Haemoglobinopathies: a pitfall in the assessment of glycosylated haemoglobin by ion-exchange chromatography

HbA1c level decreases in iron deficiency anemia

BACKGROUND

Hemoglobin A1c (HbA1c) is the major form of glycosylated hemoglobin. There are conflicting data on changes in HbA1c levels in patients with iron deficiency anemia (IDA). The present study aimed to investigate the effects of HbA1c levels in the presence of IDA, the effects of iron treatment on HbA1c levels, as well as the relationship between the severity of anemia and HbA1c levels in patients without diabetes.

DESIGN AND METHODS

A total of 263 patients without diabetes mellitus (DM) who were admitted to Cukurova University, Faculty of Medicine, Department of Endocrinology and Hematology or who were followed up in this clinic and diagnosed as having IDA were included in the study. A total of 131 patients had IDA. The control group comprised 132 age-matched and sex-matched healthy individuals.

RESULTS

The mean HbA1c level was significantly lower in the group with IDA (5.4%) than in the healthy control group (5.9%; p < 0.05). When the patients were divided into three groups according to the severity of anemia through Hb levels, HbA1c levels were observed to decrease as the severity of the anemia increased (5.5%, 5.4%, and 5%, respectively; p > 0.05). The HbA1c levels of the patients with IDA were higher after iron therapy (from 5.4 ± 0.5 to 5.5 ± 0.3; p = 0.057). The mean hemoglobin (Hb), hematocrit (Hct), mean cell volume (MCV), mean corpusculer hemoglobin (MCH), and ferritin values also increased after iron therapy (p < 0.05).

CONCLUSION

The study results showed that IDA was associated with low HbA1c levels, and increased after iron therapy. Based on the study findings, it is necessary to consider the possible effects of IDA on HbA1c levels.

Glycosylated Hemoglobin in Subjects Affected by Iron-Deficiency Anemia

Previous studies have suggested that iron-deficiency anemia affects glycosylated hemoglobin (HbA1c) measurements, but the results were contradictory. We conducted a retrospective case-control study to determine the effects of iron deficiency on HbA1c levels. Starting with the large computerized database of the Italian Hospital of Desio, including data from 2000 to 2016, all non-pregnant individuals older than 12 years of age with at least one measurement of HbA1c, cell blood count, ferritin, and fasting blood glucose on the same date of blood collection were enrolled. A total of 2,831 patients met the study criteria. Eighty-six individuals were diagnosed with iron-deficiency anemia, while 2,745 had a normal iron state. The adjusted means of HbA1c were significantly higher in anemic subjects (5.59% [37.37 mmol/mol]), than those measured in individuals without anemia (5.34% [34.81 mmol/mol]) (P<0.0001). These results suggest that clinicians should be cautious about diagnosing prediabetes and diabetes in individuals with anemia.

Influence of iron deficiency on Hb A1c levels in type 2 diabetic patients

AIMS

Hemoglobin A1c (HbA1c) is gold-standard for the assessment of glycemic control in diabetic patients. Previous studies have reported that iron deficiency may elevate A1c concentrations, independent of glycemia. This study aimed to analyze the effect of iron status on HbA1c levels in diabetic patients.

METHODS

661 patients 336 females (228 menopausal and 108 premenopausal) and 325 males (237 age> 50 years and 88 age < 50 years) were recruited. HbA1c, ferritin, fasting plasma glucose, hemogram and medical history were recorded. Analysis of variance ANOVA and Pearson's regression were applied.

RESULTS

patients were divided according gender, age, glycemia and iron status (normal, latent iron deficiency LID, iron deficiency anemia IDA).All groups presented increasing HbA1c values in parallel with iron deficiency, subclinical and anemia, but the level of significance was not homogeneous in the different groups. Controlled premenopausal women HbA1c in normal iron status and IDA groups P = 0.0048, between normal and LID, P = 0.033. Not controlled premenopausal women Normal group and IDAP < 0.001, normal iron status and LID P = 0.019. Controlled menopausal women normal group and IDAP < 0.0001, LID and IDA P = 0.01. Not controlled menopausal women normal group and IDA P = 0.04. Controlled men over 50 years normal and IDA groups P = 0.002, LID and IDA P = 0.02. Controlled young men normal group and LID P = 0.03.

