Interference of hemoglobin Hope on β-thalassemia: diagnosis by the capillary electrophoresis method

Hb Manitoba [α102(G9)Ser→Arg] in Pasifika: Tongan Case Report

Hb Manitoba [α102(G9)Ser→Arg] results from an AGC>CGC or AGC>AGA substitution at codon 102 of the HBA1 or HBA2 genes. The variant is mildly unstable but carriers typically have normal clinical presentation and hematological profile. Hb Manitoba has not been reported in Pasifika of Tongan, Samoan or New Zealand (NZ) Māori descent before. The cases presented here support the findings from existing literature but include results from alternative methodology including capillary zone electrophoresis (CZE), which may slightly underestimate the true variant percentage. The subject of our case report, a Tongan male with microcytic indices, was shown to be heterozygous for Hb Manitoba III (HBA2: c.309C>A) coinherited with the -α^3.7 (rightward) deletion.

Capillary zone electrophoresis for haemoglobinopathy diagnosis

Aims

Capillary zone electrophoresis (CE) at alkaline pH is increasingly used in haemoglobinopathy diagnosis. We report our evaluation of automated CE, using the Capillarys 2 Flex Piercing instrument, as a routine diagnostic method for the detection of variant haemoglobins and the diagnosis of β thalassaemia.

Methods

A Capillarys 2 Flex Piercing instrument with Phoresis software was evaluated in our laboratory over a 6-week period, comparisons being made with high performance liquid chromatography (HPLC) and, for haemoglobin A2 quantification, with microcolumn chromatography.

Results

The instrument was easy to use and was suitable for the quantification of haemoglobin A2. Quantification of A2 was precise and the percentage was stable with ageing of the blood specimen. Results differ among HPLC, CE and microcolumn chromatography and use of an instrument-specific, method-specific reference range is therefore recommended until such time as there is standardisation between methods and manufacturers. Common variant haemoglobins were provisionally identified without difficulty. There are some uncommon variant haemoglobins that are detected by HPLC but not by capillary electrophoresis, but the reverse also occurs.

Conclusions

Capillary electrophoresis using a Capillarys 2 Flex Piercing instrument is suitable for haemoglobinopathy diagnosis.