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      A spurious haemoglobin A(1c) result associated with double heterozygote for haemoglobin Raleigh (β1[NA1]Val → Ala) and α(+)-thalassaemia.

      Annals of Clinical Biochemistry

      alpha-Thalassemia, genetics, Cation Exchange Resins, chemistry, Chromatography, High Pressure Liquid, Base Sequence, DNA Mutational Analysis, Diagnosis, Differential, Genetic Variation, Hemoglobin A, Glycosylated, Hemoglobins, Abnormal, Heterozygote, Humans, Male, Molecular Sequence Data, Adult, Asian Continental Ancestry Group

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          Accurate measurement of haemoglobin A(1c) (HbA(1c)) is useful for long-term glycaemic control in patients with diabetes. Many Hb variants can interfere with HbA(1c) measurement and cause inaccurate results. The subject was a 31-year-old Thai man who was discovered because of an unexpected HbA(1c) result; other diabetic parameters were within the normal range. Abnormal Hb was investigated using automated high-pressure liquid chromatography (HPLC) and a capillary electrophoresis system. Mutation analysis was done by cDNA sequencing, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and multiplex allele-specific PCR assays. Evaluation of HbA(1c) by cation-exchange HPLC showed a value of 34.9% (reference interval, 4.0-6.0%), but a value of only 4.0% (reference value, 4.8-5.9%) was found with a turbidimetric immunoassay. Haematological analysis revealed a mild anaemia but other parameters were within the normal range. Hb-HPLC analysis demonstrated an unknown Hb variant (47.0%) separating from HbA (46.7%), but capillary electrophoresis identified no abnormal peaks. Mutation analysis identified the Hb Raleigh (β1[NA1]Val → Ala [GTG → GCG]) mutation in combination with an α(+)-thalassaemia, a hitherto undescribed association. The Hb Raleigh mutation could be detected by PCR-RFLP or a multiplex allele-specific PCR assay. Hb Raleigh can cause falsely increased HbA(1c) values on cation-exchange HPLC. Definitive diagnosis of this variant using combined Hb and DNA analyses is therefore essential.

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