Differences in A1C by race and ethnicity among patients with impaired glucose tolerance in the Diabetes Prevention Program

HbA1c 5·7-6·4% and impaired fasting plasma glucose for diagnosis of prediabetes and risk of progression to diabetes in Japan (TOPICS 3): a longitudinal cohort study

BACKGROUND

The clinical relevance of the diagnostic criteria for prediabetes to prediction of progression to diabetes has been little studied. We aimed to compare the prevalence of prediabetes when assessed by the new glycated haemoglobin A(1c) (HbA(1c)) 5·7-6·4% criterion or by impaired fasting glucose, and assessed differences in progression rate to diabetes between these two criteria for prediabetes in a Japanese population.

METHODS

Our longitudinal cohort study included 4670 men and 1571 women aged 24-82 years without diabetes at baseline (diabetes was defined as fasting plasma glucose ≥7·0 mmol/L, self-reported clinician-diagnosed diabetes, or HbA(1c) ≥6·5%) who attended Toranomon Hospital (Tokyo, Japan) for a routine health check between 1997 and 2003. Participants with a baseline diagnosis of prediabetes according to impaired fasting glucose (fasting plasma glucose 5·6-6·9 mmol/L) or HbA(1c) 5·7-6·4%, or both, were divided into four groups on the basis of baseline diagnosis of prediabetes. Rate of progression to diabetes was assessed annually.

FINDINGS

Mean follow-up was 4·7 (SD 0·7) years. 412 (7%) of 6241 participants were diagnosed with prediabetes on the basis of the HbA(1c) 5·7-6·4% criterion. Screening by HbA(1c) alone missed 1270 (61%) of the 2092 prediabetic individuals diagnosed by a combination of impaired fasting glucose and HbA(1c) 5·7-6·4%. Overall cumulative probability of progression to diabetes did not differ significantly between participants with prediabetes discordantly diagnosed by either HbA(1c) or impaired fasting glucose alone (incidence was 7% for HbA(1c) alone [n=412 individuals and 30 incident cases] and 9% for impaired fasting glucose alone [n=1270, 108 cases]; log-rank test, p=0·3317). Multivariate-adjusted hazard ratios for incident diabetes were 6·16 (95% CI 4·33-8·77) for those diagnosed with prediabetes by impaired fasting glucose alone and 6·00 (3·76-9·56) for diagnosis by HbA(1c) alone, and were substantially increased to 31·9 (22·6-45·0) for diagnosis by both impaired fasting glucose and HbA(1c) compared with normoglycaemic individuals.

INTERPRETATION

Diagnosis of prediabetes by both the new HbA(1c) criterion and impaired fasting glucose identified individuals with an increased risk of progression to diabetes. Although the new HbA(1c) criterion identified fewer individuals at high risk than did impaired fasting glucose, the predictive value for progression to diabetes assessed by HbA(1c) 5·7-6·4% was similar to that assessed by impaired fasting glucose alone. The two tests used together could efficiently target people who are most likely to develop diabetes and allow for early intervention.

FUNDING

Japan Society for the Promotion of Science; Ministry of Health Labor and Welfare, Japan.

The general use of glycated haemoglobin for the diagnosis of diabetes and other categories of glucose intolerance: still a long way to go

Glycated haemoglobin (HbA(1c)) is considered the 'gold standard' for monitoring metabolic control in diabetes. An International Expert Committee recently recommended HbA(1c) as a better method than measurement of glucose to use in the diagnosis of diabetes, based on its strong association with microvascular complications, a lower day-to-day variability and ease of use, not necessarily in the fasting state. These recommendations have been embraced by the American Diabetes Association (ADA), which stated in its Standards of Medical Care in Diabetes 2010 that "A(1c), fasting plasma glucose or the 2 h 75 g oral glucose tolerance test (OGTT) are appropriate for testing diabetes and assessing the risk of future diabetes," and that "a confirmed A(1c) ≥ 6.5% is diagnostic for diabetes." Measuring HbA(1c) has several advantages over glucose measurements, but its exclusive use should only be considered if the test is conducted under standardised conditions and its limitations are taken into due account. The impact of its use on the epidemiology of diabetes and other categories of glucose intolerance, as seen from recent reports, is also discussed.

Usefulness of hemoglobin A1c as a criterion to define the metabolic syndrome in a cohort of italian nondiabetic white subjects

We compared the performance of hemoglobin A1c (HbA1c) versus the fasting plasma glucose (FPG) in diagnosing the metabolic syndrome and assessed the diagnostic accuracy of the metabolic syndrome definition using HbA1c in identifying insulin-resistant subjects. The cardiometabolic risk factors, HbA1c, and glucose tolerance were analyzed in 774 nondiabetic white subjects. Insulin sensitivity was estimated with an oral glucose tolerance test-derived insulin sensitivity index. Insulin resistance was defined as the lower quartile of insulin sensitivity index. A 90.9% agreement existed between the use of HbA1c and the FPG for diagnosis of the metabolic syndrome (κ coefficient = 0.813); however, the proportion of subjects who met the metabolic syndrome criteria using the HbA1c was greater (42.1% vs 39.7%). Compared to the subjects who met the metabolic syndrome criteria using the FPG alone, those with the metabolic syndrome using the HbA1c-alone criterion were younger, had greater visceral adiposity, greater levels of inflammatory markers and liver enzymes, and lower blood pressure. In a logistic regression analysis with adjustment for age and gender, the subjects with the metabolic syndrome using the HbA1c criterion only had a 3.6-fold increase risk of having insulin resistance, defined as the lowest quartile of the insulin sensitivity index. A similar risk (3.8-fold) was observed in those who met the metabolic syndrome criteria using FPG alone. Insulin-resistant subjects who did not meet the criteria for the metabolic syndrome using the HbA1c had an unfavorable cardiovascular disease risk profile. In conclusion, although a good agreement existed between the HbA1c and FPG criteria for the diagnosis of the metabolic syndrome, appreciably different groups of subjects were classified using each method.

Glycated hemoglobin predicts all-cause, cardiovascular, and cancer mortality in people without a history of diabetes undergoing coronary angiography

OBJECTIVE

Glycated hemoglobin has been suggested to be superior to fasting glucose for the prediction of vascular disease and death from any cause. The aim of the present work was to analyze and compare the predictive value of glycated hemoglobin and fasting glucose on all-cause and cause-specific mortality in subjects who underwent coronary angiography.

RESEARCH DESIGN AND METHODS

We studied 2,686 participants of the Ludwigshafen Risk and Cardiovascular health study without a history of diabetes. The majority of this cohort had coronary artery disease. Glycated hemoglobin was measured at the baseline examination. The mean (± SD) duration of the follow-up for all-cause, cardiovascular, and cancer mortality was 7.54 ± 2.1 years.

RESULTS

A total of 508 deaths occurred during the follow-up. Of those, 299 were accounted for by cardiovascular diseases and 79 by cancer. Baseline glycated hemoglobin was predictive of all-cause, cardiovascular, and cancer mortality. The multivariable-adjusted hazard ratios (HR) (95% CI) for glycated hemoglobin values of <5.0, 5.0-5.4, 5.5-5.9, 6.0-6.4, 6.5-7.4, and ≥7.5% for all-cause mortality were 1.36 (0.85-2.18), 1.00 (0.76-1.32), 1.00 (reference), 1.11 (0.88-1.41), 1.39 (1.07-1.82), and 2.15 (1.32-3.53), respectively. Similar J-shaped relationships were found between glycated hemoglobin and cardiovascular and cancer mortality. The associations of glycated hemoglobin with all-cause and cardiovascular mortality remained significant after inclusion of fasting glucose as a covariate. However, fasting glucose was not significantly related to mortality when adjusting for glycated hemoglobin.

