Validation of repeated self-reported n-3 PUFA intake using serum phospholipid fatty acids as a biomarker in breast cancer patients during treatment

Table 5 Spearman correlation coefficients (ρ) and cross-classification for selected fatty acids, n = 49

Fatty acid		FFQ v. PFD				PFD v. Biomarker				FFQ v. Biomarker
				Cross-classification				Cross-classification				Cross-classification
	time‡	ρ	95% CI	ST	OT	ρ	95% CI	ST	OT	ρ	95% CI	ST	OT
n-3†	0	0.50*	0.26, 0.69	53	10	0.19	−0.09, 0.45	35	16	0.28*	0.00, 0.52	37	14
	6					0.40*	0.13, 0.61	45	14
	12	0.51*	0.27, 0.69	47	8	0.56*	0.33, 0.73	57	6	0.50*	0.26, 0.69	47	8
EPA	0	0.53*	0.30, 0.71	57	6	0.10	−0.18, 0.37	35	16	0.30*	0.02, 0.54	45	14
	6					0.32*	0.04, 0.55	33	10
	12	0.46*	0.20, 0.65	55	12	0.56*	0.33, 0.73	53	6	0.38*	0.11, 0.60	41	10
DHA	0	0.51*	0.27, 0.69	59	8	0.17	−0.12, 0.43	33	14	0.33*	0.05, 0.56	41	14
	6					0.38*	0.11, 0.60	59	12
	12	0.48*	0.23, 0.67	47	12	0.44*	0.18, 0.64	51	8	0.51*	0.27, 0.69	55	8

CI Confidence interval, PFD pre-coded food diary, FFQ food frequency questionnaire
Cross-classification, % classified in ST: same tertile, OT: opposite tertile, grossly misclassified
†n-3: sum n-3 (ALA (18:3n-3), EPA (20:5n-3), DPA (22:5n-3), DHA (22:6n-3)) for biomarker and total n-3 PUFAs for PFD/FFQ
‡time 0: around surgery (FFQ: presurgery, PFD; postsurgery, biomarker; presurgery), time 6: 6 months postsurgery, time 12: 12 months postsurgery
* p<0.05

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