George E, Jamal A R, Khalid F, Osman K A
Unit Hematology, Department of Pathology.
Malays J Med Sci. 2001 Jul;8(2):40-6.
Beta-thalassaemia is characterized by a decrease (β(+)) or absence (β(0)) in the synthesis of β-globin chains of human haemoglobin. The heterozygous state for β(+) or β(0) result in β-thalassaemia trait in which the hallmark is the presence of an elevated level of Haemoglobin (Hb) A(2) (α(2)δ(2)). In the past, the traditional methods such as cellulose acetate electrophoresis with elution and microcolumn chromatrography have been the techniques used by the majority of the laboratories in Malaysia for the estimation of (Hb) A(2) levels. The recommended method currently is high performance liquid chromatography which has only been introduced in a few laboratories in the country.
To determine the cut-off level for (Hb) A(2) when estimated by high performance liquid chromatography (HPLC) in the diagnosis of classical beta-thalassaemia trait, a condition in the homozygous state that results in beta-thalassaemia major and red blood cell transfusion dependency.
High performance liquid chromatography (HPLC) as a method for the measurement of (Hb) A(2) was rapid, and technically easy. A cut-off level of (Hb) A(2) >4.0 % predict the majority of carriers of classical beta-thalassaemia.
A full blood count (FBC), together with red blood cell indices generated on an automated blood counter in conjunction with the measurement of Hb A(2) on the VARIANT-BioRad, an automated HPLC machine and the beta-thal short program is an appropriate approach for the screening and presumptive identification of carriers of classical beta-thalassaemia prior to DNA studies for definitive diagnosis. In carriers for classical beta-thalassaemia, the MCV and MCH are <75 fl and <27 pg respectively with a Hb A(2) cut-off level > 4.0% [range 5.9 (4.5-8.1)] on the VARIANT-BioRad.
β地中海贫血的特征是人类血红蛋白β珠蛋白链合成减少（β(+)）或缺失（β(0)）。β(+)或β(0)的杂合状态导致β地中海贫血特征，其标志是血红蛋白（Hb）A2（α2δ2）水平升高。过去，马来西亚大多数实验室使用传统方法，如醋酸纤维素电泳洗脱法和微柱色谱法来测定Hb A2水平。目前推荐的方法是高效液相色谱法，该国只有少数实验室采用了该方法。
通过高效液相色谱法（HPLC）测定Hb A2，以确定其在诊断典型β地中海贫血特征时的临界值，典型β地中海贫血特征是一种纯合状态，会导致重型β地中海贫血和红细胞输血依赖。
高效液相色谱法（HPLC）作为测定Hb A2的方法快速且技术操作简便。Hb A2>4.0%的临界值可预测大多数典型β地中海贫血携带者。
全血细胞计数（FBC），连同自动血液计数器生成的红细胞指数，结合在VARIANT-BioRad自动HPLC机器上测定Hb A2以及β地中海贫血短程序，是在进行DNA研究以明确诊断之前，筛查和初步鉴定典型β地中海贫血携带者的合适方法。对于典型β地中海贫血携带者，在VARIANT-BioRad上，平均红细胞体积（MCV）和平均红细胞血红蛋白含量（MCH）分别<75 fl和<27 pg，Hb A2临界值>4.0%[范围5.9（4.5 - 8.1）]。
