Positive predictive value, RR, Relative risk, sIgE, Specific IgE

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Atopic dermatitis (eczema) is the most common inflammatory skin disease in childhood, with prevalence estimates of up to 20%.¹ Eczema is commonly associated with increased levels of total serum IgE antibodies and aberrant IgE-mediated responses to environmental agents. However, up to 50% of infants and children with eczema do not exhibit detectable specific IgE (sIgE) antibodies.², ³, ⁴ In those with early sensitization, the spectrum shifts from common food allergens (hen’s egg, cow’s milk, wheat, and soy) at age 1 year to aeroallergens at age 6 years.⁵ Notably, subjects can have allergic sensitization to food allergens, as determined by skin prick testing or sIgE measurement, without having clinical symptoms on exposure to those foods.⁶ Therefore diagnosis of IgE-mediated food allergy requires both the presence of sensitization and the development of specific signs and symptoms on exposure (ie, noneczematous immediate-type anaphylactic symptoms, eczematous delayed-type reactions, or combinations of both). Through not yet understood mechanisms, the time course of food allergy resolution in children varies by food and mostly occurs in early school-aged years.⁷

Eczema runs a chronic fluctuating course; about two thirds of children with early-onset eczema show spontaneous remission until early adolescence, whereas up to 20% have persistent eczema, and a further 17% show intermittent symptoms by age 7 years. Known risk factors for persisting eczema include severe disease, early allergic sensitization, and 2 or more first-degree relatives with atopic disease.⁸

Up to 50% of patients with childhood eczema go on to have asthma later in life.⁵, ⁹, ¹⁰ However, it has been suggested that not eczema per se but rather early-onset eczema with specific allergic sensitization constitutes a risk for asthma.⁸, ¹¹ In particular, early sensitization to hen’s egg¹², ¹³ and persistent (>1 year) sensitization to food allergens in children with early eczema¹⁴ were reported to increase the risk for subsequent asthma and rhinitis. Findings from the German Multicenter Allergy Study (MAS) imply that allergic rhinitis until the age of 5 years is associated with wheezing between the ages of 5 and 13 years, yet this association is not attributable to eczema.¹⁵

To date, null mutations in the filaggrin gene (FLG) are the strongest and most widely replicated risk factor for eczema, particularly early-onset and persistent eczema with allergic sensitizations, and asthma in the context of eczema.¹⁶, ¹⁷, ¹⁸ A very recent work indicated that FLG mutations might also be of relevance for peanut allergy independently from the presence of eczema.¹⁹

On the basis of observations made in the MAS cohort, it was further suggested that the combination of eczema, sensitization to food allergens, and FLG haploinsufficiency predicts childhood asthma with a specificity and a positive predictive value (PPV) of as much as 100%.²⁰ This is of great interest because it would mean that every infant with this combination will have asthma, that these infants could be identified early in life with the help of simple and rather easily measurable parameters, and that they could be subjected to early interventions and targeted prevention measures.²¹ Overestimation of absolute risk, however, might lead to inadequate or inappropriate intervention in subjects whose asthma risk is actually lower than anticipated. Therefore we were interested to validate these observations and also to evaluate the usefulness of food sensitization and FLG mutation status for the prediction of the course of eczema. To this end, we investigated the German GINI and LISA birth cohorts, as well as a collection of carefully phenotyped children with eczema with or without confirmed food allergy.

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Methods 

Study populations and phenotyping 

For the German Infant Nutritional Intervention (GINI) birth cohort, a total of 5991 full-term newborn infants were recruited from 2 regions of Germany (Munich and Wesel) between 1995 and 1998. The cohort is composed of intervention (n = 2252) and nonintervention (n = 3739) groups. For the current study, the intervention group was used. Briefly, the intervention study was a prospective, randomized double-blind trial designed primarily to examine the effect of different hydrolyzed infant formulas on the development of allergic diseases. Children with a positive family history of allergic disease were enrolled and invited to clinical examinations at 1, 4, 8, 12, and 36 months of age. For the first, second, and third years, diagnosis of eczema was made by using an algorithm of diagnostic criteria, as described previously.²² sIgE levels against cow’s milk, casein, α-lactalbumin, β-lactoglobulin, egg white, and soy allergen were measured at ages 12 and 36 months (Pharmacia and Upjohn Diagnostics AB, Uppsala, Sweden). Sensitization was defined as levels of 0.70 kU/L or greater (RAST class ≥2) against at least 1 of these allergens at 12 or 36 months. The whole birth cohort was followed up to now 10 years by self-administered questionnaires. At 6 and 10 years, a visit to the study center for clinical examination and blood sampling was offered. In participants of the 10-year follow-up visit, sIgE levels against aeroallergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae, German cockroach, cat dander, mixed molds, timothy grass, mugwort, English plantain, ribwort, wall pellitory, and birch pollen) were determined. Sensitization was defined as an sIgE concentration of 0.35 kU/L or greater against at least 1 of the allergens.

