The overall 1997 estimate of 5.5 percent was inflated by 19.4% (method 1 using study group 1 results) and 33.8% (method 2 using study group 2 results) to yield modified 1997 asthma prevalence estimates of 6.5 % and 7.3 %, respectively. Accounting for the multiple sources of sampling error, we calculated 95% confidence intervals for each of the adjusted 1997 asthma prevalence estimates: 6.5% (95% confidence interval (CI): 5.6%, 7.5%) for method 1 and 7.3% (95% CI: 6.4%, 8.2%) for method 2. This exercise was repeated for years 1998 through 2000.

Using age/race/ethnicity-adjusted values, we found alternative modified 1997 asthma prevalence estimates for methods 1 and 2 to be 6.5% (95% CI: 4.2%, 8.7%) and 7.2% (95% CI: 4.2%, 9.7%), respectively. This second set of estimates demonstrates that taking race/ethnicity and age group differences into account does not change the modified estimates substantially. Therefore, these results are not shown on the chart on the next page.