Determining the relative validity and reproducibility of a complementary food frequency questionnaire to assess nutrient intake in New Zealand infants aged 9 to 12 months : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand
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Date
2018
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Massey University
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Abstract
Background: Obtaining information on dietary intake in infants is challenging but
necessary to help understand the relationship between diet and growth and
development. Food frequency questionnaires (FFQ) are commonly used to investigate
dietary intake as they are suited for use in large population groups, can determine intake
over multiple days and minimise participant and researcher burden, and associated
costs. FFQs need to be specific to the population they are to be used in and validated so
that their results can be interpreted with greater confidence. There are currently no
simple, validated dietary assessment methods that are available to assess nutrient
intake for New Zealand infants.
Objective: To validate a complementary food frequency questionnaire (CFFQ) against a
reference method of a four-day weighed food record (4dWFR) for assessing nutrient
intakes of New Zealand infants aged 9 to 12 months. A secondary objective was to assess
the reproducibility of the CFFQ by having it completed on two separate occasions, four
weeks apart.
Methods: A cross-sectional study design was used including ninety-five infants aged 10
± 1 months and their primary caregiver, who completed the CFFQ twice (CFFQ-1 and
CFFQ-2), approximately four weeks apart (to assess reproducibility). Four days of
weighed food records (4dWFR) were collected on non-consecutive days between CFFQ
administrations (validity). Validity and reproducibility were assessed for intakes of
energy, macronutrients and micronutrients using paired t-tests, Pearson’s correlation
coefficients, cross-classification and Bland-Altman analysis. Two data sets were created,
one that included milk intake (breast milk and formula) and one that excluded milk
intake. The data was also adjusted for energy intake, before being reassessed for validity
and reproducibility.
Results: For validity, most nutrient intakes from the CFFQ were comparable to the
4dWFR (range <1% up to 27% different). The CFFQ produced significantly higher nutrient
intakes for fat and saturated fat, but significantly lower nutrient intakes for
carbohydrate, fibre, folate, potassium, thiamin, riboflavin, niacin and vitamin C (p<0.01).
Correlation coefficients ranged from r=0.18 (saturated fat) to r=0.81 (iron; mean r=0.52).
Over half of participants had the same tertile classification by both the 4dWFR and the CFFQ (mean 53.9%, range 39.0% (selenium) to 67.4% (iron)). Between 2.1% (iron and
calcium) and 14.7% (saturated fat) of participants (mean 7.1%) were misclassified into
opposite tertiles. Most of the nutrients showed acceptable agreement between
methods (κ=0.20–0.60). Saturated fat and selenium showed poor agreement (κ<0.20)
and iron showed good agreement (κ>0.60). Removing milk intake weakened the
correlations (range r=0.21 for vitamin E to r=0.60 for niacin, mean r=0.44) and reduced
the agreement between methods (50.3% correctly classified and 9.2% grossly
misclassified). Adjustment for energy intake showed comparable correlation
coefficients (range r=0.24 for fibre and r=0.78 for calcium and iron, mean r=0.52) and
improved the agreement between methods (56.2% correctly classified and 6.8% grossly
misclassified). The CFFQ had adequate performance for reproducibility for all nutrients
and energy with acceptable correlations (r≥0.20) and good cross-classification (>50%
correctly classified and <10% grossly misclassified) apart from fat and saturated fat (40.9%
and 47.3% correctly classified, respectively). All nutrients showed acceptable to good
agreement between the CFFQ-1 and CFFQ-2 (κ>0.20). When milk intake was excluded
and when the data was adjusted for energy intake, there was comparable acceptable to
good correlations and cross-classification.
Conclusion: Although there were some differences in absolute energy and nutrient
intakes between the methods, the CFFQ appears to have acceptable validity for
assessing 14 nutrients and good reproducibility for assessing 18 nutrients and energy in
infants aged 9-12 months. The CFFQ could be used in future research to investigate
infant nutrient intakes where using a simple tool with little participant burden is
beneficial.
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Keywords
Infants, Nutrition, New Zealand, Questionnaires, Evaluation, dietary assessment, reliability, validation, questionnaire, nutrients