Details of the design, recruitment, and follow-up of the study have been described previously.²², ²³, ²⁴, ²⁵ The outcomes presented here are based on parental reports in the 10-year follow-up questionnaire. Asthma and eczema were defined as present if any physician had diagnosed asthma or eczema during the last 4 years, if the child was treated for asthma (eczema) in the last 12 months, or both. In the present analysis we included subjects with a clinical diagnosis of eczema in the first 3 years, known status of food sensitization, and available FLG genotypes who participated in the 10-year follow-up by questionnaire.

For the Influence of Lifestyle-related Factors on the Immune System and the Development of Allergies in Childhood (LISA) birth cohort, 3097 newborns were initially recruited between 1997 and 1999 from 4 German cities: Munich, Leipzig, Wesel, and Bad Honnef. Data on the children’s health and on lifestyle factors were collected by using repeated parent-completed questionnaires at regular time intervals during the first 2 years of life (6, 12, 18, and 24 months) and at 4, 6, and 10 years of age. Early eczema was defined if 1 positive answer was given to the following question: “Has a doctor diagnosed your child with allergic or atopic eczema in the past 6 months?”

Blood samples were drawn at 2, 6, and 10 years of age. At 2 years of age, total IgE and sIgE levels against a set of common food allergens (egg white, cow’s milk, wheat, peanut, soybean, and codfish) were measured by using the CAP-RAST FEIA system (Pharmacia Diagnostics, Freiburg, Germany). Allergic sensitization against food allergens was defined as a specific serum IgE concentration of 0.7 kU/L or greater against at least 1 of the allergens. The design and objectives of this prospective birth cohort study were described in detail elsewhere.²⁶ Total IgE and sIgE levels against aeroallergens were measured at 10 years of age. The definition of outcome variables at age 10 years is identical to that of the GINI cohort.

Of children with eczema aged 0 to 2 years who had been recruited in Munich for genetic studies between 2004 and 2006 (for details, see Weidinger et al¹⁶) and whose parents had given informed consent to be recontacted for follow-up, we randomly selected and reinvited 50 children with well-defined food allergy, as well as 50 children without any detectable sensitization and no history of adverse reactions to food. sIgE data from an enzyme immunoassay (CAP-FEIA; Pharmacia, Uppsala, Sweden) for a panel of food allergens (egg white, cow’s milk, α-lactalbumin, β-lactoglobulin, peanut, soybean, wheat, codfish, and casein) and aeroallergens (mixed grass pollen, D pteronyssinus, D farinae, birch pollen, mugwort pollen, cat dander, dog dander, and Cladosporium herbarum) were available from these children.

Food allergy was defined by (1) a convincing history of reactions to egg white and/or cow’s milk and/or peanut and/or other food; (2) detectable IgE antibodies against the suspected food in serum (positively defined as ≥0.7 kU/L); and (3) positive results on double-blind, placebo-controlled food challenges (DBPCFCs) performed at the time of recruitment, as described previously²⁷ and in accordance with national guidelines.²⁸

Parents were invited to answer a mail-in questionnaire, which included items on respiratory and allergic diseases taken from the European Community Respiratory Health Survey and International Study of Asthma and Allergies in Childhood questionnaires²⁹, ³⁰ to collect information on health outcomes, allergic symptoms, a physician’s diagnosis of allergic diseases, and covariates, such as children’s nutrition, environmental tobacco smoke exposure, and pet ownership. Overall, 75 (75%) subjects returned the completed questionnaire, and of those, 65 agreed to take part in clinical examinations at the local study center between 2009 and 2010. The respective children underwent a skin examination by experienced dermatologists and venous blood sampling. Both total IgE and sIgE levels against the same panel of food allergens and aeroallergens were measured (CAP-FEIA).

Subjects were classified as having asthma or allergic rhinitis when they reported a history of a physician’s diagnosis of asthma or rhinitis at follow-up, whereas eczema was diagnosed on the basis of the skin examination using the UK diagnostic criteria for eczema.

All study methods followed the Declaration of Helsinki protocols and were approved by the ethics committee of the Bavarian Medical Chamber.

Genotyping 

Genotyping for FLG mutations (R501X and 2282del4 in the GINI and LISA cohorts and R501X, 2282del4, R2447X, and S3247X in the case series) was performed as described previously.¹⁷, ³¹

Statistical analysis 

Descriptive statistics for quantitative and qualitative values are presented as means ± SDs and relative frequencies or absolute numbers, respectively.

