Hemoglobin A1c levels in a diabetes detection program

Evaluation of HbA1c from CGM traces in an Indian population

Introduction

The development of continuous glucose monitoring (CGM) over the last decade has provided access to many consecutive glucose concentration measurements from patients. A standard method for estimating glycated hemoglobin (HbA1c), already established in the literature, is based on its relationship with the average blood glucose concentration (aBG). We showed that the estimates obtained using the standard method were not sufficiently reliable for an Indian population and suggested two new methods for estimating HbA1c.

Methods

Two datasets providing a total of 128 CGM and their corresponding HbA1c levels were received from two centers: Health Centre, Savitribai Phule Pune University, Pune and Joshi Hospital, Pune, from patients already diagnosed with diabetes, non-diabetes, and pre-diabetes. We filtered 112 data-sufficient CGM traces, of which 80 traces were used to construct two models using linear regression. The first model estimates HbA1c directly from the average interstitial fluid glucose concentration (aISF) of the CGM trace and the second model proceeds in two steps: first, aISF is scaled to aBG, and then aBG is converted to HbA1c via the Nathan model. Our models were tested on the remaining 32 data- sufficient traces. We also provided 95% confidence and prediction intervals for HbA1c estimates.

Results

The direct model (first model) for estimating HbA1c was HbA1cmmol/mol = 0.319 × aISFmg/dL + 16.73 and the adapted Nathan model (second model) for estimating HbA1c is HbA1cmmol/dL = 0.38 × (1.17 × ISFmg/dL) - 5.60.

Discussion

Our results show that the new equations are likely to provide better estimates of HbA1c levels than the standard model at the population level, which is especially suited for clinical epidemiology in Indian populations.

Hemoglobin A1c and diagnosis of diabetes

The prevalence of diabetes is increasing markedly worldwide, especially in China. Hemoglobin A1c is an indicator of mean blood glucose concentrations and plays an important role in the assessment of glucose control and cardiovascular risk. In 2010, the American Diabetes Association included HbA1c ≥6.5% into the revised criteria for the diagnosis of diabetes. However, the debate as to whether HbA1c should be used to diagnose diabetes is far from being settled and there are still unanswered questions regarding the cut-off value of HbA1c for diabetes diagnosis in different populations and ethnicities. This review briefly introduces the history of HbA1c from discovery to diabetes diagnosis, key steps towards using HbA1c to diagnose diabetes, such as standardization of HbA1c measurements and controversies regarding HbA1c cut-off points, and the performance of HbA1c compared with glucose measurements in the diagnosis of diabetes.

An Update on the Diagnosis of Diabetes

This update on the diagnosis of carbohydrate metabolism abnormalities fo cuses on a more rational evaluation of glucose metabolism with a clear line of demarcation between overt diabetes and impaired glucose tolerance levels. This approach has eliminated the confusion over a definition of mild asymptomatic diabetes in contradistinction to overt disease. In addition, there is a limited promise of diagnosis in certain instances by means of hemoglobin A1C determi nations.

Plasma glucose and hemoglobin A1c for the detection of diabetes in Chinese adults

BACKGROUND

The aim of the present study was to evaluate the performance of plasma glucose (PG) and HbA1c for the detection of diabetes in the general population in China.

METHODS

A cross-sectional analysis was conducted in a nationally representative sample of 98,658 Chinese adults aged ≥18 years. Fasting plasma glucose and HbA1c levels were measured in all participants after at least a 10-h overnight fast. An oral glucose tolerance test (OGTT) was conducted among participants without a self-reported history of diagnosed diabetes.

RESULTS

An HbA1c ≥6.5% could identify 4.57% of Chinese adults as having newly detected diabetes, followed by fasting PG (FPG) and 2-h PG at 4.52% and 3.50%, respectively. Approximately 1.95% of the total population was detected by HbA1c but not by FPG or 2-h PG. However, FPG plus HbA1c could identify most (85.2%) diabetic individuals identified by any of the three tests (i.e., FPG, 2-h PG, and HbA1c). Levels of most cardiovascular risk factors, such as body mass index, waist circumference, and cholesterol, were higher in diabetes detected by HbA1c alone than in diabetes identified by the OGTT.

CONCLUSIONS

Although HbA1c ≥6.5% has been recommended by the American Diabetes Association as one of the diagnostic tests for diabetes, caution should be used to avoid potential overdiagnosis when interpreting diabetes identified by elevated HbA1c alone.

Application and applicability of non-invasive risk models for predicting undiagnosed prevalent diabetes in Africa: A systematic literature search

BACKGROUND AND PURPOSE

Prediction algorithms are increasingly advocated in diabetes screening strategies, particularly in developing countries. We conducted a systematic review to assess the application and applicability of existing non-invasive prevalent diabetes risk models to populations within Africa.

DESIGN

systematic review data sources A systematic search of English literatures in Medline via PubMed from 1999 until June, 2014. Study selection Included studies had to report on the development, validation or implementation of a model that was primarily constructed to predict prevalent undiagnosed diabetes using non-laboratory based predictors.

DATA EXTRACTION

Data were extracted on the type of statistical model, type and range of predictors in the model, performance measures in both internal and external validation, and whether the model was developed from, validated or implemented in an African population.

RESULTS

Twenty-three studies reporting on non-invasive prevalent diabetes models were identified. Ten from Europe (some with multiethnic populations), nine models were developed among Asian population, two from the USA and two from the Middle-East. The c-statistics for these models ranged from 0.65 to 0.88 in the development studies, and from 0.63 to 0.80 in the validation studies. Twenty models were validated, and none in Africa. Among predictors commonly included in models, parental/family history of diabetes and personal history of hypertension appear to be more prone to measurement errors in the African context.

CONCLUSION

Existing prevalent diabetes prediction models have not been applied to African populations, and issues with the measurement of key predictors make their applicability likely inaccurate.

A history of HbA1c through Clinical Chemistry and Laboratory Medicine

HbA(1c) was discovered in the late 1960s and its use as marker of glycemic control has gradually increased over the course of the last four decades. Recognized as the gold standard of diabetic survey, this parameter was successfully implemented in clinical practice in the 1970s and 1980s and internationally standardized in the 1990s and 2000s. The use of standardized and well-controlled methods, with well-defined performance criteria, has recently opened new directions for HbA(1c) use in patient care, e.g., for diabetes diagnosis. Many reports devoted to HbA1c have been published in Clinical Chemistry and Laboratory Medicine (CCLM) journal. This review reminds the major steps of HbA(1c) history, with a special emphasis on the contribution of CCLM in this field.

