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Variations in sensitivity, specificity, and predictive value of a dietary fat screener modified from Block et al
1Division of Research of the Kaiser Permanente Medical Care Program of Northern California, Oakland 94611-5714, USA.
Objective:
To evaluate the ability of a fat screener modified from Block et al to discriminate persons whose diets consist of 38% of kilocalories or more from fat from the remainder of the population.
Design:
Sensitivity, specificity, and positive predictive value of the adapted screener were calculated. Percentage of kilocalories from fat was assessed by means of a semi-quantitative food frequency questionnaire. Three cutoff points from the fat screener were used to examine which best identified those whose diets consisted of 38% of kilocalories or more from fat.
Subjects:
Nine hundred ninety-seven persons responded to a food frequency questionnaire sent to a random sample of 2,000 members of a health maintenance organization.
Results:
Sensitivity and specificity varied depending on which cutoff point from the fat screener was used. Sensitivity reached a high of 83.3% and specificity reached a high of 92.1%, but the screener was never highly sensitive and specific simultaneously, and the results did not vary considerably by race. The screener had low rates of gross misclassification into quintiles (< or = 2.7%) and was more effective at classifying respondents into quintiles of total fat intake (64.9% to 85.5% classified in the same quintile) than into quintiles of percentage of kilocalories from fat (43.2% to 60.5% classified in the same quintile).
Conclusions:
The adapted fat screener may be used in conjunction with other dietary evaluation methods, but it exhibits insufficient sensitivity and specificity to be used as a single assessment method.