A Two-sample Approach for State Estimates of a Chronic Condition Outcome

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  • 1. A Two-sample Approach for State Estimates of a Chronic Condition Outcome
    Peter F. Graven
    2010 National Conference on Health Statistics
    August 17, 2010 Washington, DC
  • 2. Acknowledgements
    Research funded by a grant from the Robert Wood Johnson Foundation (RWJF) to the State Health Access Data Assistance Center (SHADAC) at the University of Minnesota, School of Public Health
    Travel funded by the National Center for Health Statistics
    2
  • 3. Objective
    To produce state estimates of health information in the NHIS (chronic condition, pre-existing condition, etc.)
    NHIS does not include state in its public use file
    restricted access file provides some opportunity but sample design not intended for state-level estimates
    To calculate appropriate errors for the estimates for comparison between states or as inputs in other analyses
    Predict/impute an outcome measure (condition status) in a survey with state-level sample design (CPS, ACS) using NHIS data
    3
  • 4. Method
    Applying elements of method used in (Schenker, N., Raghunathan, T., Bondarenko, I., 2010) *
    imputed clinical values of hypertension, diabetes and obesity in NHIS with self-reported values and both clinical and self-reported values from NHANES
    self-reported rates were lower than clinical values
    requires multiple imputation techniques and propensity scores
    *Schenker, N., Raghunathan, T., Bondarenko, I., “Improving on analyses of self-reported data in a large-scale health survey by using information from an examination-based survey”. Statistics in Medicine, Volume 29, Issue 5, pages 533–545, February 2010
    4
  • 5. Method-Data
    National Health Interview Survey (NHIS) 1997-2001, 2004-2008
    Minnesota Population Center and State Health Access Data Assistance Center, Integrated Health Interview Series:  Version 2.0.  Minneapolis: University of Minnesota. http://www.ihis.us
    Harmonizes the data and documentation for the NHIS
    1,000’s of vars, 38 years, linkable to NHIS data supplements
    Current Population Survey (CPS) 1999, 2006
    Miriam King, Steven Ruggles, J. Trent Alexander, Sarah Flood, Katie Genadek, Matthew B. Schroeder, Brandon Trampe, and Rebecca Vick. Integrated Public Use Microdata Series, Current Population Survey: Version 3.0. [Machine-readable database]. Minneapolis: University of Minnesota, 2010.
    5
  • 6. Method-Primary Steps
    1) Assemble Data
    2) Identify outcome status in NHIS
    3) Create identically coded covariates in NHIS and CPS
    4) Predict survey of observation using covariates, create subgroups for model
    4b) Predict key variable using covariates
    5) Impute missing CPS values using predicted survey, covariates (or predicted key variable) and interactions
    6) Produce estimates of outcome using imputed data
    6
  • 7. Method- Data Assembly
    7
    *Reference period of survey not the year it was conducted
  • 8. Method-Data Assembly
    8
    Same as original
    Impute these values
  • 9. Method-Identify Outcome status
    Chronic condition
    Limitation of activity due to chronic condition
    asked of all persons
    ~12% of population nationally
    9
  • 10. Method- Create Identical Covariates
    10
    *NHIS missing values imputed using sequential hotdeck
  • 11. Method-Predict Survey Propensity
    Why do you predict the survey?
    although the values of covariates are coded the same, the responses in two surveys may not truly be identical.
    Therefore, by predicting the survey there is a single dimension to assess how likely the observations are to be similar.
    Why predict propensities? Isn’t that used for matching studies?
    for the imputation we are looking for similar observations in different surveys to predict a likely values
    Survey propensity model: age, sex, race, education, marital status, birthplace insurance status, wages, poverty, region
    11
  • 12. Method-Predict Survey Propensity
    Survey propensity: this predicts which survey an observation is from based on its covariates.
    Ideally, you would have very similar distributions implying observations are similarly likely in either dataset.
    This strengthens the case for using NHIS observations to impute CPS observations
    12
  • 13. Method-Predict Survey Propensity
    13
    1= NHIS, 0=CPS
    mean>50% because there are more NHIS obs than CPS obs in the imputation sample
    Similar and narrow shape indicates coding is similar between surveys.
  • 14. Results- Model Sensitivity
    Full Imputation Model
    All covariates interacted by propensity group
    Possible due to large sample size
    Parsimonious Imputation Model
    predicted health status interacted by propensity group
    very similar results due to strength of common health status variable
    Two-Step Model
    Fit all covariates on NHIS, predict on CPS
    Standard errors of state means too small
    14
  • 15. Results-Chronic Prevalence by Survey and Covariates
    15
  • 16. Results- State Means
    16
  • 17. Results-Selected State Means of Chronic by Model
    17
    Highest 10 States
    Lowest 10 States
  • 18. Results-Region vs. State
    Using state instead of region results in 21 states with significantly different rates
    18
  • 19. Limitations/Future Research
    Limitations
    Model selection not optimized, primarily an exercise
    Testing effects would require common variables that should also be included in imputation model
    Future Research
    Investigate why national means are different
    Identify more commonly coded variables between surveys
    Create outcomes that align with pre-existing condition definitions
    Consider applications for other surveys (MEPS, BRFSS)
    19
  • 20. Summary
    Newer accessible methods allows for creative integration of data sources with appropriate uncertainty incorporated
    The ability to make valid state estimates is valuable for health policy
    could be used to develop state estimates of those with pre-existing conditions eligible for the temporary high risk pool
    20
  • 21. Extra: Results-Upper bound of Unexplained Error at State level
    From 1997-2001 NHIS released MSA names
    Data assembled for 1999 CPS with matching MSA and non-MSA (region) codes.
    only MSAs with over 1,000 observations in the 5 years of NHIS were used. Others grouped into their region
    The MSA portion of the MSA/Non-MSA(Region) code have smaller populations than states
    provides an approximate upper bound on the error in the state imputation
    21
  • 22. Extra: Results-MSA/Region Comparison
    22
  • 23. Extra: Results-Survey Correlation for MSA/Region
    Scatterplot of CPS vs NHIS MSA/Region observations
    23