Ethnic differences in peanut allergy patterns in South African children with atopic dermatitis.
BACKGROUND
The prevalence of peanut allergy in South Africa is unknown, but previously thought to be low, particularly in black South Africans. This study aimed to determine the prevalence of component patterns and predictive values of screening tests in peanut allergy in South African children with atopic dermatitis (AD).


METHODS
This was a prospective, observational study in a pediatric university hospital in Cape Town. Children with AD, aged 6 months to 10 years, were recruited randomly. They were assessed for sensitization and allergy to peanut by questionnaire, skin prick tests (SPT), Immuno Solid Phase Allergen Chip test, ImmunoCAP component tests to Ara h 1, 2, 3, 8, and 9, and incremental food challenges.


RESULTS
A total of 100 participants (59 black Africans and 41 of mixed race) were enrolled, median age 42 months. There was a high and comparable rate of peanut sensitization in both black African (41%) and mixed race patients (50%), but a significantly lower prevalence of peanut allergy in the black African group (15% vs. 38%, p = 0.01). The component Ara h 2 was the most useful in differentiating allergy from tolerance in both ethnic groups, but had a significantly lower predictive value for peanut allergy in blacks (53%) vs. mixed race (93%). Overall, SPT and Ara h 2 produced the highest area under the receiver operating characteristic curve. A total of 95% positive predictive values (PPV) for SPT, peanut-specific IgE, and Ara h 2 levels varied significantly between the two ethnic groups.


CONCLUSIONS
The prevalence of peanut allergy is high in South African children with AD, but significantly lower in blacks compared to mixed race patients. The component Ara h 2 is useful for differentiating allergy from tolerance in both ethnic groups. Ninety-five% PPV for peanut allergy tests may need to be revised by ethnic group.
Division of Allergology, Red Cross War Memorial Children's Hospital, Cape Town, South Africa.
Claudia L
CL
Gray
Division of Allergology, Red Cross War Memorial Children's Hospital, Cape Town, South Africa.
Michael E
ME
Levin
Department of Paediatrics and Child Health, Red Cross War Memorial Children's Hospital, University of Cape Town, Cape Town, South Africa.|King's College London, King's Health Partners, MRM & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.|Department of Paediatric Allergy, Guy's and St Thomas' NHS Foundation Trust, London, UK.
George
G
du Toit
D000485:Allergens / Q000276:immunology; D044383:Black People; D002648:Child; D002675:Child, Preschool; D003876:Dermatitis, Atopic / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007114:Immunization; D007223:Infant; D008297:Male; D021183:Peanut Hypersensitivity / Q000175:diagnosis / Q000453:epidemiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012882:Skin Tests; D013019:South Africa
D000485:Allergens
95% positive predictive values; Ara h 2; Black Africans; atopic dermatitis; ethnic differences; peanut allergy; peanut components; protective factors