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

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

BACKGROUND

Numerous laboratory tests are used in the diagnosis and management of diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for laboratory analysis in screening, diagnosis, or monitoring of diabetes. The overall quality of the evidence and the strength of the recommendations were evaluated. The draft consensus recommendations were evaluated by invited reviewers and presented for public comment. Suggestions were incorporated as deemed appropriate by the authors (see Acknowledgments). The guidelines were reviewed by the Evidence Based Laboratory Medicine Committee and the Board of Directors of the American Association for Clinical Chemistry and by the Professional Practice Committee of the American Diabetes Association.

CONTENT

Diabetes can be diagnosed by demonstrating increased concentrations of glucose in venous plasma or increased hemoglobin A1c (HbA1c) in the blood. Glycemic control is monitored by the people with diabetes measuring their own blood glucose with meters and/or with continuous interstitial glucose monitoring (CGM) devices and also by laboratory analysis of HbA1c. The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of ketones, autoantibodies, urine albumin, insulin, proinsulin, and C-peptide are addressed.

SUMMARY

The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended.

Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus

BACKGROUND

Numerous laboratory tests are used in the diagnosis and management of diabetes mellitus. The quality of the scientific evidence supporting the use of these assays varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for laboratory analysis in screening, diagnosis, or monitoring of diabetes. The overall quality of the evidence and the strength of the recommendations were evaluated. The draft consensus recommendations were evaluated by invited reviewers and presented for public comment. Suggestions were incorporated as deemed appropriate by the authors (see Acknowledgments). The guidelines were reviewed by the Evidence Based Laboratory Medicine Committee and the Board of Directors of the American Association of Clinical Chemistry and by the Professional Practice Committee of the American Diabetes Association.

CONTENT

Diabetes can be diagnosed by demonstrating increased concentrations of glucose in venous plasma or increased hemoglobin A1c (Hb A1c) in the blood. Glycemic control is monitored by the people with diabetes measuring their own blood glucose with meters and/or with continuous interstitial glucose monitoring (CGM) devices and also by laboratory analysis of Hb A1c. The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of ketones, autoantibodies, urine albumin, insulin, proinsulin, and C-peptide are addressed.

SUMMARY

The guidelines provide specific recommendations based on published data or derived from expert consensus. Several analytes are found to have minimal clinical value at the present time, and measurement of them is not recommended.

Definition and Classification of Diabetes and Prediabetes and Emerging Data on Phenotypes

Diabetes diagnosis has important implications for individuals. Diagnostic criteria for fasting and 2-hour plasma glucose and HbA1c are universally agreed. Intermediate hyperglycemia/prediabetes is a risk factor for diabetes and cardiovascular disease. Because risk is a continuum, determining cut-point is problematic and reflected in significant differences in recommended fasting glucose and HbA1c criteria. Many types of diabetes are recognized. Diabetes classification systems are limited by a lack of understanding of etiopathogenetic pathways leading to diminished β-cell function. The World Health Organization classification system is designed to assist clinical care decisions. Newly recognized phenotypic clusters of diabetes might inform future classification systems.

Associations of HbA1c and fasting plasma glucose with incident diabetes: Implications for pre-diabetes thresholds in a Japanese population

AIMS

This study assessed pre-diabetes (pre-DM) cutoffs for HbA1c and fasting plasma glucose (FPG) that were associated with an increased risk of incident DM.

METHODS

We evaluated 2267 non-diabetic Japanese health-check examinees (HbA1c: <6.5% [<48mmol/mol] and FPG: <7.0mmol/L) who were 30-79 years old and were followed-up for 5 years. Incident DM was defined as HbA1c of ≥6.5% (≥48mmol/mol), FPG of ≥7.0mmol/L, or physician-diagnosed DM.

RESULTS

During 11047 person-years, we identified 99 incident DM cases (4.3%). The incidence of DM increased with increasing baseline HbA1c or FPG levels, and the change points (95% confidence intervals) were 5.7% (5.6-5.7%; 39mmol/mol [38-39mmol/mol]) for HbA1c and 5.5mmol/L (5.5-5.6mmol/L) for FPG. The adjusted hazard ratios (HRs) for incident DM per one standard deviation-increase in HbA1c and FPG were 5.5 (4.4-6.8) and 4.0 (3.2-4.8), respectively. The adjusted HRs for incident DM were significantly higher at HbA1c of 5.7-6.4% (39-46mmol/mol) or FPG of 5.5-6.9mmol/L, compared to HbA1c of <5.7% (<39mmol/mol) or FPG of <5.5mmol/L.

