Relative Validity and Reproducibility of a Food Frequency Questionnaire to Assess Food Group Intake in Pregnant Jordanian Women

BackgroundResearch on the relationship between maternal diet and pregnancy outcomes requires valid dietary assessment tools in pregnancy.ObjectiveThis study aimed to develop and examine the relative validity and reproducibility of a quantitative food frequency questionnaire (FFQ) to estimate food group intake in a sample of pregnant Jordanian women.DesignIn this validation study, food group intake from a culturally sensitive quantitative FFQ was compared with food group intake from three 24-hour dietary recalls.Participants and settingThe validation study was conducted from 2015 to 2017 at the maternity clinics in Jordan University Hospital among 131 healthy singleton pregnant Jordanian women. Of these women, 30 also took part in the reproducibility phase, which involved repeated completion of the FFQ in a time frame of 1 month. Pregnant women who had gestational diabetes, preeclampsia, and chronic diseases were excluded.Main outcome measuresRelative validity and reproducibility of a 117-item quantitative FFQ used to estimate usual food intake over a period of 1 month.Statistical analyses performedIntraclass correlation coefficients and weighted κ statistics were calculated to test the reproducibility between the two administrations of the FFQ. Pearson correlations were estimated to validate the FFQ against 24-hour dietary recalls. Cross-classification and Bland-Altman plots were used to examine the agreement between the two dietary assessment methods.ResultsThe intraclass correlation coefficients between the two FFQs ranged from 0.24 for legumes to 0.93 for processed meats. A moderate level of agreement was observed between two FFQs. De-attenuated and energy-adjusted correlations ranged from 0.08 for sweets and sugar to 0.93 for sugary drinks. On average, 50.9% and 45.2% of participants were classified by the FFQ and the 24-hour dietary recalls into the same quartile based on their crude and energy-adjusted food group intake, respectively. Bland-Altman plots showed satisfactory agreement between two methods for most food groups.ConclusionsThe FFQ showed moderate reproducibility and good relative validity for most food groups.     

Validity and reproducibility of the food-frequency questionnaire used in the Shanghai men's health study

We evaluated the validity and reproducibility of the FFQ used in the Shanghai Men's Health Study (SMHS). The study included 195 randomly selected participants of the SMHS who completed one FFQ at baseline, twelve 24-hour dietary recalls (24-HDR) (once a month for twelve consecutive months) and a second FFQ at the end of the study. The FFQ accounted for 88.78% of the foods recorded in the 24-HDR surveys. The validity of the FFQ was evaluated by comparing nutrient and food group intake levels from the second FFQ and the multiple 24-HDR. Correlation coefficients ranged from 0.38 to 0.64 for macronutrients, 0.33 to 0.58 for micronutrients and 0.35 to 0.72 for food groups. Misclassification to opposite quartiles for nutrients and food groups was rare, ranging from 1.5 to 7.7%, while exact agreement rates were between 31.8 and 53.3%. The reliability of the FFQ was assessed by comparing the intake levels from the two FFQ. Correlation coefficients were 0.39 to 0.53 for macronutrients, 0.38 to 0.52 for micronutrients and 0.39 to 0.64 for food groups. Exact agreement rates for quartile distribution were between 31.8 and 49.2%, while misclassification to opposite quartiles was between 1.5 and 6.2%. These data indicate that the SMHS FFQ can reasonably categorise usual intake of nutrients and food groups among men living in urban Shanghai.     

