Measuring Health Disparities By Income Level using California Health Interview Survey (CHIS) Colorectal Cancer Screening Data

In this exercise, we will calculate several measures of health disparities by poverty index for colorectal cancer screening using California Health Interview Survey (CHIS) data. We will use CHIS screening percentages from 2001 to 2007 to see if the disparities have narrowed or widened over that time period.

For this example you will not be using SEER*Stat. Your data will come from the California Health Interview Survey. The instructions in Step A assume that you are familiar with the survey, and that you already know how to retrieve data from the CHIS public-use datasets. (Please note: Other population based health data can be imported into HD*Calc in a comma delimited or fixed column format.)

HD*Calc requires a variable that specifies time points (e.g. Year), and one that specifies the groups to be compared for disparities. In addition there must be a statistic (e.g. a Rate or a Percentage) for which disparities can be measured, and a population count. Other variables can be included but are not essential to create the summary disparity measures.

Step A: Create an export file from CHIS data

  1. Use all of California as your Geographic Area, but limit your population to persons 40 years old and older (the ages for which colorectal screening would apply).
  2. Select the following question from the Cancer Prevention/Screening section of the survey:
    Had a Colonoscopy/SIG/FOBT in Past Five Years (CRC_SCRN)
  3. Use Gender and Federal Poverty Level (FPL) as your "Compare By" variables.
    • Be sure to include all groupings for Poverty Index (Income % of FPL):
      • 0-99%
      • 100-199%
      • 200-299%
      • 300+%
    • For Gender use both of the following groupings:
      • Male
      • Female
  4. Retrieve data for the years 2001, 2003, 2005, and 2007. If each year is analyzed separately, you will need to combine the results for all years into a single file with the year value as a field (column), and with the extra column headings removed. The following fields should be included in each year's data
    • Screening Percent (% with Yes responses)
    • Population
    • Confidence Estimates (Standard Errors)
  5. Request your output in Excel comma-delimited format. You can download and compare your resulting file with this sample: health.disp.chis.colon.fpl.csv (CSV, 3 KB) .

Step B: Import the Data into the HD*Calc Program

  1. When you start the HD*Calc application you will get a message that reminds users to open a data file in order to view the disparity measures.
  2. Select Open... from the File Menu to open your data file. In the Select Health Disparities Input File dialog, change the File Type at the bottom to Import Text File (*.csv). Find the same file that you generated from CHIS in Step A.5 above.
  3. When your file is opened, you will be taken to the HD*Calc Data Import dialog where you will provide all the information needed to identify the fields in your input file. In the edit box at the top please provide a Title for your input data. This title will be displayed with the resulting disparity measures.
  4. Use the Dictionary edit box to select a file for storing your data input specifications.
  5. The checkbox indicating that your Data File Contains Column Headers should not be checked.
  6. Check the box to indicate that your Statistics are Sorted by All Variables In Their Order. This will speed up retrieval of records during computation.
  7. The Fields Are Character Delimited radio button should be selected, and Comma should be selected as the Delimiter.
  8. You must now specify a Field Type for each field in the List of Fields. To do this, select each Field individually (one field at a time) and press the Change button to the right. You will be taken to the Edit Format dialog:
    Select a Field Type from the dropdown at the top:
    • Gender is a Stratification Variable
      For Gender, you must specify the format values and enter them into the text box:
      • 1=Male
      • 2=Female
    • Poverty Index is the Disparity Variable
      For Poverty Index, you must specify the format values and enter them into the text box:
      • 1=0-99% FPL
      • 2=100-199% FPL
      • 3=200-299% FPL
      • 4=300% FPL and Above
    • Survey Year is the Time Variable
      For Survey Year, you must specify the format values and enter them into the text box:
      • 2001=2001
      • 2003=2003
      • 2005=2005
      • 2007=2007
    • Percent is your Rate Statistic
    • Population is your Population Count
    • SE % is your Standard Error Statistic
    • For all the others, select Ignored as your field type
  9. When all your file fields have been defined, press OK. You will then be taken to the main Disparity Measures dialog where your results will be displayed (Step C).

Step C: View Disparity Measures In HD*Calc

  1. When the Disparity Measures (results) dialog opens you will be asked to specify whether the disparity groups in your data are ranked (e.g. by income or education). There are some disparity measures that will only be presented if the groups are ranked. Since this example uses Poverty Index as the basis for the disparity groups, there is an inherent ranking, so press Yes as your response.
  2. Use the Selection dropdown list to select Male or Female sex from your input data. Whenever you choose from that list, all the disparity measures are re-calculated for the selected set of records.
  3. On the Disparity Groups tab, in the Ranking Disparity Groups box, see that the groups in your file are ranked and that the least advantaged group is first. The checkbox below that indicating that a higher rate means healthier (i.e. more screening), should be unchecked. Upon changing this option, a warning dialog box will appear alerting you that some of your resulting disparity measures will be inverted if that setting is incorrect. Press OK.
  4. On the Disparity Table tab you will see all the measures that have been calculated for your data. If you click on the title of a disparity measure, the help system will display a description of that measure.
  5. On the Disparity Chart tab, you can select any measures you wish to view in the graph. You can use the checkbox (top right) to show the percent change over time instead of the actual measures.
  6. The Data Table and Data Chart tabs show the rates read from you data, and some additional fields calculated from your data for use in the computation of disparity measures.
  7. The Combined Chart tab can be used to present input data values and disparity measures on the same graph at the same time.
  8. The Pair Comparison tab allows you to select any two disparity groups to be compared. For the two groups, the Rate Difference and Rate Ratio are calculated and presented on the graph.