Continuous NHANES Web Tutorial: Locate Variables: Task 2

Task 2: How to Identify Variable Names and File Locations

To identify the variable names and file locations for the variables in your analysis, you will need to check the variable list for each of the four components:

Demographics
Examination
Laboratory
Questionnaire

Step 1: Demographics

First, you will check the demographics variable list to identify the age and gender variable names and file names.

If you are still at the PDF file of the laboratory survey documentation, click your browser's Back button twice to return to the NHANES 2001-2002 page. If you returned to the NHANES homepage, click the Datasets and Related Documentation link, then click the NHANES 2001-2002 link.

Click the Demographics link, then click the Demographics Variable List link. For your analysis you need the age and gender variables. Find them on the list and note the variable names, their SAS labels, and the file name that the variables are in. Your notes might look like the table below.

Item	Label	Variable	File Name
gender	Gender - Adjudicated	RIAGENDR	DEMO_B
age	Age at Screening Adjudicated - Recode	RIDAGEYR	DEMO_B

Step 2: Examination

Now, you will find the examination variable list and locate the variables that contain blood pressure measurements and apply to your analysis.

From the Demographics variable list, click your browser's Back button twice to return to the NHANES 2001-2002 page. Click the Examination link, and then the Variable List link. This PDF file has many more variables than the Demographic variable list, so use the search feature to locate variables related to "blood pressure." Note the variable names, their SAS labels, and the file name that the variables are in.

Step 3: Laboratory

From the Examination variable list, click your browser's Back button twice to return to the NHANES 2001-2002 page. Click the Laboratory link, and then the Variable List link. Use the search feature to locate variables related to "cholesterol." Note the variable names, their SAS labels, and the file name that the variables are in. There will be two data files with cholesterol variables — l13_b and l40_b. You will need to consult additional documentation to determine which one is appropriate to use in your analysis.

Step 4: Questionnaire

You should also check the Questionnaire variable list to determine which questions pertain to previous hypertension diagnoses and if the sample person is taking mediation or action to control his/her blood pressure. You'll do this one on your own and check your work when you are finished.

Please note that you may find multiple results when searching for your variables. For instance, the results on the search "cholesterol" will render results from both Lab 13 and Lab 40. You should always read the documentation carefully in order to select appropriate variables for your analysis. The documentation recommends that you to use serum total cholesterol and HDL from Lab 13, which contains total cholesterol results using the reference analytic method, rather than Lab 40, which also has total cholesterol as part of the general chemistry. For LDL and Triglycerides, the documentation recommends that you use data from Lab 13AM, which is the morning fasting subsample, as the fasting values on LDL and Triglycerides are the appropriate ones to use for analysis.

Close Window to return to module page.