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

Efficacy and safety of biphasic insulin aspart 70/30 in type 2 diabetes patients of different race or ethnicity (INITIATEplus trial)

OBJECTIVE

To determine if self-titration using biphasic insulin aspart 70/30 (BIAsp 30) had a different impact on efficacy and safety across different racial/ethnic subgroups.

RESEARCH DESIGN/METHODS

This was an exploratory, post hoc analysis by race (White vs. Black/African-American) and ethnicity (Hispanic/Latino vs. non-Hispanic/Latino) of data from the INITIATEplus trial. Participants were treated twice-daily with BIAsp 30 over 24 weeks.

TRIAL REGISTRATION

NCT00101751.

MAIN OUTCOME MEASURES

Efficacy endpoints included reductions in mean glycated hemoglobin (A1C) and fasting plasma glucose (FPG). Safety endpoints included hypoglycemia rates (events/patient-year) and adverse events. Body weight changes were also measured.

RESULTS

Glycemic control improved by a similar extent for all demographic groups. Observed mean decreases in A1C ranged from 2.4% to 2.6% after 24 weeks' treatment. Baseline-adjusted mean A1C decreases for White vs. Black/African-American subjects were 2.56% and 2.13% (p < 0.0001), and for Hispanic/Latino vs. non-Hispanic/Latino subjects were 2.45% and 2.42% (p = 0.677), respectively. Final FPG values were similar among all groups (141-146 mg/dL [7.83-8.10 m mol/L]), and baseline-adjusted FPG decreases were not significantly different (p > 0.025) between groups. Hypoglycemia was low for White, Black/African-American, Hispanic/Latino, and non-Hispanic/Latino subjects (0.08, 0.04, 0.03, and 0.07 major events/patient-year, with 0.60, 0.30, 0.37, and 0.52 minor events/patient-year, respectively). Body weight increases were 3.17 and 3.06 kg (White vs. African-American) and 2.69 and 3.19 kg (Hispanic/Latino vs. non-Hispanic/Latino). Final weight-adjusted total daily insulin doses were 0.60 U/kg for Black/African-American subjects vs. 0.78 U/kg for White subjects (p < 0.0001), and 0.71 U/kg for Hispanic/Latino subjects vs. 0.74 U/kg for non-Hispanic/Latino subjects (p = 0.42).

LIMITATIONS

The trial was not designed or powered for comparisons across racial or ethnic groups, subjects were not stratified for pre-baseline medication regimens between each race and ethnic group, and unequal subject numbers and baseline A1C disparities existed between the pairs of groups being compared.

CONCLUSIONS

Diabetes self-management with BIAsp 30 using an easily followed self-titration algorithm produced low hypoglycemia rates. All subgroups achieved A1C reductions >2.1% and FPG declines >82 mg/dL that were similar across groups, demonstrating that self-titration of BIAsp 30 can successfully be pursued in a primary care setting by patients who had previously failed to meet ADA A1C targets under oral antidiabetes therapy, with race or ethnicity not an obstacle to achieving better glycemic control.

Ethnicity modifies the relation between fasting plasma glucose and HbA1c in Indians, Malays and Chinese

AIMS

To study whether HbA(1c) , and its relationship with fasting plasma glucose, was significantly different among Chinese, Malays and Indians in Singapore.

METHODS

A sample of 3895 individuals without known diabetes underwent detailed interview and health examination, including anthropometric and biochemical evaluation, between 2004 and 2007. Pearson's correlation, analysis of variance and multiple linear regression analyses were used to examine the influence of ethnicity on HbA(1c) .

RESULTS

As fasting plasma glucose increased, HbA(1c) increased more in Malays and Indians compared with Chinese after adjustment for age, gender, waist circumference, serum cholesterol, serum triglyceride and homeostasis model assessment of insulin resistance (P-interaction < 0.001). This translates to an HbA(1c) difference of 1.1 mmol/mol (0.1%, Indians vs. Chinese), and 0.9 mmol/mol (0.08%, Malays vs. Chinese) at fasting plasma glucose 5.6 mmol/l (the American Diabetes Association criterion for impaired fasting glycaemia); and 2.1 mmol/mol (0.19%, Indians vs. Chinese) and 2.6 mmol/mol (0.24%, Malays vs. Chinese) at fasting plasma glucose 7.0 mmol/l, the diagnostic criterion for diabetes mellitus.

CONCLUSIONS

Using HbA(1c) in place of fasting plasma glucose will reclassify different proportions of the population in different ethnic groups. This may have implications in interpretation of HbA(1c) results across ethnic groups and the use of HbA(1c) for diagnosing diabetes mellitus.