A Food Frequency Questionnaire can Detect Pregnancy-Related Changes in Diet

Objective To determine whether a food frequency questionnaire (FFQ) can detect changes in dietary intake before pregnancy to mid-pregnancy relative to a 4-day food record.Design FFQs and 4-day, weighed food records (4DRs) were completed during similar time intervals before pregnancy and again near mid-pregnancy by women served by a large health maintenance organization in the Minneapolis-St Paul, Minn, area. The outcome of interest was change in the intake of energy and 16 nutrients. Participants were members of the Diana Project, a prospective study of relationships among prepregnancy and pregnancy nutritional and other exposures and reproductive outcomes. Fifty-six (51%) of the eligible women completed the study.Subjects Well-educated, healthy, white women.Statistical analyses performed Spearman rank order correlations.Results Mean energy and nutrient intake levels estimated using the 4DR were generally higher than those estimated using the FFQ. Correlations between change in energy and nutrient intakes measured by the 4DR and FFQ ranged from 0.75 for vitamin C to 0.02 for cholesterol and averaged 0.48.Applications Comparisons with 4DRs indicate that the FFQ used in this study is appropriate for obtaining reliable estimates of prepregnancy to mid-pregnancy changes in intake of energy and a number of nutrients in similar groups of women. J Am Diet Assoc. 1996; 96:262-266.     

Reproducibility and validity of a food frequency questionnaire among Vietnamese in Ho Chi Minh City

OBJECTIVE: Our objective was to assess the reproducibility and validity of a food frequency questionnaire (FFQ) among individuals living in Ho Chi Minh City, Vietnam. METHODS: A total of 116 food items in our FFQ were selected by ranking food items according to their contribution to the population intake of nutrients, based on multiple 24-hour recalls (24HRs) from 144 participants in July 2001. The FFQ was validated by using three 24HRs for 118 men and women in Ho Chi Minh City, Vietnam in August 2002. The reproducibility of the FFQ was assessed by repeated administration at 7 +/- 3.4 days. RESULTS: The reproducibility study showed that Spearman correlation coefficients, adjusted for energy intake, ranged from 0.47 to 0.72, and that weighted kappa values ranged from 0.42 for lipid to 0.65 for potassium. In the validation study, correlation coefficients, adjusted for energy intake, between the FFQ and the 24HRs ranged from 0.16 (calcium) to 0.45 (retinol). The proportion of subjects classified by the FFQ into the same third as determined by the 24HRs was between 42% and 62%. CONCLUSIONS: This food frequency questionnaire measured the usual intake of major nutrients for Vietnamese adults living in Ho Chi Minh City and its urban area, where dietary patterns are similar to those of the Vietnamese population.     

Validity and reproducibility of the food frequency questionnaire used in the Shanghai Women's Health Study

To evaluate the validity and reliability of the food frequency questionnaire (FFQ) used in the Shanghai Women's Health Study (SWHS), 200 SWHS participants were recruited for a dietary calibration study. Study participants completed an FFQ at baseline and 24-h dietary recalls (24-HDR) twice per month consecutively for 12 months. At the end of the study, a second FFQ was administered. Of the 200 study participants, 196 completed 24 or more days of 24-h dietary recalls, 191 completed two FFQs from whom the results of this report were based. The FFQ included the foods that accounted for 86% of the foods recorded in the 24-HDR surveys. Validity of the FFQ was evaluated by comparing intake levels of major nutrients and foods obtained from the second FFQ with those derived from the multiple 24-HDR. The median intake for major nutrients, rice, poultry and meat derived from the second FFQ and the 24-HDR was similar, with the differences ranging from 1.3 to 12.1%. The FFQ tended to overestimate the intake level of total vegetables and total fruits, and the differences were explained mainly by over-reporting seasonal vegetables and fruits consumption in the FFQ. Nutrient and food intake assessed by the FFQ and the multiple 24-HDR correlated very well, with the correlation coefficients being 0.59-0.66 for macronutrients, 0.41-0.59 for micronutrients, and 0.41-0.66 for major food groups. The reliability of the FFQ was assessed by comparing the correlation and median intake of nutrients and food groups obtained from the two FFQs that were administered approximately 2 y apart. The median intake levels for selected nutrients and food groups derived from the two FFQs were similar with differences below 10%. At the individual level, the intake levels of these dietary variables obtained from two FFQs also correlated well. When nutrient and food group intakes were categorized into quartiles, FFQ and 24-HDR produced exact agreement rates between 33 and 50%. Misclassification to adjacent quartile was common, ranging from 34-48%, while misclassification to an extreme quartile was rare (1-6%). These data indicate that the SWHS FFQ can reliably and accurately measure usual intake of major nutrients and food groups among women in Shanghai.     