CONCLUSION

The lower cut-offs for pre-DM may be 5.7% (39mmol/mol) for HbA1c and 5.5mmol/L for FPG in this Japanese population.

Incidence of type 2 diabetes using proposed HbA1c diagnostic criteria in the european prospective investigation of cancer-norfolk cohort: implications for preventive strategies

OBJECTIVE

To evaluate the incidence and relative risk of type 2 diabetes defined by the newly proposed HbA(1c) diagnostic criteria in groups categorized by different baseline HbA(1c) levels.

RESEARCH DESIGN AND METHODS

Using data from the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort with repeat HbA(1c) measurements, we estimated the prevalence of known and previously undiagnosed diabetes at baseline (baseline HbA(1c) ≥6.5%) and the incidence of diabetes over 3 years. We also examined the incidence and corresponding odds ratios (ORs) by different levels of baseline HbA(1c). Incident diabetes was defined clinically (self-report at follow-up, prescribed diabetes medication, or inclusion on a diabetes register) or biochemically (HbA(1c) ≥6.5% at the second health assessment), or both.

RESULTS

The overall prevalence of diabetes was 4.7%; 41% of prevalent cases were previously undiagnosed. Among 5,735 participants without diabetes at baseline (identified clinically or using HbA(1c) criteria, or both), 72 developed diabetes over 3 years (1.3% [95% CI 1.0-1.5]), of which 49% were identified using the HbA(1c) criteria. In 6% of the total population, the baseline HbA(1c) was 6.0-6.4%; 36% of incident cases arose in this group. The incidence of diabetes in this group was 15 times higher than in those with a baseline HbA(1c) of <5.0% (OR 15.5 [95% CI 7.2-33.3]).

CONCLUSIONS

The cumulative incidence of diabetes defined using a newly proposed HbA(1c) threshold in this middle-aged British cohort was 1.3% over 3 years. Targeting interventions to individuals with an HbA(1c) of 6.0-6.4% might represent a feasible preventive strategy, although complementary population-based preventive strategies are also needed to reduce the growing burden of diabetes.

Estimation of the contribution of biomarkers of different metabolic pathways to risk of type 2 diabetes

The contribution of different biological pathways to the development of type 2 diabetes was quantified in a case-cohort design based on circulating blood biomarkers from participants aged 35-65 years in the EPIC-Potsdam Study. The analytic sample included 613 participants with incident diabetes and 1965 participants without diabetes. The proportion that each biomarker contributed to the risk of diabetes was quantified using effect decomposition method. Summarized risk of each biomarker was estimated by an index based on quintiles of gamma-glutamyltransferase (GGT), HDL-cholesterol, hs-CRP, and adiponectin. Cox proportional hazard regression was used to estimate relative risks adjusted for age, sex, body mass index, waist-circumference, education, sport activity, cycling, occupational activity, smoking, alcohol intake, and consumptions of red meat, coffee and whole grain bread. Adiponectin explained a total of 32.1% (CI = 16.8, 49.1%) of the risk related to index. For the other biomarkers the corresponding proportions were 23.5% (CI = 10.1, 37.8%) by HDL-cholesterol, 21.5% (CI = 11.5, 32.8%) by GGT, and 15.5% (CI = 4.44, 27.3%) by hs-CRP. The results support the hypothesis that the different biological pathways reflected by GGT, HDL-cholesterol, hs-CRP and adiponectin independent from each other contribute to the risk of type 2 diabetes. Of these pathways the highest contribution was observed for adiponectin which contributed one-third to the risk and that equal proportion was contributed by GGT and HDL-cholesterol, although the contribution of inflammation was lower.

