Measurement error adjustment in essential fatty acid intake from a food frequency questionnaire: alternative approaches and methods

Table 1 Distribution of fatty acid groups and ratios Q₁, M, N, Q₂ and Q₃ : Mean ± SD; ARIC (1987–1995)¹

	Q₁	M	N	Q₂	Q₃
	(n = 7,814)	(n = 2,251)		(n = 634)
Fatty acid groups and ratios j ²
6p	4.43 ± 1.43	55.22 ± 4.46	22.03 ± 2.59	4.29 ± 1.40	4.19 ± 1.36
3p	0.41 ± 0.09	0.41 ± 0.10	0.14 ± 0.05	0.40 ± 0.09	0.41 ± 0.10
6H	0.08 ± 0.03	9.11 ± 1.70	15.80 ± 2.10	0.07 ± 0.03	0.07 ± 0.03
3H	0.18 ± 0.16	1.01 ± 0.39	3.44 ± 1.05	0.17 ± 0.15	0.16 ± 0.15
6	4.50 ± 1.43	63.31 ± 4.01	37.73 ± 1.78	4.37 ± 1.41	4.27 ± 1.36
3	0.60 ± 0.19	1.42 ± 0.43	3.59 ± 1.05	0.57 ± 0.18	0.57 ± 0.18
3p/6p	0.10 ± 0.04	0.01 ± 0.00	0.01 ± 0.00	0.10 ± 0.02	0.11 ± 0.05
3H/6H	2.27 ± 1.87	0.11 ± 0.05	0.22 ± 0.08	2.22 ± 1.71	2.12 ± 1.69
3/6	0.15 ± 0.07	0.02 ± 0.01	0.09 ± 0.03	0.14 ± 0.07	0.15 ± 0.07

¹ Q₁: Food frequency questionnaire measurement at visit 1 of fatty acid group intake as % of energy intake or ratio of n-3 to n-6 groups. M: biomarker of fatty acid intake in cholesteryl ester fraction of plasma; N: biomarker of fatty acid intake in phospholipid fraction of plasma; Q₂: Repeat of Q₁ measured at visit 2 among a subset of the cohort; Q₃: Repeat of Q₁ measured at visit 3 among the surviving baseline cohort. ² (3P) n-3 C₁₈ polyunsaturated fatty acids: 18:3+18:4n-3 (6P) n-6 C₁₈ polyunsaturated fatty acids: 18:2+18:3n-6 (3H) n-3 C₂₀ and C₂₂ highly unsaturated fatty acids (HUFAs): 20:5+22:5+22:6n-3 and (6H) n-6 HUFAs: 20:3+20:4+22:4+22:5n-6. Sums of fatty acid intake as percent of energy included (3) = (3P)+(3H) and (6) = (6P)+(6H). Ratios of interest: 3P/6P, 3H/6H and (3P+3H)/(6P+6H) also denoted as 3/6. Notation: The chemical structure of each fatty acid is as follows: "Total number of carbon atoms" : "# of double bonds" n-"carbon number with first double bond starting from the methyl end.

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