Study Participant Characteristics
Table 1 shows the socio-demographic characteristics of the study participants. Of the 120 participants, 115 (95.8%) completed both the 2 day 24-hour dietary recall and the FFQ. A total of 105 study participants were included in the final analysis, of which 43 (41%) were male and 62 (59%) female. The mean age of participants was 31.9 years (SD: 9.2), 33.3% of them had primary education, and 43 (41%) were housewives.
Table 1. Socio-demographic characteristics of study participants (n=105)
Characteristics of participants
|
Frequency
|
Percent
|
Sex
|
Male
|
43
|
41
|
Female
|
62
|
59
|
Age category
|
20-29
|
49
|
46.7
|
30-39
|
35
|
33.3
|
40-49
|
13
|
12.4
|
50-65
|
8
|
7.6
|
Education
|
Primary
|
35
|
33.3
|
Secondary
|
21
|
20
|
College/university
|
10
|
9.5
|
No formal education
|
39
|
37.2
|
Occupation
|
Farmer and housewife
|
5
|
4.8
|
Housewife
|
43
|
41
|
Employee/private
|
3
|
2.9
|
Merchant
|
25
|
23.8
|
Daily laborer
|
8
|
7.6
|
Unemployed
|
8
|
7.6
|
Development of Food Frequency Questionnaire
The developed FFQ consisted of 89 food and drink items. The food groups include cereals, bread and potatoes, Legumes and pulses, Roots and tubers, vegetables, fruits, egg, milk and dairy, fish and fish-products, meat and poultry, fat and oil, sweets, drinks, and fast foods and pastry. Information obtained from the focal grouped discussion included foods during the different seasons, traditional and ceremonial dishes consumed and foods that are infrequently consumed. The aim is to use the tool particularly for chronic disease dietary risk assessment; for this we compared the mean nutrient intakes previously hypothesized to be associated with chronic diseases. Which includes: macronutrients (carbohydrate, energy, protein and, fat), micronutrients (calcium, iron, vitamin A, vitaminB1, B2) and food groups.
Relative validity analysis
Table 2 shows the mean (SD), median, and 25th, 75th percentiles daily nutrient intakes estimated by the average of two 24-HRs and the FFQ. The mean energy and macronutrient intakes obtained from the FFQ were significantly higher than the average of two 24-HRs. The highest mean difference was for energy 367.6 (CI: 259.0, 476.1), while the lowest was for total fat intake 4.1 (CI: 2.5, 5.7). Similarly, a significant median difference was found in micronutrient intakes between the two measures. The median difference ranged from 0.09mg/day for vitamin B2 to 391.8ugRAE for vitamin A intake.
Table 2. Mean (SD), median, and 25th, 75th percentiles of daily Energy and nutrients intakes estimated by the average of two 24-Hour dietary recalls and FFQ
Energy and nutrients
|
Average of 24-Hour
Dietary Recalls
|
FFQ
|
Independent sample
t-test
|
Mean
|
SD
|
Mean
|
SD
|
Energy (Kcal)
|
1449.50
|
421.60
|
1817.10
|
482.30
|
367.60 *
|
Protein (g)
|
39.40
|
12.20
|
49.90
|
12.50
|
10.50*
|
Total fat (g)
|
17.20
|
5.70
|
21.30
|
6.10
|
4.10*
|
Carbohydrate (g)
|
297.60
|
92.30
|
375.20
|
109.30
|
77.60*
|
|
Median
|
IQR
(25%, 75%)
|
Median
|
IQR
(25%, 75%)
|
Wilcoxon signed Rank test
|
Calcium (mg)
|
463.10
|
337.60, 587.90
|
684.40
|
518.00, 796.80
|
0.000**
|
Iron (mg)
|
56.00
|
41.90, 83.70
|
67.40
|
54.30, 86.80
|
0.009**
|
Vitamin A (ugRAE)
|
259.30
|
51.50, 581.40
|
651.10
|
295.90, 976.60
|
0.000**
|
Vitamin B1 (mg)
|
0.70
|
0.49, 0.98
|
0.81
|
0.54, 1.17
|
0.002**
|
Vitamin B2 (mg)
|
0.70
|
0.54, 0.84
|
0.79
|
0.64, 0.94
|
0.002**
|
*p-value ≤ 0.05 **p- value < 0.01
Table 3 presents the results of correlations between nutrient intakes obtained from the average of two 24-HRs and the FFQ. The Pearson correlation coefficient varied from 0.05 (total fat) to 0.32 (carbohydrate). Except for total fat the correlations were statistically significant. Spearman correlation (rho) obtained for micronutrients ranged from 0.1 (calcium) to 0.49 (vitamin B1). A statistically significant correlation was obtained for vitamin A (p < 0.05) and vitamin B1 (p < 0.05).
