<Q> 503 children with asthma from a population of 5384 looks
like 9.3%, not 11.4%.
<A> As indicated by Dr. Sherman, the percentage of children
with asthma in the sample of children surveyed was 9.3%. But because the
NHANES oversampled minority populations, we reported the weighted
estimate, that is the percentage or prevalence of children with asthma
that is representative of the U.S. population (11.4%).
<Q> How did you accomplish skin testing when the only patient
contact you describe is through a survey?
<A> NHANES III (National Health and Nutrition Examination
Survey III), conducted by the National Center for Health Statistics,
Centers for Disease Control, includes an interview, medical evalution,
hearing tests, phlebotomy and, for children 6-16 years of age, skin tests
for some common allergens. We used the term survey in the broader sense
to indicate a full examination or "survey" of the study population.
<P> Your previous publication (Pediatr 2001;107:505) showed an
increased OR for ETS in patients less than 6 yrs at the time of the
survey. Both surveys used the response to "Were you ever told by a doctor
that your child had asthma?" as the diagnostic criteria for asthma. Asthma
before age 6 should have been a positive response for both studies. Why is
it, then, that exposure to ETS was not a significant risk factor in the 6
to 16 yr group?
<A> ETS is a risk factor or irritant for asthma in younger
children, but its role in asthma among older children and adolescents is
less clear. The discrepancy identified by Dr. Sherman may indicate that
allergen-induced asthma overwhelms any contribution of ETS to asthma in
older children. It may also indicate recall bias by the parents who have
children that no longer have asthma.
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