Hemoglobin AI in community care

In order to investigate the potential usefulness of knowing the blood concentrations of HbAI in primary care, HbAI was measured in diabetic subjects attending a primary care centre. The values were compared with concentration of HbAI in a reference group on non-diabetics. The reference group had a mean value in HbAI of 7.6+/-0.1% with a tendency to increased values with advancing age. The diabetic subjects had a mean value in HbAI of 10.8+/-0.2%. Diabetics under good control had lower values (10.2+/-0.2%), than patients under poor control (12.0+/-0.2%) (p less than 0.001). There was a correlation (r=0.50, p less than 0.001) between HbAI and fasting blood glucose levels. It is concluded that determination of HbAI can be an aid in the control of diabetics in primary care. However, the method requires good technical management, and the results are most reliable when the same person analyses all samples. The objective in diabetic therapy in this respect should no doubt be to depress the concentrations of HbAI towards normal values.

The clinical value of HbAI-determinations

Determination of glycosylated hemoglobin, HbAI, has become of great interest in diabetic patients as the values seem to reflect mean blood glucose values over longer periods of time. Several methods for determination of HbAI are now available. We have used a microchromatographic procedure which seems suitable for routine clinical work. In 94 healthy subjects HbAI was 6.5 +/- 0.8% (mean +/- S.D.). The corresponding value obtained in 126 diabetics was 9.6 +/- 1.8%. Particularly in patients treated with insullin HbAI-determinations are of value for assessment of the carbohydrate state, since in these patients the glucose values are prone to great variations. The exact relationship between the HbAI-values and the mean blood glucose level might vary between patients, however. Thus erythrocyte survival and renal function may influence the HbAI-values and more experience is needed in the interpretation of values. Nevertheless, preliminary data from a study in progress support the expectation that HbA1-determinations are likely to become a valuable adjunct in the routine management of diabetic patients.

HbA1c and the diagnosis of diabetes mellitus

To evaluate the usefulness of haemoglobin A1c (HBA1C) determinations in the diagnosis of diabetes mellitus, the outcome of a standard oral glucose tolerance test (OGTT) and HbA1c values were compared in 178 consecutive subjects referred for a diagnostic OGTT. The subjects were mainly in age groups in which non-symptomatic diabetes mellitus predominates. The prevalences of elevated fasting plasma glucose and abnormal OGTT were found to increase with increasing age. One third of the total series had impaired or diabetic OGTT. In the group with normal OGTT, 16% had fasting plasma glucose concentrations above the upper normal limit, but the range of HbA1c values did not differ from that of healthy controls. In the group with impaired OGTTs (n = 20), elevated HbA1c values were found only in subjects with elevated fasting plasma glucose and the highest two-hour OGTT values (n = 4). In the group with diabetic OGTT, 86-94% had HbA1c values above the upper normal limit, and HbA1c was elevated in all subjects with a fasting plasma glucose higher than 10.5 mmol/l or a 2-hour OGTT glucose value above 14.4 mmol/l. Using the results of the OGTT as the true diagnosis, HbA1c had a diagnostic specificity of 0.78 and sensitivity of 0.96. Only subjects with a substantially reduced glucose tolerance may be diagnosed by HbA1c determinations.

Hemoglobin A1c: past, present and future

Hemoglobin A1c (HbA1c) has been used for decades to monitor the control of glycemia in diabetes. Although HbA1cis currently undergoing a reassessment, and major developments have been underway in recent years, HbA1c is not recommended at present for diabetes screening or diagnosis. The objective of this review is to summarize the recent developments and to review a potential diagnostic role for HbA1c. Implementation of changes in HbA1c results and units of measurements have been suggested for the purpose of test standardization. These include lower reference ranges (by about 1.5-2 points) and measurement units expressed in percentage (%), as mg/dL (mmol/L) or mmol/mol (or a combination of these units). In diabetes screening and diagnosis, the current diagnostic guidelines use measurement of plasma glucose either fasting or after glucose load. These diagnostic methods have shortcomings warranting a potential diagnostic role for HbA1c. While recent developments in HbA1c methodologies are acknowledged, it is not yet known which changes will be implemented, and how soon. Given the recent literature supporting HbA1c diagnostic abilities, and given the shortcomings of the current guidelines, it is possible that a diagnostic role for HbA1c may be considered in future practice guidelines, globally. Very recently, the first of such recommendations has been proposed by an expert panel, as announced by the US Endocrine Society.

[Diagnosing type 2 diabetes mellitus: in primary care, fasting plasma glucose and glycosylated haemoglobin do the job]

OBJECTIVE

To determine the validity of glycosylated hemoglobin (HbA1c) values as a method to diagnose type 2 diabetes mellitus (DM2) in a population at risk seen in primary care.

DESIGN

Cross-sectional analytical study.

SETTING

Data were obtained for the Raval Sud study population (epidemiologic study of alterations in glucose metabolism in a population at risk).

PARTICIPANTS

454 subjects from this population (mean age, 65 +/- 3 years; 52% male) at high risk for DM2, seen at a primary care center, were included in the study.

MAIN MEASURES

We recorded demographic data and laboratory values for fasting plasma glucose (FPG), oral glucose tolerance test (OGTT), and HbA1c. The diagnostic criteria used for DM2 were those published by the WHO in 1999. Values for HbA1c were expressed as the number of standard deviations (SD) above the mean.

RESULTS

Levels of HbA1c correlated with FPG (r=0.72) and glucose levels 2 h after oral glucose overload (r=0.43). Thirty percent of the patients with FPG between 110 and 125 mg/dL had HbA1c values higher than the reference limits. A combined technique based on FPG>125 mg/dL or FPG 110-125 mg/dL with HbA1c > or = 3 SD (5.94%) showed a sensitivity of 92% and a specificity of 95%.

CONCLUSIONS

When FPG is inconclusive (110-125 mg/dL), an HbA1c value more than 3 standard deviations above the mean (>5.94%) is useful in suggesting a likely diagnosis of diabetes and identifying patients who require treatment.

Two prospective studies found that elevated 2-hr glucose predicted male mortality independent of fasting glucose and HbA1c

OBJECTIVE

To quantify the relative contribution of elevated 2-hr glucose, fasting glucose (FPG), and HbA1c to all-cause mortality.

STUDY DESIGN AND SETTING

A joint analysis of two prospective studies with baseline glycemia measurements.

