HbA1c Standardization: Understanding NGSP, IFCC, Traceability and Result Reporting
HbA1c is measured by many different analytical methods and laboratory platforms worldwide. For HbA1c results to be clinically meaningful and comparable between measurement systems, laboratories and countries, appropriate standardization and traceability are essential.
Two systems are central to modern HbA1c standardization: the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference measurement system and the National Glycohemoglobin Standardization Program (NGSP).
Although these systems use different units and serve different roles within the standardization framework, they are mathematically linked and together support consistent interpretation of HbA1c results.
Why Is HbA1c Standardization Important?
HbA1c can be measured using multiple analytical technologies, including ion-exchange HPLC, immunoturbidimetry, enzymatic methods, affinity chromatography and capillary electrophoresis.
Without standardization, different methods could potentially produce systematically different results for the same patient sample. This would make it difficult to compare results between laboratories, instruments or clinical studies.
The objective of HbA1c standardization is not to make every analytical method identical. It is to ensure that appropriately standardized measurement systems produce results that are traceable to established reference systems and clinically comparable.
The Two Key HbA1c Standardization Systems
NGSP
The NGSP standardizes HbA1c results to the clinical evidence established by the Diabetes Control and Complications Trial (DCCT) and the United Kingdom Prospective Diabetes Study (UKPDS).
NGSP results are traditionally reported as the percentage of total hemoglobin represented by HbA1c.
HbA1c %
IFCC
The IFCC established a higher-order reference measurement system for HbA1c using defined reference measurement procedures and reference materials.
IFCC results are expressed as the amount of HbA1c relative to total hemoglobin in SI-compatible units.
mmol/mol
What Is the NGSP?
The National Glycohemoglobin Standardization Program was established to standardize HbA1c test results to those used in major clinical studies such as the DCCT and UKPDS.
These studies established important relationships between HbA1c levels, glycemic control and the risk of long-term diabetes complications.
NGSP therefore provides an important connection between laboratory HbA1c measurement and the clinical evidence used in diabetes care.
NGSP Manufacturer Certification
Manufacturers may submit HbA1c analytical systems for NGSP certification. The certification process evaluates the performance of a defined analytical system against an NGSP reference laboratory.
Importantly, NGSP manufacturer certification applies to the specific combination of analytical method, reagent/calibrator configuration and instrumentation evaluated during certification.
An NGSP certificate should therefore be interpreted as certification of the specific analytical configuration tested, rather than as a blanket certification covering every possible analyzer application of the reagent.
What Is the IFCC HbA1c Reference System?
The IFCC developed a reference measurement system intended to provide metrological traceability for HbA1c measurement.
The reference system uses defined reference materials, reference measurement procedures and a network of reference laboratories.
The IFCC reference measurement procedures are based on highly specific analytical techniques, including mass spectrometry and capillary electrophoresis.
1 IFCC Reference System
2 Reference Laboratories
3 Manufacturer Calibration
4 Routine HbA1c Assay
5 Patient Result
This traceability chain helps connect routine laboratory measurements to a higher-order reference measurement system.
What Is the Difference Between NGSP and IFCC Units?
NGSP and IFCC describe the same HbA1c measurement using different numerical scales.
| System |
Unit |
Example |
| NGSP |
% HbA1c |
7.0% |
| IFCC |
mmol/mol |
53 mmol/mol |
A result of 7.0% HbA1c in NGSP units corresponds to approximately 53 mmol/mol in IFCC units.
The numerical values differ because the reporting systems use different units and scales. The difference does not mean that one patient has two different HbA1c concentrations.
How Are NGSP and IFCC Results Converted?
The relationship between the NGSP and IFCC reference networks has been evaluated and is described by an established master equation.
NGSP (%) = 0.09148 × IFCC (mmol/mol) + 2.152
The equation may also be rearranged to convert an NGSP percentage to an IFCC value:
IFCC (mmol/mol) = 10.93 × NGSP (%) − 23.50
Common HbA1c Conversion Values
| NGSP (%) |
IFCC (mmol/mol) |
| 5.0% |
31 mmol/mol |
| 6.0% |
42 mmol/mol |
| 7.0% |
53 mmol/mol |
| 8.0% |
64 mmol/mol |
| 9.0% |
75 mmol/mol |
| 10.0% |
86 mmol/mol |
| 11.0% |
97 mmol/mol |
| 12.0% |
108 mmol/mol |
What Is Estimated Average Glucose (eAG)?
Estimated average glucose, commonly abbreviated as eAG, is a calculated value that expresses the statistical relationship between HbA1c and average glucose in units that may be more familiar from routine glucose monitoring.
Based on the ADAG study, the relationship between HbA1c and estimated average glucose can be expressed as:
eAG (mg/dL) = 28.7 × HbA1c (%) − 46.7
For example, an HbA1c value of approximately 7.0% corresponds to an estimated average glucose of approximately 154 mg/dL.
| NGSP HbA1c |
IFCC HbA1c |
Estimated Average Glucose |
| 5.0% |
31 mmol/mol |
97 mg/dL |
| 6.0% |
42 mmol/mol |
126 mg/dL |
| 7.0% |
53 mmol/mol |
154 mg/dL |
| 8.0% |
64 mmol/mol |
183 mg/dL |
| 9.0% |
75 mmol/mol |
212 mg/dL |
| 10.0% |
86 mmol/mol |
240 mg/dL |
eAG is an estimate derived from the statistical relationship between HbA1c and average glucose. It should not be interpreted as a direct measurement of the individual patient's mean glucose concentration.