CONCLUSIONS

Glycated hemoglobin significantly and independently of fasting glucose predicts all-cause and cardiovascular mortality in whites at intermediate to high cardiovascular risk.

Utility of hemoglobin A(1c) for diagnosing prediabetes and diabetes in obese children and adolescents

OBJECTIVE

Hemoglobin A(1c) (A1C) has emerged as a recommended diagnostic tool for identifying diabetes and subjects at risk for the disease. This recommendation is based on data in adults showing the relationship between A1C with future development of diabetes and microvascular complications. However, studies in the pediatric population are lacking.

RESEARCH DESIGN AND METHODS

We studied a multiethnic cohort of 1,156 obese children and adolescents without a diagnosis of diabetes (male, 40%/female, 60%). All subjects underwent an oral glucose tolerance test (OGTT) and A1C measurement. These tests were repeated after a follow-up time of ∼2 years in 218 subjects.

RESULTS

At baseline, subjects were stratified according to A1C categories: 77% with normal glucose tolerance (A1C <5.7%), 21% at risk for diabetes (A1C 5.7-6.4%), and 1% with diabetes (A1C >6.5%). In the at risk for diabetes category, 47% were classified with prediabetes or diabetes, and in the diabetes category, 62% were classified with type 2 diabetes by the OGTT. The area under the curve receiver operating characteristic for A1C was 0.81 (95% CI 0.70-0.92). The threshold for identifying type 2 diabetes was 5.8%, with 78% specificity and 68% sensitivity. In the subgroup with repeated measures, a multivariate analysis showed that the strongest predictors of 2-h glucose at follow-up were baseline A1C and 2-h glucose, independently of age, ethnicity, sex, fasting glucose, and follow-up time.

CONCLUSIONS

The American Diabetes Association suggested that an A1C of 6.5% underestimates the prevalence of prediabetes and diabetes in obese children and adolescents. Given the low sensitivity and specificity, the use of A1C by itself represents a poor diagnostic tool for prediabetes and type 2 diabetes in obese children and adolescents.

Diagnosis of diabetes using hemoglobin A1c: should recommendations in adults be extrapolated to adolescents?

OBJECTIVE

To compare test performance of hemoglobin A1c (HbA1c) for detecting diabetes mellitus/pre-diabetes for adolescents versus adults in the United States.

STUDY DESIGN

Individuals were defined as having diabetes mellitus (fasting plasma glucose [FPG] ≥ 126 mg/dL; 2-hour plasma glucose (2-hr PG) ≥ 200 mg/dL) or pre-diabetes (100 ≤ FPG < 126 mg/dL; 140 ≤ 2-hr PG < 200 mg/dL. HbA1c test performance was evaluated with receiver operator characteristic (ROC) analyses.

RESULTS

Few adolescents had undiagnosed diabetes mellitus (n = 4). When assessing FPG to detect diabetes, an HbA1c of 6.5% had sensitivity rates of 75.0% (30.1% to 95.4%) and 53.8% (47.4% to 60.0%) and specificity rates of 99.9% (99.5% to 100.0%) and 99.5% (99.3% to 99.6%) for adolescents and adults, respectively. Additionally, when assessing FPG to detect diabetes mellitus, an HbA1c of 5.7% had sensitivity rates of 5.0% (2.6% to 9.2%) and 23.1% (21.3% to 25.0%) and specificity rates of 98.3% (97.2% to 98.9%) and 91.1% (90.3% to 91.9%) for adolescents and adults, respectively. ROC analyses suggested that HbA1c is a poorer predictor of diabetes mellitus (area under the curve, 0.88 versus 0.93) and pre-diabetes (FPG area under the curve 0.61 versus 0.74) for adolescents compared with adults. Performance was poor regardless of whether FPG or 2-hr PG measurements were used.

CONCLUSIONS

Use of HbA1c for diagnosis of diabetes mellitus and pre-diabetes in adolescents may be premature, until information from more definitive studies is available.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence-Based Laboratory Medicine Committee of the American Association for Clinical Chemistry jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (HbA(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of HbA(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus

BACKGROUND

Multiple laboratory tests are used to diagnose and manage patients with diabetes mellitus. The quality of the scientific evidence supporting the use of these tests varies substantially.

APPROACH

An expert committee compiled evidence-based recommendations for the use of laboratory testing for patients with diabetes. A new system was developed to grade the overall quality of the evidence and the strength of the recommendations. Draft guidelines were posted on the Internet and presented at the 2007 Arnold O. Beckman Conference. The document was modified in response to oral and written comments, and a revised draft was posted in 2010 and again modified in response to written comments. The National Academy of Clinical Biochemistry and the Evidence Based Laboratory Medicine Committee of the AACC jointly reviewed the guidelines, which were accepted after revisions by the Professional Practice Committee and subsequently approved by the Executive Committee of the American Diabetes Association.

CONTENT

In addition to long-standing criteria based on measurement of plasma glucose, diabetes can be diagnosed by demonstrating increased blood hemoglobin A(1c) (Hb A(1c)) concentrations. Monitoring of glycemic control is performed by self-monitoring of plasma or blood glucose with meters and by laboratory analysis of Hb A(1c). The potential roles of noninvasive glucose monitoring, genetic testing, and measurement of autoantibodies, urine albumin, insulin, proinsulin, C-peptide, and other analytes are addressed.

SUMMARY

The guidelines provide specific recommendations that are based on published data or derived from expert consensus. Several analytes have minimal clinical value at present, and their measurement is not recommended.

Antepartum A1C, maternal diabetes outcomes, and selected offspring outcomes: an epidemiological review

Between 1989 and 2004, the prevalence of gestational diabetes mellitus (GDM) in the United States increased by 122%. Glycated haemoglobin, as measured by haemoglobin A1C (A1C), can potentially identify pregnant women at high risk for adverse outcomes associated with GDM including macrosomia and post-partum glucose intolerance. Our objective was to systematically review the literature with respect to A1C levels during pregnancy and associated maternal and offspring outcomes. We used MEDLINE to identify relevant publications from 1975 to 2009. We included articles if they met the following criteria: original full text articles in English; primary exposure of antepartum A1C; women with GDM at baseline or who developed GDM during the study; primary outcome of GDM, insulin use, post-partum abnormal glucose or type 2 diabetes (T2DM), birthweight, macrosomia or large for gestational age. Case series and case reports were excluded. Twenty studies met our criteria. A1C at GDM diagnosis was positively associated with post-partum abnormal glucose. Women with post-partum T2DM or impaired glucose tolerance had mean A1C at GDM diagnosis higher than those with normal post-partum glucose (P ≤ 0.002) and a 1% increase in A1C at GDM diagnosis was associated with 2.36 times higher odds of post-partum abnormal glucose 6 weeks after delivery [95% confidence interval 1.19, 4.68]. The association of A1C and birthweight varied substantially between studies, with correlation coefficients ranging from 0.11 to 0.51. A1C, a less burdensome and costly measure than an oral glucose tolerance test, appears to be an attractive measure for identifying women at high risk of adverse outcomes associated with GDM.

