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 transferrin (CDT) as assessed by their electrophoretic migration patterns. The predominant Tf C1 allele encodes a protein for which the most prevalent isoform has a pI of 5.4, i.e., four sialic acids and two bound ion molecules. Carriers of allele D encode Tfs with different amino acid sequences, for which the pI is > 5.7, despite their identical iron and carbohydrate composition. We used isoelectric focusing, immunoblotting, and laser densitometry (IEF-IB-LD) to distinguish Tf D variants from CDT. Alcohol abusers carrying the D chi allele tested CDT+; D chi nondrinkers were CDT-. Although normal controls (< 15 g of alcohol per day for 7-10 consecutive days) carrying variants D1, D2, or D chi exhibited abnormal IEF banding patterns, they did not generate false-positive results for CDT. D3 variants expressed isoforms that migrate at the same pI as CDT bands. Thus, IEF-IB-LD yields a highly resolved banding pattern to distinguish most Tf D variants from CDT.
Bean
P
P
Specialty Laboratories, Inc., Santa Monica, CA 90404-3900.
Peter
J B
JB
D000437:Alcoholism / Q000097:blood / Q000175:diagnosis*; D000483:Alleles; D003720:Densitometry; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D014644:Genetic Variation; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D007526:Isoelectric Point; D007834:Lasers; D019158:N-Acetylneuraminic Acid; D012794:Sialic Acids / Q000032:analysis; D014168:Transferrin / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry / Q000235:genetics
D012794:Sialic Acids; D014168:Transferrin; C056759:carbohydrate-deficient transferrin; D019158:N-Acetylneuraminic Acid