THE LABORATORY DIAGNOSIS OF HEMOGLOBINOPATHIES

The laboratory diagnosis of haemoglobinopathies, including the thalass emias, is of growing importance, particularly because of an increasing requirement for antenatal diagnosis of significant disorders of globi n chain synthesis. This guideline discusses the laboratory tests which are most useful in the diagnosis of haemoglobinopathies and describes their role in specific clinical circumstances. Of the newer technical methods, high-performance liquid chromatography (HPLC) is of consider able importance whereas isoelectric focusing (IEF) and immunoassay for variant haemoglobins have a more minor role. Specific recommendations have been formulated for testing in relation to genetic counselling a nd for neonatal diagnosis. Methods used in specialized laboratories fo r fetal diagnosis have been tabulated. Genetic counselling requires: ( i) identification of haemoglobins S,C, D-Punjab, O-Arab, E, Lepore and H and (ii) the detection of carriers of alpha-degrees and beta thalas semia. It is recommended that subjects of all ethnic groups be screene d for Beta-thalassemia trait, all except Northern European Caucasians for variant haemoglobins, and selected ethnic groups for alpha-degree- thalassemia trait. Testing for beta-thalassemia trait should be carrie d out when the mean cellular haemoglobin (MCH) is less-than 27 pg and testing for alpha-degree-thalassemia trait should be considered when t he MCH is less-than 25 pg. Appropriate methods include HPLC or haemogl obin electrophoresis for identification of variant haemoglobins and HP LC or microcolumn chromatography for quantification of haemoglobin A2.