HbA1c and glucose intolerance in obese children and adolescents

AIMS

Childhood obesity is associated with an increased likelihood for having impaired glucose tolerance, dyslipidaemia and diabetes. The aim of the study was to evaluate HbA(1c) as a screening test for impaired glucose tolerance in obese children and adolescents and identify the optimal HbA(1c) threshold.

METHODS

We studied 126 obese and overweight children (BMI > 85 th percentile for age and gender) 4-17 years of age referred to the endocrine clinic at Ajou University Hospital in Korea. All subjects underwent HbA(1c) and oral glucose tolerance test.

RESULTS

Thirty-four patients (27%) out of 126 had impaired glucose tolerance. Silent diabetes was diagnosed in 10 adolescents (7.9%). Based on the receiver operating characteristic curve, the optimal cut point of HbA(1c) related to impaired glucose tolerance diagnosed by oral glucose tolerance test was 40 mmol/mol (5.8%), which was associated with a 64.7% sensitivity and 61.6% specificity, with an area under the receiver operating characteristic curve of 0.651 (95% CI 0.529-0.772).

CONCLUSIONS

Obesity is associated with an increased risk of impaired glucose tolerance. An HbA(1c) value of 40 mmol/mol (5.8%) should be used as a screening tool to identify children and adolescents with impaired glucose tolerance.

[The value of hemoglobin A1c for diagnosis of diabetes mellitus and other changes in carbohydrate metabolism in women with recent gestational diabetes mellitus]

INTRODUCTION

Women with gestational diabetes mellitus (GDM) have an increased risk for developing diabetes mellitus (DM). Their postpartum metabolic classification using a 75g oral glucose tolerance test (75g OGTT) is recommended. The purpose of this study was to assess the value of hemoglobin A1c for postpartum evaluation in women with recent gestational diabetes mellitus.

PATIENTS AND METHODS

Fifty-six women with recent GDM underwent a 75g OGTT at our center to assess postpartum changes in carbohydrate metabolism and were classified using diagnostic criteria of the American Diabetes Association (ADA). Receiver operating characteristic (ROC) curves analysis was used to assess the diagnostic performance of hemoglobin A1c, and kappa index was used to evaluate diagnostic agreement between hemoglobin A1c and 75g OGTT.

RESULTS

DM was diagnosed in 7 women, and other categories of increased risk for DM in 25 women. Kappa index for diagnosis agreement was 0,22. Hemoglobin A1c ≥ 5.7% had 47% sensitivity and 71% specificity for identifying any change in carbohydrate metabolism. A hemoglobin A1c value ≥ 6.5 had 29% sensitivity and 100% specificity for diagnosis of DM. Area under the ROC curve was 0.57 for identifying any change in carbohydrate metabolism and 0.81 for diagnosis of DM.

CONCLUSION

Using ADA cutoff values, hemoglobin A1c is not appropriate for postpartum glucose tolerance evaluation in women with recent gestational diabetes mellitus.

Cardiometabolic risk profiles and carotid atherosclerosis in individuals with prediabetes identified by fasting glucose, postchallenge glucose, and hemoglobin A1c criteria

OBJECTIVE

We evaluated whether cardiometabolic risk profiles differ for subjects identified as having prediabetes by A1C, fasting glucose (FPG), or 2-h postchallenge glucose (2-PG) criteria.

RESEARCH DESIGN AND METHODS

Atherosclerosis risk factors, oral glucose tolerance test, and ultrasound measurement of carotid intima-media thickness (IMT) were analyzed in 780 nondiabetic individuals.

RESULTS

Poor agreement existed for A1C and FPG criteria for identification of subjects with prediabetes (κ coefficient = 0.332). No differences in cardiometabolic risk profiles were observed among the three groups of individuals with prediabetes by A1C only, FPG only, and both A1C and FPG. Poor agreement also existed for A1C and 2-PG criteria for identification of individuals with prediabetes (κ coefficient = 0.299). No significant differences in cardiometabolic risk factors were observed between IGT-only and individuals with prediabetes by A1C and 2-PG. Compared with subjects with prediabetes identified by A1C only, IGT-only individuals exhibited a worse cardiometabolic risk profile, with significantly higher systolic blood pressure, pulse pressure, 2-h postchallenge insulin, triglycerides, high-sensitivity C-reactive protein, and carotid IMT, and lower HDL cholesterol levels and insulin sensitivity.

