The Tromsø Study: the positive predictive value of gamma-glutamyltransferase and an alcohol questionnaire in the detection of early-stage risk drinkers.

Abstract

Based on the measurement of gamma-glutamyltransferase and a questionnaire on frequency of alcohol intake, 338 early-stage risk drinkers were identified from more than 20,000 participants in a health survey programme. Two-thirds (225) of these subjects were questioned regarding their 'true' alcohol intake at the first consultation. Positive predictive values were calculated for true daily intake of 30 and 40 g alcohol d-1 for men (20 and 30 g alcohol d-1 for women) on the basis of gamma-glutamyltransferase activity and the response to a questionnaire. The positive predictive values for a risk intake of 30 g d-1 in men increased from 0.49 to 0.88, with increasing values for gamma-glutamyltransferase activity and increasing frequency of alcohol intake. The corresponding values for a risk intake of 40 g d-1 were 0.34-0.75. In women, increasing gamma-glutamyltransferase activity gave no increase in positive predictive values. The estimates for increasing frequency of alcohol intake were unreliable due to small numbers.