Effect of Asthma Call-back Survey methodology changes on work-related asthma estimates, 19 states, 2007-2012

Asthma Call-back Survey methodology has been changed recently, as a new sampling design, weights calculation (2011-2012), and revised work-related asthma (WRA) section (2012) were implemented. To assess the effect of these changes on the WRA and possible WRA estimates among ever-employed adults with current asthma, we analyzed 2007-2012 data for 37 505 ever-employed adults (≥18 years) collected from 19 US states (representing an estimated 10 million adults each year).

Using data from landline telephone (LLP) households, we calculated estimates applying poststratification weights (2007-2010) and "raking" weights (2011-2012). Also, using data from LLP/cellular telephone (CP) households combined, we calculated estimates applying "raking" weights (2012).

Based on LLP household data, the WRA estimates ranged from 7.8% to 9.7% during 2007-2010, was 9.1% in 2011 and 15.4% in 2012. Possible WRA estimates ranged from 35.1% to 38.1% during 2007-2010, was 38.1% in 2011 and 39.8% in 2012. Using the 2012 LLP/CP household data, the WRA and possible WRA estimates were 15.4% and 38.9%, respectively.

Implementation of "raking" weights did not substantially change the WRA or possible WRA estimates among ever-employed adults with current asthma. The WRA and possible WRA estimates based on LLP and LLP/CP samples in 2012 were comparable, as CP users are younger and less likely to have WRA. The substantial upward shift in the 2012 WRA estimates likely was associated with the revision to the WRA section.