RESULTS

The multivariate adjusted hazard ratios (HRs) corresponding to a one standard deviation increase in HbA1c were 1.14 (95% CI 1.03-1.25), 1.08 (0.98-1.19) for FPG and 1.15 (1.05-1.27) for 2-hr glucose, respectively. Entering the 2-hr glucose to the model based on the FPG and HbA1c significantly improved the prediction of mortality, whereas neither FPG, nor HbA1c added significant information once 2-hr glucose was in the models. In subjects with FPG <7.0 mmol/L and HbA1c < or = 6.5%, the HR was 1.35 (1.03-1.78) in men with 2-hr glucose > or = 7.8 mmol/L compared with men with 2-hr glucose <7.8 mmol/L.

CONCLUSION

Elevated 2-hr glucose was a predictor of mortality independent of the levels of fasting glucose and HbA1c.

Electronic monitoring and counseling to improve medication adherence

Electronic caps, pill caps that record the date and time of pill bottle opening provide an objective measure of adherence to prescribed medication. A promising intervention to improve adherence, cue-dose training, involves reviewing patients' pill cap-generated reports concerning their medication-taking and offering individualized recommendations for remembering to take medications at specific times of day. In this preliminary study, 79 patients prescribed the antihyperglycemic medication metformin had adherence assessed during a 4-week baseline period. Adherence, defined as proportion of prescribed doses taken within a predetermined 4-h window, was measured using electronic MEMS caps. Those who had less than 80% baseline adherence (n = 33) were randomly assigned to either receive 4 months of cue-dose training (n = 16) or to a control group (n = 17). Cue-dose training was associated with significantly better adherence to metformin (mean improvement of 15%). The effects of cue-dose training on adherence to other antihyperglycemic medication did not reach statistical significance. Glycosylated hemoglobin (a measure of blood sugar control) did not differ between groups. Data from nine patients who reviewed pill cap-generated data with their primary care providers suggested that both patients and providers found the discussion moderately helpful and not at all uncomfortable.

Neuropsychological correlates of suboptimal adherence to metformin

The goal of this study was to determine if neuropsychological function is associated with adherence to prescribed medication. Altogether, 79 patients with type II diabetes at a VA primary care clinic had adherence to the antihyperglycemic drug metformin measured with MEMS caps over a 4-week period. They completed several tests of neuropsychological function: Mini-Mental Status Exam (MMSE), Trails A and B, Stroop, Digit Span, Digit Symbol, and Grooved Pegboard. In separate multivariate analyses, Stroop word score and time to complete Trails B were independently associated with adherence, as was age. Secondary analyses of the relationship between neuropsychological variables and other adherence-related measures were conducted. Low scores on the MMSE and non-Caucasian ethnicity were associated with missed appointments. None of the neuropsychological variables were associated with glycosylated hemoglobin. These results suggest that cognitive abilities should be considered when counseling patients concerning their adherence.

Increase of serum phosphatidylcholine hydroperoxide dependent on glycemic control in type 2 diabetic patients

In order to clarify the relationship between serum phosphatidylcholine hydroperoxide (PCOOH) levels and blood glucose control in type 2 diabetes patients (DM), DM (n = 61) and normal control (n = 11) were enrolled. High-density lipoprotein (HDL) was separated from serum by the addition of sodium phosphotungstate and magnesium chloride, and the precipitated fraction was prepared as non-HDL. Phospholipids were extracted from whole serum, non-HDL and HDL to estimate PCOOH level with chemiluminescence high performance liquid chromatography (CL-HPLC). PCOOH level (nmol/l, mean +/- S.D.) was higher in DM than in control (33.1 +/- 9.5 vs. 23.0 +/- 8.2 for serum; P < 0.01, 17.0 +/- 5.5 vs. 10.6 +/- 3.8 for non-HDL; P < 0.01, and 16.1 +/- 6.3 vs. 12.3 +/- 5.5 for HDL; not significant, respectively). DM was divided into five groups according to hemoglobin A(1c) (HbA(1c)) levels (%): (1) less than 6, (2) 6-6.4, (3) 6.5-6.9 (4) 7.0-7.4, and (5) over than 7.5. Increase of PCOOH levels was dependent on HbA(1c). We concluded that (1) serum and non-HDL PCOOH increased in DM, (2) the level was strongly correlated with diabetic control, and (3) approximately a half amount of serum PCOOH was present in HDL of both control and DM.

Estimation of glycated hemoglobin by 2,6-dimethylphenol: Sulphuric acid conventional method

Glycated hemoglobin levels in hemolysate of normal and diabetic patients were determined by the 2,6-dimethylphenol:57.5% sulphuric acid conventional method and the values were 0.39±025 and 0.69±0.21 moles of hydroxymethylfurfural(HMF)/mole of globin, respectively. The mean increase in glycated hemoglobin values in diabetics (1.8fold) was highly significant (p<0.001). A good correlation (r=0.95) was found between the glycated hemoglobin values obtained by this method and the phenol:sulphuric acid method. The values obtained by former method were about 1.2-1.4 times the values by the phenol:sulphuric acid method. This study indicates that conventional 2,6-dimethylphenol: 57.5% sulphuric acid method is more sensitive for the estimation of glycated hemoglobin than any other method based on the same principle. It is less time consuming, reliable and hence can be employed for the routine laboratory estimation of glycated hemoglobin for the assessment of glycemic control.

Hospital management of diabetes

The degree of hyperglycemia may be an important predictor of morbidity and mortality among patients with MI or stroke, and in those undergoing surgical procedures including coronary artery bypass. Hyperglycemia should be aggressively controlled from the time of hospital admission regardless of the patient's primary medical problem or previous diabetes status. Innovative systems for monitoring glucose and for delivering insulin coupled with new pharmacologic therapy, such as long-acting insulin analogues, may help reduce the morbidity and mortality occurring in the estimated 6 million annual hospitalizations that are accompanied by hyperglycemia in the United States.

Diagnostic utility of glycosylated hemoglobin concentrations in the cat

Changes in glycosylated hemoglobin (GHb) concentrations, K values (% disappearance of glucose/min after an intravenous injection of 1 g/kg dextrose), and blood glucose concentrations were examined in eight cats before and during the induction of diabetes, and in four of these cats after they were placed on insulin treatment. There was a statistically significant separation of GHb, K values, and fasting blood glucose concentrations between healthy and diabetic cats. Changes in GHb correlated best with the K value and single weekly fasting glucose concentrations averaged over eight periods for each cat while diabetes was induced (R = 0.80 and 0.78, respectively); however, fasting blood glucose concentrations obtained on the day of the GHb measurement were also highly correlated (R = 0.69; P < 0.001). The correlation between GHb and single weekly glucose concentrations obtained in insulin-treated cats at the time of insulin peak action and averaged over an 8-wk time period for each cat was less but still significant (R = 0.53; P < 0.001). It is concluded that GHb measurements are a simple and reliable way to monitor changes in glucose control in the diabetic cat over a prolonged period.

