ALLELIC D-VARIANTS OF TRANSFERRIN IN EVALUATION OF ALCOHOL-ABUSE - DIFFERENTIAL-DIAGNOSIS BY ISOELECTRIC FOCUSING-IMMUNOBLOTTING-LASER DENSITOMETRY

In the diagnosis of alcohol abuse transferrin (Tf) allelic D variants generate false-positive test results for carbohydrate-deficient transf errin (CDT) as assessed by their electrophoretic migration patterns. T he predominant Tf C-1 allele encodes a protein for which the most prev alent isoform has a pi of 5.4, i.e., four sialic acids and two bound i ron molecules. Carriers of allele D encode Tfs with different amino ac id sequences, for which the pi is > 5.7, despite their identical iron and carbohydrate composition. We used isoelectric focusing, immunoblot ting, and laser densitometry (IEF-IB-LD) to distinguish Tf D variants from CDT Alcohol abusers carrying the D, allele tested CDT+; D-chi non drinkers were CDT-. Although normal controls (< 15 g of alcohol per da y for 7-10 consecutive days) carrying variants D-1, D-2, or D-chi exhi bited abnormal IEF banding patterns, they did not generate false-posit ive results for CDT. D-3 variants expressed isoforms that migrate at t he same pi as CDT bands. Thus, IEF-IB-LD yields a highly resolved band ing pattern to distinguish most Tf D variants from CDT.