Agreement between interview data and a self-administered questionnaire on dietary supplement use

E. Dorant, P.A. van den Brandt, R.A. Goldbohm, R.J.J. Hermus, F. Sturmans

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Agreement between interview data and a self-administered questionnaire on dietary supplement use.

Dorant E, van den Brandt PA, Goldbohm RA, Hermus RJ, Sturmans F.

Department of Epidemiology, University of Limburg, Maastricht.

OBJECTIVE: To study the relative validity of an open-ended question on the consumption of dietary supplements in the preceding five-year period, incorporated in a self-administered questionnaire used in the NLCS, The Netherlands Cohort Study on diet and cancer (120,852 men and women aged 55-69 years). DESIGN: Questionnaire data were compared with reference information from three personal interviews carried out within a period of 10 months. SETTING AND SUBJECTS: A randomly selected subgroup (59 men and 50 women) of the cohort living in 12 municipalities in the eastern and western regions of The Netherlands. RESULTS AND CONCLUSIONS: The overall sensitivity of the questionnaire concerning the use of any dietary supplement was 65.9%, the specificity was 98.5%; kappa as measure of agreement was estimated at 0.69. A high percentage recall was observed among women, users of at least three types of dietary supplements, long-term supplement users and those in the oldest age group. Recall of intake of specific supplements ranged from 77.8% for garlic preparations to 11.8% for 'other' supplements. Estimates of consumption of specific supplements (garlic and vitamin preparations) may provide enough precision to correctly classify individuals as users or non-users of those supplements
Original languageEnglish
Pages (from-to)180-188
JournalEuropean Journal of Clinical Nutrition
Issue number3
Publication statusPublished - 1 Jan 1994

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