Table 3. Correlations of daily Energy and nutrient intakes when comparing the FFQ to the average of two 24-Hour dietary recalls
Macro-nutrients
|
Pearson correlation (95% CI)
|
Bland-Altman statistics
|
Mean Difference (95% CI)
|
95% Limit of Agreement
|
Energy (Kcal)
|
0.24* (0.05, 0.41)
|
367.6 (259.0, 476.1) *
|
-731.9, 1467.1
|
Protein (g)
|
0.22* (0.03, 0.36)
|
10.5 (7.6, 13.5) *
|
-19.7, 40.8
|
Total fat (g)
|
0.05 (-0.14, 0.24)
|
4.4 (2.5, 5.7) *
|
-13.7, 22.5
|
Carbohydrate (g)
|
0.32* (0.14, 0.48)
|
77.6 (54.5, 100.6) *
|
-155.9, 311
|
Micro-nutrients
|
Spearman correlation (95% CI)
|
Bland and Altman statistics for Log transformed data
|
Mean Difference (95% CI)
|
95% Limit of Agreement
|
Calcium (mg)
|
0.10 (-0.09, 0.29)
|
0.15 (0.11, 0.18) *
|
-0.26, 0.55
|
Iron (mg)
|
0.12 (-0.07, 0.30)
|
0.06 (0.007, 0.11) *
|
-0.45, 0.61
|
Vitamin A (ugRAE)
|
0.45* (0.28, 0.59)
|
0.5 (0.34, 0.66) *
|
-1.1, 2.1
|
Vitamin B1 (mg)
|
0.49* (0.33, 0.62)
|
0.1 (0.02, 0.11) *
|
-0.4, 0.5
|
Vitamin B2 (mg)
|
0.17 (-0.02, 0.35)
|
0.05 (0.01, 0.09) *
|
-0.41, 0.51
|
*p-value ≤ 0.05 **p- value < 0.01
CI: Confidence Interval;
Table 4 shows cross-classification and weighted Kappa statistics of daily intakes of energy, nutrients and food group in quartiles assessed with average of two 24-HRs and the FFQ. The proportion of individuals classified by the FFQ and the average of two 24 hour dietary recalls into the same quartile ranged from 13.4% for total fat to 38.1% for vitamin A. However, the proportion classified into opposite quartiles varied from 3.8% (vitamin B1) to 23.8% (total fat). Weighted kappa values ranged from -0.04 (total fat) to 0.18 (vitamin A).
Table 4. Cross-classification and Weighted Kappa statistics of daily Energy and nutrient intakes of in quartiles as assessed with the average of two 24-Hour dietary recall and the FFQ.
