Hb Tacoma is difficult to detect and may cause false results with different HbA1c methods

Area of Science:

• Clinical Chemistry
• Haematology
• Biochemistry

Background:

• The haemoglobin variant Hb Tacoma (HBB:c.93G>T;CD30(Arg>Ser)) is found in about 1 in 1000 patients undergoing HbA1c testing.
• Homozygous individuals for Hb Tacoma show no severe hematological issues.

Purpose of the Study:

• To evaluate the impact of Hb Tacoma on various HbA1c measurement methods.
• To identify reliable methods for accurate HbA1c quantification in the presence of Hb Tacoma.

Main Methods:

• Comparison of HbA1c results from different analytical platforms including cation exchange chromatography, immunoassays, affinity, and enzymatic methods.
• Investigation of chromatogram interpretation for Hb Tacoma heterozygotes using the Bio-Rad Variant II system.

Main Results:

• The Bio-Rad Variant II method showed significantly lower HbA1c values (approx. 40% lower) due to coelution of glycated Hb Tacoma.
• Immunoassays (Roche Tina-quant Gen. 3, Siemens DCA Vantage), affinity, and enzymatic methods provided accurate HbA1c results.
• Bio-Rad D-100 and Tosoh G11 methods showed unpredictable deviations or positive bias.
• Sebia Capillarys 3 Tera capillary electrophoresis exhibited high imprecision with Hb Tacoma samples.

Conclusions:

• Certain HbA1c testing methods, particularly cation exchange chromatography like Bio-Rad Variant II, can lead to misinterpretation and inaccurate results in the presence of Hb Tacoma.
• Immunoassays and other specific methods demonstrate reliability for HbA1c measurement in individuals with this haemoglobin variant.