Hemoglobin A1c testing alone does not sufficiently identify patients with prediabetes

Whether hemoglobin A(1c) (HbA(1c)) values are suitable for diagnosing diabetes has been debated. We sought to assess the prevalence of elevated HbA(1c) levels in a prediabetes patient population. Oral glucose tolerance tests and HbA(1c) levels were analyzed for patients entering a diabetes prevention program between January 1, 2007, and September 13, 2009. We calculated the percentage of patients with impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT) who had HbA(1c) values in the 6.0% to 6.4% range or in the 5.7% to 6.4% range. The mean age of the 242 patients was 62 years; 64.0% were women, and 88.0% were white. Isolated IFG was detected in about 56.2% of patients and combined IFG and IGT in about 37.2%. Only 28.5% of patients had HbA(1c) values in the 6.0% to 6.4% range, whereas 65.3% had values in the 5.7% to 6.4% range. Our data suggest that reliance on HbA(1c) testing alone to identify candidates for a diabetes prevention program would miss a substantial number of eligible patients.

Implications of using hemoglobin A1C for diagnosing diabetes mellitus

Until 2010, the diagnosis of diabetes mellitus was based solely on glucose concentration, but the American Diabetes Association (ADA) recommendations now include a new criterion: hemoglobin A1C ≥6.5%. Because this change may have significant implications for diabetes diagnosis, we conducted a comprehensive literature review including peer-reviewed articles not referenced in the ADA report. We conclude that A1C and plasma glucose tests are frequently discordant for diagnosing diabetes. A1C ≥6.5% identifies fewer individuals as having diabetes than glucose-based criteria. Convenience of A1C test might increase the number of patients diagnosed, but this is unproven. Diagnostic cut-points for both glucose and A1C are based on consensus judgments regarding optimal sensitivity and specificity for the complications of hyperglycemia. A1C may not accurately reflect levels of glycemia in some situations, but in comparison with glucose measurements, it has greater analytic stability and less temporal variability. When choosing a diagnostic test for diabetes, the limitations of each choice must be understood. Clinical judgment and consideration of patient preference are required to appropriately select among the diagnostic alternatives.

Regional, geographic, and racial/ethnic variation in glycemic control in a national sample of veterans with diabetes

OBJECTIVE

We performed a retrospective analysis of a national cohort of veterans with diabetes to better understand regional, geographic, and racial/ethnic variation in diabetes control as measured by HbA(1c).

RESEARCH DESIGN AND METHODS

A retrospective cohort study was conducted in a national cohort of 690,968 veterans with diabetes receiving prescriptions for insulin or oral hypoglycemic agents in 2002 that were followed over a 5-year period. The main outcome measures were HbA(1c) levels (as continuous and dichotomized at ≥8.0%).

RESULTS

Relative to non-Hispanic whites (NHWs), HbA(1c) levels remained 0.25% higher in non-Hispanic blacks (NHBs), 0.31% higher in Hispanics, and 0.14% higher in individuals with other/unknown/missing racial/ethnic group after controlling for demographics, type of medication used, medication adherence, and comorbidities. Small but statistically significant geographic differences were also noted with HbA(1c) being lowest in the South and highest in the Mid-Atlantic. Rural/urban location of residence was not associated with HbA(1c) levels. For the dichotomous outcome poor control, results were similar with race/ethnic group being strongly associated with poor control (i.e., odds ratios of 1.33 [95% CI 1.31-1.35] and 1.57 [1.54-1.61] for NHBs and Hispanics vs. NHWs, respectively), geographic region being weakly associated with poor control, and rural/urban residence being negligibly associated with poor control.

CONCLUSIONS

In a national longitudinal cohort of veterans with diabetes, we found racial/ethnic disparities in HbA(1c) levels and HbA(1c) control; however, these disparities were largely, but not completely, explained by adjustment for demographic characteristics, medication adherence, type of medication used to treat diabetes, and comorbidities.

Hemoglobin A1c as a diagnostic tool for diabetes screening and new-onset diabetes prediction: a 6-year community-based prospective study

OBJECTIVE

Various cutoff levels of hemoglobin A(1c) (A1C) have been suggested to screen for diabetes, although more consensus about the best level, especially for different ethnicities, is required. We evaluated the usefulness of A1C levels when screening for undiagnosed diabetes and as a predictor of 6-year incident diabetes in a prospective, population-based cohort study.

RESEARCH DESIGN AND METHODS

A total 10,038 participants were recruited from the Ansung-Ansan cohort study. All subjects underwent a 75-g oral glucose tolerance test at baseline and at each biennial follow-up. Excluding subjects with a previous history of diabetes (n = 572), the receiver operating characteristic curve was used to evaluate the diagnostic accuracy of the A1C cutoff. The Cox proportional hazards model was used to predict diabetes at 6 years.

RESULTS

At baseline, 635 participants (6.8%) had previously undiagnosed diabetes. An A1C cutoff of 5.9% produced the highest sum of sensitivity (68%) and specificity (91%). At 6 years, 895 (10.2%) subjects had developed incident diabetes. An A1C cutoff of 5.6% had the highest sum of sensitivity (59%) and specificity (77%) for the identification of subsequent 6-year incident diabetes. After multivariate adjustment, men with baseline A1C ≥5.6% had a 2.4-fold increased risk and women had a 3.1-fold increased risk of new-onset diabetes.

CONCLUSIONS

A1C is an effective and convenient method for diabetes screening. An A1C cutoff of 5.9% may identify subjects with undiagnosed diabetes. Individuals with A1C ≥5.6% have an increased risk for future diabetes.

Levels of acculturation and effect on glycemic control in Mexicans and Mexican Americans with type 2 diabetes

BACKGROUND

Acculturation of Mexican Americans toward the predominant American culture has been shown to influence health outcomes. Little is known about the role of acculturation in diabetes control.

OBJECTIVE

To measure the association between acculturation and diabetes control in Mexicans and Mexican Americans with type 2 diabetes mellitus (T2DM).

DESIGN

Cross-sectional survey and chart review.

SETTING

Ambulatory family medicine clinics.

PATIENTS

Sixty-six Mexican and Mexican American adults with T2DM for ≥ 1 year. INSTRUMENT AND OUTCOMES: A survey tool was developed that included the General Acculturation Index developed by Balcazar et al to measure acculturation. Basic demographics, psychosocial factors, patient satisfaction, and patients' most recent hemoglobin A(1c) (HbA(1c)) levels were also obtained.

RESULTS

There was no significant correlation between acculturation score and HbA(1c) levels. On binary logistic regression, HbA(1c) levels were associated with patient satisfaction in having their questions answered (odds ratio [OR], 0.44; P < 0.05), interference of diabetes with daily life (OR, 1.4; P < 0.05), male gender (OR, 3.93; P < 0.01), and number of diabetes complications (OR, 1.81; P < 0.05). In the multivariate linear regression model, age (beta, -0.348; P < 0.05) and frequency of physician visits (beta, -0.403; P < 0.05) were the only variables significantly associated with glycemic control. Variables included in the model that were not associated with glycemic control include family history of diabetes and confidence in diabetes treatment efficacy.

CONCLUSIONS

Acculturation was not associated with glycemic control in this population. Family physicians should not assume that acculturation difficulties explain poor glycemic control in their Mexican American patients with T2DM.

Racial differences in glycemic markers: a cross-sectional analysis of community-based data

BACKGROUND

Although differences between black and white persons in hemoglobin A(1c) (HbA(1c)) values are well established, recent studies suggest that this might not reflect differences in glycemia.

OBJECTIVE

To investigate racial disparities in glycemic markers, including those that reflect biological processes independent of hemoglobin glycation and erythrocyte turnover.

DESIGN

Cross-sectional.

SETTING

Community-based.

PARTICIPANTS

1376 nondiabetic and 343 diabetic adults in a substudy of the Atherosclerosis Risk in Communities Study.