CONCLUSIONS

These results suggest that considerable discordance between A1C, FPG, and 2-PG exists for the identification of individuals with prediabetes and that the cardiometabolic risk profile of these individuals varies by metabolic parameter, with 2-PG showing the stronger association with cardiometabolic risk factors and subclinical atherosclerosis than FPG or A1C.

Race-ethnic differences in the association of genetic loci with HbA1c levels and mortality in U.S. adults: the third National Health and Nutrition Examination Survey (NHANES III)

Background

Hemoglobin A_1c (HbA_1c) levels diagnose diabetes, predict mortality and are associated with ten single nucleotide polymorphisms (SNPs) in white individuals. Genetic associations in other race groups are not known. We tested the hypotheses that there is race-ethnic variation in 1) HbA_1c-associated risk allele frequencies (RAFs) for SNPs near SPTA1, HFE, ANK1, HK1, ATP11A, FN3K, TMPRSS6, G6PC2, GCK, MTNR1B; 2) association of SNPs with HbA_1c and 3) association of SNPs with mortality.

Methods

We studied 3,041 non-diabetic individuals in the NHANES (National Health and Nutrition Examination Survey) III. We stratified the analysis by race/ethnicity (NHW: non-Hispanic white; NHB: non-Hispanic black; MA: Mexican American) to calculate RAF, calculated a genotype score by adding risk SNPs, and tested associations with SNPs and the genotype score using an additive genetic model, with type 1 error = 0.05.

Results

RAFs varied widely and at six loci race-ethnic differences in RAF were significant (p < 0.0002), with NHB usually the most divergent. For instance, at ATP11A, the SNP RAF was 54% in NHB, 18% in MA and 14% in NHW (p < .0001). The mean genotype score differed by race-ethnicity (NHW: 10.4, NHB: 11.0, MA: 10.7, p < .0001), and was associated with increase in HbA_1c in NHW (β = 0.012 HbA_1c increase per risk allele, p = 0.04) and MA (β = 0.021, p = 0.005) but not NHB (β = 0.007, p = 0.39). The genotype score was not associated with mortality in any group (NHW: OR (per risk allele increase in mortality) = 1.07, p = 0.09; NHB: OR = 1.04, p = 0.39; MA: OR = 1.03, p = 0.71).

Conclusion

At many HbA_1c loci in NHANES III there is substantial RAF race-ethnic heterogeneity. The combined impact of common HbA_1c-associated variants on HbA_1c levels varied by race-ethnicity, but did not influence mortality.

Hemoglobin A1c and postpartum abnormal glucose tolerance among women with gestational diabetes mellitus

OBJECTIVE

To analyze the association of hemoglobin A1c (HbA1c) at gestational diabetes mellitus (GDM) diagnosis with postpartum abnormal glucose in a cohort of women with GDM.

METHODS

Women with singleton pregnancies treated for GDM at a large diabetes and pregnancy program located in Charlotte, North Carolina, who completed a postpartum 2-hour oral glucose tolerance test were eligible for inclusion in this retrospective cohort study. Clinical information, including maternal HbA1c at diagnosis, was abstracted from medical records. A parametric survival model was used to assess the association of HbA1c at GDM diagnosis with postpartum maternal abnormal glucose including impaired fasting glucose, impaired glucose tolerance, and any postpartum abnormal glucose.

RESULTS

Of the 277 postpartum women with GDM, 75 (32%) had impaired fasting glucose, 61 (28%) had impaired glucose tolerance, and 15 (9%) were diagnosed with type 2 diabetes mellitus after delivery. After adjustment for clinic, maternal age, parity, prepregnancy body mass index 25 or higher, nonwhite race or ethnicity, and gestational week at first HbA1c, we detected a trend of increased risk for impaired fasting glucose (P=.01), impaired glucose tolerance (P=.002), and any glucose abnormality (P<.001) associated with increased quartile of HbA1c at GDM diagnosis.

CONCLUSION

Hemoglobin A1c measured at GDM diagnosis may be a useful tool for identifying patients with GDM at highest risk of developing postpartum abnormal glucose.