Effects of nortriptyline on depression and glycemic control in diabetes: results of a double-blind, placebo-controlled trial

OBJECTIVE

Depression is a prevalent and chronic condition in diabetes and is associated with poor glucose regulation and poor compliance with diabetes treatment. This investigation evaluated the effects of nortriptyline on depression and glycemic control to see whether depression in diabetes is treatable and whether restoring mental health contributes to improved medical outcome.

METHOD

Sixty-eight diabetic patients with poor glycemic control, 28 of whom had active major depression (DSM-IIIR), completed a randomized, placebo-controlled, double-blind trial involving 8 weeks of treatment with nortriptyline targeted to therapeutic plasma levels (50-150 ng/ml). Depression improvement was determined with the Beck Depression Inventory; glucose control was measured by glycated hemoglobin levels. Compliance behavior was assessed using medication dispensing devices and glucometers equipped with electronic memory.

RESULTS

The reduction in depression symptoms was significantly greater in depressed patients treated with nortriptyline compared with those receiving placebo (-10.2 vs -5.8, p = .03). Nortriptyline was not statistically superior to placebo in reducing glycated hemoglobin of the depressed subjects (p = .5). However, path analysis indicated that the direct effect of nortriptyline was to worsen glycemic control whereas depression improvement had an independent beneficial effect on glycated hemoglobin. These findings were not explained by the relationships of nortriptyline treatment to weight change (r = -0.21, p = .31) or depression improvement to compliance with the protocol for self-monitoring of blood glucose (r = 0.01, p = .97).

CONCLUSIONS

Major depression in diabetic patients can be effectively treated with nortriptyline at the expense of a direct hyperglycemic effect. Path analysis demonstrated a treatment-independent effect of depression improvement on glycemic control, suggesting that a more ideal antidepressant agent may both restore mental health and improve medical outcome.

The course of major depression in diabetes

The course of depression in patients with comorbid medical illness is poorly understood. We report a 5-year follow-up study of 25 diabetic patients who had participated in an 8-week depression treatment trial. When a patient completed the trial, primary physicians were informed of patient outcomes and advised to monitor for relapse and treat those with ongoing depression. At the 5-year reevaluation depression was assessed using DSM-III-R criteria, and a depression severity scale was formed that reflected the presence, severity, frequency, and duration of depression episodes as well as a global assessment of functioning. Recurrence or persistence of depression occurred in 23 (92%) of the patients with an average of 4.8 depression episodes over the 5-year follow-up period. The duration of the longest episode averaged 16 +/- 4 months. Reversion to major depression occurred frequently and rapidly also in the subset that remitted during the treatment trial: 58.3% were depressed again within the first year. At the time of the follow-up interview, major depression was evident in 16 (64%) of the subjects, and glycemic control was significantly worse in this group compared with those without depression (gHb: 13.3% +/- 2.6% vs 11.1% +/- 1.9%, P = 0.03). Severity of depression over follow-up was related to the presence of neuropathy at entry and to incomplete remission during the initial treatment trial. Nineteen patients (82.6% of those who relapsed) received additional courses of antidepressant therapy, but none was treated continuously for depression prophylaxis. In this diabetic sample, depression was a recurrent condition in the vast majority of cases, and initial treatment response did not confer lasting euthymia. Whether maintenance antidepressant medication would be useful in preventing depression recurrence and promoting better glycemic control in diabetes remains to be studied.

High glycosylated hemoglobin levels increase the risk of progression to diabetes mellitus in subjects with glucose intolerance

The relationships between HbA1c level and oral glucose tolerance test (OGTT) at the initial visit and the incidence of diabetes after 5 years of follow-up were investigated in 819 subjects participating in a general health examination. The 100 g OGTT was performed. In order to use WHO criteria, the blood glucose levels of 100 g OGTT corresponding to those of 75 g OGTT were adopted according to the recommendations of the Japan Diabetes Society. Subjects other than diabetic type and IGT (impaired glucose tolerance) were divided into a normal group (fasting blood glucose < 100 mg/dl, 1-h blood glucose < 160 mg/dl, a 2-h blood glucose < 120 mg/dl) and a borderline group (the remaining subjects). In IGT, the incidence of diabetes in the low- (< or = 6.3%), intermediate- (6.4-6.7%) and high-HbA1c (> of = 6.8%) groups were 10.4%, 23.1% and 52.5%, respectively (high vs intermediate and low, P < 0.001; intermediate vs low, P < 0.05). In the borderline group, the incidence were 2.8%, 14.3% and 28.6%, respectively (high and intermediate vs low, P < 0.001). The results showed that the combination of HbA1c level and OGTT enables more precise prediction of progression to NIDDM in subjects with glucose intolerance.

Haemoglobin A(1c) measurement for diabetes among subjects with a previous history of impaired glucose tolerance

Haemoglobin A(1c) (HbA(1c)) measurement for diagnosis of diabetes and impaired glucose tolerance (IGT) was assessed during a prospective study of subjects with IGT; 183 of the 207 IGT persons underwent the second oral glucose tolerance tests (OGTT) 2.1 years, on the average, after the first tests. HbA(1c) was administered to every participant before the second OGTTs. The results of HbA(1c) were compared with those of the second OGTTs. The sensitivity of HbA(1c) test was 71% for diabetes and 41% for IGT, when the specificity was 93% at a cutoff point of 4.81%. The conclusion is that the HbA(1c) test is moderately sensitive for diabetes but insensitive for IGT, when it is specific. However, it may be useful for selecting and reducing the total number of subjects referred to 2-h OGTTs in a follow-up study of subjects with IGT, if the rate of progression to diabetes is not high.