MEASUREMENTS

Hemoglobin A(1c), fasting glucose, glycated albumin, fructosamine, and 1,5-anhydroglucitol levels.

RESULTS

Among persons with and without diabetes, black persons had significantly higher HbA(1c), glycated albumin, and fructosamine levels than white persons before and after adjustment for covariates and fasting glucose concentration. Serum 1,5-anhydroglucitol levels, which are reduced in the setting of hyperglycemia-induced glycosuria, were lower in black persons than in white persons, although this difference was statistically significant only in nondiabetic adults.

LIMITATION

The design was cross-sectional, a limited number of participants with a history of diabetes was included, and the study did not include integrated measures of circulating nonfasting glycemia.

CONCLUSION

Differences between black and white persons in glycated albumin, fructosamine, and 1,5-anhydroglucitol levels parallel differences between these groups in HbA(1c) values. Racial differences in hemoglobin glycation and erythrocyte turnover cannot explain racial disparities in these serum markers. The possibility that black persons have systematically higher levels of nonfasting glycemia warrants further study.

PRIMARY FUNDING SOURCE

National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases.

Implications of the new definition of diabetes for health disparities

In July 2009, an international committee announced a new diagnostic criterion for diabetes based on hemoglobin Alc (HbA1c) values. Our objective was to estimate how the new diabetes diagnostic criterion will affect the prevalence of diabetes among different race, age, and gender subpopulations, compared to the previously used fasting plasma glucose (FPG) criterion. We analyzed nationally representative data from The National Health and Nutrition Examination Survey (NHANES), aggregated from 1999 to 2006. We estimated the prevalence of known diabetes (prevalence static across either diagnostic criterion), unknown, and no diabetes (prevalence variable by criterion). We tested statistical significance of prevalence differences for unknown diabetes between the prior diagnostic criterion--FPG of at least 126 mg/dL--and the new diagnostic criterion--HbA1c of at least 6.5%--using conditional logistic regression. We further tested the association of these differences with demographic factors. The new HbA1c diagnostic criterion differentially affects different racial/ethnic groups. For non-Hispanic whites, the prevalence of undiagnosed diabetes was more than halved from 2.6% (95% confidence interval [CI], 2.2-3.1) with FPG diagnosis to 1.3% (95% CI, 1.0-1.7), P<.001 with HbAic diagnosis. For Hispanics and non-Hispanic blacks, the differences in prevalence by the 2 criteria were smaller and nonsignificant. Racial differences by diagnostic criteria were most pronounced among people aged over 55 years. Overall, the new definition of diabetes differentially affects ethnic groups, especially for older people. If the new criterion is widely adopted, over time, we may see an apparent widening of racial/ethnic disparities in diabetes prevalence.

Implications of alternative definitions of prediabetes for prevalence in U.S. adults

OBJECTIVE

To compare the prevalence of prediabetes using A1C, fasting plasma glucose (FPG), and oral glucose tolerance test (OGTT) criteria, and to examine the degree of agreement between the measures.

RESEARCH DESIGN AND METHODS

We used the 2005-2008 National Health and Nutrition Examination Surveys to classify 3,627 adults aged ≥ 18 years without diabetes according to their prediabetes status using A1C, FPG, and OGTT. We compared the prevalence of prediabetes according to different measures and used conditional probabilities to examine agreement between measures.

RESULTS

In 2005-2008, the crude prevalence of prediabetes in adults aged ≥ 18 years was 14.2% for A1C 5.7-6.4% (A1C5.7), 26.2% for FPG 100-125 mg/dL (IFG100), 7.0% for FPG 110-125 mg/dL (IFG110), and 13.7% for OGTT 140-199 mg/dL (IGT). Prediabetes prevalence varied by age, sex, and race/ethnicity, and there was considerable discordance between measures of prediabetes. Among those with IGT, 58.2, 23.4, and 32.3% had IFG100, IFG110, and A1C5.7, respectively, and 67.1% had the combination of either A1C5.7 or IFG100.

CONCLUSIONS

The prevalence of prediabetes varied by the indicator used to measure risk; there was considerable discordance between indicators and the characteristics of individuals with prediabetes. Programs to prevent diabetes may need to consider issues of equity, resources, need, and efficiency in targeting their efforts.

Management of type 2 diabetes: evolving strategies for the treatment of patients with type 2 diabetes

The prevalence of type 2 diabetes continues to increase at an alarming rate around the world, with even more people being affected by prediabetes. Although the pathogenesis and long-term complications of type 2 diabetes are fairly well known, its treatment has remained challenging, with only half of the patients achieving the recommended hemoglobin A(1c) target. This narrative review explores the pathogenetic rationale for the treatment of type 2 diabetes, with the view of fostering better understanding of the evolving treatment modalities. The diagnostic criteria including the role of hemoglobin A(1c) in the diagnosis of diabetes are discussed. Due attention is given to the different therapeutic maneuvers and their utility in the management of the diabetic patient. The evidence supporting the role of exercise, medical nutrition therapy, glucose monitoring, and antiobesity measures including pharmacotherapy and bariatric surgery is discussed. The controversial subject of optimum glycemic control in hospitalized and ambulatory patients is discussed in detail. An update of the available pharmacologic options for the management of type 2 diabetes is provided with particular emphasis on newer and emerging modalities. Special attention has been given to the initiation of insulin therapy in patients with type 2 diabetes, with explanation of the pathophysiologic basis for insulin therapy in the ambulatory diabetic patient. A review of the evidence supporting the efficacy of the different preventive measures is also provided.

Discordance between fasting glucose-based and hemoglobin A1c-based diagnosis of diabetes mellitus in Koreans

We analyzed data of 35,624 non-diabetic Koreans using fasting plasma glucose (FPG) criteria and HbA1c criteria in screening for diabetes. Among the 1,491 subjects newly diagnosed with diabetes, 473 (31.6%) met the FPG criteria only (≥7.0mmol/l), 350 (23.5%) met HbA1c criteria only (≥6.5%), and 668 (44.9%) met both criteria. The DM-by-HbA1c group had significantly older age, higher proportion of women, and lower hemoglobin concentration. The DM-by-FPG group had higher systolic and diastolic blood pressure, fasting serum insulin, and HOMA-IR. Further studies are needed to determine which of these criteria is superior in predicting the risks of long-term vascular complications of diabetes.

Identifying adults at high risk for diabetes and cardiovascular disease using hemoglobin A1c National Health and Nutrition Examination Survey 2005-2006

BACKGROUND

The American Diabetes Association (ADA) recently proposed the use of hemoglobin A1c as a practical and valid strategy to identify high-risk people for whom delivery of an intensive lifestyle intervention to prevent type 2 diabetes is likely to be cost effective.

PURPOSE

To estimate composite risks of developing diabetes and cardiovascular disease (CVD) for adults with different hemoglobin A1c test results and to compare those risks with those of adults who met the 2003 ADA definition for prediabetes.

METHODS

Cross-sectional data from the 2005-2006 National Health and Nutrition Examination Survey were analyzed in 2009. The method of Stern and colleagues was used to estimate the 7.5-year probability of type 2 diabetes, and the Framingham General CVD Risk Engine was used to estimate the 10-year probability of CVD for adults with different A1c results. Sample weights were used to account for sampling probability and to adjust for noncoverage and nonresponse.

