Validity and Reproducibility of an Interviewer-administered Food Frequency Questionnaire for the Assessment of Riboflavin Intake in Malaysian Women in Selangor

@#Introduction: The aim of this study was to assess the validity and reproducibility of a food frequency questionnaire (FFQ) specifically developed for the assessment of riboflavin intake among Malaysian women in Selangor. Methods: The study was carried out in Universiti Putra Malaysia (UPM), which consisted of 204 healthy women (102 Chinese and 102 Malay) aged between 19 and 45 years. The FFQs were interviewer-administered, which were completed twice; at the beginning of the study (FFQ-1) and two weeks thereafter (FFQ-2). A two-day 24-hour dietary recall (24DR) was interviewer-administered as the standard criteria method. Data were analyzed using Wilcoxon signed ranks test, Spearman correlation coefficient (SCC), intra-class correlation coefficient (ICC) and Bland-Altman plots to determine the validity and reproducibility. Results: Median riboflavin intake derived from 24DRs was significantly higher than FFQ-2 (p<0.01). Both FFQ-1 and FFQ-2 correlated significantly (p<0.01) with 24DRs with r-value of 0.264 and 0.227, respectively. As for reproducibility between FFQs, SCC value was statistically significant (p<0.01) at 0.545 whereby ICC value was 0.752, which considered as good. Most data points fell between the limits of agreements and were found closer to the horizontal line in the middle. However, the plots showed no linear trend existed between FFQ and 24DR over the range of mean riboflavin intake. Conclusion: The newly developed FFQ were found to be valid and relatively reproducible in the assessment of riboflavin intake among Malaysian women in Selangor.

Association of food intake with serum levels of phosphorus and potassium in hemodialysis patients / 한국영양학회지

PURPOSE: Elevated serum phosphorus and potassium levels are a major problem for hemodialysis (HD) patients. Hyperphosphatemia and hyperkalemia are closely related to intake of dietary phosphorus and potassium. METHODS: This study was conducted in order to investigate the effects of food consumed on serum phosphorus and potassium levels in 48 HD patients (20 males and 28 females). We collected anthropometric data, biochemical parameters, and dietary data of the subjects. Dietary data for usual intake were obtained by use of a food-frequency questionnaire (FFQ) consisting of 21 food items. RESULTS: The mean body mass index (BMI) was 22.2 +/- 3.0 kg/m2, mean serum phosphorus level was 4.50 +/- 1.52 mg/dl, and mean serum potassium level was 4.74 +/- 0.73 mEq/l. Hyperphosphatemia (> 4.5 mg/dl) was found in 45.8% of subjects, and hyperkalemia (> 5.0 mEq/l) in 35.4%. Subjects who took medication only were 56% of total, and those who took medication with dietary therapy were 27%. Patients with medication and dietary therapy showed significantly lower serum phosphorus levels compared to patients with medication only (p < 0.05). Mean duration of HD was 7.9 +/- 7.3 years and it showed positive correlation with serum potassium levels (p < 0.05). Serum phosphorus levels showed positive correlation with intake of mixed grains and soybean milk (p < 0.05). Serum potassium levels showed positive correlation with intake of mixed grains (p < 0.01), potatoes, fish, and high-potassium vegetables (p < 0.05). On the other hand, intake of white rice showed negative correlation with serum potassium levels (p < 0.05). CONCLUSION: The results of our study suggest that intake of white rice rather than mixed grains is an important factor in sustaining normal serum phosphorus and potassium levels. In addition, limiting intake of soybean milk, potatoes, and fish to under three serving per week is recommended. Finally, conduct of a strict dietary therapy along with medical treatment is desirable because inappropriate food intake increases serum phosphorus and potassium levels to a higher than normal range.

Validation and Calibration of Semi-Quantitative Food Frequency Questionnaire: With Participants of the Korean Health and Genome Study / 대한지역사회영양학회지

We carried out a validation-calibration study of the food frequency questionnaire (FFQ) that we had previously developed for a community-based cohort of the Korean Genome and Health Study of the Korea National Genome Research Institute. We have collected a total of 254 3-day diet records (DRs) from 400 subjects, 200 each randomly selected from the two study cohorts of Ansung and Ansan. FFQ was administered at the time of cohort recruitment in 2001, and DRs were collected during a two month period from January through February of 2002. The mean age was 52.2 years. Farming for men and housewife for women were the most common occupations. The majority of the subjects had undergone 6~12 years of education. The general characteristics including demographic and other data were not different from the total cohort subjects. Absolute levels of consumed nutrients including total energy (energy), protein, fat, carbohydrate, calcium, phosphorus, sodium, potassium, iron, retinol, carotene, vitamin A, thiamin, riboflavin, niacin and vitamin C were compared. The average of energy intake was not significantly different between the data collected by the 2 methods. However, consumptions of protein and fat were higher in data of DRs, whereas that of carbohydrate was higher in FFQ data. Significant correlation of each nutrient consumption between the data sets was observed (p <0.05) except in the case of iron, while the average correlation coefficient between them was 0.22 ranging from 0.33 for energy to 0.11 for iron. The results of cross classification by quantile for exact classification ranged from 25.2% (carotene) to 35.0% (phosphorus), and from 64.6% (vitamin A) to 76.4% (retinol) for adjacent classification. The proportion of completely opposite classification was 8.1% in average. Calibration slope was estimated by regression and calibration parameters ranged from 0.025 for carotene to 0.423 for niacin. We conclude that the FFQ we have developed is an appropriate tool for assessing the nutrient intakes as ranking exposures in epidemiology studies in view that amounts of consumed nutrients obtained by FFQ were similar to those collected by DRs, that correlations between consumed nutrients collected by these methods were significant, and that classification results were relatively fair. The correlation coefficients, however, were lower than expected, which may be mainly due to the survey season. In fact, any short-term dietary survey cannot accurately reflect the overall dietary intakes that change heavily depending on seasons. Further studies including the analysis of chemical indices would be helpful for the studies of causal relationship between the diet and disease.