NHIS 2010 cancer data: Discrepancy of number of people who had colonoscopy in the last 12 months?

Hello, I am studying adherence to colon cancer screening test using NHIS 2010 cancerxx data. The frequencies can be found in


The criteria for adherence is as follows:

  1. Need to be 50+years

  2. No history of colon or rectal cancer

  3. Visited doctor in the last 12 month

  4. Doctor recommended colonoscopy

  5. Colonoscopy done within 12 months

For criteria 4, using the question NAF.750_00.000: Doctor recommended you be tested

for colon/rectum problems, past 12 months, there are only 433 participants to whom the doctor recommended colonoscopy.

However when we move to criteria 5, there are more participants who actually had colonoscopy and there are 3 variables with different number of participants who had colonoscopy. The variables and their frequencies are given below (I also included a screenshot below):

  1. NAF.575_00.000: Most recent colonoscopy, time categories: frequency is 190.

  2. Recode: Most recent colonoscopy, time categories (using 2005 method): frequency of 1529

  3. Recode: Most recent colonoscopy, time categories (using 2000 method): frequency of 1636

My questions:

  1. I am not sure why these are different and which one should I use. Please suggest me the right one for my study.

  2. Why there are more participants who had colonoscopy, than doctors’ recommendations?

Thank you.

This seems like a question better suited for the team over at the CDC who work on crafting the document you’ve linked above. You can find their contact information here. However, it looks like (following the criteria you’ve stated above) that the first measure of “most recent colonoscopy” is what you are looking for. It is really the only one that seems to makes sense. Let us know you have any additional questions about IPUMS Health Surveys data.