Fetal hemoglobin in normal adults and β-thalassemia heterozygotes

A recently developed high performance liquid chromatographic (HPLC) procedure using a weak cation exchanger (PolyCAT) in columns of different sizes was used to quantify fetal hemoglobin (Hb F) in blood of normal adults and β-thalassemia (β-thal) heterozygotes with ten different types of mutations. Preparative PolyCATHPLC greatly facilitated the characterization of isolated Hb F, i.e., the determination of the relative quantities of the ^Gγ and ^Aγ chains. The method is accurate and allows quantitation of Hb F at the 0.5% level; preparative PolyCAT-HPLC allows isolation of (nearly) pure Hb F from blood samples with low (< 1%) Hb F. Adult Hb F levels were determined in 69 normal adults (including 24 diabetics); Hb F levels fell below 1% except for subjects with abnormal -^Gγ-^Gγ arrangement and a C→T mutation at position -158 relative to the Cap site of both ^Gγ genes. The effect of the same mutation in the normal-^Gγ-^Aγ-arrangement was variable. Certain β-thal mutations (namely, those at positions -29;-88; IVS-I-1; IVS-II-1) were associated with high Hb F levels in heterozygotes, while those at nucleotide (nt) positions IVS-I-6; IVS-I-110; codon 24; codon 39; codons 41/42; IVS-II-745 were not. ^Gγ values varied and often fell into two groups (high ^Gγ and low ^Gγ); high ^Gγ values were not associated with high Hb F values. The chromatographic procedure is ideally suited for Hb A₂ quantitation. Average values of Hb A₂ in β-thal heterozygotes with any one of nine of the ten mutations were twice that of normals; the one exception was the β-thal heterozygote with the IVS-I-6 (T→C) mutation with an average low Hb A₂ value of 3.6%.