Energy and nutrients
|
Cross-classification
|
Kappa statistics
|
% in same quartile individuals
|
% in opposite quartile of individuals
|
Kappa value
|
Energy (Kcal)
|
34.3
|
8.6
|
0.13
|
Protein (g)
|
33.4
|
8.6
|
0.11
|
Total fat (g)
|
13.4
|
23.8
|
-0.04
|
Carbohydrate (g)
|
34.3
|
8.6
|
0.12
|
Calcium (mg)
|
25.7
|
7.6
|
0.09
|
Iron (mg)
|
28.6
|
9.5
|
0.05
|
VitaminA (ugRAE)
|
38.1
|
5.7
|
0.18
|
Vitamin B1 (mg)
|
33.3
|
3.8
|
0.11
|
Vitamin B2 (mg)
|
33.3
|
8.6
|
0.11
|
Table 5 present’s the median, and 25th, 75th percentiles of daily food group intakes estimated by the average of two 24-HRs and FFQ. Both methods provide similar median intake estimates for fruits, eggs, meat/poultry/fish, and daily products. For roots and tubers, the two 24-HR show a higher estimate of median intake. FFQ provides a higher estimates of median vegetable intake. A statistically significant median difference was observed for roots and tubers, eggs and vegetable intake.
Table 5. Mean (SD), median, and 25th, 75th percentiles daily food group intakes estimated by the average of two 24-Hour dietary recalls and FFQ
Food group
|
Average of 24-Hour
Dietary Recalls
|
FFQ
|
|
Median
|
(25%, 75%)
|
Median
|
(25%, 75%)
|
P-value
|
Cereals
|
710
|
(548.5, 817)
|
648
|
(520.9, 852)
|
0.997
|
Legumes
|
94.5
|
(0, 145.5)
|
93
|
(21, 134.9)
|
0.347
|
Roots and Tubers
|
24.5
|
(0, 45)
|
11.2
|
(0, 31.3)
|
0.013*
|
Vegetables
|
79.5
|
(23.5, 156)
|
109
|
(45.3, 159)
|
0.048*
|
Fruits
|
0.0
|
0.0
|
0.0
|
(0, 15.4)
|
0.367
|
Eggs
|
0.0
|
0.0
|
0.0
|
0.0
|
0.000**
|
Dairy products
|
0.0
|
0.0
|
0.0
|
(0, 4.9)
|
0.087
|
Meat/Poultry/Fish
|
0.0
|
0.0
|
0.0
|
0.0
|
0.068
|
Beverages
|
243
|
(152, 334)
|
230.4
|
(183, 320.6)
|
0.971
|
Wilcoxon signed Rank test *p-value ≤ 0.05 **p- value < 0.01
Table 6 shows the correlations between food group intakes obtained from the average of two 24-HRs and the FFQ. Spearman correlation coefficients ranged from 0.12 for egg to 0.78 for legumes. Greater than 0.5 correlation coefficient was observed for legumes (r=0.78). Correlation (0.2-0.49) were observed for cereals (r=0.33), Meat/poultry/fish (r=0.47), fruits (r=0.46), dairy products (r=0.45), roots and tubers (r=0.34), vegetables (r=0.3) and beverages (r=0.2). Correlation was low (<0.2) for egg (r=0.12).
Table 6: Correlations of food group intakes when comparing the FFQ to the average of two 24-Hour dietary recalls.