For the comparison of baseline data between groups, standard tests, such as t tests or the Fisher exact test, were used, and for the comparison of follow-up data, relative risks (RRs) with 95% CIs are given. Standard measures of diagnostic tests, such as sensitivity, specificity, and positive diagnostic likelihood ratio (PLR; calculated as sensitivity/[1 − specificity]), are given to evaluate the prediction of a trait by risk factors and their combinations. PPVs and negative predictive values (NPVs) with 95% CIs were calculated for various possible proportions of the disease in populations. Statistical analyses were done with the statistical software SAS for Windows, version 9.2 (SAS Institute, Inc, Cary, NC). In the case series descriptive analyses were performed with the software R2.12.0.³²

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Results 

Characteristics of the study population 

The study populations comprised 188 GINI children, 240 LISA children, and 65 clinical cases of early eczema (eczema within the first 2 or 3 years of life). At baseline, the median objective SCORAD score was 18 (minimum, 7.1; maximum, 52) in the GINI cohort and 22 (minimum, 7.1; maximum, 75.5) in the clinical cases; the SCORAD score was not determined in the LISA cohort.

In the GINI and LISA cohorts the children were followed up to age 10 years, whereas in the clinical case series the observation period was shorter (mean, 8 years). Table I provides an overview of the clinical characteristics of the children stratified by food sensitization/allergy. The study population comprised 44 and 28 children with and 144 and 212 children without food sensitization in the GINI and LISA cohorts, respectively. FLG genotypes were available from 121 children in the GINI cohort and 139 children in the LISA cohort. The FLG mutation carrier frequencies in these children with early eczema were considerably higher in those displaying a food sensitization (24.1% vs 9.8% in the GINI cohort and 27.8% vs 8.3% in the LISA cohort). The clinical collection of early eczema cases comprised 38 children with and 23 children without food allergy. The frequency of FLG mutations in the clinical case series did not differ significantly between patients with and without food allergy (Table I).

Table I. Characteristics of early-onset eczema cases at recruitment and follow-up stratified by food allergy/sensitization

	GINI cohort		LISA cohort		Clinical cases
	Food sensitization (at 3 y)		Food sensitization (at 2 y)		Food allergy∗
	Yes (n = 44)	No (n = 144)	Yes (n = 28)	No (n = 212)	Yes (n = 38)	No (n = 23)
Sex (male/female)	26/18	68/76	19/9	106/106	30/8	8/15
Mean SCORAD score (SD)	24.2 (10.4)	18.3 (7.7)	—	—	34.5 (18.7)	27.1 (8.4)
Geometric mean of total IgE (kU/L [SD])	121.5 (3.5)	27.1 (3.3)	109.9 (3.0)	18.2 (3.3)	244.7 (6.3)	36.6 (5.2)
FLG mutation carriers, n/N	7/29 (24.1%)	8/82 (9.8%)	5/18 (27.8%)	10/121 (8.3%)	10/38 (26.3%)	8/23 (34.8%)
Follow-up
Persistent eczema, n/N	16/43 (37.2%)	38/139 (27.3%)	9/28 (32.1%)	39/210 (18.6%)	23/38 (60.5%)	16/23 (69.6%)
Mean SCORAD score (SD)	—	—	—	—	29.5 (14.26)	23.0 (9.45)
Asthma, n	10 (22.7%)	15 (10.4%)	11 (39.3%)	17 (8.0%)	18 (47.4%)	6 (26.1%)
Rhinitis, n/N	15/43 (34.9%)	32/140 (22.9%)	10/28 (35.7%)	37/207 (17.9%)	16/38 (42.1%)	10/23 (43.5%)
Geometric mean of total IgE (kU/L [SD])	247.2 (3.6)	82.3 (5.0)	244.7 (5.0)	66.7 (5.0)	473.4 (4.9)	154.5 (4.4)
Food sensitization†/allergy∗, n/N	8/31 (25.8%)	15/104 (14.4%)	8/22 (36.4%)	19/141 (13.5%)	25/38 (65.8%)	0
Sensitization against aeroallergens, n/N	25/31 (80.6%)	57/104 (54.8%)	20/22 (90.9%)	79/141 (56.0%)	36/38 (94.7%)	15/23 (65.2%)

Percentages refer to subjects with available data.

Prediction of asthma 

In the GINI and LISA study populations, at follow-up, physician-diagnosed asthma was reported by 13.6% and 11.2% of the children with early eczema, with significantly higher rates in early food-sensitized children (GINI cohort: RR, 2.2; 95% CI, 1.1-4.5; LISA cohort: RR, 4.8; 95% CI, 2.6-9.4) and in the presence of an FLG mutation (GINI cohort: RR, 2.9; 95% CI, 1.2-6.6; LISA cohort: RR, 2.7; 95% CI, 1.0-7.4). Twenty-four (36.9%) of the clinical eczema cases had developed asthma up to the follow-up examination. Children with food allergy at recruitment more often had asthma than children without food allergy (47.4% vs 26.1%; RR, 1.8; 95% CI, 0.8-7.9), whereas there was no clear difference between FLG mutation carriers and noncarriers (Table I, Table II).