Validity and reproducibility of a self-administered food frequency questionnaire in older people

This study assesses the validity and reproducibility of a 145-item self-administered food frequency questionnaire (FFQ) in a representative older population aged 63 to 80. Semi-quantitative FFQs were completed by 89% of 3,654 residents attending a community-based eye study in Sydney, Australia. The FFQ's validity was assessed against three, four-day weighed food records (WFRs) completed four months apart by 79 people. A further 152 subjects completed a repeat FFQ about a year after the baseline FFQ, of whom 131 completed a second repeat FFQ about six weeks later. Both short and long-term reproducibility of the FFQ were assessed using data from these subjects. Comparison of the FFQ with the average of the three, four-day weighed food records resulted in energy-adjusted Spearman correlations above 0.5 for most of the nutrients. The proportion of subjects correctly classified to within one quintile category for each nutrient intake ranged from 57% for zinc to 82% for vitamin C, with most nutrients correctly classified within one quintile for about 70% of subjects. Quadratic weighted kappas were reasonable, between 0.3 and 0.5 for most nutrients. The FFQ was highly reproducible in the short term, with correlations for most nutrients about 0.70 to 0.80 and acceptably reproducible in the longer term, with correlations mostly 0.60 to 0.70. The results verity that it is possible to use relatively simple, but comprehensive, self-administered FFQs to study nutrient exposures in large-scale epidemiological studies of the elderly and to expect reasonably high FFQ response rates.     

Reproducibility and relative validity of food group intake in a food frequency questionnaire developed for Nepalese diet

We developed a food frequency questionnaire (FFQ) designed to measure the dietary practices of adult Nepalese. The present study examined the validity and reproducibility of the FFQ. To evaluate the reproducibility of the FFQ, 116 subjects completed two 115-item FFQ across a four-month interval. Six 24-h dietary recalls were collected (1 each month) to assess the validity of the FFQ. Seven major food groups and 23 subgroups were clustered from the FFQ based on macronutrient composition. Spearman correlation coefficients evaluating reproducibility for all food groups were greater than 0.5, with the exceptions of oil. The correlations varied from 0.41 (oil) to 0.81 (vegetables). All crude spearman coefficients for validity were greater than 0.5 except for dairy products, pizzas/pastas and sausage/burgers. The FFQ was found to be reliable and valid for ranking the intake of food groups for Nepalese dietary intake.     

Validation of a food frequency questionnaire for Japanese pregnant women with and without nausea and vomiting in early pregnancy

Background

No previous study has shown the validity of a food frequency questionnaire (FFQ) in early pregnancy with consideration of nausea and vomiting during pregnancy (NVP). The aim of this study was to evaluate the validity of a FFQ in early pregnancy for Japanese pregnant women.

Reproducibility and validity of a Chinese food frequency questionnaire used in Taiwan

A 64-item Chinese food frequency questionnaire (FFQ) combined with open questions on types of staples and cooking oil most frequently consumed was designed for a prospective study in Taiwan to appraise participants' usual intake. We examined its reproducibility and validity. The form was administered three times at three-month intervals by face-to-face interview to 83 senior college students majoring in nutrition, in order to recall their usual dietary intake over the past six months. They also completed five-day (includes both weekends) diet records (DR) after each interview. Averaged intake levels of most nutrients assessed by the three FFQs were slightly higher than those of 15-day DR. Intraclass correlation coefficients for nutrient intakes assessed by three FFQs three months apart ranged from 0.37 for saturated fat to 0.82 for alcohol (average: 0.52). Averaged Pearson correlation coefficients between the unadjusted and energy-adjusted nutrient intakes measured by DR and by the third FFQ (which asked about diet during the six months encompassing the diet records) were 0.40 and 0.35, respectively, not including vitamins A and C. These correlations were higher (average: 0.47) after adjusting for the daily variation of the diet records. On average, 50% subjects were correctly classified into the same tertiles by both methods; 11% of the subjects were misclassified to extreme categories. These data indicate that this FFQ for Chinese-speaking people in Taiwan is reproducible and provides a useful measure of intake for many nutrients over a six-month period.     

