Kristal A R, Feng Z, Coates R J, Oberman A, George V
The Fred Hutchinson Cancer Research Center, Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle 98109-1024, USA.
Am J Epidemiol. 1997 Nov 15;146(10):856-69. doi: 10.1093/oxfordjournals.aje.a009203.
This report describes the associations of race/ethnicity and years of education with the validity, reliability, and bias of a self-administered food frequency questionnaire (FFQ) designed to be sensitive to low-fat, regional, and ethnic dietary patterns. Data were from the Women's Health Trial Feasibility Study in Minority Populations, a randomized clinical trial conducted between 1992 and 1994 to test the feasibility of a low-fat dietary intervention that targeted low-income, black, and Hispanic women. Of 1,015 participants eligible for these analyses, 28.1% were black, 16.2% were Hispanic, and 12.3% had not completed high school. The analyses focused on percentage of energy obtained from fat, and used 4-day food records as the criterion instrument. Validity at baseline, defined as the correlation between FFQs and food records, was lower among blacks than among whites (0.26 vs. 0.49; p < 0.001), did not differ between Hispanics and whites, and was lower among women with fewer years of education (0.19, 0.35, 0.49, and 0.42 for <12, 12, 13-15, and > or =16 years of education, respectively; for trend, p < 0.05). Six months after randomization, validity increased in most race/ethnicity and education subgroups, and differences across groups became small and statistically nonsignificant. Validity increased significantly among participants receiving the dietary intervention, while increases among control women were somewhat smaller. Reliability, defined as the correlation between baseline and 6-month measures among controls, was similar across racial/ethnic and educational groups. Bias at baseline, defined as the mean value from the FFQ minus the mean from the food record, was 4.6 percentage points of energy from fat; it was lowest among blacks (p < 0.01) and did not differ by years of education. These results suggest that special protocols which address participant training may be necessary when using self-administered FFQs in minority or poorly educated populations.
本报告描述了种族/族裔和受教育年限与一份旨在对低脂、地区性和民族饮食模式敏感的自填式食物频率问卷（FFQ）的效度、信度和偏差之间的关联。数据来自少数族裔人群中的女性健康试验可行性研究，这是一项在1992年至1994年期间进行的随机临床试验，旨在测试针对低收入黑人及西班牙裔女性的低脂饮食干预的可行性。在1015名符合这些分析条件的参与者中，28.1%为黑人，16.2%为西班牙裔，12.3%未完成高中学业。分析重点关注从脂肪中获取的能量百分比，并使用4天食物记录作为标准工具。基线时的效度定义为FFQ与食物记录之间的相关性，黑人中的效度低于白人（0.26对0.49；p<0.001），西班牙裔和白人之间无差异，受教育年限较少的女性中的效度较低（受教育年限<12年、12年、13 - 15年和≥16年的女性分别为0.19、0.35、0.49和0.42；趋势分析，p<0.05）。随机分组6个月后，大多数种族/族裔和教育亚组的效度有所提高，组间差异变小且无统计学意义。接受饮食干预的参与者中效度显著提高，而对照组女性的提高幅度较小。信度定义为对照组中基线与6个月测量值之间的相关性，在种族/族裔和教育组中相似。基线时的偏差定义为FFQ的平均值减去食物记录的平均值，为来自脂肪的能量的4.6个百分点；在黑人中最低（p<0.01），且不受教育年限影响。这些结果表明，在少数族裔或受教育程度低的人群中使用自填式FFQ时，可能需要制定针对参与者培训的特殊方案。
