PURPOSE OF THE STUDY.
To evaluate the long-term reproducibility of positive and negative skin prick testing (SPT) performed in young children as well as the predictive value of SPT for allergic symptoms later on in childhood and early adulthood.
Finnish cohort of 200 unselected healthy newborns in an urban environment followed prospectively from birth to age 20.
One hundred sixty-three individuals underwent clinical examination and SPT to 8 aeroallergens and 3 foods. Numbers of participants evaluated between the ages of 5 and 11, 11 and 20, and 5 and 20 were 128, 136, and 138 respectively. Structured interviews with parents were performed at ages 5 and 11, and with the participants at age 20. Respiratory clinical indices such as allergic rhinoconjunctivitis and recurrent wheezing were evaluated, as well as atopic dermatitis and food hypersensitivity.
Participants with at least 1 positive SPT (aeroallergens and/or foods) at age 5 were also positive at ages 11 and 20. New sensitization occurred in 23% of participants between the ages of 5 and 11 and 19% of participants between the ages of 11 and 20. Negative SPTs at age 5 were consistent in 72% of participants at age 11 and 53% of participants at age 20. The sensitivity of SPT at age 5 and 11 in predicting allergic symptoms was 28% and 47%, respectively; thus, 72% of participants with allergic symptoms at age 11 were SPT negative at age 5. Except for atopic dermatitis, positive SPT at the age of 5 predicted allergic symptoms by age 11 with a specificity of 94% and by age 20 with a specificity of 91%. Of the participants who were symptom-free with positive SPT at age 5, 64% developed allergic symptoms by age 11. Of the patients with allergic symptoms at age 20, 77% had been SPT negative at age 5. Twelve of the 13 participants who were SPT positive but symptom-free at age 5 were evaluated at age 20. Five continued to be symptom free, and 7 of them had developed clinical symptoms.
Positive SPT at age 5 predicts positive SPT later in childhood and adolescence. Clinically, positive SPT predicts allergic symptoms, especially respiratory symptoms, but not atopic dermatitis. Individuals with negative SPT at age 5 may still develop clinical symptoms and positive SPT at a later age.
It is unclear how many of the original 163 participants evaluated at age 5 were also evaluated at ages 11 and 20. This makes it difficult for the reader to evaluate the reported data during each age interval, and the reader must rely on the conclusions drawn by the authors. The food allergen sensitization data must be interpreted with caution. Although there is some description of the clinical histories of participants with positive SPT to foods, the study fails to break down the data for foods alone and does not disclose whether these participants were eating the foods. The conclusion that positive SPT predicts respiratory symptoms should not be extrapolated to include foods. SPT is useful in the evaluation of aeroallergen and food sensitivity but only when performed in conjunction with a thorough clinical history and physical examination. Screening SPT should not be performed and interpreted in isolation.
- Copyright © 2015 by the American Academy of Pediatrics