Why Is Traceability Important for HbA1c?
Traceability provides a documented relationship between a routine laboratory result and a recognized reference system through an unbroken chain of calibrations and comparisons.
In HbA1c testing, appropriate traceability helps support:
| Objective |
Why It Matters |
| Comparability Between Laboratories |
Supports interpretation of HbA1c results obtained at different laboratories. |
| Comparability Between Methods |
Helps reduce systematic differences between appropriately standardized analytical systems. |
| Clinical Interpretation |
Connects routine HbA1c results with established clinical evidence and decision frameworks. |
| Manufacturer Calibration |
Provides a reference framework for assigning values to calibrators and analytical systems. |
| Long-Term Result Consistency |
Supports meaningful comparison of HbA1c measurements over time. |
Standardization Does Not Replace Laboratory Quality Control
A standardized or NGSP-certified HbA1c system still requires appropriate laboratory quality management.
Calibration, internal quality control, reagent handling, analyzer maintenance, sample preparation and external quality assessment all contribute to the reliability of routine HbA1c results.
Traceability establishes the measurement framework; quality control verifies that the laboratory is operating effectively within that framework.
HbA1c Reporting with Archem HbA1c II DIRECT
Archem HbA1c II DIRECT supports HbA1c result reporting according to both major reporting systems:
| Reporting System |
Unit |
| NGSP |
% HbA1c |
| IFCC |
mmol/mol |
The assay is intended for quantitative HbA1c determination in human whole blood using compatible automated clinical chemistry analyzers.
Archem NGSP-Certified HbA1c Systems
Archem has completed NGSP Manufacturer Certification for specified HbA1c analytical configurations across multiple automated clinical chemistry platforms.
For the certification period May 1, 2026 – May 1, 2027, certified systems include:
| Manufacturer |
NGSP-Certified Platform |
| Abbott |
Alinity C |
| Abbott |
ARCHITECT c4000 |
| Abbott |
ARCHITECT c8000 |
| Beckman Coulter |
DxC 700 AU |
| Olympus |
AU480 |
| Olympus |
AU5800 |
| Mindray |
BS2000M |
| Mindray |
BS800 / BS800M |
The certified systems are traceable to the Diabetes Control and Complications Trial reference framework through NGSP certification.
NGSP manufacturer certification applies to the specific analytical method, reagent/calibrator configuration and instrumentation evaluated during certification.
Archem HbA1c II DIRECT
HbA1c II DIRECT is a liquid, dual-reagent immunoturbidimetric HbA1c assay developed for quantitative determination of HbA1c in human whole blood on compatible automated clinical chemistry analyzers.
| Method |
Immunoturbidimetric |
| Reporting |
NGSP (%) / IFCC (mmol/mol) |
| Measuring Interval |
4.0–15.5% / 20–140 mmol/mol |
| Sample |
Anticoagulated human venous whole blood |
| Reagent Format |
Liquid, dual reagent |
| Preparation |
Ready to use |
Frequently Asked Questions
What is the difference between NGSP and IFCC HbA1c?
NGSP and IFCC are linked HbA1c standardization systems that use different reporting units. NGSP results are generally expressed as %, while IFCC results are expressed as mmol/mol.
How do you convert HbA1c from IFCC to NGSP?
The established master equation is: NGSP (%) = 0.09148 × IFCC (mmol/mol) + 2.152.
What does an HbA1c of 7% equal in IFCC units?
An HbA1c result of approximately 7.0% in NGSP units corresponds to approximately 53 mmol/mol in IFCC units.
What is NGSP certification?
NGSP manufacturer certification demonstrates that a specified HbA1c analytical system has met NGSP certification criteria when compared with an NGSP reference laboratory. Certification applies to the evaluated analytical configuration.
What is eAG in HbA1c reporting?
Estimated average glucose (eAG) is a calculated value derived from the statistical relationship between HbA1c and average glucose. For example, 7.0% HbA1c corresponds to an eAG of approximately 154 mg/dL.
Conclusion
Reliable HbA1c testing depends not only on the analytical method used, but also on the standardization and traceability framework behind the result.
The IFCC reference measurement system provides the metrological foundation for HbA1c standardization, while NGSP connects standardized HbA1c measurement with the clinical evidence established through major diabetes outcome studies.
Understanding the relationship between NGSP (%), IFCC (mmol/mol), traceability, manufacturer certification and result reporting helps laboratories, clinicians and diagnostic manufacturers interpret HbA1c results consistently across analytical systems.
References
- NGSP. National Glycohemoglobin Standardization Program. IFCC standardization, manufacturer certification and HbA1c reporting resources.
- International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). HbA1c reference measurement system and standardization resources.
- Weykamp C, et al. The IFCC Reference Measurement System for HbA1c.
- Nathan DM, et al. Translating the A1C Assay Into Estimated Average Glucose Values. Diabetes Care.
- Diabetes Control and Complications Trial Research Group. Diabetes Control and Complications Trial (DCCT).
- United Kingdom Prospective Diabetes Study Group. UK Prospective Diabetes Study (UKPDS).
- Archem Diagnostics. HbA1c II DIRECT Instructions for Use. Rev. V3.6, July 2026.