Among 2479 subjects in the analysis, 1031 (41.6%) were men and 1448 (58.4%) were women. The agreement between responses to the questionnaire and physician claims was similar for both sexes. Subjects were divided into current smokers (n=756, 30.5%), ex-smokers (n=671, 27.1%) and never-smokers (n=1051, 42.4%). Again, the agreement did not differ significantly by smoking groups. Excluding those whose asthma had not been confirmed by a physician did not improve either the kappa coefficient or sensitivity.
Table 3 compares asthma prevalence estimated by questionnaire with that obtained using physician contacts one to five years before the survey. Using physician contacts one year before the survey underestimated the prevalence of asthma determined by the questionnaire. Including additional years of physician claims improved the agreement between the two estimates of asthma prevalence. However, the kappa coefficients of Table 1 did not improve as longer time periods were used. Extending the time considered in the administrative data did not pick up the same subjects identified in the survey.
Table 3. Comparison of asthma prevalence (%) estimated by survey and database
|Survey||Experienced an asthma attack in the previous 12 months||Men5.9||Women7.5||Tota6.8|
|Taking asthma medication||6.0||7.6||6.9|
|Attack or asthma medication||7.4||9.5||8.6|
|Database claims||0-1 years||3.2||4.6||4.0|