Development of a general practice-based diagnostic asthma-risk index in young children: Reaping the benefits from an ongoing cohort study.

Asthma is the most frequent chronic illness in children. Asthma is usually
diagnosed in general practice. The availability of diagnostic facilities in
primary care is limited and not consistent until the age of 6. As a
consequence, the GP faces a diagnostic, but also a therapeutic problem in
children under 6 with recurrent cough and wheeze.

To construct a clinical asthma-risk index for 1- to 3 year old children who
visit the GP with asthma related complaints. In addition, the effectiveness of
two broad treatment strategies (aggressive versus non-aggressive) in children
with the same score on the clinical asthma-risk index will be compared
non-experimentally.

Every time the child presents with airway complaints, the GP scores a number of
airway symptoms in a standardized way.
All parents will be asked to complete a questionnaire on asthma symptoms, atopy
background, smoking habits, contact with pets and quality of life every 6
months until the children reach the age of 6.
In a subgroup of children, the presence of atopy will be demonstrated by
measuring total IgE and specific IgE (RAST) before the fourth birthday.
In the 5-year old children, the measurement of exhaled nitric oxide (NO) and a
peak flow will be performed. At the age of 6, a lung function test with
metacholine-challenge will be performed.

A lung function measurement and a metacholine challenge test will be performed
in all 6-year old children with asthma-related complaints or on asthma
medication use in the previous year. These measurements are necessary to
diagnose asthma. Children who receive asthma medication and have a negative
metacholine challenge test will be invited for spirometry and a metacholine
challenge test once more. The children on asthma medication use and who are not
hyper responsive will be invited to stop their treatment for one month. After
this period the children will be invited for spirometry and a metacholine
challenge test.

A subsample of children under 4 who tested negative at baseline, will be
invited for a second measurement of total and specific IgE. Normally, this
measurement is determined by a venepuncture. Because of the objections parents
and GPs quite often have to obtain blood by a venepuncture, a convenient method
(finger prick) for sampling blood and analyses for IgE was developed. With this
technique, measurements of total and specific IgE will not be very unpleasant.
In ARCADE we also used this technique without any problems.
All 5-year-old children, will be invited for peak flow and exhaled NO
measurements. During a two-week period peak flow will be determined. A peak
flow measurement may be an important tool for the GP to diagnose asthma. Peak
flow measurement at age 5 could be a good additional diagnostic test to predict
asthma which may result that the metacholine challenge test at age 6 necessary.
Exhaled NO will be measured off line by blowing in a Mylar balloon. Both
measurements are simple and not invasive and will be performed at the hospital
or general practice near the childrens' homes.
A lung function measurement and a metacholine challenge test will be performed
in all 6-year old children with asthma-related complaints or on asthma
medication use in the previous year. These measurements are necessary to
diagnose asthma. To determine whether the respiratory tract of the child will
be hyperactive, the child will receive little amounts of metacholine. This
could result in shortness of breath. When the provocation concentration of
metacholine induces a 20% fall in FEV1 the test will be ended. To increase FEV1
to its normal value the children will receive salbutamol. In rare cases it is
possible that children need more salbutamol to increase the FEV1 to its normal
value. At all times parents can contact the researchers with questions or for
information.
Children who receive asthma medication and have a negative metacholine
challenge test will be invited for spirometry and a metacholine challenge test
once more. The children on asthma medication use and who are not hyper
responsive will be invited to stop their treatment for one month. After this
period the children will be invited for spirometry and a metacholine challenge
test. The parents of the children will be well informed about the consequences
of stopping the treatment or a month. During this period the parents are
instructed to consult their GP when the child will develop airway complaints.
Medication will only be stopped when the GP of the children gives permission.
All the children will receive beta-mimetica. At all time the parents of the
children can contact their GP with questions or problems.