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

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

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
  1. CI Confidence interval, PFD pre-coded food diary, FFQ food frequency questionnaire
  2. Cross-classification, % classified in ST: same tertile, OT: opposite tertile, grossly misclassified
  3. †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
  4. ‡time 0: around surgery (FFQ: presurgery, PFD; postsurgery, biomarker; presurgery), time 6: 6 months postsurgery, time 12: 12 months postsurgery
  5. * p<0.05