Reproducibility and Validity of a Food Frequency Questionnaire among Vietnamese in Ho Chi Minh City

Objective: Our objective was to assess the reproducibility and validity of a food frequency questionnaire (FFQ) among individuals living in Ho Chi Minh City, Vietnam.

Methods: A total of 116 food items in our FFQ were selected by ranking food items according to their contribution to the population intake of nutrients, based on multiple 24-hour recalls (24HRs) from 144 participants in July 2001. The FFQ was validated by using three 24HRs for 118 men and women in Ho Chi Minh City, Vietnam in August 2002. The reproducibility of the FFQ was assessed by repeated administration at 7 ± 3.4 days.

Results: The reproducibility study showed that Spearman correlation coefficients, adjusted for energy intake, ranged from 0.47 to 0.72, and that weighted kappa values ranged from 0.42 for lipid to 0.65 for potassium. In the validation study, correlation coefficients, adjusted for energy intake, between the FFQ and the 24HRs ranged from 0.16 (calcium) to 0.45 (retinol). The proportion of subjects classified by the FFQ into the same third as determined by the 24HRs was between 42% and 62%.

Conclusions: This food frequency questionnaire measured the usual intake of major nutrients for Vietnamese adults living in Ho Chi Minh City and its urban area, where dietary patterns are similar to those of the Vietnamese population.     

Validity and reproducibility of food frequency questionnaire in Japanese children aged 6 years

The aim of the present study was to evaluate the validity and reproducibility of a food frequency questionnaire (FFQ) for use among young Japanese children. Forty-seven mothers of children aged 6 y completed two 3-d diet records and two FFQs over a 6-mo period. The FFQ asked the mothers how often, on average, their children consumed each of the 162 food items listed and what the usual serving size of each item was during the 6 mo prior to the study. Intakes of macro- and micronutrients were estimated by multiplying the frequency by the serving size for each food item. The validity of the FFQ was assessed by comparison of the two 3-d diet records. The reproducibility of the FFQ was based on the first and second FFQ administrations. The validity correlation ranged from 0.05 for α-tocopherol to 0.59 for retinol. The median correlation was 0.40. The reproducibility correlation was higher than 0.50 for all nutrients. For most nutrients, FFQ had acceptable reproducibility, whereas validity showed low to moderate correlations. Our FFQ could reasonably rank individuals according to dietary intake for epidemiologic studies, although the validity of the questionnaire is limited to specific nutrients.     

Relative validity of food intake estimates using a food frequency questionnaire is associated with sex, age, and other personal characteristics

We investigated the validity of food intake estimates obtained by a self-administered FFQ relative to weighed food records (WFR) and the extent to which demographic, anthropometric, and social characteristics explain differences between these methods. A community-based sample of 96 Australian adults completed a FFQ and 12 d of WFR over 12 mo. The FFQ was adapted to the Australian setting from the questionnaire used in the US Nurses' Health Study. Spearman rank correlation coefficients ranged from 0.08 for "other vegetables" to 0.88 for tea. Exact agreement by quartiles of intake ranged from 27% (eggs) to 63% (tea). Differences between FFQ and WFR regressed on personal characteristics were significantly associated with at least 1 characteristic for 20 of the 37 foods. Sex was significantly associated with differences for 17 food groups, including 5 specific vegetable groups and 2 "total" fruit and vegetable groups. Use of dietary supplements and the presence of a medical condition were associated with differences for 5 foods; age, school leaving age, and occupation were associated with differences for 1-3 foods. BMI was not associated with differences for any foods. Regression models explained from 3% (whole-meal bread) to 37% (for all cereals and products) of variation in differences between methods. We conclude that the relative validity of intake estimates obtained by FFQ is different for men and women for a large number of foods. These results highlight the need for appropriate adjustment of diet-disease relations for factors affecting the validity of food intake estimates.     