RESULTS

Among adults meeting the 2003 ADA definition for prediabetes, the probabilities for incident type 2 diabetes (over 7.5 years) and CVD (over 10 years) were 33.5% and 10.7%, respectively. Use of A1c alone, in the range of 5.5% to <6.5%, would identify a population with comparable risks for diabetes (32.4% [SE=1.2%]) and CVD (11.4% [SE=0.6%]). A slightly higher cutoff (≥5.7%) would identify adults with risks of 41.3% (SE=1.5%) for diabetes and 13.3% (SE=0.8%) for CVD-risks that are comparable to people enrolled in the Diabetes Prevention Program.

CONCLUSIONS

A1c-based testing in clinical settings should be considered as a means to identify greater numbers of adults at high risk of developing type 2 diabetes and CVD.

Insufficient sensitivity of hemoglobin A(₁C) determination in diagnosis or screening of early diabetic states

An International Expert Committee made recommendations for using the hemoglobin A(₁C) (A1C) assay as the preferred method for the diagnosis of diabetes in nonpregnant individuals. A concentration of at least 6.5% was considered as diagnostic. It is the aim of this study to compare the sensitivity of A1C with that of plasma glucose concentrations in subjects with early diabetes or impaired glucose tolerance (IGT). We chose 2 groups of subjects who had A1C not exceeding 6.4%. The first group of 89 subjects had family histories of diabetes (MODY or type 2 diabetes mellitus) and had oral glucose tolerance test (OGTT) and A1C determinations. They included 36 subjects with diabetes or IGT and 53 with normal OGTT. The second group of 58 subjects was screened for diabetes in our Diabetes Clinic by fasting plasma glucose, 2-hour plasma glucose, or OGTT and A1C; and similar comparisons were made. Subjects with diabetes or IGT, including those with fasting hyperglycemia, had A1C ranging from 5.0% to 6.4% (mean, 5.8%). The subjects with normal OGTT had A1C of 4.2% to 6.3% (mean, 5.4%), or 5.5% for the 2 groups. The A1C may be in the normal range in subjects with diabetes or IGT, including those with fasting hyperglycemia. Approximately one third of subjects with early diabetes and IGT have A1C less than 5.7%, the cut point that the American Diabetes Association recommends as indicating the onset of risk of developing diabetes in the future. The results of our study are similar to those obtained by a large Dutch epidemiologic study. If our aim is to recognize early diabetic states to apply effective prophylactic procedures to prevent or delay progression to more severe diabetes, A1C is not sufficiently sensitive or reliable for diagnosis of diabetes or IGT. A combination of A1C and plasma glucose determinations, where necessary, is recommended for diagnosis or screening of diabetes or IGT.

Status of hemoglobin A1c measurement and goals for improvement: from chaos to order for improving diabetes care

BACKGROUND

The Diabetes Control and Complications Trial (DCCT) and United Kingdom Prospective Diabetes Study (UKPDS) established the importance of hemoglobin A(1c) (Hb A(1c)) as a predictor of outcome in patients with diabetes mellitus. In 1994, the American Diabetes Association began recommending specific Hb A(1c) targets, but lack of comparability among assays limited the ability of clinicians to use these targets. The National Glycohemoglobin Standardization Program (NGSP) was implemented in 1996 to standardize Hb A(1c) results to those of the DCCT/UKPDS.

CONTENT

The NGSP certifies manufacturers of Hb A(1c) methods as traceable to the DCCT. The certification criteria have been tightened over time and the NGSP has worked with the College of American Pathologists in tightening proficiency-testing requirements. As a result, variability of Hb A(1c) results among clinical laboratories has been considerably reduced. The IFCC has developed a reference system for Hb A(1c) that facilitates metrological traceability to a higher order. The NGSP maintains traceability to the IFCC network via ongoing sample comparisons. There has been controversy over whether to report Hb A(1c) results in IFCC or NGSP units, or as estimated average glucose. Individual countries are making this decision.

SUMMARY

Variability among Hb A(1c) results has been greatly reduced. Not all countries will report Hb A(1c) in the same units, but there are established equations that enable conversion between different units. Hb A(1c) is now recommended for diagnosing diabetes, further accentuating the need for optimal assay performance. The NGSP will continue efforts to improve Hb A(1c) testing to ensure that clinical needs are met.

Progression of nephropathy in type 2 diabetes: the glycation gap is a significant predictor after adjustment for glycohemoglobin (Hb A1c)

BACKGROUND

The glycation gap has been proposed as an index of nonglycemic determinants of glycated hemoglobin (Hb A(1c)). We investigated whether it predicts progression of nephropathy in type 2 diabetic patients.

METHODS

We recorded albumin excretion rate, Hb A(1c), and serum fructosamine in 2314 patients over an average of 6.5 years. Hb A(1c) was regressed on fructosamine by using a repeated-measures longitudinal regression model and data for all visits of all patients; the raw glycation gap gg was calculated at each visit, as measured by Hb A(1c) minus the value predicted by the regression; and the mean glycation gap (GG) was defined for each patient as the mean of the values for the raw glycation gap (gg) calculated at each visit. The study group was divided into high-, medium- and low-GG groups of equal sizes, which were compared for progression of nephropathy by Cox regression analyses controlling for age, sex, duration of diabetes, initial nephropathy status, therapy, baseline Hb A(1c), mean Hb A(1c), and mean fructosamine. The design of the study was a retrospective cohort study with follow-up for 6.5 (SD 4.2) years.

RESULTS

The gg exhibited considerable stability over time. In the high- and medium-GG groups, the risk of progression of nephropathy was respectively 2.5 and 1.6 times that of the low-GG group (P < 0.0001 and P = 0.001, respectively) after adjustment as described above.

CONCLUSIONS

GG predicts the progression of nephropathy in type 2 diabetic patients independently of fructosamine and even after adjustment for Hb A(1c). The joint use of the glycation gap and fructosamine as measures of nonglycemic and glycemic determinants of glycation, respectively, may improve evaluation of the risk of nephropathy and of the glycemic control desirable for the individual patient.

Identifying dysglycemic states in older adults: implications of the emerging use of hemoglobin A1c

CONTEXT

Hemoglobin A1c (A1c) was recently added to the diagnostic criteria for diabetes and prediabetes.

OBJECTIVE

Our objective was to examine performance of A1c in comparison with fasting plasma glucose (FPG) in diagnosing dysglycemia in older adults.

DESIGN AND SETTING

We conducted a cross-sectional analysis of data from the Health, Aging, and Body Composition study at yr 4 (2000-2001) when FPG and standardized A1c measurements were available.

PARTICIPANTS

Of 3075 persons (aged 70-79 yr, 48% men, 42% Black) at study entry, 1865 participants without known diabetes who had appropriate measures were included.

MAIN OUTCOME MEASURES

Sensitivity and specificity of A1c-based diagnoses were compared with those based on FPG and the proportion of participants identified with dysglycemia by each measure.

RESULTS

Of all participants, 2.7 and 3.1% had undiagnosed diabetes by FPG≥126 mg/dl and A1c≥6.5%, respectively. Among the remaining participants, 21.1% had prediabetes by impaired fasting glucose (≥100 mg/dl) and 22.2% by A1c≥5.7%. Roughly one third of individuals with diabetes and prediabetes were identified by either FPG or A1c alone and by both tests simultaneously. Sensitivities and specificities of A1c compared with FPG were 56.9 and 98.4% for diabetes and 47.0 and 84.5% for prediabetes, respectively. Blacks and women were more likely to be identified with dysglycemia by A1c than FPG.

CONCLUSIONS

In this older population, we found considerable discordance between FPG- and A1c-based diagnosis of diabetes and prediabetes, with differences accentuated by race and gender. Broad implementation of A1c to diagnose dysglycemic states may substantially alter the epidemiology of these conditions in older Americans.