A1C level and future risk of diabetes: a systematic review

We examined ranges of A1C useful for identifying persons at high risk for diabetes prior to preventive intervention by conducting a systematic review. From 16 included studies, we found that annualized diabetes incidence ranged from 0.1% at A1C <5.0% to 54.1% at A1C >or=6.1%. Findings from 7 studies that examined incident diabetes across a broad range of A1C categories showed 1) risk of incident diabetes increased steeply with A1C across the range of 5.0 to 6.5%; 2) the A1C range of 6.0 to 6.5% was associated with a highly increased risk of incident diabetes, 25 to 50% incidence over 5 years; 3) the A1C range of 5.5 to 6.0% was associated with a moderately increased relative risk, 9 to 25% incidence over 5 years; and 4) the A1C range of 5.0 to 5.5% was associated with an increased incidence relative to those with A1C <5%, but the absolute incidence of diabetes was less than 9% over 5 years. Our systematic review demonstrated that A1C values between 5.5 and 6.5% were associated with a substantially increased risk for developing diabetes.

Predictors of development of diabetes in patients with chronic heart failure in the Candesartan in Heart Failure Assessment of Reduction in Mortality and Morbidity (CHARM) program

OBJECTIVE

The purpose of this study was to identify predictors of incident diabetes during follow-up of nondiabetic patients with chronic heart failure (CHF) in the Candesartan in Heart Failure Assessment of Reduction in Mortality and Morbidity (CHARM) program.

RESEARCH DESIGN AND METHODS

A total of 1,620 nondiabetic patients had full baseline datasets. We compared baseline demographic, medication, and laboratory data for patients who did or did not develop diabetes and conducted logistic regression and receiver operator characteristic curve analyses.

RESULTS

Over a median period of 2.8 years, 126 of the 1,620 patients (7.8%) developed diabetes. In multiple logistic regression analysis, the following baseline characteristics were independently associated with incident diabetes in decreasing order of significance by stepwise selection: higher A1C (odds ratio [OR] 1.78 per 1 SD increase; P < 0.0001), higher BMI (OR 1.64 per 1 SD increase; P < 0.0001), lipid-lowering therapy (OR 2.05; P = 0.0005), lower serum creatinine concentration (OR 0.68 per 1 SD increase; P = 0.0018), diuretic therapy (OR 4.81; P = 0.003), digoxin therapy (OR 1.65; P = 0.022), higher serum alanine aminotransferase concentration (OR 1.15 per 1 SD increase; P = 0.027), and lower age (OR 0.81 per 1 SD increase; P = 0.048). Using receiver operating characteristic curve analysis, A1C and BMI yielded areas under the curve of 0.723 and 0.712, respectively, increasing to 0.788 when combined. Addition of other variables independently associated with diabetes risk minimally improved prediction of diabetes.

CONCLUSIONS

In nondiabetic patients with CHF in CHARM, A1C and BMI were the strongest predictors of the development of diabetes. Other minor predictors in part reflected CHF severity or drug-associated diabetes risk. Identifying patients with CHF at risk of diabetes through simple criteria appears possible and could enable targeted preventative measures.

Validation of an algorithm combining haemoglobin A(1c) and fasting plasma glucose for diagnosis of diabetes mellitus in UK and Australian populations

AIM

To determine whether glycated haemoglobin (HbA(1c)) can be used in combination with fasting plasma glucose (FPG) for the diagnosis of diabetes in patients with impaired fasting glucose (IFG) and in a broader spectrum of patients.

METHODS

An algorithm was derived from oral glucose tolerance test (OGTT) capillary samples in 500 consecutive UK patients with IFG by World Health Organization criteria. It was validated in a further 500 UK patients and, with venous specimens, in 1175 unselected Australian patients.

RESULTS

The derivation cohort was aged 61 years (50-69 years) (median IQ range) with 52% male and 12% South Asian. Diabetes Control and Complications Trial-aligned HbA(1c) was 6.2% (5.8-6.6%) (reference interval < 6.0%) and FPG 6.7 mmol/l (6.3-7.2 mmol/l). FPG was in the diabetes range in 36% of patients, with an OGTT identifying a further 12% with diabetes. The derived algorithm, (HbA(1c) >or= 6.0% with FPG < 7.0 mmol/l) identified those patients requiring an OGTT to diagnose diabetes. When applied to the UK validation cohort, sensitivity was 97% and specificity 100%. The algorithm was equally effective in the unselected group, aged 59 years (49-68 years) and 54% male, with sensitivity 93% and specificity 100%. HbA(1c) was 6.0% (5.6-6.6%) and FPG 6.0 mmol/l (5.3-6.8 mmol/l), with 26% having IFG. Use of the algorithm would reduce the number of OGTTs performed in the UK validation cohort by 33% and by 66% in the Australian patients studied.

