Multiple Year (2006 ~ 2010) Child Asthma Call-back Survey Prevalence Tables – Technical Information

The Child Asthma Call-back survey (ACBS) requires use of the Behavioral Risk Factor Surveillance System (BRFSS) Random Child Selection Module and Child Asthma Prevalence Module during the BRFSS survey interview. A BRFSS survey respondent is eligible for the child ACBS if they report that the randomly selected child in the household has ever been diagnosed with asthma (lifetime asthma). The number of children with lifetime asthma identified during the BRFSS interview differs depending on the state BRFSS sample size and typically ranges from 200 to 1,000. Due to sample loss between the BRFSS interview and the asthma Call-back interview the number of completed child interviews for the ACBS ranged from 25 to 304 for the years from 2006 through 2010 (Table A). Effective in 2009, the state child data were not weighted and were not included in the annual public release file if there were fewer than 75 interview records for children due to concerns regarding the reliability of the sample weights when so few records were available. Because the ACBS annual sample size for children was limited even in states with a sufficient number to weight, the data for all states implementing the child ACBS from 2006 through 2010 were combined and reweighted. Combining records from all the years each state implemented the child ACBS provides more stable estimates of the characteristics of children with asthma in each state than those resulting from single years. Estimates of the characteristics of the child population with asthma from 35 states and the District of Columbia are included in the multiple-year child tables. Most states contributed four or five years of data to the multiple year file. Table A contains child ACBS sample sizes by year and state.

The annual child ACBS weighting process is based on the BRFSS final child weight for the randomly selected child (_CHILDWT). The sum of the BRFSS child weights for records reporting children with lifetime asthma is an estimate of the total population of children in the state with lifetime asthma. For the ACBS weight, the BRFSS child weight for the randomly selected child is adjusted for loss to sample between the BRFSS interview and the asthma Call-back interview. After adjusting for sample loss, demographic post stratification group (age/sex/race) adjustments are made to account for differential non-response. As an end result of the adjustment for sample loss and the post stratification adjustment, for each state the sum of the ACBS final weights for all ACBS child records is equal to the estimated total state population of children with lifetime asthma in the state.

The reweighting process for the multiple year data file used to produce the child estimates in tables 1 to 14 followed a procedure similar to that used on individual year data files. The multiple years of data were adjusted to represent an average individual year lifetime asthma population for each state. Based on the annual BRFSS child lifetime asthma population estimates, each year’s total estimated child lifetime asthma population was proportionately adjusted to represent that year’s relative contribution to multiple years of combined data. After the proportionate adjustment for the estimated lifetime asthma population, the weights were further adjusted by post-stratifying for differential non-response by demographic subgroups.

Additional information on the ACBS can be accessed at: https://www.cdc.gov/asthma/ACBS.htm and https://www.cdc.gov/brfss/acbs/index.htm.

^* Child data were collected, but records could not be weighted due to sample issues

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