What are main error in dietary assessment?

Measurements errors in dietary assessment

Measurements errors in dietary assessment are many sources of errors that arise during data collection and processing. Some of them are:

Respondent bias:

This term is generally used to refer the possible error/bias in information provided by respondents. These mostly occur in interviews, surveys or self-administered approaches when there is no background data to validate the respondent information. Misreporting can be:

Conscious: Respondent provide information what they think is right, not what was actually consumed to hide over and under nutrition.

Unconscious: Respondents misunderstand the asked question or are not able to recall the thing actually eaten.

Sampling or non-response bias:

Sampling or non-response bias occur in dietary survey when selected sample subject do not represent the whole population. Collection of data from specific subjects instead of randomly selected subjects result in significant non-response bias and can occur in all type of nutritional assessment system.

Interviewer/Investigation bias:

It occurs when interviewer focus on some specific question while neglecting other or record the response of subjects incorrectly. The behavior or approach of interview used by interviewer to gather information can also interfere with respondent response.

Furthermore distraction, lack of privacy or discomfort during interview may effect level of trust between interviewer and respondent.

Coding error:

Coding refer to allocation of specific code to food items prior to nutrient analysis of the food intake data. As nutritional content of different food values based on their preparation method hence, codes are allocated accordingly.

In case where no appropriate information regarding preparation method is provided unambiguous allocation of food items can be done by nutritionist in food composition database.

These error also occur when more than one person is involved in coding process. Coding error comes in meal, food and weight coding.

Incorrect estimation of portion choices:

Respondent fail to quantify accurately the amount of food consumed or from misconception of average portion size. This error is probably the largest measurement error in most dietary assessment method.

Respondent memory lipase:

This is defined as unintentional addition or omission of food in recall methods. Memory affects recall method in two ways:

Error of omissions

Error of commissions

Error of omission occur when respondent fail to recall actual food that was consumed while error of commission is recalling the food that was not actually eaten.

Error in handling of mixed dishes:

Mistakes during handling of dishes contribute to error in assessment. Two major sources of error arise in mixed dishes handling:

First error occurs during breakdown of mixed dishes in raw ingredients i.e. identifying original raw ingredients from which consumed dish was prepared.

Second arises during assignment of mix dishes to particular food groups.

Supplement usage:

Supplement usage is mostly omitted from dietary record or recall caused error in calculating nutrient intake. Discrepancies exist in terminology and method used to measure dietary supplements thus causing problem in measuring its usage.

Moreover, variability in dietary supplement brand make it difficult to measure the name and dose of supplement. Additionally, chemical form of dietary supplement affect their bioavailability and in return affect the dietary assessment.