Development and Validation of Database Indexes of Asthma
Severity and Control
Faranak Firoozi 1, Catherine Lemière 2, Marie-France Beauchesne 1, Amelie Forget 2 and Lucie Blais 1*
1 Université de Montréal, Canada
2 Centre de Recherche de l'Hôpital du Sacré-C
ur de Montréal, Canada
* To whom correspondence should be addressed. E-mail: lucie.blais{at}umontreal.ca.
Accepted 18 December 2006
 | Abstract |
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Background
The use of administrative databases to perform
epidemiologic studies in the field of asthma has
expanded in recent years. The unavailability of clinical
parameters to measure the level of asthma severity and
control is considered as one of the major limitations of
database studies. The aim of our study was to develop
and validate two database indexes, one to measure the
control of asthma and the other to measure asthma
severity.
Methods
The database index of asthma severity (3 categories) and
the database index of asthma control (2 categories) were
derived from the definitions found in the Canadian
Asthma Consensus Guidelines and were based upon
dispensed prescriptions (controller therapies, short-
acting beta2-agonists, oral corticosteroids) as well as
the medical services for asthma (ED visits and
hospitalizations), which were recorded in two large
administrative databases from the Canadian province of
Quebec; Régie de l'Assurance Maladie du Quebec (RAMQ)
and MED-ECHO over 12 months. For validation purposes, 71
asthmatic patients were randomly selected from two
asthma clinics and their spirometric lung function
measures were retrieved from their medical chart. For
these patients, we also obtained data on prescriptions
and medical services from the aforementioned databases.
The database indexes of asthma severity and control were
validated against the pulmonary function test results
using t-tests. Our database indexes of asthma severity
and control were also applied in the Quebec cohort which
was comprised of 139 283 person-years of follow-up of
asthmatic patients who were selected from RAMQ and MED-
ECHO databases between January 1st 1997 and December
31st 2004.
Results
According to the database indexes, 49.3%, 29.6% and
21.1% of patients recruited at the asthma clinics were
found to respectively have mild, moderate and severe
asthma while 53.5% were found to have controlled asthma.
The mean predicted value of the forced expiratory volume
in one second (FEV1) ranged from 89.8% for mild asthma
to 61.5% for severe asthma (p-value<0.001) whereas the
range from controlled to uncontrolled asthma was 89.5%
to 67.3% (p-value<0.0001). The ratio of the FEV1 to the
forced vital capacity (FEV1/FVC ratio) was measured for
56 patients and ranged from 75.8% for mild asthma to
61.8% for severe asthma (p-value of pairwise
comparison=0.030) whereas the range from controlled to
uncontrolled asthma was 75.3% to 65.7% (p-value
=0.0009).
Conclusions
In the absence of clinical data, our database indexes
could be used in epidemiologic studies using
administrative databases that record data on dispensed
prescriptions and medical services for asthma to
reasonably assess the severity and control of asthma.
Keywords:
Administrative databases, Asthma control, Asthma severity, Index, Validity