A reassessment of fasting plasma glucose concentrations in population screening for diabetes mellitus in a community of northern European ancestry: the Wadena City Health Study

In current clinical and research practice, the determination of diabetic status depends largely on plasma glucose levels 2 h after the ingestion of a standard 75-g glucose load, the oral glucose tolerance test (OGTT). The OGTT, however, remains inconvenient, not highly reproducible, and costly, especially for large-scale studies and population screening tests. Fasting plasma glucose (FPG) determinations are convenient, reliable, and valid measures of glucose intolerance, but the currently prescribed cut-off point of 140 mg/dl (7.8 mM) lacks sensitivity. We evaluated the reliability and validity of fasting plasma glucose (FPG) values compared with other measures of hyperglycemia for a diagnosis of diabetes in a population-based study of carbohydrate metabolism in Wadena, Minnesota, a community of predominantly northern European ancestry. As a part of this effort, a random sample of Wadena adults, stratified by age and gender, plus all known, previously diagnosed diabetics participated in 2 days of baseline testing and were followed prospectively and retested 5 years later. Cross-sectional analyses of baseline data are presented in this article. Diabetic status was ascertained by administering a standard OGTT according to National Diabetes Data Group (NDDG) specifications. Sensitivity and specificity levels obtained when using a FPG cut-off point of 6.4 mM were 95.2% and 97.4%, respectively. In study subjects with no known diagnosis of diabetes, the FPG cut-off point of 6.4 mM performed reasonably well with a sensitivity and specificity of 67.7% and 97.4%, respectively. (ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of tests for glycated haemoglobin and fasting and two hour plasma glucose concentrations as diagnostic methods for diabetes

OBJECTIVE

To compare the ability of tests measuring two hour plasma glucose, fasting plasma glucose, and glycated haemoglobin concentrations in predicting the specific microvascular complications of non-insulin dependent diabetes mellitus.

DESIGN

Cross sectional and longitudinal analysis of the relation between complications and concomitant results of the three tests.

SETTING

Gila River Indian Community, Arizona.

SUBJECTS

Pima Indians (cross sectional, n = 960), aged 25 years or above who were not receiving insulin or oral hypoglycaemic treatment at the baseline examination.

MAIN OUTCOME MEASURES

Development of retinopathy and nephropathy.

RESULTS

Cross sectionally, frequency distributions of logarithms of the three sets of results were bimodal, with the prevalence of retinopathy and nephropathy being, respectively, 12.0-26.7 and 3.9-4.2 times as high above as below cut off points which minimised overlap (two hour plasma glucose concentration 12.6 mmol/l; fasting plasma glucose concentration 9.3 mmol/l; glycated haemoglobin (HbA1c) concentration 7.8%). Longitudinally, each of the three measures of glycaemia significantly predicted the development of retinopathy (P < 0.0001) and nephropathy (P < 0.05). Receiver operating characteristic curves showed that two hour plasma glucose concentration was superior to fasting plasma glucose concentration (P < 0.05) for prevalent cases of retinopathy, but otherwise no variable had a significant advantage for detecting incident or prevalent cases of either complication.

CONCLUSIONS

These findings suggest that determination of glycated haemoglobin or fasting plasma glucose concentrations alone may be acceptable alternatives to measuring glucose concentration two hours after challenge with 75 g glucose for the diagnosis of diabetes.

The relationship of blood glucose and haemoglobin A1 levels in diabetic subjects

Recommendations exist that fasting plasma glucose (FPG) levels can be substituted for glycosylated haemoglobin A1 (HbA1) in Type II diabetic subjects (DM II), which have potential important financial implications. The present study was designed to expand this examination and to include Type I DM (DMI) patients and random blood glucose (RBG) values. Data were obtained from 234 DM II and 104 DM I patients, over 3 years. Correlation of HbA1 with FPG levels in DM II yielded an r value of 0.61. Correlation of HbA1 with RBG and 2 h post prandial glucose measurements yielded r values of 0.59 and 0.51 respectively, p < 0.001. In DM I, similar correlations gave r values ranging between 0.27 and 0.38, p < 0.01-0.001. Thus while significant correlations exist between HbA1 and FPG and RBG measurements in both DM I and DM II, clinically applicable information on long-term diabetic control can only be achieved from glucose measurements in DM II but the correlation is not sufficiently tight to recommend substitution of plasma glucose for HbA1 determinations, despite the cost advantages.

Glycated haemoglobin predicts progression to diabetes mellitus in Pima Indians with impaired glucose tolerance

Glycated haemoglobin could offer several practical advantages over the OGTT for assessing glucose metabolism. Initial cross-sectional studies (1983-1985) on 381 subjects (mostly Pima Indians) described the relationship between HbA1c (a specific glycated Hb) and the OGTT. We performed follow-up OGTTs and HbA1c measurements on 257 of these same subjects 1.6-6.1 years later. Subjects were again grouped according to both the result of the OGTT (normal, IGT or diabetes, by WHO criteria) and HbA1c result (normal or elevated based on mean +/- 1.96 SD of normal). Of 66 subjects with IGT at baseline, 47 (71%) had normal HbA1c and 19 (29%) had elevated HbA1c. Twenty-six (39%) of these subjects had diabetes at follow-up. Of these subjects with IGT, a significantly greater percentage of subjects with elevated HbA1c at baseline (68%) showed worsening to diabetes than those with a normal HbA1c (28%); (chi-square = 7.8, df = 1, p < 0.01). Thus, in subjects with IGT, glycated Hb may be a useful predictor of progression to diabetes.

Fructosamine. A new parameter for diagnosis and metabolic control in diabetic dogs and cats

Fructosamines are glycated serum proteins that, depending on their life span, reflect glycemic control over the previous 2 to 3 weeks. The nitroblue tetrazolium reduction method adapted to auto analysis appeared to be a practical means to assay fructosamine quickly, economically, and accurately. The upper limit of the reference range is 374 mumol/L in dogs (95% percentile) and 340 mumol/L in cats (95% percentile). Newly diagnosed diabetic dogs and cats that had not undergone previous insulin therapy had significantly higher fructosamine concentrations than nondiabetic animals. In diabetic dogs that were receiving insulin therapy, the fructosamine test reflected the glycemic state far more accurately than did individual blood glucose measurements. Animals with satisfactory metabolic control revealed fructosamine concentrations within the reference range, whereas fructosamine concentrations above 400 mumol/L indicated insufficient metabolic control. On the basis of fructosamine concentrations, cats with a transitory hyperglycemia and cats with diabetes mellitus were differentiated. The fructosamine test is a valuable parameter for the diagnosis and metabolic control of diabetes mellitus in dogs and cats.

