There are four basic steps involved in using the DHQ and Diet*Calc:
- Are the DHQ and Diet*Calc right for your study?
- Do you need to make changes to the DHQ instrument?
- What costs can I expect to incur using the DHQ and Diet*Calc?
- How does Diet*Calc work?
1. Are the DHQ and Diet*Calc right for your study?
What is the DHQ and how is it available?
The Diet History Questionnaire (DHQ) is a food frequency questionnaire (FFQ) that consists of 124 food items and includes both portion size and dietary supplement questions. Background of the DHQ describes the instrument itself as well as validation studies that were conducted, details about the foods database, and information about response rates and the length of the questionnaire.
The DHQ II is available in a variety of file formats. As a result, you must determine the method that you will use to capture the data before downloading and printing copies to distribute to study participants. However, you may view or print DHQ1.2007 [PDF - 615 KB] as a sample. It may not be appropriate to use this PDF for processing (this will be discussed in subsequent steps).
What is calculated by Diet*Calc and how do I use the output?
Diet*Calc is software that is used to analyze DHQ data. To use Diet*Calc, you must create a text file containing the questionnaire data. This file is typically created by scanning paper forms (as described in Step 3), although other methods may be used. If you would like to review a summary of the type of output generated by Diet*Calc and view sample files, see Analysis of the DHQ.
2. Do you need to make changes to the DHQ?
Many researchers add, delete, or modify questions on the DHQ. Be aware that revising the questionnaire creates more work and, potentially, more expense for you. First, you must follow specific guidelines in the structure of additional questions. Second, you should create a detailed codebook for your questionnaire and use Diet*Calc's dictionary editor to define the changes for the analysis program. If you are adding food questions, you must obtain nutrient data and add it to the foods database. It is recommended that you use Diet*Calc on test data to verify this process. Finally, you must create your version of the instrument. Typically, this means printing scannable paper forms with your changes. The expense involved in obtaining modified, scannable DHQ forms will vary depending on the IT resources available at your institution and the extent of the changes to the instrument.
3. What costs can I expect to incur using the DHQ and Diet*Calc?
The estimated costs of using the DHQ can vary greatly depending on whether you modify the forms; how you print, distribute, and collect the forms; and how you capture the data. The Diet*Calc software is available at no cost.
4. How does Diet*Calc work?
The Diet*Calc analysis software generates nutrient estimates using:
- the food frequency data collected on the DHQ forms and stored in an ASCII text file; and
- the food and nutrient database, which has the nutrient content for each food (by sex and serving size)
If you would like to submit information regarding your experience with the DHQ, please contact the technical support staff. You will receive a response within two business days.