Table II. Basic description of early-onset eczema cases stratified by FLG genotype

	GINI cohort		LISA cohort		Clinical cases
	FLG mutation		FLG mutation		FLG mutation
	Yes (n = 19)	No (n = 118)	Yes (n = 15)	No (n = 134)	Yes (n = 20)	No (n = 45)
Mean SCORAD score	24.2 (12.3)	19.2 (7.7)	—	—	38.3 (12.9)	29.9 (16.4)
Geometric mean of total IgE (kU/L [SD])	40.4 (5.0)	33.1 (4.5)	3.3 (1.1)	3.1 (1.4)	99.5 (5.5)	109.9 (8.2)
Food sensitization∗/allergy,† n/N	7/15 (46.7%)	22/96 (22.9%)	5/15 (33.3%)	13/124 (10.5%)	10/18 (55.1%)	28/43 (65.1%)
Follow-up
Persistent eczema, n/N	6/18 (33.3%)	33/116 (28.4%)	4/15 (26.7%)	23/133 (17.3%)	14/20 (70.0%)	28/45 (62.2%)
Mean SCORAD score (SD)	—	—	—	—	43.07 (11.58)	32.52 (17.09)
Asthma, n	6 (31.6%)	13 (11.0%)	4 (26.7%)	13 (9.7%)	6 (30.0%)	18 (40.0%)
Rhinitis, n/N	6/19 (31.6%)	32/115 (27.8%)	4/15 (26.7%)	24/130 (18.5%)	12/20 (60.0%)	16/45 (35.6%)
Geometric mean of total IgE (kU/L [SD])	221.4 (3.7)	121.5 (4.5)	5.0 (2.0)	4.3 (1.6)	221.4 (4.5)	330.3 (5.5)
Sensitization against aeroallergens, n/N	10/14 (71.4%)	57/91 (62.6%)	10/11 (90.9%)	67/113 (59.3%)	17/20 (85.0%)	38/45 (84.4%)

Percentages refer to subjects with available data.

For food sensitization, we observed PLRs of 1.9 (95% CI, 1.1-3.4) and 5.5 (95% CI, 2.8-10.8), and for FLG mutations, we observed PLRs of 2.9 (95% CI, 1.2-6.6) and 2.8 (95% CI, 1.0-7.9) in the GINI and LISA cohorts, respectively. If both predictors were used, PLRs did not increase significantly (Table III). In the GINI cohort the best predictor was FLG status, whereas in the LISA cohort and in the clinical cases the best predictor was food allergy/sensitization. Logistic regression models confirmed the results, also after adjustment for sex, parental education, and atopy (see Table E1 in this article’s Online Repository at www.jacionline.org). Assuming a prevalence of asthma in children with early eczema of 30% (as observed in MAS), the PPV of food sensitization in combination with the presence of an FLG mutation was estimated to be 52.3% (95% CI, 18.9% to 83.8%) and 66.9% (95% CI, 26.8% to 91.8%) in the GINI and LISA cohorts, respectively. In the clinical cases food allergy plus an FLG mutation reached a PPV of 30.6% (95% CI, 12.2% to 58.4%; Table IV and see Fig E1 in this article’s Online Repository at www.jacionline.org). Specificity was rather high (94.8%, 97.5%, and 83.8% in the GINI cohort, the LISA cohort, and the clinical cases, respectively), whereas sensitivity was very low (13.3%, 11.8%, and 16.7%, respectively; Table III, Table IV).

Table III. Prediction of asthma at age 7 to 10 years in children with early eczema from the GINI and LISA cohorts

	No. not missing predictors, N	Frequency of positive predictors (%)	TP, n	FP, n	TN, n	FN, n	Sensitivity (% [95% CI])	Specificity (% [95% CI])	PLR	PPV for prevalence of 30%	NPV for prevalence of 30%
Predictor: food sensitization
GINI cohort	188	23.4	10	34	129	15	40.0 (21.1-61.3)	79.1 (72.1-85.1)	1.9 (1.1-3.4)	45.1 (31.8-59.1)	75.5 (68.9-81.1)
LISA cohort	240	11.7	11	17	195	17	39.3 (21.5-59.4)	92.9 (88.5-96.0)	5.5 (2.8-10.8)	70.3 (54.8-82.3)	78.1 (72.6-82.8)
Predictor: FLG mutation
GINI cohort	137	13.9	6	13	105	13	31.6 (12.6-56.6)	89.0 (81.9-94.0)	2.9 (1.2-6.6)	55.2 (34.8-74.9)	75.2 (69.0-80.6)
LISA cohort	149	10.1	4	11	121	13	23.5 (6.8-49.9)	91.7 (85.6-95.8)	2.8 (1.0-7.9)	54.8 (30.3-77.2)	73.7 (68.1-78.4)
Predictor: FLG mutation and food sensitization
GINI cohort	111	6.3	2	5	91	13	13.3 (1.7-40.6)	94.8 (88.3-98.3)	2.6 (0.5-12.0)	52.3 (18.9-83.8)	71.8 (67.5-75.8)
LISA cohort	139	3.6	2	3	119	15	11.8 (1.5-36.4)	97.5 (93.0-99.5)	4.8 (0.9-26.6)	66.9 (26.8-91.8)	72.1 (68.4-75.5)