A1C and diabetes diagnosis among Filipino Americans, Japanese Americans, and Native Hawaiians

OBJECTIVE

To examine the sensitivity and specificity of A1C ≥ 6.5% to diagnose diabetes among Filipino Americans, Japanese Americans, and Native Hawaiians.

RESEARCH DESIGN AND METHODS

This was a cross-sectional study among middle-aged adults without prior diagnosis of type 2 diabetes who completed a 2-h 75-g oral glucose tolerance test (OGTT) and A1C measures.

RESULTS

The 933 participants had a mean age of 54.2 years, and 73% were women. A total of 425 (45.5%) subjects had impaired fasting glucose or impaired glucose tolerance, 145 (15.5%) had type 2 diabetes (by OGTT), and 83 (8.9%) had A1C ≥ 6.5%. The sensitivity and specificity of A1C ≥ 6.5% to define diabetes (by OGTT) was 40.0 and 96.8% and 68.9 and 95.3%, respectively (by fasting plasma glucose only). However, (64.8%) of Filipino and Japanese subjects with diabetes had isolated postchallenge hyperglycemia; AIC ≥ 6.5% sensitivity and specificity was 19.1 and 92.1%, respectively, to define isolated postchallenge hyperglycemia in the total sample.

CONCLUSIONS

A1C ≥ 6.5% had low sensitivity and may delay diagnosis of type 2 diabetes without OGTT. This limitation is exacerbated by isolated postchallenge hyperglycemia in Asian Americans.

New diagnostic criteria for diabetes: is the change from glucose to HbA1c possible in all populations?

AIM

Recently, a change of the diagnostic tool for diabetes from an oral glucose tolerance test (OGTT) to hemoglobin A1c (HbA1c) has been suggested. The aim of the study was to assess whether ethnicity modified the association between glucose levels and HbA1c and to compare diabetes prevalence according to diagnostic method among Greenland Inuit, Inuit migrants in Denmark, and a general Danish population.

METHODS

Data from two population-based surveys conducted from 1999-2002 were compared with a total of 7957 individuals, 1173 Inuit participants from the Greenland Population Study, including 256 Inuit migrants in Denmark, and 6784 Danish participants in the Inter99 study. The participants received a standard 75-g OGTT. HbA1c was analyzed by an ion-exchange HPLC Bio-Rad variant (Hercules, California). All analyses were performed in the laboratory at Steno Diabetes Centre.

RESULTS

The Inuit had significantly higher levels of HbA1c than the Danish participants at any given level of fasting and 2-h glucose and for each category of glucose tolerance: normal glucose tolerance, impaired fasting glycemia, and impaired glucose tolerance. The prevalence of diabetes diagnosed by OGTT was 11.2% among Inuit residents in Greenland, 9.8% among Inuit migrants, and 4.2% among Danes vs. 31.7% among Inuit residents in Greenland, 21.3% among Inuit migrants, and 6.7% among Danes diagnosed by HbA1c. OGTT-defined diabetes was associated with increased cardiovascular risk factors compared to HbA1c-defined diabetes.

CONCLUSION

The association between glucose and HbA1c is not the same in the two populations. The mechanism behind this difference is unknown, and studies on long-term consequences associated with HbA1c are needed.

Pitfalls in the use of HbA₁(c) as a diagnostic test: the ethnic conundrum

The purpose of a diagnostic test is to identify individuals who have a disorder and reassure those who do not. An HbA₁(c)-based diagnosis of diabetes mellitus or prediabetes fails to meet that purpose. Diabetes mellitus is a disorder of glucose, not HbA₁(c), metabolism. Microvascular complications in diabetes mellitus are driven by chronic hyperglycemia. The correlation of these complications with HbA₁(c) levels is convenient; however, unlike the direct information provided by glucose, HbA₁(c) values reflect glycemic and nonglycemic factors. The latter include modulators of glucose transport across the erythrocyte membrane, intracellular protein glycation and deglycation, erythrocyte turnover, systemic illness and hematological and medical disorders, among others. Genetic rather than glycemic factors explain most of the variance in HbA₁(c) levels. Finally, HbA₁(c) values are misleading as a measure of average blood glucose among persons of African, Asian, Hispanic and other non-European ancestry. Given the numerous pitfalls, the use of HbA₁(c) levels for diagnosing diabetes mellitus or prediabetes is ill-advised.

The potential impact and optimal cut-points of using glycated haemoglobin, HbA1c, to detect people with impaired glucose regulation in a UK multi-ethnic cohort

INTRODUCTION

Recommended diagnostic cut-points to detect impaired glucose regulation (IGR, also termed prediabetes: impaired fasting glucose and/or impaired glucose tolerance based on WHO 1999 criteria) are HbA1c 6.0-6.4% and 5.7-6.4% from an International Expert Committee and American Diabetes Association, respectively. We investigated the impact on prevalence/phenotype from using these criteria compared to IGR detected on oral glucose tolerance testing (OGTT) and determined optimal HbA1c cut-points for IGR in a multi-ethnic cohort.

METHODS

Analysis of 8696 participants in the LEADER study of primary care individuals aged 40-75 years without diabetes, in Leicestershire (UK) who underwent OGTT and had HbA1c measured.

RESULTS

Use of OGTT detected less people with IGR (n=1407, 16.2%) compared to HbA1c 6.0-6.4% (n=1610, 18.5%) and HbA1c 5.7-6.4%(n=3904, 44.9%), a 1.1- and 2.8-fold increase in prevalence, respectively. There were 930 (10.7%) and 534 (6.1%) people with IGR on OGTT not detected using HbA1c 6.0-6.4% and 5.7-6.4%, respectively. From ROC curve analysis, the optimal cut-point for detecting IGR in white Europeans was HbA1c>or=5.8%, sensitivity/specificity 61.5%/67.9%, but in south Asians HbA1c>or=6.0%, sensitivity/specificity 63.8%/69.4%.

CONCLUSION

Recommended HbA1c cut-points to detect IGR significantly increase numbers detected, however introduce a change in people identified. Using HbA1c 6.0-6.4% lacks sensitivity in white Europeans, but is a reasonable option in south Asians.

Screening for diabetes and pre-diabetes with proposed A1C-based diagnostic criteria

OBJECTIVE

An International Expert Committee (IEC) and the American Diabetes Association (ADA) proposed diagnostic criteria for diabetes and pre-diabetes based on A1C levels. We hypothesized that screening for diabetes and pre-diabetes with A1C measurements would differ from using oral glucose tolerance tests (OGTT).

RESEARCH DESIGN AND METHODS

We compared pre-diabetes, dysglycemia (diabetes or pre-diabetes), and diabetes identified by the proposed criteria (A1C ≥ 6.5% for diabetes and 6.0-6.4% [IEC] or 5.7-6.4% [ADA] for high risk/pre-diabetes) with standard OGTT diagnoses in three datasets. Non-Hispanic white or black adults without known diabetes who had A1C and 75-g OGTT measurements were included from the prospective Screening for Impaired Glucose Tolerance study (n = 1,581), and from the National Health and Nutrition Examination Survey (NHANES) III (n = 2014), and NHANES 2005-2006 (n = 1,111).