Validity and Reproducibility of a Food Frequency Questionnaire to Assess Nutrients Intake of Pregnant Women in the South-East of Spain

Proper nutrition during pregnancy is pivotal to maintain good health for the child and the mother. This study evaluates the reproducibility and validity of a food frequency questionnaire (FFQ) designed to assess nutrient intake during pregnancy in the GENEIDA (Genetics, Early life Environmental Exposures and Infant Development in Andalusia) prospective birth cohort study. In addition, the nutrient intake was estimated and then compared with European guidelines and other studies. Diet information was collected from 690 pregnant women using a FFQ administered at two periods of pregnancy (used for the reproducibility study) and 24-h dietary recall (for the validity study). Statistical approaches included Spearman’s correlation coefficient and percentage agreement, classifying women into the same or adjacent quintiles to assess reproducibility, and limits of agreement (LoA) to evaluate validity. In the study of reproducibility, significant correlations for nutrients adjusted for total energy had an average of 0.417. Moreover, the percentage of subjects classified in the same quintile for nutrient intakes were above 66%. In the validation study, the significant correlation for nutrients adjusted for total energy had an average of 0.272. Nevertheless, the percentage of results in the LoA was above 94%. Our results were similar to other studies suggesting that the FFQ used is a valid tool of collect dietary intakes for South-East Spanish pregnant women.     

Measurement characteristics of the Women's Health Initiative food frequency questionnaire

PURPOSE: The Women's Health Initiative (WHI) is the largest research program ever initiated in the United States with a focus on diet and health. Therefore, it is important to understand and document the measurement characteristics of the key dietary assessment instrument: the WHI food frequency questionnaire (FFQ). METHODS: Data are from 113 women screened for participation in the WHI in 1995. We assessed bias and precision of the FFQ by comparing the intake of 30 nutrients estimated from the FFQ with means from four 24-hour dietary recalls and a 4-day food record. RESULTS: For most nutrients, means estimated by the FFQ were within 10% of the records or recalls. Precision, defined as the correlation between the FFQ and the records and recalls, was similar to other FFQs. Energy adjusted correlation coefficients ranged from 0.2 (vitamin B12) to 0.7 (magnesium) with a mean of 0.5. The correlation for percentage energy from fat (a key measure in WHI) was 0.6. Vitamin supplement use was common. For example, almost half of total vitamin E intake was obtained from supplements. Including supplemental vitamins and minerals increased micronutrient correlation coefficients, which ranged from 0.2 (thiamin) to 0.8 (vitamin E) with a mean of 0.6. CONCLUSIONS: The WHI FFQ produced nutrient estimate, that were similar to those obtained from short-term dietary recall and recording methods. Comparison of WHI FFQ nutrient intake measures to independent and unbiased measures, such as doubly labeled water estimates of energy expenditure, are needed to help address the validity of the FFQ in this population.     

Reproducibility of a food frequency questionnaire: Korea Nurses' Health Study

BACKGROUND/OBJECTIVESThis study aimed to examine the reproducibility of food frequency questionnaires (FFQs) designed for young female nurses in the Korea Nurses'' Health Study.SUBJECTS/METHODSThe reproducibility of web-based, self-administered FFQs was evaluated among 243 Korean female nurses. The first FFQ (FFQ1) was administered from March 2014 to February 2019 and the second FFQ (FFQ2) from November 2019, with a mean interval of 2.8 years between the FFQs (range, 9 months–5.6 years). Pearson and Spearman correlation coefficients (r values) and quartile agreements between FFQ1 and FFQ2 were calculated for intakes of energy, nutrients, and foods.RESULTSPearson correlation coefficients ranged from 0.41 to 0.55 (median r = 0.51) for energy and raw nutrients and from 0.16 to 0.46 (median r = 0.36) for energy-adjusted nutrients. Spearman correlation coefficients ranged from 0.25 to 0.72 (median r = 0.41) for food items. The percentages of women who were classified into the same or adjacent quartile were 77% to 84% (median = 82%) for raw nutrients and 69% to 86% (median = 78%) for foods.CONCLUSIONSThe results indicated that the web-based FFQ used in the Korea Nurses'' Health Study has acceptable reproducibility.     

