Factors that Interfere with HbA1c Test Results

Updated 7/2014

Information for physicians and patients regarding HbS, HbC, HbE and HbD traits

More about hemoglobin variants and HbA1c can also be found at the NIDDK web site:
Sickle Cell Trait and Other Hemoglobinopathies and Diabetes: Important Information for Physicians
For People of African, Mediterranean, or Southeast Asian Heritage: Important Information about Diabetes Blood Tests

Factors that Interfere with HbA1c Measurement:  Genetic variants (e.g. HbS trait, HbC trait), elevated fetal hemoglobin (HbF) and chemically modified derivatives of hemoglobin (e.g. carbamylated Hb in patients with renal failure) can affect the accuracy of HbA1c measurements. The effects vary depending on the specific Hb variant or derivative and the specific HbA1c method. Table 1 contains information for most of the commonly used current HbA1c methods for the four most common Hb variants, elevated HbF and carbamylated Hb. Interferences from less common Hb variants and derivatives are discussed in Bry, et al [1]. All entries in Table 1 are based on published information. In addition, if a product insert indicates clearly that there is inference from a particular factor, then the interference is entered as “yes” and the product insert is cited. When selecting an assay method, laboratories should take into consideration characteristics of the patient population served, (e.g. high prevalence of hemoglobinopathies or renal failure).

Factors that affect interpretation of HbA1c Results: Any condition that shortens erythrocyte survival or decreases mean erythrocyte age (e.g., recovery from acute blood loss, hemolytic anemia) will falsely lower HbA1c test results regardless of the assay method used [2]. HbA1c results from patients with HbSS, HbCC, and HbSC must be interpreted with caution given the pathological processes, including anemia, increased red cell turnover, and transfusion requirements, that adversely impact HbA1c as a marker of long-term glycemic control. Alternative forms of testing such as glycated serum protein or glycated albumin should be considered for these patients.

Iron deficiency anemia, a major public health problem in developing countries, is associated with higher HbA1c and higher fructosamine [3]. Consistent with these observations, iron replacement therapy lowers both HbA1c and fructosamine concentrations in diabetic and non-diabetic individuals [3-5]. HbA1c , but not glycated albumin, is increased in late pregnancy in nondiabetic individuals owing to iron deficiency [6]. Insight into the mechanism was recently obtained by the observation that malondialdehyde, which is increased in patients with iron deficiency anemia [3], enhances the glycation of hemoglobin [7]. Alternative measures of glycemic assessment (e.g., glucose monitoring) must be used in the presence of significant iron deficiency anemia, at least until the iron deficiency has been successfully treated.

Chronic renal failure develops in many diabetic patients. The role of glycemic control and the value of HbA1c in diabetic subjects with renal disease are controversial. While interference from carbamylated Hb can be evaluated, the role of renal anemia, erythropoietin intake, and other factors in chronic renal failure is more difficult to evaluate. Recent reports suggest HbA1c underestimates glycemic control in diabetic patients on dialysis and that glycated albumin is a more robust indicator of glycemic control [8-11]. Further studies are needed to clarify the role of HbA1c in diabetic patients with chronic renal failure.

Table 1: Effects of frequently encountered Hb variants and derivatives on HbA1c measurement

Some interferences for some methods are highlighted in gray indicating that they have been tested using a new stricter criterion of >7% difference at 6 and 9% HbA1c to define clinical significance (13). The other methods were tested using either criteria of >10% at 6 and 9% HbA1c or some other criteria.

Method
(listed in alphabetical order by manufacturer)

Interference (Yes/No)

Hb C trait

Hb S trait

Hb E trait

Hb D trait

Elevated
HbF

Carb Hb

Abbott Architect (Seradyn Reagents)

Yes 12

Yes 12

@

@

$

-

Arkray ADAMS A1c HA-8180
(Menarini)

No 13,46

No 13,46

HbA1c not quantified 13, 46

HbA1c not quantified 46/ Yes 13

No 46

-

Axis-Shield Nycocard

No 14

No 14

@

@

$

-

Axis-Shield Afinion

No 15

No 15

No 16

No 16

$

-

Bayer A1cNow

Yes 17

Yes 17

No 16

No 16

$

-

Beckman AU System

Yes 12,18, 15

Yes 12,18, 15

No 16

No 16

Yes >10% 18

-

Beckman Synchron

No 14

No 14

No 16

No 16

$

-

Bio-Rad D-10 (short Program)