RESULTS

OGTTs revealed pre-diabetes in 35.8% and diabetes in 5.2% of combined study subjects. A1C provided receiver operating characteristic (ROC) curve areas for diabetes of 0.79-0.83, but ROC curve areas were ≤ 0.70 for dysglycemia or pre-diabetes. The proposed criteria missed 70% of individuals with diabetes, 71-84% with dysglycemia, and 82-94% with pre-diabetes. Compared with the IEC criteria, the ADA criteria for pre-diabetes resulted in fewer false-negative and more false-positive result. There were also racial differences, with false-positive results being more common in black subjects and false-negative results being more common in white subjects. With use of NHANES 2005-2006 data, ∼5.9 million non-Hispanic U.S. adults with unrecognized diabetes and 43-52 million with pre-diabetes would be missed by screening with A1C. CONCLUSIONS The proposed A1C diagnostic criteria are insensitive and racially discrepant for screening, missing most Americans with undiagnosed diabetes and pre-diabetes.

The impact of sickle cell trait on glycated haemoglobin in diabetes mellitus

AIMS

To determine the effect of sickle cell trait on measurement of glycated haemoglobin (HbA(1c)) in African American patients with diabetes mellitus.

METHODS

This is a retrospective study including 885 outpatients who underwent HbA(1c) testing. Medical record review and sickle cell trait determinations based on the HbA(1c) assay were performed in African American participants. The relationship between HbA(1c) and serum glucose measurements was analysed.

RESULTS

Data were obtained from 385 AA (109 with SCT, 22 with haemoglobin C trait and 254 without haemoglobinopathy) and 500 European American patients. In a model created through multivariate repeated-effects regression, the relationship between HbA(1c) and simultaneous serum glucose did not differ between African American subjects with and without the sickle cell trait, but differed between African American subjects without the sickle cell trait and European Americans (P = 0.0002).

CONCLUSIONS

Sickle cell trait does not impact the relationship between HbA(1c) and serum glucose concentration. In addition, it does not appear to account for ethnic difference in this relationship between African Americans and whites.

A1C between 5.7 and 6.4% as a marker for identifying pre-diabetes, insulin sensitivity and secretion, and cardiovascular risk factors: the Insulin Resistance Atherosclerosis Study (IRAS)

OBJECTIVE

A1C is an optional method for diagnosing diabetes and also for detecting individuals at increased risk of the disease. However, how A1C compares with fasting (FPG) and 2-h plasma glucose for detecting at-risk individuals is not well known.

RESEARCH DESIGN AND METHODS

A 2-h glucose tolerance test, frequently sampled intravenous glucose tolerance test, and A1C were obtained at the follow-up examination in 855 participants in the Insulin Resistance Atherosclerosis Study (IRAS). For this report, 385 individuals were at increased risk of diabetes as defined by A1C between 5.7 and 6.4%, impaired glucose tolerance (IGT), and/or impaired fasting glucose (IFG).

RESULTS

IFG and IGT identified 69.1 and 59.5% of all individuals at increased risk of diabetes, respectively. A1C 5.7-6.4% detected 23.6% of all at-risk individuals, although more African Americans (31.4%) and Hispanics (35.2%) than non-Hispanic whites (9.9%). Relative to A1C, FPG was more strongly related to fasting insulin (r = 0.38 vs. 0.26; P < 0.01), acute insulin response (r = - 0.20 vs. - 0.09; P < 0.01), and waist circumference (r = 0.43 vs. 0.25; P < 0.001) by the Spearman correlation test. Similarly, 2-h plasma glucose was more strongly related to Si (r = - 0.40 vs. - 0.27; P < 0.01) and triglycerides (r = 0.30 vs. 0.08; P < 0.001).

CONCLUSIONS

A1C 5.7-6.4% is less sensitive for detecting at-risk individuals than IFG and IGT, particularly among non-Hispanic whites. Single determinations of FPG and 2-h plasma glucose seem to be more precise correlates of insulin resistance and secretion than A1C and, in general, better for other metabolic disorders.

Cardiovascular risk factors in ethnic populations within Canada: results from national cross-sectional surveys

BACKGROUND

Differences in the prevalence of cardiovascular disease and associated risk factors have been noted across ethnic groups both within and between countries. The Canadian population is becoming increasingly diverse because of immigration. Understanding ethnic differences in cardiovascular risk factors is critically important in planning appropriate prevention strategies for the country's rapidly changing population. We sought to examine the prevalence of cardiovascular risk factors in various Canadian ethnic groups.

METHODS

We analyzed 3 cross-sectional cycles (for 2000, 2003 and 2005) of the Canadian Community Health Survey of people aged 12 years and older. The surveys were conducted by means of self-reported questionnaires. We used stratified analysis to evaluate the relation between risk factors and ethnicity. The effect of participants' ethnicity on the prevalence of risk factors was estimated by means of logistic regression, with adjustment for differences in age, sex, marital status, education, household income, language spoken, immigration status, residency type (urban or rural), household size, region (province or territory) and chronic diseases (heart disease, stroke, cancer, bronchitis, chronic obstructive pulmonary disease, bowel disease, arthritis, epilepsy, ulcers, thyroid disease and diabetes mellitus).

RESULTS

We included 371 154 individuals in the analysis. Compared with white people, people from visible minorities (i.e., neither white nor Aboriginal) had a lower prevalence of diabetes mellitus (4.5% v. 4.0%), hypertension (14.7% v. 10.8%), smoking (20.4% v. 9.7%) and obesity (defined as body mass index ≥ 30; 14.8% v. 9.7%) but a higher prevalence of physical inactivity (50.3% v. 58.1%). More specifically, after adjustment for sociodemographic characteristics, people from most visible minorities, in comparison with the white population, were less likely to smoke; were more likely to be physically inactive, with the exception of people of Korean, Japanese and Latin ethnicity; and were less likely to be obese, with the exception of people of black, Latin, Arab or West Asian ethnicity. However, relative to white people, hypertension was more prevalent among those of Filipino or South East Asian background (odds ratio [OR] 1.54, 95% confidence interval [CI] 1.23-1.93) and those of black ancestry (OR 1.69, 95% CI 1.43-2.00).

INTERPRETATION

Cardiovascular risk factors vary dramatically by ethnic group. Health professionals should increase their promotion of physical activity among visible minorities and should prioritize the detection and control of diabetes and hypertension during routine contact with patients of visible minorities, particularly those of South Asian, Filipino and black ethnicity.

Hypertension and diabetes prevalence among U.S. Hispanics by country of origin: the National Health Interview Survey 2000-2005

BACKGROUND

Despite their diverse cultural origins, Hispanics in the US are generally studied as a single ethnic group.

OBJECTIVES

1) Assess demographic and disease-related differences among U.S. Hispanics by country of origin, and 2) Examine the mediating roles of socioeconomic status and acculturation on disease prevalence in these subgroups.

DESIGN AND PARTICIPANTS

Using data from the 2000-2005 National Health Interview Survey (NHIS), we compared characteristics of Mexican-Americans with Hispanics originally from: Mexico, Puerto Rico, Central/South America, Cuba, and Dominican Republic (n = 31,240). We stratified the analysis by foreign versus US-born Hispanic subgroups and modeled hypertension and diabetes prevalence, adjusting for demographic and acculturation differences.

MAIN RESULTS

The six Hispanic subgroups were significantly diverse in all measured variables. Prevalence of hypertension (32%) and diabetes (15%) was highest in foreign-born Puerto Ricans. After adjusting for age, BMI, smoking, socioeconomic status and acculturation in foreign-born Hispanics, Puerto Ricans (OR = 1.76 [95% CI: 1.23, 2.50], p = 0.002) and Dominicans (OR = 1.93 [1.24, 3.00], p = 0.004), had higher prevalence of hypertension relative to Mexican-Americans. Adjusted diabetes prevalence among foreign-born Hispanics was half or less in Cubans (OR = 0.42 [0.25, 0.68] p < 0.001), Dominicans (OR = 0.48 [0.26, 0.91], p = 0.02) and Central/South Americans (OR = 0.51 [0.33, 0.78], p = 0.002) relative to Mexican-Americans. Among US-born Hispanic subgroups, Cubans had lower hypertension (OR = 0.53, [0.33, 0.83], p = 0.006) and Mexicans (OR = 0.76 [0.60, 0.98], p = 0.03) had lower diabetes prevalence compared to Mexican-Americans in adjusted models.

