Accuracy of quantity-frequency and graduated frequency questionnaires in measuring alcohol intake: Comparison with daily diary and commonly used laboratory markers

Aims: To ascertain the accuracy of a quantity-frequency questionnaire (QF) and a graduated frequency questionnaire (GF) as methods of obtaining self-reported alcohol intake in relation to a daily diary and biochemical tests. Methods: QF and GF data were obtained before and after a 1-month daily diary on alcohol intake in a sample of 52 volunteers aged 20-63 years, of whom 43 were female. A blood sample to measure serum aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT), gamma-glutamyltransferase (GGT) and % carbohydrate-deficient transferrin (CDT) was obtained at the outset. Results: Both QF and GF correlated closely with daily diary intake (r > 0.90). Compared with a daily diary, the mean QF intake was slightly lower, whereas the mean GF intake was 2-fold. The apparent overestimation by GF was independent of the actual consumption level. Self-reported alcohol intake by each method correlated closely with serum ASAT, ALAT and GGT (r = 0.41-0.67) but not with CDT. Conclusions: In adults motivated to recall alcohol intake, both QF and GF classify individuals in the correct rank order, but GF probably overestimates actual alcohol consumption.