MEASUREMENT OF CARBOHYDRATE-DEFICIENT TRANSFERRIN (CDT) IN A GENERAL MEDICAL CLINIC - IS THIS TEST USEFUL IN ASSESSING ALCOHOL-CONSUMPTION

The aim of this study was to measure serum carbohydrate-deficient tran sferrin (CDT) in consecutive patients attending a general medical clin ic with a range of alcohol intakes to determine its value in assessing such intake. Eighty-one consecutive patients (42 male, 39 female) age d 20-85 years (median = 49.5 years) attending an out-patient clinic we re selected for the study. Each patient completed an alcohol diary det ailing the units of alcohol consumed in the previous week, a CAGE ques tionnaire and an alcohol history, and underwent conventional blood tes ts including mean corpuscular volume (MCV), liver function tests, and gamma-glutamyl transferase (GGT). CDT was estimated using an enzyme im munoassay (CDTect, Pharmacia). The group comprised of 17 teetotallers, 28 light (<100 g/week): 23 moderate (100-400 g/week), and 13 heavy (> 400 g/week) drinkers. Median serum CDT for heavy drinkers (25.5 U/l) w as significantly higher than for the rest (median = 17 U/l, Kruskal-Wa llis test, P = 0.01). Serum CDT correlated significantly with the CAGE score (Mann-Whitney test, P= 0.01), but poorly with alcohol diary rec ords (I = 0.1, P = 0.4). However the correlations between GGT and diar y records (r = 0.43. P = 0.001) and MCV with diary records (r = 0.5, P < 0.001) were significant. Sensitivity, specificity, and positive pre dictive value for elevated serun CDT were 69. 81 and 41% respectively in detecting heavy drinking. The positive predictive values for the va rious parameters were 43% for elevated serum GGT, 41% for raised eryth rocyte MCV, and 75% for a positive score on the CAGE questionnaire. Wh en a combination of the markers CDT, GGT, and MCV was used, elevation in two of the three markers detected heavy drinking with sensitivity o f 85%, specificity of 88%, and positive predictive value of 61%. We co nclude that, in out-patients with a wide range of alcohol intakes conv entional markers such as serum GGT and erythrocyte MCV were more suita ble than serum CDT for assessing alcohol intake. Serum CDT when used i n combination with serum GGT and erythrocyte MCV was useful in detecti ng heavy drinking. The importance of careful history-taking including a standardized questionnaire is emphasized.