CONCLUSIONS

The prevalence of hypertension and diabetes varies significantly among Hispanics by country of origin. Health disparities research should include representation from all Hispanic subgroups.

The potential impact of using glycated haemoglobin as the preferred diagnostic tool for detecting Type 2 diabetes mellitus

AIMS

There are calls to simplify the diagnosis of Type 2 diabetes mellitus (T2DM) to reduce the burden of undiagnosed disease. Glycated haemoglobin (HbA(1c)) is therefore being considered as a preferred diagnostic tool to replace the need for an oral glucose tolerance test (OGTT), considered by many as cumbersome and inconvenient. The aim of this study was to examine the potential impact of the preferred use of HbA(1c) as a diagnostic tool on the prevalence and phenotype of T2DM.

METHODS

Analysis of the Leicester Ethnic Atherosclerosis and Diabetes Risk (LEADER) cohort for previously undiagnosed individuals between 40 and 75 years of age who had OGTT, repeated if within the diabetes range, and HbA(1c) results. We compared the prevalence and phenotype of subjects with T2DM based on either HbA(1c)> or =6.5% or OGTT using 1999 World Health Organization criteria.

RESULTS

From the total population of 8696, we detected 291 (3.3%) with T2DM from using an OGTT, and 502 (5.8%) had HbA(1c)> or =6.5%. Of those diagnosed with T2DM by OGTT, 93 (1.2%) had HbA(1c) <6.5% and therefore would not have been classified as having T2DM using proposed criteria. Using HbA(1c) criteria resulted in 304 (3.5%) additional cases of T2DM, approximately doubling the prevalence. Of these 304 additional people, 172 (56.7%) had impaired glucose tolerance/impaired fasting glycaemia according to 1999 World Health Organization criteria. Using HbA(1c) criteria there was an increase of 2.2- and 1.4-fold in south Asians and white Europeans detected, respectively.

CONCLUSIONS

Within this multi-ethnic cohort, we found that introducing HbA(1c)> or =6.5% as the preferred diagnostic test to diagnose T2DM significantly increased numbers detected with T2DM; however, some people were no longer detected as having T2DM.

Utility of glycated hemoglobin in diagnosing type 2 diabetes mellitus: a community-based study

CONTEXT

Although glycated hemoglobin (HbA1c) has recently been incorporated as a diagnostic test by the American Diabetes Association, its validity needs to be established in Asian Indians in a community setting.

OBJECTIVE

The objective of the study was to assess the validity of HbA1c as a screening and diagnostic test in individuals with newly detected diabetes mellitus.

DESIGN AND SETTING

Community based randomized cross sectional study in urban Chandigarh, a city in north India, from April 2008 to August 2009.

SUBJECTS

Subjects included 1972 subjects aged 20 yr or older.

INTERVENTION

Intervention included an oral glucose tolerance test and glycated hemoglobin in all the subjects.

MAIN OUTCOME MEASURES

Utility of HbA1c as a diagnostic method in newly detected diabetes mellitus subjects was evaluated.

RESULTS

Using World Health Organization criteria for diagnosis of diabetes mellitus, 134 (6.7%) had newly detected diabetes mellitus, 192 (9.7%) known diabetes mellitus, 329 (16.6%) prediabetes, and 1317 (69.4%) were normal of 1972 people screened. Using only the ADA criteria, 38% people were underdiagnosed. An HbA1c level of 6.1% had an optimal sensitivity and specificity of 81% for diagnosing diabetes. A HbA1c level of 6.5% (+/-2 SD) and 7% (+/-2.7 SD) had sensitivity and specificity of 65 and 88% and 42 and 92%, respectively, with corresponding positive predictive value and negative predictive value of 75.2 and 96.5% and 90.4 and 94.4%, respectively, for diagnosis of newly detected diabetes mellitus.

CONCLUSION

A HbA1c cut point of 6.1% has an optimal sensitivity and specificity of 81% and can be used as a screening test, and a cut point of 6.5% has optimal specificity of 88% for diagnosis of diabetes.

Glycated haemoglobin A1c for diagnosing diabetes in Chinese population: cross sectional epidemiological survey

OBJECTIVES

To evaluate haemoglobin A1c (HbA(1c)) in diagnosing diabetes and identify the optimal HbA(1c) threshold to be used in Chinese adults.

DESIGN

Multistage stratified cross sectional epidemiological survey.

SETTING

Shanghai, China, 2007-8.

PARTICIPANTS

4886 Chinese adults over 20 years of age with no history of diabetes.

MAIN OUTCOME MEASURES

Performance of HbA(1c) at increasing thresholds for diagnosing diabetes.

RESULTS

The area under the receiver operating characteristics curve for detecting undiagnosed diabetes was 0.856 (95% confidence interval 0.828 to 0.883) for HbA(1c) alone and 0.920 (0.900 to 0.941) for fasting plasma glucose alone. Very high specificity (96.1%, 95% confidence interval 95.5% to 96.7%) was achieved at an HbA(1c) threshold of 6.3% (2 SD above the normal mean). Moreover, the corresponding sensitivity was 62.8% (57.1% to 68.3%), which was equivalent to that of a fasting plasma glucose threshold of 7.0 mmol/l (57.5%, 51.7% to 63.1%) in detecting undiagnosed diabetes. In participants at high risk of diabetes, the HbA(1c) threshold of 6.3% showed significantly higher sensitivity (66.9%, 61.0% to 72.5%) than both fasting plasma glucose >or=7.0 mmol/l (54.4%, 48.3% to 60.4%) and HbA(1c) >or=6.5% (53.7%, 47.6% to 59.7%) (P<0.01).

CONCLUSIONS

An HbA(1c) threshold of 6.3% was highly specific for detecting undiagnosed diabetes in Chinese adults and had sensitivity similar to that of using a fasting plasma glucose threshold of 7.0 mmol/l. This optimal HbA(1c) threshold may be suitable as a diagnostic criterion for diabetes in Chinese adults when fasting plasma glucose and oral glucose tolerance tests are not available.

Racial disparity in A1C independent of mean blood glucose in children with type 1 diabetes

OBJECTIVE

Mean blood glucose (MBG) and MBG-independent factors both influence A1C levels. Race was related to A1C independent of MBG in adults. The goal of this study was to determine if racial disparity exists in A1C independent of MBG in children with diabetes.

RESEARCH DESIGN AND METHODS

Participants included 276 children with type 1 diabetes. A1C and MBG were obtained from multiple clinic visits, and a hemoglobin glycation index (HGI) (an assessment of A1C levels independent of MBG) was calculated. A1C and HGI were analyzed controlling for age, diabetes duration, and MBG. RESULTS African Americans had statistically significantly higher A1C (9.1 +/- 0.1) and HGI (0.64 +/- 0.11) than Caucasians (A1C 8.3 +/- 0.1, HGI -0.15 +/- 0.07) independent of covariates.

CONCLUSIONS

Because of racial disparity in A1C, which is independent of MBG, we recommend that A1C and MBG be used together to make therapeutic decisions for children with diabetes.