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Table 3 Relative validity of the SFFQ for nutrients (n = 127)

From: Validity and reproducibility of a short food frequency questionnaire among patients with chronic kidney disease

 

Daily intakes

 

Pearson correlation coefficients

Cross-classification of nutrient distribution

24-hour recalls

SFFQ 2

SFFQ2-24-hour recalls

SFFQ2 vs. means of six 24-hour recalls

 

Mean (SD)

Means of differences (SD)

Unadjusted

Energy-adjusteda

De-attenuatedb

% of subjects classified in same or adjacent quintile

% of misclassified subjects

Energy (kcal)

1758.7 (490.6)

1748.1 (722.8)

-10.5 (669.5)

0.40

.

.

67

4

Protein (g)

75.1 (19.9)

69.7* (28.0)

-5.5 (27.1)

0.39

0.39

0.46

68

2

Carbohydrates (g)

196.3 (63.7)

201.5 (102.3)

5.2 (98.7)

0.36

0.39

0.42

65

5

Fat (g)

61.5 (19.6)

60.0 (28.3)

-1.4 (26.8)

0.44

0.34

0.40

66

1

SFA (g)

24.1 (8.6)

23.6 (13.6)

-0.5 (12.7)

0.47

0.39

0.47

66

1

MUFA (g)

20.4 (7.0)

21.5 (10.1)

1.1 (9.5)

0.43

0.31

0.39

69

2

PUFA (g)

9.2 (4.3)

8.9 (4.9)

-0.4 (5.3)

0.41

0.40

0.46

67

1

Cholesterol (mg)

263.5 (98.5)

234.2* (109.8)

-29.3 (107.5)

0.52

0.44

0.59

68

1

Sugars (g)

75.6 (29.9)

78.3 (71.7)

2.8 (65.9)

0.32

0.32

0.34

65

7

Fibre (g)

19.5 (6.3)

18.4* (8.4)

-1.1 (8.9)

0.35

0.40

0.44

67

5

Alcohol (g)c

10.5 (15.5)

10.7 (17.3)

0.2 (12.4)

0.76

  

87

0

Retinol (μg)

17.9 (66.0)

496.0* (429.8)

478.1 (428.1)

0.42

0.43

0.44

39

20

Carotene (μg)

3372.7 (1627.2)

2318.8* (1604.1)

-1054.0 (1888.6)

0.21

0.21

0.29

66

5

Vitamin B1 (mg)

1.1 (0.3)

1.0* (0.5)

-0.1 (0.5)

0.32

0.27

0.33

61

4

Vitamin B2 (mg)

1.4 (0.5)

1.4 (0.8)

0.0 (0.7)

0.36

0.41

0.47

66

5

Vitamin B3 (mg)

16.6 (5.0)

15.6 (6.8)

-1.0 (7.1)

0.27

0.22

0.29

62

3

Vitamin B5 (mg)

4.5 (1.3)

4.6 (2.3)

0.1 (2.2)

0.27

0.16

0.18

59

5

Vitamin B6 (mg)

1.7 (0.6)

1.5* (0.6)

-0.2 (0.8)

0.26

0.31

0.35

61

5

Vitamin B9

281.7 (90.4)

281.1 (134.2)

-0.6 (139.0)

0.29

0.32

0.37

60

5

Vitamin B12 (μg)c

10.3 (19.2)

5.9 (3.6)

-4.4 (19.2)

0.31

  

60

3

Vitamin C (mg)

112.2 (53.2)

107.9* (113.7)

-4.3 (112.8)

0.20

0.19

0.22

63

7

Vitamin D (μg)

9.1 (1.5)

1.9* (1.0)

-7.2 (1.7)

0.21

0.18

0.26

59

3

Vitamin E (mg)

9.3 (3.9)

10.4 (5.8)

1.1 (5.6)

0.47

0.45

0.52

73

1

Calcium (mg)

1171.0 (338.7)

956.9* (616.5)

-214.1 (560.6)

0.41

0.39

0.43

63

4

Iron (mg)

10.8 (4.0)

10.2 (4.5)

-0.6 (5.1)

0.28

0.17

0.20

61

3

Magnesium (mg)

307.5 (90.2)

329.3 (152.4)

21.8 (138.9)

0.31

0.27

0.29

60

4

Zinc (mg)

10.3 (4.1)

8.8* (3.6)

-1.5 (4.5)

0.33

0.19

0.24

66

5

Phosphorus (mg)

1083.5 (267.9)

1067.8 (492.5)

-15.7 (457.0)

0.36

0.34

0.39

69

6

Manganese (mg)

3.3 (1.7)

11.0* (5.1)

7.7 (4.9)

0.20

0.11

0.11

54

8

Potassium (mg)

2959.8 (793.5)

2983.1 (1547.5)

23.3 (1491.1)

0.31

0.29

0.32

66

6

Iodine (μg)

121.3 (62.3)

108.6* (52.5)

-12.7 (68.1)

0.32

0.22

0.27

65

5

Copper (mg)

2.3 (1.2)

2.3 (1.4)

0.0 (1.6)

0.41

0.37

0.41

69

2

Sodium (mg)

5058.4 (1734.1)

2319.3* (1066.2)

-2739.1 (1875.6)

0.22

0.10

0.12

64

6

Water (g)

2681.7 (604.0)

2674.0 (1454.4)

-7.7 (1458.4)

0.11

0.10

0.10

65

9

  1. SFA Saturated fatty acids, MUFA Monounsaturated fatty acids, PUFA Polyunsaturated fatty acids
  2. Means and cross-classification were computed on crudes variables. All variables were log transformed before computing Pearson correlation coefficients, to improve normality
  3. *Significantly different from the value of the mean of the six 24-h recalls, according to Wilcoxon signed rank tests
  4. aEnergy adjustment according to the residual method
  5. bDe-attenuated and energy-adjusted Pearson’s correlation coefficient (corrected for within-person variation in six 24- h recalls)
  6. cSpearman correlation coefficients were performed because normality was not respected
  7. The statistical tests provided p-values <0.05 for each Pearson correlation coefficient, except for those in bold
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BMC Nephrology

ISSN: 1471-2369

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