The value of glycosylated haemoglobin as a substitute for the oral glucose tolerance test in the detection of impaired glucose tolerance (IGT)

In a prospective study of South African Indian subjects with IGT, glycosylated hemoglobin [specifically HbA1 (HbA1(a+b+c)] and its relationship to the oral glucose tolerance test (OGTT) was studied in 128 study subjects who were classified IGT a year previously (Year 0 of study) and in 64 control subjects. At Year 1 of the study, the standard 75-g OGTT was performed on all subjects; study subjects were further divided into three groups based on World Health Organisation criteria [Normal (N), impaired glucose tolerance (IGT), diabetes mellitus (D)]. HbA1, a glycosylated hemoglobin (GHb), was measured by a cation-exchange microchromatographic method. Based on OGTT results, 47 of the 128 study subjects were classified IGT, 41 diabetes (newly-diagnosed diabetes) and 40 subjects had normal glucose tolerance. Mean GHb was significantly higher in the D group (7.61 +/- 1.76%) compared to the control group (6.99 +/- 1.22%) and the N group (6.9 +/- 1.12%), respectively (P less than 0.05); there was no significant difference between the IGT group (7.48 +/- 1.44%) and each of the other three groups. Compared to the OGTT, GHb was relatively insensitive in the diagnosis of IGT or diabetes mellitus: only 17% of the IGT group and 26.8% of the D group has elevated GHb values; the specificity of GHb as a measure of normal glucose tolerance was 85.9%. The majority of subjects, irrespective of the category of glucose tolerance, had GHb levels within the normal range and there was marked overlap between the four groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Nicardipine does not cause deterioration of glucose homoeostasis in man: a placebo controlled study in elderly hypertensives with and without diabetes mellitus

The effect of the calcium antagonist nicardipine on insulin secretion and glucose homoeostasis was investigated in elderly hypertensives with and without diabetes mellitus; 15 patients with essential hypertension for at least 10 years and normal glucose tolerance according to standard criteria (Group I) and 15 elderly hypertensive patients affected by Type 2 diabetes mellitus and on treatment with diet or oral drugs (Group 2). In the basal state, all patients were submitted to an oral glucose tolerance test (OGTT, 75 g) and an iv arginine test (30 g), on two different days and in random order. The same tests were repeated after one month of treatment with nicardipine 60 mg/day, in three spaced doses, the last being given 1 h before the post-treatment test. Nicardipine did not change overall glucose homoestasis, as assessed by haemoglobin Alc and fructosamine, nor did it significantly affect the plasma insulin response either to glucose or arginine in Groups 1 and 2. Only the glucagon response to arginine was significantly reduced in diabetic hypertensives. Small, non-significant variations in the metabolic and hormonal parameters were seen in additional two groups of patients (Groups 3 and 4), matched with Groups 1 and 2 for age, sex and diseases, who took capsules containing placebo. Thus, nicardipine did not produce any significant overall alteration in glucose homoestasis when given to elderly diabetic or nondiabetic hypertensive subjects.

Growth hormone treatment in Turner's syndrome: short and long-term effects on metabolic parameters

OBJECTIVE

The effect of GH administration on various metabolic parameters and on growth and bone age development was studied in patients with Turner's syndrome.

DESIGN

Patients were treated with daily s.c. GH (20 IU/m2/week) and ethinyloestradiol p.o. (100 ng/kg/day) during the first year and with additional oxandrolone (0.125 mg/kg/day) during the second year. The responses of free fatty acids (FFA), urinary excretion of hydroxyproline (HP) and IGF-I were evaluated after short-term GH application. Glucose tolerance was investigated before any therapy, during treatment with GH and oestradiol and after adding oxandrolone, respectively. The course of growth, bone age and IGF-I levels was followed throughout the study.

PATIENTS

Eleven patients with Turner's syndrome aged 12.6 +/- 1.9 years (mean +/- SD) were included.

RESULTS

Free fatty acids increased significantly 4 hours after one s.c. injection of GH (0.7 +/- 0.2-1.1 +/- 0.3 mmol/l; mean +/- SD). Mean urinary hydroxyproline excretion remained unchanged after 6 weeks of GH therapy (337 +/- 206-299 +/- 145 mumol/m2/24 h), but there was a significant negative correlation between individual hydroxyproline values and the peak serum GH followed stimulation. IGF-I was in the prepubertal range and increased significantly after 3 days of GH injection (30.0 +/- 10.0-42.5 +/- 10.0 nmol/l). Growth velocity (in Turner's syndrome related SD) increased from 0.0 +/- 0.3 SD before treatment to 0.9 +/- 0.8 SD after the first year and to 3.4 +/- 1.3 SD during the second year of treatment. There was no undue acceleration of bone age. During long-term treatment, IGF-I increased significantly only when oxandrolone was added. Two patients had impaired glucose tolerance prior to GH therapy and three additional children developed impaired or abnormal glucose tolerance after GH therapy. Insulin concentrations increased significantly only after introduction of oxandrolone.

CONCLUSIONS

Patients with Turner's syndrome who had lower basal IGF-I levels had significantly higher responses of IGF-I, free fatty acids and hydroxyproline (P less than 0.01 for all parameters) after short-term GH application. The data indicate adequate endocrine and metabolic responses in patients with Turner's syndrome which are the basis for growth promoting action. A considerable number of patients had impaired glucose tolerance during GH treatment.

Epidemiological features of glycated haemoglobin A1c-distribution in a healthy population. The Telecom Study

HbA1c was measured in 3240 healthy non-diabetic adult individuals in a working population. There was no difference in HbA1c between sexes. The distribution of HbA1c was approximately normal with a slight difference between mean and median values at all ages in both sexes. HbA1c increased with deterioration of glucose tolerance and with all the known risk factors for diabetes (age, obesity, family history of diabetes, history of a large newborn delivery); age but not body mass index appeared as a factor influencing HbA1c independently. In women, HbA1c levels rose particularly at the age of menopause but the use of oral contraceptives or oestrogens made no difference. In both sexes, HbA1c was higher in smokers than in non-smokers. No consistent seasonal variation was observed. Haematologic factors had a negligible influence on HbA1c level. HbA1c was more highly correlated with fasting plasma glucose than with 2 h-plasma/glucose (r = 0.20 vs 0.11). In a stepwise multiple regression analysis, age followed by fasting plasma glucose were the only two significant factors associated with the level of HbA1c. These data indicate that HbA1c is influenced only by factors closely linked to diabetes.