Reproducibility and validity of dietary patterns assessed by a food frequency questionnaire used in the 5-year follow-up survey of the Japan Public Health Center-Based Prospective Study

Background

Analysis of dietary pattern is increasingly popular in nutritional epidemiology. However, few studies have examined the validity and reproducibility of dietary patterns. We assessed the reproducibility and validity of dietary patterns identified by a food frequency questionnaire (FFQ) used in the 5-year follow-up survey of the Japan Public Health Center-Based Prospective Study (JPHC Study).

Methods

The participants were a subsample (244 men and 254 women) from the JPHC Study. Principal component analysis was used to identify dietary patterns from 28- or 14-day dietary records and 2 FFQs. To assess reproducibility and validity, we calculated Spearman correlation coefficients between dietary pattern scores derived from FFQs separated by a 1-year interval, and between dietary pattern scores derived from dietary records and those derived from a FFQ completed after the dietary records, respectively.

Results

We identified 3 Japanese dietary patterns from the dietary records and 2 FFQs: prudent, westernized, and traditional. Regarding reproducibility, Spearman correlation coefficients between the 2 FFQs ranged from 0.55 for the westernized Japanese pattern in men and the prudent Japanese pattern in women to 0.77 for the traditional Japanese pattern in men. Regarding validity, the corresponding values between dietary records and the FFQ ranged from 0.32 for the westernized Japanese pattern in men to 0.63 for the traditional Japanese pattern in women.

Conclusions

Acceptable reproducibility and validity was shown by the 3 dietary patterns identified by principal component analysis based on the FFQ used in the 5-year follow-up survey of the JPHC Study.Key words: dietary patterns, Japanese, reproducibility, validity     

A Review of Food Frequency Questionnaires Developed ?and Validated in Japan

Background

The food frequency questionnaire (FFQ) has been used throughout the world for epidemiological purposes. Because dietary habits vary greatly, the FFQ must be tailored for use with specific populations. The usefulness of FFQs in Japan was assessed by reviewing questionnaires developed and validated in that country.

Methods

A literature search was conducted to identify articles on the development and/or validation of FFQs for Japanese populations. For each FFQ identified, validation studies were used to abstract its characteristics and information. The correlation coefficients between diet records (DRs) and FFQ estimates and those between the same FFQs completed twice were used to evaluate validity and reproducibility, respectively, of the questionnaires.

Results

Twenty-one eligible FFQs were identified. They were found to be reasonably valid and reproducible. The median of correlation coefficients between DRs and FFQs ranged from 0.31 to 0.56 for target nutrients, and that between the same FFQs completed twice within a period of 9 months to 1 year ranged from 0.50 to 0.72. Relatively poor validity was found for FFQ estimates on consumption of potatoes, seaweed, sodium, niacin, and polyunsaturated fatty acids. For the purpose of analysis, FFQs were divided into long FFQs (97 or more food items) and short FFQs (<70 items); the former had slightly higher validity.