CONCLUSIONS

Use of this algorithm would simplify procedures for diagnosis of diabetes and could also be used for monitoring pre-diabetes. Validation is now required in other populations and patient groups.

Determinants of progression from impaired fasting glucose and impaired glucose tolerance to diabetes in a high-risk screened population: 3 year follow-up in the ADDITION study, Denmark

AIMS/HYPOTHESIS

We sought to identify determinants of progression from impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) to diabetes in high-risk screened individuals.

METHODS

In general practices in Denmark, stepwise screening for type 2 diabetes mellitus in persons aged 40 to 69 years included a risk questionnaire, random blood glucose, HbA1c, fasting blood glucose and an OGTT. The 1,821 individuals with IGT or isolated IFG (WHO 1999) were re-invited after 1 and 3 years. Follow-up data on glucose measurements were available in 1,510 individuals and additional clinical data in 1,002 collected at the 3-year visits. Regression models using interval censoring were used.

RESULTS

Progression rates from IFG and IGT to diabetes over 3.5 years were 11.8 and 17.0 per 100 person-years, respectively and were particularly high in the first year. Baseline determinants of progression were: IFG: glucose measures, BMI [per kg/m2, rate ratio (RR) 1.04 (95% CI, 1.01-1.08)] and triacylglycerol [per twofold increase, RR 2.19 (1.49-3.22)]; and IGT: glucose measures and known hypertension [RR 1.46 (1.11-1.93)]. Weight reduction and decreased triacylglycerol were inversely associated with development of diabetes in IFG individuals [per 1 kg/year, RR 0.81 (0.66-0.98) and per 1 mmol l(-1) year(-1), RR 0.08 (0.01-0.51), respectively], whereas in IGT participants only weight reduction was inversely associated [per 1 kg/year, RR 0.80 (0.67-0.96)].

CONCLUSIONS/INTERPRETATION

Higher levels of glucose measures, larger BMI, known hypertension and hypertriacylglycerolaemia are significant determinants of progression in high-risk screened individuals. Weight loss of 1 kg/year or reduction of hypertriacylglycerolaemia markedly reduced the risk of diabetes.

Annual incidence and relative risk of diabetes in people with various categories of dysglycemia: a systematic overview and meta-analysis of prospective studies

BACKGROUND

Several estimates of the risk of progression to diabetes in people with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) have been reported.

OBJECTIVE

To provide an estimate of the risk of progression to diabetes and regression to normoglycemia in these populations.

DESIGN

Systematic overview and meta-analysis of prospective cohort studies published from 1979 until 2004.

SETTING

Global cohort studies.

PATIENTS

People with IFG or IGT detected by a screening oral glucose tolerance test.

MEASUREMENTS

Fasting and post-load plasma glucose levels.

RESULTS

The absolute annual incidence of diabetes in individuals with various categories of IFG or IGT varied from 5 to 10%. Compared to normoglycemic people the meta-analyzed relative risk and 95% confidence interval for diabetes was: 6.35 (4.87-7.82) in people with IGT; 5.52 (3.13-7.91) in people with isolated IGT; 4.66 (2.47-6.85) in people with IFG; 7.54 (4.63-10.45) in people with isolated IFG; and 12.13 (4.27-20.00) in people with both IFG and IGT. People with IGT were 0.33 times as likely to be normoglycemic after 1 year compared to people with normal glucose tolerance (95% CI 0.23-0.43).

LIMITATIONS

Studies that used differing criteria for IFG and IGT were included, and participants were classified on the basis of only one test.

CONCLUSION

IFG and IGT are associated with similar, high relative risk for incident diabetes. The combined abnormality of IFG plus IGT is associated with the highest relative risk.

Hemoglobin A1c predicts diabetes but not cardiovascular disease in nondiabetic women

BACKGROUND

Hemoglobin A1c (HbA1c) is a marker of cumulative glycemic exposure over the preceding 2- to 3-month period. Whether mild elevations of this biomarker provide prognostic information for development of clinically evident type 2 diabetes and cardiovascular disease among individuals at usual risk for these disorders is uncertain.

