Aims: To investigate whether in Malaysia, a mean corpuscular volume (MCV) less than 80 fl and a mean corpuscular haemoglobin (MCH) less than 27 pg will identify carriers in pregnant women with severe forms of thalassaemia, a-thal 1 (a0) and classical b (b0)-thalassaemia. The results from this study will aid the implementation of a national program to screen for thalassaemia.
Methods: For classical b (b0)-thalassaemia, blood samples collected in EDTA from 153 pregnant women were taken for full blood counts and haemoglobin subtyping by automated blood counting and high performance liquid chromatography (HPLC) respectively. For a-thal 1 (a0), the full blood counts were obtained from archives of 30 pregnant women who were genotyped positive for the a-thal 1 (a0) during prenatal diagnosis for Hb Barts hydrops fetalis. The effects of storage on MCV, MCH and Hb A2 were determined by tests done daily for 3 weeks.
Results: By correlating red cell indices with high performance liquid chromatography and genotypic data, we show that mean corpuscular volume (MCV) <80 fl and mean corpuscular haemoglobin <27pg is able to detect all heterozygous carriers of a-thal 1 (a0) and classical b (b0)-thalassaemia. On storage, the MCV of heterozygous carriers with classical b (b0)-thalassaemia rose at 1% a day after 24 hours reaching a mean of 80 fl by day 15. However, the MCH and Hb A2 were stable for 3 weeks.
Conclusion: A mean corpuscular volume (MCV) <80 fl and mean corpuscular haemoglobin <27pg should be recommended as cut-off values for screening of carriers of a-thal 1 (a0) and classical b (b0)-thalassaemia. In blood samples, not processed within a day, MCH with a cut-off value of 27 pg is the recommended choice for screening of carriers. Keywords: Screen, thalassaemia, pregnant, MCV, MCH
The study concerned the identification of the beta-thalassaemia mutations that were present in 24 patients with beta-thalassaemia major who were transfusion dependent. The application of a modified polymerase chain reaction, the amplification refractory system (ARMS) was found to be an effective and rapid method for the identification of the beta-thalassaemia mutations. Six different mutations were detected. Seventy five percent of the patients were Chinese-Malaysians and showed the commonly occurring anomalies: 1. frameshift codon 41 and 42 (-TCTT); 2. the C to T substitution at position 654 of intron 2 (IVS-2); 3. the mutation at position -28(A to G); and the nonsense mutation A to T at codon 17. In the Malays, the common mutations seen were: 1. the G to C mutation at position 5 of IVS-1; 2. the G to T mutation at position 1 of intron 1 (IVS-1); and the A to T at codon 17. The delineation of the specific mutations present will enable effective prenatal diagnosis for beta-thalassaemia to be instituted.
Haemoglobin Bart's hydrops fetalis is the result of complete absence of functional alpha-globin genes where the fetus is homozygous for the alpha 0-thal gene. Prenatal diagnosis can be made by analysis of fetal DNA from chorionic villus, amniotic cells and fetal blood. Earlier studies for analysing genomic DNA needed digestion with restriction enzymes and hybridisation to radiolabelled probes which took 2 weeks. We have used the polymerase chain reaction (PCR) and non-radioactive primers to identify specific target sequences with results available within 1-3 days for the diagnosis of haemoglobin Bart's syndrome. With fetal blood samples, complete absence of alpha-chain synthesis is confirmed by globin chain electrophoresis on cellulose acetate pH 6.0.
Paraproteinemia is one of the diagnostic features of multiple myeloma. A commonly used method is the detection of paraprotein by agarose gel electrophoresis (AGE) followed by by immunofixation electrophoresis (IFE) to confirm monoclonality. Due to their smaller size, immunoglobulin A (IgA) and light chain only paraproteins may appear at the beta or even alpha 2 protein fractions. Here, we discuss a case report of a 47-year-old man who presented with pathological fracture of third thoracic (T3) vertebra. Serum protein electrophoresis (SPE) was initially reported as no paraprotein detected. However, a bone biopsy was reported to show plasma cell proliferation with light chain restriction. A repeat sample for protein electrophoresis together with IFE revealed lambda light chain paraprotein co-migrating at the beta region. The beta band plus paraprotein was quantitated as 4.3 g/L (7.0%), which was within normal limits of the beta protein fraction. Hence, it has to be remembered that if the SPE is negative, it does not necessarily mean that the paraprotein is absent in cases which are highly suspicious.