FN, False negative; FP, false positive; TN, true negative; TP, true positive.

Table IV. Prediction of asthma and persistent eczema in clinical eczema cases

Predictor	No. not missing predictors, N	Frequency of positive predictors (%)	TP, n	FP, n	TN, n	FN, n	Sensitivity (% [95% CI])	Specificity (% [95% CI])	PLR	PPV for prevalence of 30%	NPV for prevalence of 30%
Outcome: asthma
Food allergy	61	62.3	18	20	17	6	75.0 (53.3-90.2)	46.0 (29.5-63.1)	1.4 (0.9-2.0)	37.3 (29.9-46.5)	81.1 (66.4-90.3)
FLG mutation	65	30.8	6	14	27	18	25.0 (9.8-46.7)	65.9 (49.4-79.9)	0.7 (0.3-1.7)	23.9 (12.2-41.5)	67.2 (59.8-73.8)
Food allergy + FLG mutation	61	16.4	4	6	31	20	16.7 (4.7-37.4)	83.8 (71.0-93.7)	1.0 (0.3-3.3)	30.6 (12.2-58.4)	70.1 (65.1-74.7)
Outcome: persistent eczema
Food allergy	61	62.3	23	15	7	16	59.0 (42.1-74.4)	31.8 (13.9-54.9)	0.9 (0.6-1.3)	27.0 (20.1-35.3)	64.4 (46.9-78.8)
FLG mutation	65	30.8	14	6	17	28	33.3 (19.6-49.6)	73.9 (51.6-89.8)	1.3 (0.6-2.9)	35.4 (19.6-55.1)	72.1 (65.2-78.1)
Food allergy + FLG mutation	61	16.4	8	2	20	31	20.5 (9.3-36.5)	90.9 (70.8-98.9)	2.3 (0.5-9.7)	49.1 (18.3-80.6)	72.7 (68.4-76.6)

FN, False negative; FP, false positive; TN, true negative; TP, true positive.

Results for wheezing as the outcome were similar to those for asthma (see Table E2 in this article’s Online Repository at www.jacionline.org).

Risk for persistent eczema 

In the GINI and LISA cohorts persistent eczema was defined if parents reported a physician’s diagnosis of eczema in the 7th to 10th year or treatment of eczema in the 10th year. In the case series we used report of “itchy rash during the previous 12 months” plus a clinical diagnosis of eczema during the skin examination at follow-up.

In total, 30.3% of the GINI children, 20.6% of the LISA children, and 64.6% of the children with clinical cases of early eczema still had eczema at follow-up. In the GINI and LISA cohorts persistent eczema was observed slightly more often in children who had displayed early food sensitization and in those carrying an FLG mutation; however, this difference was not statistically significant. In the clinical cases no significant difference between children with and without food allergy was observed, and the presence of an FLG mutation slightly but not significantly increased risk for persistent eczema (Table I, Table II).

In the birth cohorts a specificity of 78.9% or greater and 88.3% or greater and a sensitivity of 30.9% or less and 15.4% or less was observed for food sensitization and FLG mutations as diagnostic criteria to predict eczema persistence, whereas sensitivity for both predictors was low (6.7% and 8.3%). In the GINI and LISA cohorts PLRs were 1.5 (95% CI, 0.9-2.5) and 1.9 (95% CI, 0.9-3.9) for food sensitization and 1.3 (95% CI, 0.5-3.3) and 2.8 (95% CI, 1.0-7.9) for FLG mutations, respectively (Table V). No clear effects were observed in the clinical case series (Table IV). If both predictors were used in combination, only a very moderate improvement was observed in the clinical cases and the LISA cohort (Table IV, Table V). For an estimated prevalence of persistent eczema in 7- to 10-year-old children with a history of early-onset eczema of 30%, the PPV of the combination of food sensitization/allergy and the presence of an FLG mutation for persistent eczema was 36.0% (GINI cohort), 57.8% (LISA cohort), and 49.1% (clinical cases; Table IV, Table V).