METHODS

We examined baseline HbA1c levels as a predictor of incident clinical diabetes and cardiovascular disease (nonfatal myocardial infarction, coronary revascularization procedure, ischemic stroke, or death from cardiovascular causes) in a prospective cohort study beginning in 1992 of 26,563 US female health professionals aged 45 years or more without diagnosed diabetes or vascular disease (median follow-up 10.1 years).

RESULTS

During follow-up, 1238 cases of diabetes and 684 cardiovascular events occurred. In age-adjusted analyses using quintiles of HbA1c, a risk gradient was observed for both incident diabetes and cardiovascular disease. After multivariable adjustment, HbA1c remained a strong predictor of diabetes but was no longer significantly associated with incident cardiovascular disease. In analyses of threshold effects, adjusted relative risks for incident diabetes in HbA1c categories of less than 5.0%, 5.0% to 5.4%, 5.5% to 5.9%, 6.0% to 6.4%, 6.5% to 6.9%, and 7.0% or more were 1.0, 2.9, 12.1, 29.3, 28.2, and 81.2, respectively. Risk associations persisted after additional adjustment for C-reactive protein and after excluding individuals developing diabetes within 2 and 5 years of follow-up.

CONCLUSIONS

These prospective findings suggest that HbA1c levels are elevated well in advance of the clinical development of type 2 diabetes, supporting recent recommendations for lowering of diagnostic thresholds for glucose metabolic disorders. In contrast, the association of HbA1c with incident cardiovascular events is modest and largely attributable to coexistent traditional risk factors.

HbA(1c) as a screening tool for detection of Type 2 diabetes: a systematic review

AIM

To assess the validity of glycated haemoglobin A(1c) (HbA(1c)) as a screening tool for early detection of Type 2 diabetes.

METHODS

Systematic review of primary cross-sectional studies of the accuracy of HbA(1c) for the detection of Type 2 diabetes using the oral glucose tolerance test as the reference standard and fasting plasma glucose as a comparison. RESULTS Nine studies met the inclusion criteria. At certain cut-off points, HbA(1c) has slightly lower sensitivity than fasting plasma glucose (FPG) in detecting diabetes, but slightly higher specificity. For HbA(1c) at a Diabetes Control and Complications Trial and UK Prospective Diabetes Study comparable cut-off point of > or = 6.1%, the sensitivity ranged from 78 to 81% and specificity 79 to 84%. For FPG at a cut-off point of > or = 6.1 mmol/l, the sensitivity ranged from 48 to 64% and specificity from 94 to 98%. Both HbA(1c) and FPG have low sensitivity for the detection of impaired glucose tolerance (around 50%). CONCLUSIONS HbA(1c) and FPG are equally effective screening tools for the detection of Type 2 diabetes. The HbA(1c) cut-off point of > 6.1% was the recommended optimum cut-off point for HbA(1c) in most reviewed studies; however, there is an argument for population-specific cut-off points as optimum cut-offs vary by ethnic group, age, gender and population prevalence of diabetes. Previous studies have demonstrated that HbA(1c) has less intra-individual variation and better predicts both micro- and macrovascular complications. Although the current cost of HbA(1c) is higher than FPG, the additional benefits in predicting costly preventable clinical complications may make this a cost-effective choice.

Use of HbA1c in predicting progression to diabetes in French men and women: data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR)

OBJECTIVE

Early identification of subjects at high risk for diabetes is essential, and random HbA(1c) (A1C) may be more practical than fasting plasma glucose (FPG). The predictive value of A1C, in comparison to FPG, is evaluated for 6-year incident diabetes.

RESEARCH DESIGN AND METHODS

From the French cohort study Data from an Epidemiological Study on the Insulin Resistance Syndrome (DESIR), 1,383 men and 1,437 women, aged 30-65 years, were volunteers for a routine health check-up. Incident diabetes was defined by FPG >or=7.0 mmol/l or treatment by antidiabetic drugs. Multivariate logistic regression models were used to predict diabetes at 6 years. Receiver operating characteristic curves compared the predictive values of A1C and FPG.

RESULTS

At 6 years, 30 women (2.1%) and 60 men (4.3%) had developed diabetes. Diabetes risk increased exponentially with A1C in both sexes (P < 0.001). After stratifying on FPG, A1C predicted diabetes only in subjects with impaired fasting glucose (IFG) (FPG >or=6.10 mmol/l): the odds ratio (95% CI) for a 1% increase in A1C was 7.20 (3.00-17.00). In these subjects, an A1C of 5.9% gave an optimal sensitivity of 64% and specificity of 77% to predict diabetes.

