Dietary fat intake was assessed with the 'Dobson short fat questionnaire' [ 20], which ranks subjects according to their fat intake.
Although dietary recalls and food records are used to assess dietary intake at individual level and over shorter periods, food frequency questionnaires (FFQ) are used to rank subjects of a given population according to their nutrient intake over longer periods.
In general the shorter version yields lower total energy intake reports but rank subjects in the same order [ 21].
In addition, FFQs are only suitable for ranking subjects rather than estimating the level of nutrient intake [ 14].
The methods used were validated, but especially for the FFQs, which aim to rank subjects according to intake rather than to estimate absolute intake levels a calibration step may be needed when different cohorts are combined (47).
We have already shown these dietary data are robust enough for epidemiologic studies, when used either to compare group means or with rank subjects according to the levels of food consumption or nutrient intake (Mishra et al, 2003).
We have already shown that these dietary data are robust enough for epidemiologic studies, when used either to compare group means or with rank subjects according to the levels of food consumption [ 39].
Examiners were instructed to rank subjects separately for active caries and for filled surfaces as 0, no decayed or filled surfaces; 1, mild (1 2 affected surfaces); 2, moderate (3 6 affected surfaces); and 3, severe (>6 affected surfaces).
Further, selenium measures based on nail samples have been shown to reflect selenium intake integrated over the previous 6 12 months (Morris et al, 1983) and can be used to rank subjects according to long-term dietary selenium intake (Longnecker et al, 1996).
In addition, we found a significant difference in mean ranks between subjects enrolled in 2001 and 2002 but no difference in mean ranks between subjects enrolled in 2003 and 2004.