Conclusion

FFQs are useful for assessing dietary intake in Japan, although careful consideration is required for the food groups and nutrients for which FFQs had low validity.Key words: food frequency questionnaire, validity, reproducibility, nutrient, food group     

Food-based validation of a dietary questionnaire: the effects of week-to-week variation in food consumption

The reproducibility and validity of responses for 55 specific foods and beverages on a self-administered food frequency questionnaire were evaluated. One hundred and seventy three women from the Nurses' Health Study completed the questionnaire twice approximately 12 months apart and also recorded their food consumption for seven consecutive days, four times during the one-year interval. For the 55 foods, the mean of correlation coefficients between frequencies of intake for first versus second questionnaire was 0.57 (range = 0.24 for fruit punch to 0.93 for beer). The mean of correlation coefficients between the dietary records and first questionnaire was 0.44 (range = 0.09 for yellow squash to 0.83 for beer and tea) and between the dietary records and the second questionnaire was 0.52 (range = 0.08 for spinach to 0.90 for tea). Ratios of within- to between-person variance for the 55 foods were computed using the mean four one-week dietary records for each person as replicate measurements. For most foods this ratio was greater than 1.0 (geometric mean of ratios = 1.88), ranging from 0.25 (skimmed milk) to 14.76 (spinach). Correlation coefficients comparing questionnaire and dietary record for the 55 foods were corrected for the within-person variation (mean corrected value = 0.55 for dietary record versus first questionnaire and 0.66 versus the second). Mean daily amounts of each food calculated by the questionnaire and by the dietary record were also compared; the observed differences suggested that responses to the questionnaire tended to over-represent socially desirable foods. This analysis documents the validity and reproducibility of the questionnaire for measuring specific foods and beverages, as well as the large within-person variation for food intake measured by dietary records. Differences in the degree of validity for specific foods revealed in this type of analysis can be useful in improving questionnaire design and in interpreting findings from epidemiological studies that use the instrument.     

A simple food frequency questionnaire for Japanese diet--Part II. Reproducibility and validity for nutrient intakes.

A self-administered 97-item simple food frequency questionnaire (FFQ), without portion size questions for most items, was completed twice at an one-year interval by 88 men and women in central Japan to evaluate its reproducibility. This FFQ was further validated by referring to four 4-day weighed dietary records (DRs) which were performed at 3-month intervals. Mean energy and 18 nutrient intakes measured by the first and the second FFQs were quite similar to those measured by the DRs. In our reproducibility study, Pearson and intraclass correlation coefficients, adjusted for energy intake, sex and age, ranged from 0.48 to 0.82 (median = 0.67). In the validation study, adjusted and de-attenuated correlation coefficients between the second FFQ and the DRs ranged from 0.42 for iron to 0.83 for calcium (median = 0.61). The proportion of subjects classified by the FFQ into the same or adjacent quintiles defined by the DRs was between 65.9% and 83.0% (median = 69.9%). These findings essentially suggested that our FFQ is well reproducible and sufficiently valid, and therefore, reasonably useful for nutritional epidemiological studies for Japanese diets, particularly for those of Tokai Area.     

Reproducibility and validity of an interviewer-administered semi-quantitative food frequency questionnaire to assess dietary intake of urban adults in southern India

We report on the reproducibility and validity of a food frequency questionnaire (FFQ) developed for southern India. One hundred and two adult subjects aged > or =20 years drawn from the Chennai Urban Rural Epidemiology Study participated. The FFQ was developed based on local foods and habits, and was administered three times at 0, 6 and 12 month periods (called FFQ1, FFQ2 and FFQ3) to assess the reproducibility. To test the validity of the FFQ, multiple 24-h recalls collected at 2-monthly intervals for a period of 1 year and the estimated energy intake/basal metabolic rate (EI/BMR) ratio were used. The 'EpiNu' in-house food and nutrient database was used to compile dietary intakes, which were analyzed for statistical analysis. The intraclass correlation coefficient for all three FFQs ranged from 0.72 for carbohydrates to 0.45 for folate. The de-attenuated Pearson correlation for the energy adjusted nutrients between FFQ3 and 24-h recalls ranged from 0.73 for carbohydrates to 0.35 for calcium. Bland and Altman plots for energy intake between the two methods showed the limits of agreement ranged from 768 to -1358 calories/day (+/-2 standard deviations). Misclassification was low for most of the nutrients. Under-reporting of the energy intake (EI/BMR ratio<1.2) was higher in females than males. This FFQ appears to be a robust tool to measure dietary intakes in southern India.