Table V. Prediction of persistent eczema at age 7 to 10 years in children with early eczema from the GINI and LISA cohorts

	No. not missing predictors, N	Frequency of positive predictors (%)	TP, n	FP, n	TN, n	FN, n	Sensitivity (% [95% CI])	Specificity (% [95% CI])	PLR	PPV for prevalence of 30%	NPV for prevalence of 30%
Predictor: food sensitization
GINI cohort	183	24.0	17	27	101	38	30.9 (19.1-44.8)	78.9 (70.8-85.6)	1.5 (0.9-2.5)	38.6 (27.2-51.3)	72.7 (68.6-76.5)
LISA cohort	238	11.8	9	19	171	39	18.8 (9.0-32.6)	90.0 (84.8-93.9)	1.9 (0.9-3.9)	44.6 (28.0-62.5)	72.1 (69.1-74.9)
Predictor: FLG mutation
GINI cohort	133	12.8	6	11	83	33	15.4 (5.9-30.5)	88.3 (80.0-94.0)	1.3 (0.5-3.3)	36.1 (18.3-58.6)	70.9 (67.6-73.9)
LISA cohort	148	10.1	4	11	110	23	14.8 (4.4-33.7)	90.9 (84.3-95.4)	2.8 (1.0-7.9)	41.1 (19.4-66.9)	71.3 (67.8-74.6)
Predictor: FLG mutation and food sensitization
GINI cohort	108	5.6	2	4	74	28	6.7 (0.8-22.1)	94.9 (87.4-98.6)	1.3 (0.25-6.7)	36.0 (9.8-74.4)	70.4 (68.0-72.6)
LISA cohort	138	3.6	2	3	111	22	8.3 (1.0-27.0)	97.4 (92.5-99.5)	3.2 (0.6-17.9)	57.8 (19.3-88.6)	71.3 (68.6-73.7)

FN, False negative; FP, false positive; TN, true negative; TP, true positive.

Sensitization patterns 

In the 2 birth cohorts, total IgE levels were significantly higher in those sensitized to food allergens at baseline both at recruitment and follow-up (P < .001). Specific sensitizations against aeroallergens at follow-up were present in 80.6% and 90.9% of the children with early eczema and food sensitization versus 54.8% and 56.0% of the children with early eczema without food sensitization at recruitment (P = .008 and P = .002), respectively. In the clinical case series at follow-up, specific sensitizations against aeroallergens were observed in 36 (94.7%) compared with 15 (65.2%, P = .003), with a median number of sensitizations against 10 and 2 allergens, respectively. Twenty-five (65.8%) of the children with food allergy at baseline reported persistence of this food allergy at follow-up (Table I), with the majority of them having allergy to egg (see Table E3 in this article’s Online Repository at www.jacionline.org). Geometric mean total IgE levels did not differ by FLG mutation status neither at recruitment nor at follow-up in any of the sets.

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Discussion 

In this study we analyzed the effect of early food sensitization or food allergy and FLG haploinsufficiency in children with early eczema on the course of eczema and the risk for asthma. To this end, we used a complementary approach and investigated 2 large birth cohorts (the GINI and LISA cohorts) and a well-characterized series of tertiary care patients who had undergone DBPCFCs.

Although in general children with early eczema, food sensitization, and FLG mutations more often had asthma than children with early eczema and no food sensitization or FLG mutations, our observations do not confirm the results from a previous report from the MAS cohort,²⁰ which found that the combination of early eczema, sensitization to food allergens within the first 3 years of life, and the presence of an FLG mutation predicts the development of asthma with a PPV of 100%. In fact, using comparable criteria in the GINI and LISA cohorts, we estimated PPVs of 52.3% and 66.9% for sensitization and the presence of an FLG mutation. Notably, the combination of FLG null alleles and sensitization to food allergens did not substantially improve the prediction of asthma beyond the single factors.

The observations made in MAS relied on a subgroup of high-risk children, which was further enriched for children with infantile eczema (n = 180 with complete data) and finally comprised 10 children with the hypothesized combination of risk factors.²⁰ Food sensitization in the previous study, as well as in our birth cohorts, was defined as the presence of an sIgE level of 0.70 kU/L or greater. Although the absence of sIgE reliably excludes the presence of IgE-mediated food allergy, high cutoff levels are needed to correctly identify children as having food allergy.³³, ³⁴ To specifically investigate food allergy as trait of interest, we therefore examined also a collection of 38 infants with early eczema and symptomatic IgE-mediated food allergy, as confirmed by means of DBPCFCs, and 23 infants with early eczema but without food allergy. Also in this collection the PPV of food allergy plus an FLG mutation for asthma was only 30.6%, and no improved prediction was observed for the combination of the parameters.

