Validation of the MEDFICTS dietary questionnaire: A clinical tool to assess adherence to American Heart Association dietary fat intake guidelines

This study contains data from 164 active-duty U.S. Army personnel who completed both the MF and Block FFQ. Subjects completed the surveys during the same intake interview for a primary prevention intervention trial – the Prospective Army Coronary Calcium (PACC) Study. The study was approved by the Department of Clinical Investigation of the Walter Reed Army Medical Center.

The methods of the PACC Study have been previously described.[13] Briefly, since October 1998, active-duty Army personnel from 39 through 45 of age who were stationed in the National Capital Area of the Walter Reed Health Care System were recruited at the time of a periodic, Army-mandated physical examination. Persons who had a history of coronary heart disease or who reported a history of angina pectoris on the Rose questionnaire were ineligible. Between October 26, 1998 and November 4, 1999, 705 eligible participants were screened and 630 provided written informed consent to undergo electron beam computed tomography (EBCT) in addition to the required physical examination procedures. A subset of these subjects also volunteered to participate in a randomized, controlled trial to assess the impact of the knowledge of EBCT results and nurse-based case management on risk factor modification. The 164 subjects included in this dietary assessment study are a consecutive sample of subjects who both consented to participate in the randomized controlled trial and who also completed the MF and Block FFQ questionnaires. Demographic characteristics of the study participants are shown in Table 1.

Each participant filled out a series of questionnaires that included the 2 dietary assessment tools: the validated and reduced version of the Block FFQ and the full version of the MF. The reduced version of Block FFQ is a validated food survey that contains 60 food items and is intended to capture all nutrients in the diet including dietary fat intake. The survey requires approximately 15 minutes to self-administer, however, the survey requires a relatively detailed analysis, thus the results are not immediately available for patient counseling. This study focuses only on those variables from the Block FFQ that are relevant to dietary fat intake within the dietary guidelines of the American Heart Association (AHA). This includes total calories, percentage of calories from fat and saturated fat, and cholesterol intake.

The MF questionnaire was specifically designed to evaluate patient adherence to the National Cholesterol Education Program (NCEP) Step 1 and Step 2 diets adopted by the American Heart Association (AHA). The main objective of these dietary steps is incrementally reduce coronary heart disease risk through diet-induced reduction in LDL cholesterol. Both the AHA Step 1 and 2 diets focus on reducing total fat to 30% or less of daily energy, and progressively reducing saturated fat and cholesterol intake (Step 1: 7–10% of energy from saturated fat and <300 mg cholesterol; Step 2: <7% of energy from saturated fat and <200 mg cholesterol). The AHA Step 1 diet is recommended for all healthy persons for the prevention of coronary heart disease, and is recommended to precede pharmacotherapy of LDL cholesterol. The Step 2 diet is recommended to further reduce LDL cholesterol for patients that have already achieved their Step 1 dietary goals. Additionally, the Step 2 diet is the initially recommended diet for patients with either a high-risk cholesterol level (>240 mg/dL) or with known coronary heart disease.

The MEDFICTS questionnaire is a brief instrument consisting of 8 food categories: Meats, Eggs, Dairy, Fried foods, fat In baked goods, Convenience foods, fats added at the Table, and Snacks. The first column of the questionnaire addresses each of these food categories. Within each category, food items are assigned to either group 1 (desirable) or group 2 (undesirable) based upon total fat content. Numeric values are assigned to each food group, with weightings based upon weekly consumption and serving size. The questionnaire is scored using totaling the quality-adjusted intake quantity yielding a possible range of scores from 0 to 216 points. Lower MF scores indicate diets containing less dietary fat. Prior validation literature indicated that a score of <40 points is consistent with a Step 2 diet, a score between 40 to 69 is consistent with a Step 1 diet, and a score of >70 is considered as high fat diet. The MF can be self-administered in 3 to 5 minutes, and scored by the healthcare provider in approximately 2 minutes. Thus, the MF is an efficient tool enabling health care providers to quickly assess the adherence of patients to the fat components of a Step 1 or 2 diet, and identify patients consuming a diet higher in total fat, saturated fat, and cholesterol.

The two dietary questionnaires were independently scored. The reduced version Block FFQ was coded and analyzed by the same investigator to provide consistency in scoring. The validation of MF scores with Block FFQ dietary variables (percent of fat, percentage of saturated fat, and cholesterol level) was evaluated by Spearman's rho, because both dietary scores were not normally distributed. The level of inter-test agreement between the two dietary instruments was assessed using the kappa statistic. Receiver operating characteristic (ROC) Curve analysis was applied to measure the sensitivity and specificity of the alternative MF cutpoints. All analyses were performed using SPSS for Windows (v 10.05, Chicago, IL). Data are presented as mean ± SD. A two-tailed P value of ≤ 0.05 was considered to indicate statistical significance.