CONCLUSIONS

A1C predicted diabetes, even though the diagnosis of diabetes was based on FPG, but it was less sensitive and specific than FPG. It could be used as a test if fasting blood sampling was not available or in association with FPG. In subjects with IFG, A1C is better than glucose to evaluate diabetes risk, and it could be used to select subjects for intensive early intervention.

Dietary carbohydrates and glycated proteins in the blood in non diabetic subjects

OBJECTIVES

To evaluate in non diabetic subjects the association of dietary carbohydrates with fructosamine, a measure of total non enzymatic glycated proteins in the blood associated with mortality, particularly from cardiovascular diseases.

METHODS

A population sample of 252 subjects (137 men and 115 women, mean age 57) without diabetes and with fasting serum glucose <126 mg/100 mL, participated in the study. Diet and dietary glycemic load were measured with a validated food frequency questionnaire. Fructosamine was measured with a standard colorimetric method. Multiple linear regression was used to analyze the data.

RESULTS

Serum fructosamine was positively associated with dietary glycemic load. Moreover, it was positively associated with intake of polyunsaturated fats and alcohol; and negatively with intake of monounsaturated fats, and with physical activity.

CONCLUSION

The quality of carbohydrate and fat, as well as physical activity, may explain the variation of non enzymatic glycated serum proteins in non diabetic subjects.

Insulin resistance syndrome in children : pathophysiology and potential management strategies

The simultaneous presence of various cardiovascular risk factors in the same individual is not rare, even in the pediatric age group. The clustering of risk factors can be termed insulin resistance syndrome (IRS) because of the putative central role of tissue insulin insensitivity in the background of the inter-related metabolic disturbances. Fasting hyperinsulinemia, impaired glucose tolerance, dyslipidemia, and hypertension are considered to represent the basic abnormalities of IRS. The most prevalent related disturbances are increased plasma levels of plasminogen activator inhibitor-1, fibrinogen, uric acid, homocysteine, and C-reactive protein, as well as visceral adiposity, microalbuminuria, disturbed essential fatty acid metabolism, low availability of lipid-soluble antioxidant vitamins, and enhanced expression of tumor necrosis factor-alpha in adipose tissues. Certain genetic abnormalities have been associated with IRS, but explain only a small part of the variability in insulin resistance. The exact prevalence of IRS in children remains to be defined; it was found to be 9% in one survey among children with obesity seeking medical attention. Modification of lifestyle, i.e. reduction of energy intake and enhancement of physical activity, are unquestionable prerequisites for long-term success in the management of IRS. In at least two randomized controlled studies, metformin proved to be clinically effective in increasing insulin sensitivity in hyperinsulinemic, nondiabetic adolescents. Thiazolidinediones have been successfully tested for the treatment of insulin resistance in adults, but not in children as yet. Prevention of the development of IRS in children is obviously of great significance for the health status of the community. However, the efficacy of various preventive approaches should be investigated further in carefully designed controlled trials.

Incidence of diabetes in American Indians of three geographic areas: the Strong Heart Study

OBJECTIVE

To estimate incidence rates of diabetes and associated risk factors among participants of the Strong Heart Study.

RESEARCH DESIGN AND METHODS

Of the 4,549 Strong Heart Study participants examined at baseline, 3,638 returned for a similar examination after an average of 4 years. The 1985 World Health Organization criteria for diabetes were used to identify new diabetes cases. Rates of diabetes among participants who did not have diabetes at baseline examination were determined. The relationships between the incidence rates of diabetes and a number of risk factors measured at baseline examination were studied.

RESULTS

Significant variables associated with the development of diabetes included triglycerides, obesity, fasting plasma glucose, insulin, and degree of American Indian blood among participants with NGT at baseline. For those with IGT at baseline, significant predictors included fasting plasma glucose, 2-h glucose, BMI, degree of American Indian blood, and albuminuria.

CONCLUSIONS

The high incidence rates found in this study were alarming. To slow down the rapid increase of this disease in the American Indian population, preventive programs must be designed and implemented. Patients with IGT should be treated with diabetes medication or put on a rigid weight-reduction program to reduce the risk of progression to diabetes.