CONCLUSION

This study found a positive correlation between iron deficiency and increased HA1c levels. In diabetic patients with IDA should be interpreted with caution, due to the possibility of spurious increment in HbA1c.

Effect of iron deficiency anemia on hemoglobin A1c levels

BACKGROUND

Iron deficiency anemia is the most common form of anemia in India. Hemoglobin A1c (HbA1c) is used in diabetic patients as an index of glycemic control reflecting glucose levels of the previous 3 months. Like blood sugar levels, HbA1c levels are also affected by the presence of variant hemoglobins, hemolytic anemias, nutritional anemias, uremia, pregnancy, and acute blood loss. However, reports on the effects of iron deficiency anemia on HbA1c levels are inconsistent. We conducted a study to analyze the effects of iron deficiency anemia on HbA1c levels and to assess whether treatment of iron deficiency anemia affects HbA1c levels.

METHODS

Fifty patients confirmed to have iron deficiency anemia were enrolled in this study. HbA1c and absolute HbA1c levels were measured both at baseline and at 2 months after treatment, and these values were compared with those in the control population.

RESULTS

The mean baseline HbA1c level in anemic patients (4.6%) was significantly lower than that in the control group (5.5%, P<0.05). A significant increase was observed in the patients' absolute HbA1c levels at 2 months after treatment (0.29 g/dL vs. 0.73 g/dL, P<0.01). There was a significant difference between the baseline values of patients and controls (0.29 g/dL vs. 0.74 g/dL, P<0.01).

CONCLUSIONS

In contrast to the observations of previous studies, ours showed that HbA1c levels and absolute HbA1c levels increased with treatment of iron deficiency anemia. This could be attributable to nutritional deficiency and/or certain unknown variables. Further studies are warranted.

A case of type 2 diabetes mellitus developing hypothyroidism discovered as a result of a discrepancy between glycated hemoglobin and glycated albumin values

We report a case of type 2 diabetes mellitus presenting hypothyroidism due to overeating of seaweed that was noticed as a result of a discrepancy between glycated albumin (GA) and glycated hemoglobin (GHb). A 71-year-old woman was undergoing managed treatment with oral medicines and insulin for diabetes mellitus with no sign of thyroid disease. Her thyroid function was euthyroid without aid of thyroid hormone. All of the patient's thyroid autoantibodies were negative. Fifteen weeks prior to indications of hypothyroidism, she had started to consume large amounts (100-200 g dry weight equivalent) of cooked "wakame" seaweed every morning. Just before admission to our hospital, her GA was 26.9%, while GHb and fasting plasma glucose remained within normal ranges (less than 5.6%, and 106 mg, respectively). This discrepancy between GA and GHb drew our attention to the development of complications. Naive interview of the patient led us to believe a thyroid hormone deficiency existed, though without any related complaints or findings, such as non-pitting edema, cold intolerance, or easy fatiguing. Seaweed consumption was stopped and periodic observation of thyroid function started. As thyroid hormone levels moved into normal range, GA and GHb returned to their normal relative ratio after 3 months. Thus, measurement of the relative ratio of GA and GHb may be useful for glycemic monitoring, with the potential as a readily available glycemic control marker for patients with changeable complications.

Effects of beta thalassemia minor on results of six glycated hemoglobin methods

BACKGROUND

Beta-thalassemia minor (BTM) is a common benign condition that can be present in patients with diabetes mellitus. There are conflicting reports about the effect of BTM on glycated hemoglobin (gHb) measurements. We evaluated 6 gHb methods using samples from non-diabetic subjects with BTM.

METHODS

Samples submitted for hemoglobin phenotype analysis were evaluated. A total of 57 samples (30 controls and 27 with BTM) from non-diabetic subjects were selected. GHb analysis was performed by Tosoh A1c 2.2+, Primus CLC 330, Bayer DCA 2000, Beckman Coulter, Synchron CX7 and LX20, and Roche Tina-quant II assays.

RESULTS

The A1c 2.2+, CLC 330, DCA 2000 and Tina-quant II assays showed no statistically significant difference between the control and BTM groups. In contrast, BTM results were significantly higher than controls on the Synchron CX7 analyzer and borderline significant on the Synchron LX20 (p=0.051). Further investigation demonstrated an increase in Synchron %HbA(1c) results with decreasing hemoglobin concentrations.

