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

Ann Clin Biochem. 2012 Sep;49(Pt 5):445-9. doi: 10.1258/acb.2012.011234. Epub 2012 Jul 24.

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

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

Substances

  • Cation Exchange Resins
  • Glycated Hemoglobin A
  • Hemoglobins, Abnormal
  • hemoglobin Raleigh