Yes 17 /No 15

No 15,17

No 16

No 16

Yes >10% 20

No 47

Bio-Rad D-10 (extended   program)

No 15

No 15

No 16

No 16

-

No 47

Bio-Rad in2it

Yes 13,21

No 13,21

Yes 13,21

No 13,21

$

-

Bio-Rad Variant II A1c (NU)

-

-

No 16

No 16

Yes >10% 20

No 47

Bio-Rad Variant II Turbo (270-2415/2417)

No 15

No 15

Yes 16

Yes 16

Yes >5% 20

No 47

Bio-Rad Variant II Turbo 2.0

No 13,21

No 13,21

No 13,21, Yes 45,53

No 13,21

Yes >25% 20

No 47-

Diazyme Direct Enzymatic HbA1c

No 15,23

No 15,23

No 16,23

No 16

-

No 47

 Drew Scientific DS5

No 17

Yes 17

-

-

-

-

 Helena Glyco-Tek

Yes 14,24

No 14,24

@

@

$

-

 JEOL BM Test HbA1c on JCA-BM 6010/C

No 51

No 51

No 51

No 51

-

-

Menarini HA-8140

No 14

Yes 14

Yes 1, 25

Yes 26

No 1, 25

Yes 19, 27, 28

Menarini HA-8160 (Diabetes Mode)

No 17

No 17

Yes 16

Yes 16, 52

-

No 47

Menarini HA-8160 (Thalassemia Mode)

-

-

No 16

HbA1c not quantifed 16

-

-

 Ortho-Clinical Vitros

No 15,29

No 15,29

No 16

No 16

$

-

 Pointe Scientific Hemoglobin A1c

No 15,29

No 15,29

No 16

No 16

$

-

 Randox Haemoglobin A1c

Yes 30

Yes 30

@

@

Yes >10% 30

-

Roche Cobas Integra Gen2

No 15,31,32

No 15,31,32

No 16

No 16

$

No 47

Roche Tina-quant II on   Hitachi

No 1, 33,35

No 1, 33,35

No 1, 6,35

No 16

$

No 1, 27, 28

Sebia Capillarys 2 Flex Piercing

No 13

No 13

No 13

No 13

Yes >15% 48

No 48,49, 50

Siemens Advia HbA1c (original version)

Yes 34

Yes 34

@

@

$

-

Siemens Advia A1c (new version)

No 22,36

No 22,36

@

@

$

-

Siemens DCA 2000/DCA Vantage

No 1, 24,33,37 /yes 38

No 1, 24

No 1, 16,39,40

No 16

Yes >10% 41,43

No 27, 42, 47

Siemens Dimension

No 17

No 17

No 16

No 16

$

-

Tosoh G7

Yes 13,21 /No 15,17

No 13, 15, 17,21

Yes 13,16, 21

No 13,16, 21

No ≤30% 20, 41, 43

No 47

Tosoh G8

No 13,21, 22

No 13,21, 22

Yes 13,16, 21

No 13,16, 21

No ≤30% 20

No 47

Trinity (Primus) Boronate Affinity HPLC

No 1, 15, 17,33

No 1, 15, 17,33

No 1, 16, 39

No 16

Yes >15% 20,41, 43

No 1, 27, 42,44

@ In the absence of specific method data, it can generally be assumed that immunoassay methods do not have clinically significant interference from HbE and HbD because the E and D substitution are distant from the N-terminus of the hemoglobin beta chain (16).
$ In the absence of specific method data, it can generally be assumed that both immunoassay and boronate affinity methods show interference from HbF levels above ~10-15% (20, 43).

Yes/No indicates that there is conflicting data in the literature.  The indicator in bold is the opinion of the NGSP based on review of the literature cited.
- Not yet evaluated

NOTE:

  • Many other publications have been reviewed.  Only those with conclusions that are reasonably supported by data are included.
  • For ion-exchange HPLC methods, interference from Hb variants and adducts may be dependent on the lot of reagents used (33).

References:

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