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Table 3 Reliability tests comparing dietary choline intake between quantitative food frequency questionnaire interviews

From: Development and validation of a quantitative choline food frequency questionnaire for use with drinking and non-drinking pregnant women in Cape Town, South Africa

  Group-level Individual-level Summary
Agreement Agreement Agreement Bias Strength of association Agreement including chance Agreement excluding chance
Wilcoxon signed rank test p Percentage difference Bland-Altman LOA index Bland-Altman Spearman correlation p Spearman correlation2 Tertile classification Kappa statistic Group-level tests at “Good” or “Acceptable” (of 4 tests) Individual-level tests at “Good” or “Acceptable” (of 5 tests)
Same tertile Opposite tertile Weighted for tertiles Above vs. below AI
Heavy drinkers:
 Visit 1 vs. 2 (n = 112) .001 M -0.4% 4.5% < .001 .52 54.5% 9.8% .44 < .001   
 Interpretation1 Poor Good Good Poor Good Good Good Acceptable Poor 2 4
 Visit 1 vs. 3 (n = 78) .026 M -2.8% 7.7% < .001 .43 47.4% 14.1% .28 < .001   
 Interpretation1 Poor Good Poor Poor Acceptable Poor Poor Acceptable Poor 1 2
 Visit 2 vs. 3 (n = 78) .606 M -18.4% 5.1% < .001 .56 50.0% 9.0% .41 < .001   
 Interpretation1 Good Acceptable Good Poor Good Good Good Acceptable Poor 2 4
Abstainers/light-drinkers:
 Visit 1 vs. 2 (n = 72) .522 M -7.1% 4.2% .001 .42 56.9% 2.8% .50 .001   
 Interpretation1 Good Good Good Poor Acceptable Good Good Acceptable Poor 3 4
 Visit 1 vs. 3 (n = 42) < .001 M 9.1% 4.8% < .001 .37 47.6% 2.4% .49 < .001   
 Interpretation1 Poor Good Good Poor Acceptable Poor Good Acceptable Poor 2 3
 Visit 2 vs. 3 (n = 42) .014 M 16.2% 2.4% < .001 .50 50.0% 4.8% .47 < .001   
 Interpretation1 Poor Acceptable Good Poor Good Good Good Acceptable Poor 2 4
  1. 1Interpretation criteria [37]:
  2. Wilcoxon signed rank test: Good: p > 0.05; Poor: p ≤ 0.05
  3. Percentage difference: Good: 0.0 – < 11%; Acceptable: 11 - 20.0%; Poor: > 20%
  4. Bland-Altman LOA index (% outside of limit of agreement): Good: ≤ 5%; Poor: > 5%
  5. Bland-Altman Spearman correlation coefficient: Good: p > 0.05; Poor: p ≤ 0.05
  6. Spearman correlation coefficient: Good: ≥ 0.50; Acceptable: 0.20 – 0.49; Poor < 0.20
  7. Tertile classification (% in same tertile): Good: ≥ 50%; Poor: < 50%
  8. Tertile classification (% in opposite tertile): Good: ≤ 10%, Poor: > 10%
  9. Weighted Kappa statistic: Good: ≥ 0.60; Acceptable: 0.20 – 0.59; Poor: < 0.20
  10. 2p < .001 for all Spearman values
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