A longitudinal study of adult-onset asthma incidence among HMO members.
BACKGROUND
HMO databases offer an opportunity for community based epidemiologic studies of asthma incidence, etiology and treatment. The incidence of asthma in HMO populations and the utility of HMO data, including use of computerized algorithms and manual review of medical charts for determining etiologic factors has not been fully explored.


METHODS
We identified adult-onset asthma, using computerized record searches in a New England HMO. Monthly, our software applied exclusion and inclusion criteria to identify an "at-risk" population and "potential cases". Electronic and paper medical records from the past year were then reviewed for each potential case. Persons with other respiratory diseases or insignificant treatment for asthma were excluded. Confirmed adult-onset asthma (AOA) cases were defined as those potential cases with either new-onset asthma or reactivated mild intermittent asthma that had been quiescent for at least one year. We validated the methods by reviewing charts of selected subjects rejected by the algorithm.


RESULTS
The algorithm was 93 to 99.3% sensitive and 99.6% specific. Sixty-three percent (n = 469) of potential cases were confirmed as AOA. Two thirds of confirmed cases were women with an average age of 34.8 (SD 11.8), and 45% had no evidence of previous asthma diagnosis. The annualized monthly rate of AOA ranged from 4.1 to 11.4 per 1000 at-risk members. Physicians most commonly attribute asthma to infection (59%) and allergy (14%). New-onset cases were more likely attributed to infection, while reactivated cases were more associated with allergies. Medical charts included a discussion of work exposures in relation to asthma in only 32 (7%) cases. Twenty-three of these (72%) indicated there was an association between asthma and workplace exposures for an overall rate of work-related asthma of 4.9%.


CONCLUSIONS
Computerized HMO records can be successfully used to identify AOA. Manual review of these records is important to confirm case status and is useful in evaluation of provider consideration of etiologies. We demonstrated that clinicians attribute most AOA to infection and tend to ignore the contribution of environmental and occupational exposures.
Sama
Susan R
SR
Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. ssama@hsph.harvard.edu
Hunt
Phillip R
PR
Cirillo
C I H Priscilla
CI
Marx
Arminda
A
Rosiello
Richard A
RA
Henneberger
Paul K
PK
Milton
Donald K
DK
D000328:Adult; D017668:Age of Onset; D000465:Algorithms; D001249:Asthma / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D005260:Female; D006279:Health Maintenance Organizations / Q000706:statistics & numerical data*; D006801:Humans; D007239:Infections / Q000453:epidemiology / Q000209:etiology; D008137:Longitudinal Studies; D008297:Male; D008499:Medical Records; D008875:Middle Aged; D009511:New England / Q000453:epidemiology; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology