Data Capture

Mode of Administration

• Typically interviewer-administered, either face-to-face or by telephone, but may be self-administered.
• Format can be either on paper or electronic (Learn More about Technology in Dietary Assessment).

Population Considerations

• Appropriate for a variety of eating cultures.
• If interviewer-administered, appropriate for groups with literacy challenges.
• Relies on [glossary term:] specific memory and requires respondent (or [glossary term:] surrogate) to be able to report all foods and beverages consumed in the past 24 hours or on the previous day from midnight to midnight.
• Some groups cannot answer for themselves (for example, children or some people with disabilities). Proxy reporting is possible, but data collected may be limited by knowledge of the [glossary term:] surrogate reporter (Learn More about Surrogate Reporting).

Resource Requirements

• Data entry system is required, typically either paper or electronic. For NCI's ASA24, access to high-speed Internet is required.
• Interviewer-administration requires highly-trained interviewer; self-administration requires completely self-explanatory interface.
• Aids that portray different portion sizes may enhance [glossary term:] accuracy of report.

Study Design Considerations

For greater detail on the following issues when considering whether to use a 24HR to answer a particular research question, see Choosing an Approach for Dietary Assessment.

General Considerations

• Recalls should be unannounced so as to avoid potential [glossary term:] reactivity bias.
• The number of recalls needed per person depends on the research question.
• The population's diet can differ systematically by factors called [glossary term:] nuisance effects, such as day of week (Learn More about Day-of-Week Effect), season (Learn More about Season Effect), and sequence for multiple administrations. For all research objectives, these nuisance effects should be considered in design and/or analysis.
• The collection of [glossary term:] recovery biomarkers in a subsample of participants should be considered; these can be used as [glossary term:] reference instruments to reduce [glossary term:] bias for some nutrients.

Guidance for Specific Research Objectives

• If your research objective is to estimate [glossary term:] mean intakes of a group, a single recall per person is sufficient.
• If your research objective is to estimate [glossary term:] usual dietary intake distributions for a group (for example, for the purpose of examining percentiles or estimating the proportion above or below some threshold), at least two non-consecutive recalls are needed among at least a portion of the group to correct for [glossary term:] day-to-day variation (a source of [glossary term:] within-person random error) (Learn More about Usual Dietary Intake).
  
  A larger number of recalls per person may be needed to examine dietary components that are [glossary term:] episodically consumed (for example, Vitamin A, dark green vegetables) as opposed to those that are [glossary term:] non-episodically consumed (for example, protein, total grains).
• If your research objective is to analyze the [glossary term:] association between diet as an [glossary term:] independent variable and another variable (e.g., diet at baseline and later onset of cancer), a single 24HR can be used as the [glossary term:] main dietary assessment instrument, but at least two and up to six non-consecutive 24HRs are preferable. The additional recalls allow correction for day-to-day variation in analyses and thus provide more [glossary term:] precision in estimates of individual intake.
  
  Alternatively, the 24HR can be used as a [glossary term:] reference instrument when a less detailed instrument, such as an [glossary term:] FFQ, is used as the main instrument. In such cases, a 24HR (preferably more than one) is collected from a subsample to allow for regression [glossary term:] calibration of the less detailed instrument (this is called an [glossary term:] internal calibration sub-study). Alternatively, data from an external source (called an [glossary term:] external calibration study) can be used (Learn More about Calibration).
• If your research objective is to analyze the association between one or more independent variables (e.g., socioeconomic status) and diet as a dependent variable, variables known to affect quality of report, such as body mass index, should be assessed and later included as [glossary term:] covariates in analyses.
• If your research objective is to analyze change in dietary intake as a result of an [glossary term:] intervention (e.g., to evaluate the effectiveness of an educational program to encourage fruit and vegetable intake), it is important to consider the potential for [glossary term:] differential response bias between study groups (i.e., whether the bias in each group is similar or different). This is of concern in intervention studies because [glossary term:] exposure to the intervention itself can create differential error in reporting in the treatment group(s) relative to the control group.
  
  To avoid the effects of these potential biases, an objective measure, such as serum carotenoids as a marker for fruit and vegetable intake, could be considered. In addition, collecting and adjusting for other non-dietary self-report information (e.g., social desirability scale) may help characterize individuals who may be more prone to [glossary term:] response bias (Learn More about Social Desirability).
• If your research objective is limited to assessing changes in mean intake of the study groups over time, a single recall at each relevant time may be sufficient. Furthermore, if, at baseline, assignment to the intervention and control groups is randomized, and if thus you assume that the pre-intervention mean intake does not significantly differ between the two groups, the difference between the two groups in post-intervention mean intake may be ascribed to the intervention.
• If your research objective is to compare usual dietary intake distributions between the control and intervention groups, multiple recalls are required.