CONCLUSIONS

In this study using samples from subjects with normal or near-normal gHb, BTM does not affect gHb measurements per se. However, the Synchron methods yielded higher results for samples with lower hemoglobin concentrations, like those that can be seen in BTM. The Synchron method was improved at the end of 2003, which minimized this problem.

Hemoglobin variants and determination of glycated hemoglobin (HbA1c)

Measurement of glycated hemoglobin in diabetic patients is an established procedure for evaluating long-term control of diabetes. The Diabetes Control and Complications Trial (DCCT), as well as the United Kingdom Prospective Diabetes Study (UKPDS), confirmed the direct relationship between the degree of glycemic control as estimated by glycohemoglobin (GHb) determinations and the development and progression of long-term complications in diabetic patients. Samples with known interferences of HbA(1c) determination as hemoglobinopathies are specifically excluded from certification testing and there are no guidelines or requirements for comparability of samples containing hemoglobin (Hb) variants. This paper reviews the interference of Hb variants on determination methods of glycated hemoglobin as they result in false HbA(1c) results.

The inter-relationships between albuminuria, plasma albumin concentration and indices of glycaemic control in non-insulin-dependent diabetes mellitus

We studied the relationship between albuminuria (measured as albumin/creatinine ratio (alb/Cr) in a random urine sample) and measures of glycaemic control (fructosamine, HbA1 and glucose) in 470 patients with non-insulin-dependent diabetes mellitus (NIDDM). Albumin excretion was in the microalbuminuric range (alb/Cr ratio > 5.4-40.3) in 112 (23.8%) and in the macroalbuminuric range (alb/Cr ratio > 40.3 mg/mmol) in 89 patients (18.9%). Fourteen percent (n = 67) of patients had a normal plasma HbA1 (< or = 8.5%) while 27% (n = 127) had a normal plasma fructosamine concentration (< or = 2.2 mmol/l). Using stepwise multiple regression analysis, plasma fructosamine concentration was found to be independently and negatively associated with urine albumin/creatinine ratio (B = 0.24, P < 0.006) in the macroalbuminuric group. Further analysis of the relationship between plasma albumin concentration and indices of glycaemic control showed that plasma albumin concentration correlated negatively with random plasma glucose concentration in the normoalbuminuric patients (r = -0.16, P = 0.008) but not in microalbuminuric or macroalbuminuric groups. HbA1 was not correlated with plasma albumin concentration. Our results indicate that albuminuria has an effect on the plasma fructosamine concentration which is independent of plasma albumin concentration.

Effect of long-term monitoring of glycosylated hemoglobin levels in insulin-dependent diabetes mellitus

BACKGROUND

The value of routine measurements of glycosylated hemoglobin (hemoglobin A1c) in the care of patients with diabetes mellitus is uncertain. We undertook this study to determine whether knowledge of hemoglobin A1c values would result in improved metabolic control in a group of patients with insulin-dependent diabetes mellitus (IDDM).

METHODS

We randomly assigned 240 patients with IDDM to one of two groups that were comparable in age, sex, duration of diabetes, and initial hemoglobin A1c levels. The patients were followed for a year, and the hemoglobin A1c concentration was measured at three-month intervals. The hemoglobin A1c values were used in assessing glycemic control and modifying therapy in one of the two groups. In the other, care givers were not aware of the hemoglobin A1c levels and relied on blood or urine glucose measurements to monitor treatment.

RESULTS

Among the 222 patients still being followed after one year, the mean hemoglobin A1c value decreased significantly--from 10.1 to 9.5 percent (P less than 0.005)--in the group whose hemoglobin A1c level was monitored (n = 115), whereas the initial and one-year values in the control group (n = 107) were 10.0 and 10.1 percent, respectively. The proportion of patients with poor control, defined as those having a hemoglobin A1c value above 10.0 percent, decreased from 46 to 30 percent (P less than 0.01) in the group whose hemoglobin A1c level was monitored but did not change significantly (45 to 50 percent) in the control group. The patients in the group whose hemoglobin A1c level was monitored were seen and their insulin regimens changed more often, but they were hospitalized for acute care of their diabetes less often than those in the control group. A similar decrease in hemoglobin A1c values occurred in the control group in the following year, when their care givers knew their hemoglobin A1c values.