Determinants of glycated haemoglobin in the general population: associations with diet, alcohol and cigarette smoking

OBJECTIVE

We evaluated cigarette smoking, alcohol intake and consumption of different foods as determinants of glycated haemoglobin in a general population sample.

DESIGN

Cross-sectional survey.

SETTING

England.

SUBJECTS

Representative sample of 15 809 adults aged 16 y and older. Data analysed for 9772 non-diabetic, white European subjects.

MAIN OUTCOME MEASURES

Glycated haemoglobin (GHb). Analyses were adjusted for age, sex, body mass index (BMI), waist-hip circumference ratio, activity level, and educational attainment.

RESULTS

After adjusting for confounding, GHb was 0.277% (95% confidence interval 0.218 to 0.336) higher in current smokers of 20 or more per day, compared with non-smokers. GHb was 0.189% (0.101 to 0.277) lower in those drinking 42 or more units of alcohol per week than in non-drinkers. GHb was not associated with frequency of consumption of pulses, fruit, vegetables and salads, cakes, bread or confectionery. GHb was higher in subjects who took sugar in tea (0.051%, 0.015 to 0.087%) or in coffee (0.069%, 0.034 to 0.105%). GHb was higher in subjects who used solid fat for cooking (0.082%, 0.022 to 0.142%), or who drank whole rather than reduced-fat milk (0.088%, 0.036 to 0.140%), or used butter or hard margarine rather than low-fat spreads (0.075%, 0.029 to 0.121%).

CONCLUSIONS

In the general population, higher GHb may be associated with cigarette smoking, or frequent consumption of fat-containing foods. Consumption of alcohol may be associated with lower GHb.

SPONSORSHIP

None.

Relationship of impaired glucose tolerance to left ventricular structure and function: The Strong Heart Study

BACKGROUND

We have identified increased left ventricular (LV) mass, wall thickness, relative wall thickness, and reduced systolic function in diabetic individuals after adjusting for blood pressure and body mass index. However, the cardiovascular correlates of impaired glucose tolerance (IGT), a precursor of diabetes, are unknown.

METHODS

We compared LV measurements between 457 American Indian participants in the Strong Heart Study with IGT (34% men) by World Health Organization criteria and 888 participants (49% men) with normal glucose tolerance.

RESULTS

Participants with IGT were older (60 vs 59 years, P < .01), more overweight (body mass index, 32 +/- 6 vs 29 +/- 5 g/m(2)), and had higher systolic blood pressure (129 +/- 20 vs 124 +/- 18 mm Hg, P < .001) and heart rate (67 +/- 10 vs 66 +/- 11 beats/min, P = .011). In univariate analyses, women but not men with IGT had higher LV mass (mean, 150 vs 138 g, P < .001) and cardiac index (2.6 vs 2.5 L/min/m(2), P < .05). LV wall thicknesses and relative wall thickness were greater in women and men with IGT. Regression analysis, adjusting for multiple covariates in the entire study population, identified independent associations of IGT with higher LV relative wall thicknesses, LV mass/height(2.7), and cardiac output/height(1.83).

CONCLUSIONS

IGT is associated with increased LV wall thickness, mass, and cardiac output independent of effects of relevant covariates.

Prevention of type 2 diabetes

Type 2 diabetes is a major cause of morbidity and mortality resulting from its microangiopathic and macroangiopathic complications. Current approaches to its management and to the prevention of diabetic complications are difficult to implement effectively, and there is little evidence to date that these approaches are reducing the impact of this disease. The recognition that type 2 diabetes usually has a prolonged prediabetic phase raises the possibility that the emergence of hyperglycemia and the atherosclerotic complications associated with diabetes may be preventable by the institution of early treatment modalities. Sufficient data suggest that life-style modification or pharmacotherapy directed at improving insulin sensitivity or insulin secretion in subjects with impaired glucose tolerance may reduce progression to diabetes. Two long-term prospective, controlled trials have been initiated to test this hypothesis.