Across the 3 samples, the specificity of asthma prediction by food sensitization and the presence of an FLG mutation was rather high (83.3% to 97.5%), whereas the sensitivity was very low (11.8% of 16.7%), indicating a high proportion of false-negative predictions; that is, a considerable proportion of children at risk for asthma are missed.

In this context also the technical requirements for a conclusive FLG test result and the potential for variability between different FLG genotyping methods have to be considered. Although a small typing error rate is tolerable for rapid large-scale genotyping of large collections, for routine use in clinical practice, where clinical decisions have to be made with confidence, a thorough analytic validation of testing methods together with a high standard of quality assurance would be critical to develop an accurate and reliable FLG mutation test assay.

Notably, PPV, NPV, sensitivity, and specificity reflect population characteristics and do not easily translate to individual patients. Likelihood ratios for a test result are a more useful way of expressing the power of diagnostic tests in estimating how much a test result will change the odds of having the condition. PLRs of greater than 10 are generally considered conclusive, indicating high accuracy. In our study the PLRs for the combination of food sensitization or food allergy and the presence of an FLG mutation were rather small (GINI cohort, 2.6; LISA cohort, 4.8; and clinical cases, 1.0) and not high enough for clinical purposes. In addition, the PLRs of the combined parameters were not superior of those of each parameter considered in isolation.

When interpreting our results compared with those of the previous study, it should be considered that whereas in MAS asthma was defined as an episode of wheeze during the previous year, a definition that might be overly sensitive, we used a parental report of physician-diagnosed asthma, which is the International Study of Asthma and Allergies in Childhood definition used in many large-scale epidemiologic and genetic studies of childhood asthma. However, in our sets, results for wheeze in the past 12 months were comparable to those for parental report of asthma. As in the original report, in our analyses only a limited number of children displayed the risk factors of interest. Finally, the methods of follow-up assessment were different across our cohorts. However, we think that the use of 3 independent sets (ie, a high-risk birth cohort [GINI], a population-representative birth cohort [LISA], and a clinical collection of children with eczema with and without food allergy) allowed us to critically assess the previously reported results. We found that in line with previous studies,⁸, ³⁵ FLG mutations, more severe disease (as reflected by our clinical case series), and early food sensitization each increase the risk for persistent eczema and the development of inhalational allergies. However, the predictive value of the combination of food sensitization and FLG mutations with regard to asthma is considerably lower than proposed, and their clinical utility to predict asthma is further limited by a very low sensitivity. We suggest that our results reflect the complexity of atopic diseases, their still insufficiently understood interrelationship, and the yet limited knowledge on their pathophysiology. It appears unlikely that a reliable prediction of asthma can be achieved by evaluating a few risk factors only, but we suggest that a better understanding of different risk factors and predictors might aid in the definition of patient subpopulations for more effective modes of care and the development of more targeted sets of preventive strategies. From a public health perspective, our results are important and demonstrate the need for other risk prediction scores that include specific biomarkers that are sufficiently uncorrelated with established clinical risk factors and achieve clinical utility.

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Appendix 1 

The GINIplus study group: Helmholtz Zentrum München, Institute of Epidemiology, Munich, Germany (J. Heinrich, H. E. Wichmann, A. Schoetzau, M. Mosetter, J. Schindler, A. Höhnke, K. Franke, B. Laubereau, U. Gehring, S. Sausenthaler, A. Thaqi, A. Zirngibl, A. Zutavern, M. Schnappinger, and C. M. Chen); the Department of Pediatrics, Marien-Hospital, Wesel, Germany (D. Berdel, A. von Berg, B. Filipiak-Pittroff, B. Albrecht, A. Baumgart, C. Beckmann, S. Büttner, S. Diekamp, I. Groß, T. Jakob, K. Klemke, S. Kurpiun, M. Möllemann, and A. Varhelyi); the Department of Pediatrics, Ludwig-Maximilians-Universität, Munich, Germany (S. Koletzko, D. Reinhardt, H. Weigand, I. Antonie, B. Bäumler-Merl, C. Tasch, R. Göhlert, D. Mühlbauer, C. Sönnichsen, T. Sauerwald, A. Kindermann, M. Waag, and M. Koch); the Department of Pediatrics, Technische Universität München, Munich, Germany (C. P. Bauer, A. Grübl, P. Bartels, I. Brockow, A. Fischer, U. Hoffmann, F. Lötzbeyer, R. Mayrl, K. Negele, E.-M. Schill, B. Wolf, and M. Paschke); IUF–Institut für Umweltmedizinische Forschung at the Heinrich-Heine-University, Dusseldorf, Germany (U. Krämer, E. Link, U. Ranft, R. Schins, D. Sugiri, and C. Cramer); and the Centre for Allergy and Environment, Technische Universität München, Munich, Germany (H. Behrendt, J. Grosch, and F. Martin).