The relative value of glycated albumin, hemoglobin A1c and fructosamine when screening for diabetes mellitus

We compared the usefulness of three glycated serum proteins, glycated albumin (GA), glycated hemoglobin (HBA1c) and fructosamine (FA), for diabetic screening purposes. We measured these indices in 302 adults, most of whom underwent yearly physical examinations. We measured GA and HbA1c with high precision using high-performance liquid chromatography (interassay coefficients of variation 4.9 and 4.0%, respectively) and FA using commercial reagents (interassay coefficient of variation 1.65%). All the individuals underwent a 75-g oral glucose tolerance test, which revealed significant correlations between the values of the three glycated proteins and the four plasma glucose concentrations measured as well as the sum of these glucose concentrations, sigma BS (GA, r = 0.80; HbA1c, r = 0.80; FA, r = 0.65). On the basis of the test, 130 of the subjects were classified as normal (N), 123 as borderline and 49 as having diabetes mellitus (D) according to the criteria of the Japan Diabetes Society. Of the 123 borderline cases, 26 showed impaired glucose tolerance (IGT) according to the WHO criteria. The normal group values of GA, HbA1c and FA were 17.8 +/- 0.17% (mean +/- SEM), 5.02 +/- 0.03%, and 2.55 +/- 0.02 mM/l, respectively. Borderline and IGT subjects had significantly more GA and HbA1c than normal but not more FA (P less than 0.01). We divided the subjects into 10 groups on the basis of their sigma BS values; those with values higher than 671 +/- 4.7 mg/dl had significantly more GA and HbA1c than normal, while those with values higher than 1068 +/- 40.9 mg/dl (the most extreme cases) had significantly more FA.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical usefulness of serum fructosamine and HbAlc in patients with NIDDM

To evaluate the clinical values of serum fructosamine and HbAlc, serum fructosamine and HbAlc were assessed in 50 normal controls and 36 patients with NIDDM (non-insulin-dependent diabetes mellitus). And we studied 10 patients selected at random among the 36 patients with NIDDM. The values of serum fructosamine and HbAlc in controls were 2.1 mmol/L and 5.3%, respectively. The levels of serum fructosamine and HbAlc were significantly higher in NIDDM patients (3.27 mmol/L and 8.8%, respectively, p less than 0.005) compared with those in the controls. The serum fructosamine was significantly correlated with fasting plasma glucose and HbAlc (r = 0.78, p less than 0.78, p less than 0.001; r = 0.76, p less than 0.005, respectively). Also, in retrograde study, serum fructosamine concentration had a significant correlation to fasting plasma glucose determined 2 weeks before (r = 0.72, p less than 0.002), and 4 weeks before (r = 0.54, p less than 0.005). It is concluded that serum fructosamine measurement may be useful in monitoring short-term control of plasma glucose in patients with NIDDM.

Glycated serum proteins and glucose tolerance

Glycated serum proteins (GSP), stable glycated hemoglobin (HbA1c) together with some metabolic parameters were evaluated in 120 subjects, 30 with normal glucose tolerance (NGT), 30 with impaired glucose tolerance (IGT), 30 with non-insulin-dependent diabetes mellitus (NIDD), and 30 with insulin-dependent diabetes mellitus (IDD). GSP levels were significantly higher in IGT, NIDD and IDD than in NGT. HbA1c levels were not significantly higher in IGT in comparison with NGT, but were significantly higher in NIDD and in IDD than in NGT and IGT. GSP correlated better than HbA1c with all metabolic parameters considered. Taking into account the distribution of the values, GSP showed a smaller overlap than HbA1c in all four groups studied. Moreover, only 9 subjects (30%) with IGT showed GSP levels above the normal range. Therefore, GSP assay is able to distinguish between normal and diabetic subjects but is unable by itself to discriminate subjects with normal from those with reduced glucose tolerance.

Oral glucose tolerance: relationship with hemoglobin A1c

Fifty-two normal non-obese males and 77 male offspring of two diabetic parents, aged 15-72 years, were studied to identify possible reasons for discordance between the oral glucose tolerance test (OGTT) and hemoglobin A1c (Hb A1c). Subjects were classified into four study groups: group 1 (n = 83), normal OGTT and normal Hb A1c; group 2 (n = 19), normal OGTT and abnormal Hb A1c; group 3 (n = 9), abnormal OGTT and normal Hb A1c; and group 4 (n = 18), abnormal OGTT and abnormal Hb A1c. Glucose and insulin response were analyzed in each study group. Group 2 showed slightly higher mean glucose areas during the first 60 min of OGTT testing when compared with group 1 (P less than 0.01). Insulin levels, insulin areas and insulin/glucose regression coefficients on group 2 did not differ significantly from group 1 during OGTT. Group 3 showed significantly higher mean blood glucose levels than subjects in group 1 (P less than 0.0001) or group 2 (P less than 0.001), but significantly lower mean blood glucose levels than subjects in group 4 (P less than 0.04) throughout the OGTT. During the OGTT, group 3 showed marked absolute hyperinsulinism when compared with all other groups (P less than or equal to 0.002). Also, relative hyperinsulinism in group 3 was suggested by the elevated insulin/glucose regression coefficient (1.86 +/- 0.50) when compared with group 1 (1.17 +/- 0.09), group 2 (0.92 +/- 0.011) or group 4 (0.55 +/- 0.17) (P less than or equal to 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The glycohaemoglobin assay as a screening test for diabetes mellitus: the Islington Diabetes Survey

Blood glucose 2 h after an oral glucose load (2hBG) and glycohaemoglobin (GHb) (Corning agar-gel electrophoresis) levels were used as screening tests in a general practice diabetic screening programme. The diagnosis of diabetes (DM) was based on a separate oral glucose tolerance test (OGTT) in 223 of 1040 screened subjects, selected as a stratified sample biased towards higher levels of 2hBG and GHb. The GHb assay was also repeated at the recall examination and urine was tested for glycosuria before and after glucose administration. At a cut-off level of 8.1%, the screening GHb assay correctly identified 90% of all probable diabetics with a specificity of 85.3% (95% Cl 83.3-87.3%) and a positive predictive value of 14.0% (9.0-19.0%). The specificity of the screening GHb assay as a screening test for true DM was 45.8% (39.0-52.4%) at 90% sensitivity, and that of the recall GHb assay was 64.5% (57.9-71.1%). The screening 2hBG was 93.3% (88.9-97.7%) specific at 90% sensitivity as a screening test for true DM diagnosed by OGTT at recall. The test characteristics for fasting glycosuria were: sensitivity 16.7% (0-37.8%) and specificity 98.0% (96.0-100.0%). Equivalent values for the post-glucose test for glycosuria were: 72.7% (46.4-99.0%) and 77.4% (70.1-84.7%), respectively. While GHb assay is a poorer screening test for DM than the 2hBG at the single cut-off level quoted, comparison of the accuracy of the two tests shows that the GHb assay is only marginally less accurate. It is superior to testing for glycosuria as a screening test for DM and can be performed on any random blood sample, facilitating its use in population screening.

