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Method comparison and agreement of a fluorescence immunoassay-based HbA1c test with a routine HPLC method
Harresh Adikesavalu1, Neema Raja Beaulah Budithi1, Suja Ramanathan2
1Athenese-Dx Private Limited, Chennai, Tamil Nadu India.
Background:
Glycated hemoglobin (HbA1c) is widely used for diabetes diagnosis and long-term monitoring. Although high-performance liquid chromatography (HPLC) is the accepted method, its requirement for specialized instrumentation and infrastructure can limit its accessibility in some settings. Rapid point-of-care platforms based on fluorescence immunoassay (FIA) technology enable more accessible alternative. This study evaluated the analytical agreement between the TRUSTlight HbA1c fluorescence immunoassay and the HPLC comparator method.
Methods:
A total of 200 anonymized residual samples collected from a diagnostic laboratory in Chennai, India, between January and February 2026 were included. HbA1c levels were measured using the ion-exchange HPLC method and compared with the TRUSTlight Glycosylated Hemoglobin Test Kit. Method agreement was assessed using Bland-Altman analysis and Passing-Bablok regression. Classification agreement at the 6.5% HbA1c threshold was assessed in comparison with the HPLC comparator method.
Results:
Mean HbA1c values were 6.97 ± 1.90% and 6.98 ± 1.80% for HPLC and TRUSTlight FIA, respectively. Positive and negative classification agreement was 91.84 and 89.22%, with overall agreement of 90.50%. Bland-Altman analysis showed a mean bias of 0.008% and 95% limits of agreement of - 0.987% to 1.003%. At the 6.5% diagnostic cutoff, these limits corresponded to approximately - 15.2% to + 15.4% relative differences and were wider than the ± 5% NGSP manufacturer certification criterion. Passing-Bablok regression showed no significant constant or proportional bias.
Conclusion:
The TRUSTlight FIA showed a small mean bias relative to the HPLC comparator, although the observed limits of agreement were wider than the ± 5% NGSP manufacturer certification criterion. Further validation is needed to determine its suitability for longitudinal HbA1c monitoring.
Supplementary Information:
The online version contains supplementary material available at https://doi.org/10.1007/s13340-026-00936-z.