Observing Protein & Energy Nutrition (OPEN) Study

The information on this page is archived and provided for reference purposes only.


What is the OPEN Study?

The Observing Protein and Energy Nutrition (OPEN) Study was an NCI-sponsored study designed to assess dietary measurement error by comparing results from self-reported dietary intake data with four dietary biomarkers: doubly labeled water and urinary nitrogen, sodium, and potassium. The study was conducted from July 1999 to March 2000 and included 484 men and women, aged 40-69 years old, living in Montgomery County, Maryland.

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Why is it important to assess dietary measurement error?

Nutritionists routinely conduct research and monitoring activities that depend on self-reported dietary intake information from questionnaires and interviews. Dietary recommendations aimed at encouraging people to follow dietary patterns to promote health and reduce disease risks are also based in part on information gathered through these means. Food frequency questionnaires, which measure a person's usual intake over a defined period of time, and 24-hour recalls, in which a person records everything eaten or drunk during the previous 24 hours, are among the methods of choice for collecting information about what people are consuming.

The problem is that people don't always report accurately. In addition, these commonly used dietary assessment instruments are subject to substantial error, both random and systematic. Interpreting findings from epidemiology and monitoring research is critically dependent on understanding the nature and extent of the measurement error contained in these instruments.

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How did the OPEN Study assess the FFQ and 24-Hour Recall?

Over the course of the study, OPEN participants completed two Food Frequency Questionnaires (FFQ), two 24-recall interviews, and filled out several other health-related questionnaires. They were dosed with doubly labeled water (a biomarker used for measuring energy expenditure), provided several spot urine samples to complete the doubly labeled water assessment, completed two 24-hour urine collections and had their height and weight measured. Investigators analyzed the 24-hour urines for several nutrients: nitrogen, sodium and potassium, biomarkers that measure protein, sodium, and potassium intakes, respectively. The questionnaires and samples allowed study investigators to compare what participants said they ate and drank against the objective evidence provided by the biomarkers and thus, to get a better sense of the extent and nature of error in the FFQs and 24-hour recalls.

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What is the current status of the OPEN study?

A number of manuscripts have been published (see the list below) and others are in draft form. These papers describe the details of the study, the extent of underreporting, the structure of measurement error, the impact of energy adjustment, psychosocial correlates of underreporting and issues to consider in using 24-hour recalls in nutritional epidemiology or dietary surveillance. These findings will lead to an improved understanding of how to use and interpret data from dietary assessment methods in future research.

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Multifactor Screener in the OPEN Study

The Multifactor Screener may be useful to assess approximate intakes of fruits and vegetables, percentage energy from fat, and fiber. The screener asks respondents to report how frequently they consume foods in 16 categories. The screener also asks one question about the type of milk consumed. No portion size questions are asked. This screener does not attempt to assess total diet.

The foods selected to compose the screener were identified through an analysis of USDA's 1994-96 Continuing Survey of Food Intakes of Individuals (CSFII), a nationally representative survey of the food intakes of the US population available from the USDA's Food Surveys Research GroupExternal Web Site Policy. NCI's Risk Factor Assessment Branch staff used stepwise regression to identify the food groups that would best predict the three dietary exposures. Some of the foods in the screener predict all three exposures; some predict only one or two of the exposures.

The Multifactor ScreenerExternal Web Site Policy was self-administered in the OPEN study. An interviewer-administered version was used in the 2000 NHIS Cancer Control SupplementExternal Web Site Policy.

The process of scoring the individual response data is described in Scoring Procedures. A SAS program is included. Guidelines for the appropriate uses of the screener-estimated dietary intakes are the same as those described in Uses of Screener Estimates in the 2000 NHIS Cancer Control SupplementExternal Web Site Policy. Validation data for the Multifactor Screener in OPEN is presented in Validation Results. The data dictionary for the screener is available in RTF [58KB] and PDF [67KB] formats.

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The information on this page is archived and provided for reference purposes only.