Conclusions about children's reporting accuracy for energy and macronutrients over multiple interviews depend on the analytic approach for comparing reported information to reference information

Abstract

Objective: Validation study data are used to illustrate that conclusions about children's reporting accuracy for energy and macronutrients over multiple interviews (ie, time) depend on the analytic approach for comparing reported and reference information-conventional, which disregards accuracy of reported items and amounts, or reporting-error-sensitive, which classifies reported items as matches (eaten) or intrusions (not eaten), and amounts as corresponding or overreported.

Subjects and design: Children were observed eating school meals on 1 day (n=12), or 2 (n=13) or 3 (n=79) nonconsecutive days separated by >or=25 days, and interviewed in the morning after each observation day about intake the previous day. Reference (observed) and reported information were transformed to energy and macronutrients (ie, protein, carbohydrate, and fat), and compared.

Main outcome measures: For energy and each macronutrient: report rates (reported/reference), correspondence rates (genuine accuracy measures), and inflation ratios (error measures).

Statistical analyses: Mixed-model analyses.

Results: Using the conventional approach for analyzing energy and macronutrients, report rates did not vary systematically over interviews (all four P values >0.61). Using the reporting-error-sensitive approach for analyzing energy and macronutrients, correspondence rates increased over interviews (all four P values <0.04), indicating that reporting accuracy improved over time; inflation ratios decreased, although not significantly, over interviews, also suggesting that reporting accuracy improved over time. Correspondence rates were lower than report rates, indicating that reporting accuracy was worse than implied by conventional measures.

Conclusions: When analyzed using the reporting-error-sensitive approach, children's dietary reporting accuracy for energy and macronutrients improved over time, but the conventional approach masked improvements and overestimated accuracy. The reporting-error-sensitive approach is recommended when analyzing data from validation studies of dietary reporting accuracy for energy and macronutrients.

Figure. Comparing the sets of reference information and reported information using reporting-error-sensitive variables (as illustrated for energy)

^a Set of reference information: Food items (consisting of matches and omissions) and their respective amounts that were actually eaten. ^b Set of reported information: Food items (consisting of matches and intrusions) and their respective amounts that were reported eaten. ^c Omission: A food item that was actually eaten but was not reported eaten. ^d Match: A food item that was actually eaten and was reported eaten. ^e Intrusion: A food item that was not eaten, but was reported eaten. ^f Corresponding amount from a match: The smaller of the reported and reference amounts (or the reported amount if it is equal to the reference amount) for a match. In the figure, for energy, the corresponding amount from matches = 60 (from ¾ c milk) + 100 (from ¼ c baked beans) + 200 (from 1 biscuit) + 230 (from 1 brownie) + 50 (from ½ c grits) + 60 (from ½ c orange juice) = 700 kcal. ^g Unreported amount from a match: The part of the reference amount that exceeds the reported amount (or zero if the reference amount is smaller than the reported amount) for a match. In the figure, for energy, the unreported amount from matches = 20 (from ¼ c milk) + 100 (from ¼ c baked beans) = 120 kcal. ^h Overreported amount from a match: The part of the reported amount that exceeds the reference amount (or zero if the reported amount is smaller than the reference amount) for a match. In the figure, for energy, the overreported amount from matches = 25 (from ¼ c grits) + 30 (from ¼ c orange juice) = 55 kcal. ⁱ Unreported amount from an omission: The entire reference amount for an omission. In the figure, for energy, the unreported amount from omissions = 100 (from 1 sausage) + 260 (from 1 hamburger) = 360 kcal. ^j Overreported amount from an intrusion: The entire reported amount for an intrusion. In the figure, for energy, the overreported amount from intrusions = 70 (from ½ c peaches) + 230 (from 1 hot dog) = 300 kcal. Reference amount: Corresponding amount from matches + unreported amount from matches + unreported amount from omissions. In other words, reference = (corresponding) + (unreported). In the figure, for energy, reference = (60 + 100 + 200 + 230 + 50 + 60) + ([20 + 100] + [100 + 260]) = 1,180 kcal. Reported amount: Corresponding amount from matches + overreported amount from matches + overreported amount from intrusions. In other words, reported = (corresponding) + (overreported). In the figure, for energy, reported = (60 + 100 + 200 + 230 + 50 + 60) + ([25 + 30] + [70 + 230]) = 1,055 kcal. Reporting errors: Reporting errors include a) intrusions, the amounts of which are overreported, and b) overreported amounts from matches. (Although both omissions and unreported amounts from matches are sources of reporting errors, these are more appropriately described as “unreported errors.”) Report rate: For an individual for energy or any nutrient, report rate = (reported ÷ reference) × 100. It is a conventional measure of reporting accuracy that disregards reporting errors. It has a lower bound of 0%, which indicates that no energy or specific nutrient was reported eaten (assuming that some was actually eaten), and no upper bound because there is no limit on what an individual can report eating. Conventional interpretation of this measure is that values close to 100% indicate high reporting accuracy. For an individual, report rate = correspondence rate + inflation ratio. In the Figure, the report rate for energy is (1,055 ÷ 1,180) × 100 = 89%. Correspondence rate: For an individual for energy or any nutrient, correspondence rate = (corresponding amount from matches ÷ reference amount) × 100. It is the percentage of the reference amount to which the aggregate reported amount corresponds. It is a genuine measure of reporting accuracy that is sensitive to reporting errors. A correspondence rate has a lower bound of 0%, which indicates that nothing in the reference set was reported eaten, and an upper bound of 100%, which indicates that all items and amounts in the reference set were reported correctly. Higher correspondence rates reflect better reporting accuracy. In the Figure, the correspondence rate for energy is (700 ÷ 1,180) × 100 = 59%. Inflation ratio: For an individual for energy or any nutrient, inflation ratio = (overreported amount from matches and intrusions ÷ reference amount) × 100. It is a measure of reporting error. An inflation ratio has a lower bound of 0%, which indicates no overreporting from intrusions and overreported amounts of matches, and no upper bound because there is no limit on what an individual can overreport. Lower inflation ratios reflect better reporting accuracy. In the Figure, the inflation ratio for energy is (355 ÷1,180) × 100 = 30%.