Table 2 Best Practice Guidelines for dietary assessment in health research

E/D^a

1

What? — Characteristics of the main dietary component of interest

E

1.1

Clearly define what needs to be measured (e.g. intake of energy, food groups, specific or a range of macro- or micro-nutrients)

E

1.2

Determine how the dietary data will be analysed and presented (e.g. total daily or meal level intakes, food groups or nutrients)

2

Who? — Considerations around the characteristics of study participants

E

2.1

Define the target sample in terms of characteristics (e.g. life stage, ethnicity, health status, body mass index (BMI), socio-economic level, country/region and setting — home, school, hospital)

E

2.2

Identify other issues that could affect the choice of DAT (e.g. literacy, numeracy, language, cultural, disability, time or familiarity with technology)

E

2.3

Consider the study sample size required in relation to the level of variation of your dietary component of interest and study power

3

When? — Time frame considerations

E

3.1

Are you interested in ‘actual’/short-term (hours or several days, up to one week) or ‘usual’/long-term intake (e.g. months or years)? Consider what reference period (e.g. daily, weekly, monthly, yearly) would be best suited to your dietary component of interest

E

3.2

Will data collection in your study be retrospective or prospective?

4

Consider and appraise the different DAT types

E

4.1

In relation to your research question, consider the suitability, strengths and weaknesses of different DAT types^b

E

4.2

Think about participant burden (e.g. study participants’ potential willingness, time, ability, ethical considerations, interest in using different tools and access issues associated with different DATs)

E

4.3

Identify the availability of resources (e.g. staff skill, time, finances)

5

Research and evaluate available tools of interest

E

5.1

Read any available published validation studies:

• Has the DAT been evaluated to measure the dietary component you are interested in?

• Has the DAT been evaluated in a population similar to your population of interest?

• Is the nutrient database used appropriate?

• Are the portion sizes used relevant?

D

5.2

Assess the quality of validation in terms of:

• Has the DAT been compared to an objective method (e.g. biomarkers)?

• Has the DAT been compared to a subjective method (e.g. a different self-reported diet assessment)?

• What were the limitations of the validation study?

D

5.3

The strength of agreement between the two methods:

• Is there any evidence of bias; do the methods agree on average?

• Is there any evidence of imprecision; how closely do the methods agree for an individual?

6

If, based on the validation studies, none of the existing DATs is entirely or wholly suitable, consider the need to modify or update an existing DAT, or create a new DAT and evaluate it

E

6.1

Decide whether an existing tool can be improved. Investigate whether:

• Foods and portion sizes included are characteristic of your target population, and frequency categories are appropriate

• The time period that the questionnaire refers to could be modified to better suit your needs

D

6.2

Consider the face validity of existing tools. Is there evidence the tool has been used to measure dietary intake in your population of interest?

D

6.3

Updated or modified tools may require re-evaluation. Consider if validation can be integrated into your study

7

Consider issues relating to the chosen DAT and the measurement of your dietary component of interest

E

7.1

Obtain information regarding DAT logistics (e.g. tool manual, relevant documents and other requirements from the DAT developer)

E

7.2

Check that the chosen DAT has the most appropriate food/nutrient database and software

E

7.3

Check the requirements for dietary data collection (e.g. entry, coding and software)

D

7.4

Consider collecting additional related data (e.g. was intake typical, supplement use)

8

Prepare an implementation plan to reduce potential biases when using your chosen DAT

E

8.1

Consider potential sampling/selection bias and track non-participation/dropout/withdrawal at different stages

E

8.2

Minimise interviewer bias (e.g. ensure staff qualifications and training are appropriate, develop standardised training protocols and monitoring procedures)

E

8.3

Minimise respondent biases (e.g. use prompts, clear instructions)

E

8.4

Quantify misreporting