The LISAplus study group: Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Epidemiology, Munich, Germany (J. Heinrich, H. E. Wichmann, S. Sausenthaler, C. M. Chen, and M. Schnappinger); the Department of Pediatrics, Municipal Hospital “St. Georg,” Leipzig, Germany (M. Borte and U. Diez); Marien-Hospital Wesel, Department of Pediatrics, Wesel, Germany (A. von Berg, C. Beckmann, and I. Groß); Pediatric Practice, Bad Honnef, Germany (B. Schaaf); Helmholtz Centre for Environmental Research–UFZ, Department of Environmental Immunology/Core Facility Studies, Leipzig, Germany (I. Lehmann, M. Bauer, C. Gräbsch, S. Röder, and M. Schilde); the University of Leipzig, Institute of Hygiene and Environmental Medicine, Leipzig, Germany (O. Herbarth, C. Dick, and J. Magnus); IUF–Institut für Umweltmedizinische Forschung, Dusseldorf, Germany (U. Krämer, E. Link, and C. Cramer); Technische Universität München, Department of Pediatrics, Munich, Germany (C. P. Bauer and U. Hoffmann U); and ZAUM–Center for Allergy and Environment, Technische Universität München, Munich, Germany (H. Behrendt, J. Grosch, and F. Martin).

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• Fig E1. 

  PPVs and NPVs (probability from 0 to 1) for the prediction of asthma at 7 to 10 years in children with early eczema for the prevalence of asthma (probability between 0 and 0.5) by different predictors.

Table E1. Influence of interested predictors on asthma by logistic models in the GINI and LISA cohorts

Values are presented as odds ratios with 95% CIs.

Table E2. The prediction of wheezing in the 10th year of life in children with early eczema from the GINI and LISA cohorts

	No. not missing predictors, N	Frequency of positive predictors (%)	TP, n	FP, n	TN, n	FN, n	Sensitivity (% [95% CI])	Specificity (% [95% CI])	PLR	PPV for prevalence of 30%	NPV for prevalence of 30%
Predictor: food sensitization
GINI cohort	192	22.9	11	33	128	20	35.5 (19.2-54.6)	79.5 (72.4-85.5)	1.7 (0.99-3.0)	42.6 (29.7-56.6)	74.2 (68.6-79.1)
LISA cohort	233	12.0	10	18	182	23	30.3 (15.6-48.7)	91.0 (86.2-94.6)	3.6 (1.9-6.9)	59.1 (42.2-74.0)	75.3 (70.8-79.3)
Predictor: FLG mutation
GINI cohort	140	13.6	4	15	102	19	17.4 (5.0-38.8)	87.2 (79.7-92.6)	1.4 (0.5-3.7)	36.8 17.5-61.5)	71.1 (66.9-75.1)
LISA cohort	148	10.1	4	11	122	11	26.7 (7.8-55.1)	91.7 (85.7-95.8)	3.2 (1.2-8.9)	58.0 (33.4-79.1)	74.5 (68.2-79.9)
Predictor: FLG mutation and food sensitization
GINI cohort	114	6.1	2	5	91	16	11.1 (1.4-34.7)	94.8 (88.3-98.3)	2.1 (0.4-10.2)	47.8 (16.1-81.3)	71.3 (67.7-74.7)
LISA cohort	138	3.6	2	3	121	12	14.3 (1.8-42.8)	98.4 (94.3-99.8)	8.8 (1.3-57.6)	79.3 (36.8-96.2)	72.8 (68.4-76.9)

FN, False negative; FP, false positive; TN, true negative; TP, true positive.

Table E3. Description of children with eczema and food allergy

No. of children with milk allergy at recruitment	24 (63.2%)
No. of children with egg allergy at recruitment	29 (76.3%)
No. of children with peanut allergy at recruitment	7 (18.4%)
No. of children with other food allergy at recruitment	5 (13.2%)
No. of children with gastrointestinal symptoms at recruitment —
in the context of milk allergy	4
in the context of egg allergy	10
in the context of peanut allergy	0
No. of children with skin symptoms at recruitment —
in the context of milk allergy	24
in the context of egg allergy	23
in the context of peanut allergy	5
No. of children with lung symptoms —
in the context of milk allergy	2
in the context of egg allergy	3
in the context of peanut allergy	3
No. of children with anaphylactic symptoms at recruitment —
in the context of milk allergy	0
in the context of egg allergy	1
in the context of peanut allergy	1
No. of children with other symptoms at recruitment —
in the context of milk allergy	0
in the context of egg allergy	1
in the context of peanut allergy	0
No. of children with persistent food allergy at follow-up	25 (65.79%)

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