Nonenzymatically glycosylated proteins

Nonenzymatic glycosylation takes place in all proteins with a free-reacting lysine or valine in the presence of glucose. The formation of glycosylated plasma albumin, hemoglobin (Hb A1c), and skin collagen provides a diagnostic index of short- to long-term time-concentration of glucose in vivo. A wide range of assay methods are available, with affinity chromatographic, isoelectric focusing, and spectrophotometric methods providing the best accuracy and versatility. Glycosylated hemoglobin assays indicate glucose pressure over the previous 2 to 3 months and are of diagnostic value in general diabetic control, while glycosylated plasma albumin determinations are preferable in acute episodes in the life of a diabetic (e.g., pregnancy, infection, stress, trauma, surgery), since they provide an overview of changing blood glucose values of the previous 2 to 4 weeks. Glycosylated collagen estimations reflect tissue aging and are relevant in healing processes. Glycosylation alters the biologic activity of proteins, and these may relate to the manifold complications concomitant on the lifelong elevation of blood and tissue glucose in the diabetic (C6a). Assays for glycosylated hemoglobin have been routinely performed in clinical chemistry laboratories for a decade, and convenient determination for other nonenzymatically glycosylated proteins is proceeding apace.

Glycosylated serum protein level as a screening and diagnostic test for gestational diabetes mellitus

Glycosylated serum protein assay was examined as an alternative to standard glucose screening and glucose tolerance testing. In a comparison of two groups of gravid women having abnormal 1-hour 50 gm glucose screening tests, there was no difference in glycosylated protein level in the group with abnormal glucose tolerance test results (9.4% +/- 2.0%, mean +/- SD; n = 8) versus normal results (9.2% +/- 1.07%, mean +/- SD; n = 11). Furthermore, correlation of glycosylated serum protein level with glucose screening test results was poor (r = 0.185, p = 0.23, n = 17). Glycosylated serum protein assay is not useful in detecting mild metabolic aberrations associated with gestational diabetes.

Glucose tolerance test and glycosylated haemoglobin measurement for diagnosis of diabetes mellitus--an assessment of the criteria of the WHO Expert Committee on Diabetes Mellitus 1980

Fasting glycosylated haemoglobin was analysed in 535 consecutive patients having an oral 75 g glucose tolerance test for diagnostic purposes. A reference range for fasting glycosylated haemoglobin was established from patients with a non-diabetic glucose tolerance test as defined by the World Health Organisation Expert Committee on Diabetes Mellitus. The predictive value of a glycosylated haemoglobin of over 10.0% (mean normal +/- 3 SD) for detecting a diabetic glucose tolerance test was 89% but sensitivity was only 43%. A raised glycosylated haemoglobin is useful for confirming the diagnosis of diabetes mellitus in patients with long-standing hyperglycaemia but glycosylated haemoglobin is within the reference range in many patients with newly developed diabetes or other minor abnormalities of glucose tolerance. The glucose tolerance test must remain the test of choice in these patients.

Clinical usefulness of estimation of serum fructosamine concentration as a screening test for diabetes mellitus

Fructosamine, a putative measure of serum glycosylated proteins, was measured in 74 subjects referred for oral glucose tolerance tests. A normal range (mean (2 SD] of 1.6 (0.4) mmol/l (40(10) mg/100 ml) derive from results obtained in 83 healthy non-diabetic volunteers permitted the detection of 15 out of 17 (88%) subjects with proved diabetes and yielded only five (9%) false positive diagnoses. Fructosamine concentrations correlated significantly (p less than 0.001) with fasting plasma glucose concentrations (r = 0.76) and glycosylated haemoglobin concentrations (r = 0.70). A longitudinal study suggested that fructosamine concentration was an index of intermediate term (one to three weeks) blood glucose control. Fructosamine concentration was not related to uraemia and did not depend on albumin or total protein concentrations, provided that serum albumin concentrations remained above 30 g/l. Estimation of fructosamine concentrations is a fully automated procedure and may provide a simple means of screening for diabetes mellitus.

The relationship between glycosylated haemoglobin levels and various degrees of glucose intolerance

To assess the use of glycosylated haemoglobin to discriminate between various degrees of glucose intolerance, glycosylated haemoglobin levels were determined in 107 subjects (48 males and 59 females, age range 18-80 years). Following a 75 g oral glucose tolerance test and according to World Health Organization criteria, subjects were classified as normal (n = 32), diabetic (n = 46) or as having impaired glucose tolerance (n = 29). Mean glycosylated haemoglobin levels were 5.8 +/- 1.3% (range 4%-9%) in normal subjects, 7.1 +/- 1.7% in subjects with impaired glucose tolerance (range 4.1%-10.1%) and 10.1 +/- 2.6% (range 4.7%-18.8%) in diabetic patients. The difference between the groups was highly significant (p less than 0.01). Twelve per cent of normal subjects exceeded and 52% of subjects with impaired glucose tolerance fell below 7.4% (mean +/- 2SD, considered as the upper limit of normal values). A significant correlation was observed between glycosylated haemoglobin values and fasting blood glucose (r = 0.68, p less than 0.01). These results provide evidence that glycosylated haemoglobin levels are influenced by slightly reduced carbohydrate tolerance. Glycosylated haemoglobin may be a useful test to improve the specificity of the oral glucose load to select and to follow-up subjects with impaired glucose tolerance.

Comparison of hemoglobin A1c and hemoglobin A1 in diabetic patients

Hemoglobin A1 (HbA1) and hemoglobin A1c (HbA1c) values were compared in 934 samples from 686 subjects with diabetes mellitus. Linear regression analysis revealed the two parameters to be highly related with HbA1 = 1.18 HbA1c + 1.67, and a correlation coefficient of 0.97. Samples with HbA1 greater than predicted from the measured HbA1c had been stored significantly longer (approximately 1 day) than other samples, suggesting that sample storage may slightly alter the relationship between these parameters. Serial HbA1 and HbA1c values in all 9 patients for whom data was available from at least 5 time points changed in parallel regardless of the time interval between sampling or the magnitude of the interval change of HbA1c and HbA1. These data indicate that the potentially simpler measurement of HbA1 gives results equivalent to HbA1c for clinical applications.