Data Capture

Mode of Administration

Population Considerations

  • Cultural adaptation may be required to ensure that the screener questions capture the relevant foods or behaviors in the particular study population, and that the questions are understood as intended.
  • Interviewer-administration is appropriate for low-literacy groups; self-administration is not.
  • Some groups cannot answer for themselves (e.g., children or some people with disabilities). Proxy reports can be done, but may be limited by knowledge of the [glossary term:] surrogate reporter (Learn More about Surrogate Reporting).
  • A frequency-type screener is not appropriate for populations that are cognitively or numerically challenged.

Resource Requirements

  • Data collection and data entry system is required, either paper or electronic.
  • Electronic versions require that respondents have computer and/or Internet access.

Study Design Considerations

For more details on the following issues when considering whether to use a screener to answer a particular research question, see Choosing an Approach for Dietary Assessment.

General Considerations

  • Choice of time frame (e.g., past year or past month), should be guided by your study objective and may also be informed by factors related to seasonality (i.e., how often and how much food is consumed in season and not in season) or cognitive abilities.
  • The population's diet can differ systematically by season (Learn More about Season Effect), which can be addressed in study design or analysis. The effect of season of administration on reporting [glossary term:] accuracy has not been studied extensively. One study examining an FFQ found a small difference in reporting frequency over the past year depending on season of administration [10], and presumably this would be relevant to frequency-type screeners.
  • Even though intakes are known to vary from day to day (e.g., from weekdays to weekend days), this [glossary term:] day-of-week effect is not a factor for frequency-type screeners. They can be administered on any day of week when the time frame queried is longer than a week (Learn More about Day-of-Week Effect).
  • [glossary term:] Within-person random error in screeners is due to individuals reporting their diet differently at two time periods. Although this is not much of an issue with screeners, a second administration some months after the first allows measurement of and statistical correction for within-person random error, assuming no change in diet in that time interval.

Guidance for Specific Research Objectives

  • If your research objective is to estimate the [glossary term:] mean intakes of a group, a single administration of the screener may be sufficient. An [glossary term:] internal calibration sub-study in which multiple non-consecutive 24HRs or food records are administered in conjunction with the screener on at least a portion of the sample allows statistical adjustment for [glossary term:] systematic error in data from screeners. Alternatively, data from an external source (called an [glossary term:] external calibration study) can be used (Learn More about Calibration). If not available, [glossary term:] scoring algorithms developed in a different population can be applied (Learn More about Scoring Algorithms for Screeners).
  • If your research objective is to estimate [glossary term:] usual dietary intake distributions for a group (e.g., to examine percentiles or estimate the proportion above or below some threshold), the use of a screener without [glossary term:] calibration is not recommended. Distributions estimated from a screener are narrower than true distributions. Thus, prevalence estimates in the tails of the distribution are biased (Learn More about Usual Dietary Intakes).
  • 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 onset of cancer), a single administration of a screener can be used, but multiple administrations will allow correction for any within-person random error that is present.

    • More importantly, conducting an internal calibration sub-study allows for some statistical correction using [glossary term:] regression calibration of [glossary term:] bias. Alternatively, data from an external calibration study can be used. If not available, scoring algorithms developed in a different population can be applied to reduce bias.

  • If your research objective is to analyze the association between an independent variable and diet as a [glossary term:] dependent variable (e.g., age and diet), 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 the screener has been administered twice.

    • A study in which multiple non-consecutive 24HRs or food records are administered in conjunction with the screener, on at least a portion of the sample, allows for some statistical correction of bias.

  • If your research objective is to analyze change in diet as a result of an intervention (e.g., to evaluate the effectiveness of an educational program to encourage fruit and vegetable intake), the sole use of a screener is not recommended because of overall bias and potential [glossary term:] differential response bias. To avoid the effects of these potential biases, an objective measure, such as measurement of serum carotenoids as a marker for fruit and vegetable intake, should be considered.

    • If the screener is used as the [glossary term:] main dietary assessment instrument, an internal calibration sub-study with the collection of objective measures is recommended to assess and adjust for overall bias. If objective measures are not feasible, multiple non-consecutive 24HR collected at each relevant time period and for each group (i.e., treatment and control) may allow adjustment of biases in estimates of the means. However, the ability of 24HRs to accomplish such adjustment is questionable because recalls themselves may be subject to differential response bias in an intervention setting. 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).

    The screener used should be sufficiently sensitive to detect changes of interest.