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Comparison of IFCC-calibrated HbA(1c) from laboratory and point of care testing systems
Susan E Manley1, Laura J Hikin2, Rachel A Round2
1Clinical Biochemistry and Haematology, University Hospitals Birmingham NHS Foundation Trust, Birmingham, UK; Division of Medical Sciences, University of Birmingham, Birmingham, UK.
Insights
This study compared various methods for measuring Hemoglobin A1c (HbA1c), a key marker for diabetes. Differences between methods can impact diabetes diagnosis, emphasizing the need to consider the specific analyser used.
Area of Science:
- Clinical Chemistry
- Diabetes Diagnostics
- Analytical Methods
Background:
- International guidelines from WHO, IDF, and ADA recommend specific HbA1c thresholds for diagnosing diabetes and pre-diabetes.
- Accurate HbA1c measurement is crucial for effective diabetes management and epidemiological studies.
- Variations in analytical methods can lead to discrepancies in HbA1c results.
Purpose of the Study:
- To compare the performance of several HbA1c measurement methods against the IFCC secondary reference method.
- To evaluate the impact of different analytical platforms on glycaemic marker research.
- To assess the clinical relevance of observed differences in HbA1c measurements.
Main Methods:
- HbA1c levels were measured in 128 diabetic patients using high-performance liquid chromatography (HPLC) analysers (Bio-Rad Variant II NU, Menarini HA8160, Tosoh G8).
- Point-of-care testing (POCT) systems (A1cNow+ and DCA 2000®+) and affinity chromatography (Primus Ultra2) were also utilized.
- Comparisons were made against the IFCC secondary reference method, with Menarini HA8160 calibrated using the IFCC SRM protocol.
Main Results:
- Median HbA1c on the IFCC SRM was 7.5% (58 mmol/mol).
- HPLC methods showed varying offsets compared to IFCC SRM: Bio-Rad Variant II NU (+0.33%), Tosoh G8 (+0.22%), and Menarini HA8160 (-0.04%).
- POCT methods exhibited lower precision and negative offsets: DCA 2000®+ (-0.13%) and A1cNow+ (-0.70%). Positive biases in Tosoh and Bio-Rad were later corrected through recalibration.
Conclusions:
- Minor discrepancies exist between IFCC-calibrated and NGSP-certified HbA1c methods across a broad measurement range.
- These analytical variations can influence estimates of diabetes prevalence.
- The choice of analyser and calibrator is critical when interpreting diagnostic HbA1c data.
Objective:
WHO, IDF and ADA recommend HbA(1c) ≥6.5% (48 mmol/mol) for diagnosis of diabetes with pre-diabetes 6.0% (42 mmol/mol) [WHO] or 5.7% (39 mmol/mol) [ADA] to 6.4% (47 mmol/mol). We have compared HbA(1c) from several methods for research relating glycaemic markers.
Research Design And Methods:
HbA1c was measured in EDTA blood from 128 patients with diabetes on IE HPLC analysers (Bio-Rad Variant II NU, Menarini HA8160 and Tosoh G8), point of care systems, POCT, (A1cNow+ disposable cartridges and DCA 2000(®)+ analyser), affinity chromatography (Primus Ultra2) and the IFCC secondary reference method (Menarini HA8160 calibrated using IFCC SRM protocol).
Results:
Median (IQ range) on IFCC SRM was 7.5% (6.8-8.4) (58(51-68) mmol/mol) HbA(1c) with minimum 5.3%(34 mmol/mol)/maximum 11.9%(107 mmol/mol). There were positive offsets between IFCC SRM and Bio-Rad Variant II NU, mean difference (1SD), +0.33%(0.17) (+3.6(1.9) mmol/mol), r(2)=0.984, p<0.001 and Tosoh G8, +0.22%(0.20) (2.4(2.2) mmol/mol), r(2)=0.976, p<0.001 with a very small negative difference -0.04%(0.11) (-0.4(1.2) mmol/mol), r(2)=0.992, p<0.001 for Menarini HA8160. POCT methods were less precise with negative offsets for DCA 2000(®)+ analyser -0.13%(0.28) (-1.4(3.1) mmol/mol), r(2)=0.955, p<0.001 and A1cNow+ cartridges -0.70%(0.67) (-7.7(7.3) mmol/mol), r(2)=0.699, p<0.001 (n=113). Positive biases for Tosoh and Bio-Rad (compared with IFCC SRM) have been eliminated by subsequent revision of calibration.
Conclusions:
Small differences observed between IFCC-calibrated and NGSP certified methods across a wide HbA(1c) range were confirmed by quality control and external quality assurance. As these offsets affect estimates of diabetes prevalence, the analyser (and calibrator) employed should be considered when evaluating diagnostic data.