Tracking of glycated hemoglobin in the original cohort of the Framingham Heart Study

Glycated hemoglobin measures average blood glucose over the preceding 2 to 3 months. The authors examined the tracking of the major glycated hemoglobin A1c (HbA1c), over a period of 4 to 6 years. Two HbA1c measurements were obtained between 1986 and 1993 from 639 elderly, presumptively nondiabetic members of the original cohort of the Framingham Heart Study, Framingham, Massachusetts. Mean +/- standard deviation (SD) baseline and follow-up HbA1c were 5.43% +/- 0.7 and 5.71% +/- 0.9, respectively. Intraclass correlation of 0.59 between baseline and follow-up measurements indicated good reliability of a single HbA1c measurement. Ninety-one percent of follow-up measurements were within +/- 20% of baseline value; HbA1c values tended to move 15% closer to the baseline mean over time. There was a modest tendency for HbA1c values to increase with time; the mean difference between measurements was 0.28% +/- 0.7 SD (p < 0.0001). Change in HbA1c was positively associated with age and body mass index at baseline examination, and negatively associated with cigarette smoking, even after controlling for age and body mass index. These effects were very small, however. We conclude that glycated hemoglobin reliably categorizes the glucose control of nondiabetic subjects over a period of 4 to 6 years, confirming its value as an epidemiological measure.

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.

Fasting proinsulin and 2-h post-load glucose levels predict the conversion to NIDDM in subjects with impaired glucose tolerance: the Hoorn Study

The aims of the present study were to observe the natural history of impaired glucose tolerance and to identify predictors for development of non-insulin-dependent diabetes mellitus (NIDDM). A survey of glucose tolerance was conducted in subjects aged 50-74 years, randomly selected from the registry of the middle-sized town of Hoorn in the Netherlands. Based on the mean values of two oral glucose tolerance tests subjects were classified in categories of glucose tolerance according to the World Health Organization criteria. All subjects with impaired glucose tolerance (n = 224) were invited to participate in the present study, in which 70% (n = 158) were subsequently enrolled. During follow-up subjects underwent a repeated paired oral glucose tolerance test. The mean follow-up time was 24 months (range 12-36 months). The cumulative incidence of NIDDM was 28.5% (95% confidence interval 15-42%). Age, sex, and anthropometric and metabolic characteristics at baseline were analysed simultaneously as potential predictors of conversion to NIDDM using multiple logistic regression. The initial 2-h post-load plasma glucose levels and the fasting proinsulin levels were significantly (p < 0.05) related to the incidence of NIDDM. Anthropometric characteristics, the 2-h post-load specific insulin levels and the fasting proinsulin/fasting insulin ratio were not related to the incidence of NIDDM. These results suggest that beta-cell dysfunction rather than insulin resistance plays the most important role in the future development of diabetes in a high-risk Caucasian population.

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.

Glucose tolerance in patients with cystic fibrosis: five year prospective study

OBJECTIVES

To study prevalence and incidence of diabetes mellitus in patients with cystic fibrosis.

DESIGN

Five year prospective study with annual oral glucose tolerance tests.

SETTING

CF Center Copenhagen, Denmark.

SUBJECTS

191 patients with cystic fibrosis aged above 2 years.

MAIN OUTCOME MEASURES

Glucose tolerance, plasma glucose concentrations after fasting and after glucose loading, and haemoglobin A1c levels.

RESULTS

Prevalence of diabetes increased from 11% (n = 21) to 24% (n = 46) during study, with annual age dependent incidence of 4-9%. Diabetes was diagnosed at median age of 21 (range 3-40). At diagnosis of diabetes, symptoms of hyperglycaemia were present in 33% of patients, fasting hyperglycaemia (> or = 7.8 mmol/l) was seen in 16%, and increased haemoglobin A1c levels (> 6.4%) were seen in 16%. Impaired glucose tolerance implied higher risk for development of diabetes than normal glucose tolerance (odds ratio 5.6). In 58% of cases with impaired glucose tolerance, however, glucose tolerance was normal at next annual test. Normal glucose tolerance was found in only 37% of patients at all five tests. Within this group of patients, median plasma glucose concentrations after fasting and after glucose loading and haemoglobin A1c levels increased by 6-8% during study.

CONCLUSIONS

Prevalence and incidence of diabetes in cystic fibrosis patients was high and increased with age. Since hyperglycaemic symptoms, fasting hyperglycaemia, and increased levels of glycated haemoglobin did not reliably identify diabetes mellitus, we recommend annual oral glucose tolerance tests in all cystic fibrosis patients aged over 10 years.