CONCLUSIONS

Regular measurements of hemoglobin A1c lead to changes in diabetes treatment and improvement of metabolic control, indicated by a lowering of hemoglobin A1c values.

Unexplained variability of glycated haemoglobin in non-diabetic subjects not related to glycaemia

We have studied levels of glycated haemoglobin in a sample of 223 people aged over 40 years without known diabetes mellitus screened in a community study. Each had a glucose tolerance test and glycated haemoglobin measured by four methods - agar gel electrophoresis with and without removal of Schiff base, affinity chromatography and isoelectric focusing. The correlation coefficients between 2 h blood glucose and levels of glycated haemoglobin were between 0.43 and 0.64. This poor correlation was not explained on the basis of assay or biological variability of either 2 h blood glucose or glycated haemoglobin. Multiple regression analysis showed that other assays of glycated haemoglobin contributed to the variance of any single glycated haemoglobin value by 0.1%-52.9% (median 12.8%) compared to the variance of 18.6%-41.4% (median 30.8%) explained by 2 h blood glucose alone, suggesting that in a non-diabetic population, the degree of glucose intolerance may explain only one third of the variance of glycated haemoglobin levels, but other factors operate to produce consistent changes in levels of glycated haemoglobin. Investigation of 42 subjects with consistently high (20 subjects) or low (22 subjects) levels of glycated haemoglobin relative to their 2 h blood glucose level showed no difference in age, gender, body mass index, haemoglobin levels or smoking, although 50% of low glycators had impaired glucose tolerance. Neither ambient blood-glucose levels, as estimated on two five-point blood-glucose profiles, nor dietary intake of carbohydrate, starch, sugars, fibre or alcohol, explained the difference between high and low glycators. The determinants of the consistent interindividual differences in levels of glycated haemoglobin in non-diabetic subjects remain to be determined.

Hb Hope, beta 136(H14)Gly----Asp, in a diabetic Japanese female and its functional characterization

A beta-variant hemoglobin, first misjudged as a marked elevation of Hb A1, was found in a 68-year-old Japanese female with diabetes mellitus. This hemoglobin was isolated by Bio-Rex 70 chromatography combined with chromatofocusing, and was found to be Hb Hope, beta 136(H14)Gly----Asp, by classical and high performance liquid chromatographic peptide mapping techniques. Intrinsic oxygen affinity of this hemoglobin was approximately one-third as compared with that of Hb A0. This property was still observed in the constituent beta subunits isolated. Effects of such allosteric effectors as H+ (at a fixed concentration of Cl-), anion (Cl-), 2,3-diphosphoglycerate and carbon dioxide were more or less depressed. Among others, a marked reduction in the carbamate effect should be noted in a structural interpretation of the functional modifications. Subunit cooperativity, on the contrary, was not different from that in Hb A0 (n = 2.8-2.9). Explanation of these altered functions were attempted on the basis of the altered structure. The reduced stability of Hb Hope is also described.

Hemoglobin J-Baltimore (beta 16(A13)Gly----Asp): interference with the assay of HbA1c

Three independent cases of Hemoglobin J-Baltimore(beta 16(A13)Gly----Asp) were detected through the assay of HbA1c in diabetic patients. Using chromatography on Bio-Rex 70 resin, one large peak replaced the usually well resolved peaks of HbA1a + b and HbA1c. The species that overlapped the latter fractions was identified as HbJ1c. HbJ-Baltimore itself was identified using HPLC of the beta-chain tryptic peptides. This observation emphasizes the errors that hemoglobin variants may introduce in the assay of HbA1c.

Measurement of glycated albumin in diabetic patients by biospecific affinity chromatography

The percentage of glycated plasma albumin was measured by a procedure involving ammonium sulphate precipitation and Affi-Gel-Blue and phenylboronate chromatographies. The value correlates well with the amount of ketoamine-bound sugars determined by colorimetric assay (r = 0.98, n = 39). The normal mean value is 3.9 +/- 0.3% (mean +/- S.D., coefficient of variation = 7.7%, n = 32) and varies from 3.9 to 21% in diabetics (n = 54). A good correlation is found with the mean blood glucose value of the preceding twenty days (r = 0.92, n = 57). Because of its relative ease of determination, glycated albumin constitutes a good short-term glycemic index and an alternative to glycated haemoglobin in some specific cases.