Food groups
|
Spearman correlation (95% CI)
|
Bland-Altman statistics
|
Mean Difference (95% CI)
|
95% Limit of Agreement
|
Cereals
|
0.33* (0.15, 0.49)
|
9.9 (-41.9, 61.8)
|
535.3, -515.5
|
Legumes
|
0.79* (0.71, 0.85)
|
2.6 (-8.9, 14.1)
|
-113.8, 118.9
|
Vegetables
|
0.33* (0.15, 0.49)
|
7.1 (-15.7, 29.8)
|
-223.7, 237.8
|
Beverages
|
0.20* (0.01,0.38)
|
2.9 (-30.9, 36.6)
|
-339, 344.7
|
|
Spearman correlation (95% CI)
|
Bland and Altman statistics
|
Bland and Altman statistics for Log transformed data
|
Mean Difference (95% CI)
|
95% Limit of Agreement
|
Mean Difference (95% CI)
|
95% Limit of Agreement
|
Roots and Tubers
|
0.34* (0.16, 0.45)
|
16.2 (6.2,26.3) *
|
-87.5, 120.1
|
-0.04(-0.23,0.15)
|
-1.96, 1.88
|
Fruits
|
0.46* (0.23, 0.56)
|
7.9 (1.4, 14.6) *
|
-60.2, 76.2
|
0.15 (0.01,0.29) *
|
-1.25, 1.55
|
Eggs
|
0.12 (-0.07, 0.30)
|
-2.1 (-3.4,0.8) *
|
-15.9, 11.7
|
0.19 (0.11,0.27) *
|
-0.64, 1.03
|
Dairy products
|
0.45* (0.29, 0.59)
|
6.2 (1.9, 10.4) *
|
-37.8, 50.1
|
0.04 (-0.07, 0.14)
|
-1.03, 1.1
|
Meat/Poultry/Fish
|
0.47* (0.31, 0.61)
|
3.8 (-0.8, 8.4)
|
-43.2, 50.8
|
0.06 (-0.01, 0.13)
|
-0.68, 0.8
|
*p-value ≤ 0.05 **p- value < 0.01
Table 7 shows cross-classification and weighted Kappa statistics of daily intakes of food groups in quartiles as assessed with average of two 24-HRs and the FFQ. The highest correct classification into the same quartile was observed for cereals and legumes-i.e., 50.5% and 51.4%, respectively. For the other food groups, the classification into same quartile ranged from 30.5% (beverages) to 40% (roots and tubers). Oppositely classified individuals ranged from 1% (cereals) to 11.4% (beverages). No gross misclassification was observed for intake of legumes. The weighted kappa values ranged from 0.07 (beverages) to 0.35 (legumes).
Table 7. Cross-classification and Weighted Kappa statistics of daily intakes of food group in quartiles as assessed with the average of two 24-Hour dietary recall and the FFQ
Food groups
|
Cross-classification
|
Kappa statistics
|
% in same quartile individuals
|
% in opposite quartile of individuals
|
Kappa value
|
Cereals
|
50.5
|
1
|
0.32
|
Legumes
|
51.4
|
0
|
0.35
|
Roots and Tubers
|
40
|
7.6
|
0.18
|
Vegetables
|
38.1
|
6.7
|
0.17
|
Beverages
|
30.5
|
11.4
|
0.07
|
Figure 1 presents the Bland-Altman plots for energy, protein, carbohydrate, total fat, vitamin B1, vitamin A, vitamin B2, calcium and iron. The Bland-Altman plot was used to evaluate the agreement between the FFQ and 24-HR by plotting for each nutrient the difference between the two methods versus the average of the two methods and calculating the limits of agreement and their corresponding 95% CI. Visual inspection of the Bland-Altman plots for both energy and macronutrients shows no consistent trend across the intake values. The FFQ overestimated energy and macronutrient intakes. Except for total fat intake, increased variability of data points was observed for all nutrients both at low, average and high values (wider limits of agreement). Overall, majority of the data points lied between the Limits of Agreements (LOAs). Some outliers were observed for energy and macro-nutrients. Since differences in nutrient intakes were associated with the mean measurement, data related to the micro-nutrient intake were log transformed for Bland and Altman statistics. The result indicates a trend as the FFQ consistently over estimated vitamin A and iron intake at lower value.
Figure 2 shows the Bland-Altman plots for legumes, cereals, vegetables, beverages, roots and tubers, fruits, egg, dairy product and meat/poultry/fish. Data related to roots and tubers was log transformed for Bland and Altman statistics. A systematic trend of overestimation for roots and tubers and FFQ underestimate beverage intakes at higher values. Majority of the data points are in the 95% of LOA for almost all food groups. A wide LOA was observed for roots and tubers. A wide limit of agreement was observed for roots and tubers.