Racial and ethnic differences in the relationship between HbA1c and blood glucose: implications for the diagnosis of diabetes

Hemoglobin A1c (HbA1c) is widely used as an index of mean glycemia in diabetes, as a measure of risk for the development of diabetic complications, and as a measure of the quality of diabetes care. In 2010, the American Diabetes Association recommended that HbA1c tests, performed in a laboratory using a method certified by the National Glycohemoglobin Standardization Program, be used for the diagnosis of diabetes. Although HbA1c has a number of advantages compared to traditional glucose criteria, it has a number of disadvantages. Hemoglobinopathies, thalassemia syndromes, factors that impact red blood cell survival and red blood cell age, uremia, hyperbilirubinemia, and iron deficiency may alter HbA1c test results as a measure of average glycemia. Recently, racial and ethnic differences in the relationship between HbA1c and blood glucose have also been described. Although the reasons for racial and ethnic differences remain unknown, factors such as differences in red cell survival, extracellular-intracellular glucose balance, and nonglycemic genetic determinants of hemoglobin glycation are being explored as contributors. Until the reasons for these differences are more clearly defined, reliance on HbA1c as the sole, or even preferred, criterion for the diagnosis of diabetes creates the potential for systematic error and misclassification. HbA1c must be used thoughtfully and in combination with traditional glucose criteria when screening for and diagnosing diabetes.

Impact of HbA1c Criterion on the Detection of Subjects with Increased Risk for Diabetes among Health Check-Up Recipients in Korea

BACKGROUND

We performed the study to examine the impact of hemoglobin A1c (HbA1c) criterion on the screening of increased risk for diabetes among health check-up subjects in Korea.

METHODS

We retrospectively analyzed clinical and laboratory data of 37,754 Korean adults (age, 20 to 89 years; 41% women) which were measured during regular health check-ups. After excluding subjects with previously diagnosed diabetes mellitus (n=1,812) and with overt anemia (n=318), 35,624 subjects (21,201 men and 14,423 women) were included in the analysis.

RESULTS

Among the 35,624 subjects, 11,316 (31.8%) subjects were categorized as increased risk for diabetes (IRD) by fasting plasma glucose (FPG) criteria, 6,531 (18.1%) subjects by HbA1c criteria, and 13,556 (38.1%) subjects by combined criteria. Therefore, although HbA1c criteria alone identifies 42% [(11,316-6,531)/11,316] fewer subjects with IRD than does FPG criteria, about 20% [(13,556-11,316)/11,316] more subjects could be detected by including new HbA1c criteria in addition to FPG criteria. Among the 13,556 subjects with IRD, 7,025 (51.8%) met FPG criteria only, 2,240 (16.5%) met HbA1c criteria only, and 4,291 (31.7%) met both criteria. Among subjects with impaired fasting glucose, 65% were normal, 32% were IRD, and 3% were diabetes by HbA1c criterion. In receiver operating characteristic curve analysis, cutoff point of HbA1c with optimal sensitivity and specificity for identifying IRD was 5.4%.

CONCLUSION

Although HbA1c criteria alone identifies fewer subjects with IRD than does FPG criteria, about 20% more could be detected by addition of HbA1c criteria. Further studies are needed to define optimal cutoff point of HbA1c and to establish screening and management guidelines for IRD.

Biomarkers in diabetes: hemoglobin A1c, vascular and tissue markers

Biomarkers are conventionally defined as "biological molecules that represent health and disease states." They typically are measured in readily available body fluids (blood or urine), lie outside the causal pathway, are able to detect subclinical disease, and are used to monitor clinical and subclinical disease burden and response to treatments. Biomarkers can be "direct" endpoints of the disease itself, or "indirect" or surrogate endpoints. New technologies (such as metabolomics, proteomics, genomics) bring a wealth of opportunity to develop new biomarkers. Other new technologies enable the development of nonmolecular, functional, or biophysical tissue-based biomarkers. Diabetes mellitus is a complex disease affecting almost every tissue and organ system, with metabolic ramifications extending far beyond impaired glucose metabolism. Biomarkers may reflect the presence and severity of hyperglycemia (ie, diabetes itself) or the presence and severity of the vascular complications of diabetes. Illustrative examples are considered in this brief review. In blood, hemoglobin A1c (HbA1c) may be considered as a biomarker for the presence and severity of hyperglycemia, implying diabetes or prediabetes, or, over time, as a "biomarker for a risk factor," ie, hyperglycemia as a risk factor for diabetic retinopathy, nephropathy, and other vascular complications of diabetes. In tissues, glycation and oxidative stress resulting from hyperglycemia and dyslipidemia lead to widespread modification of biomolecules by advanced glycation end products (AGEs). Some of these altered species may serve as biomarkers, whereas others may lie in the causal pathway for vascular damage. New noninvasive technologies can detect tissue damage mediated by AGE formation: these include indirect measures such as pulse wave analysis (a marker of vascular dysfunction) and more direct markers such as skin autofluorescence (a marker of long-term accumulation of AGEs). In the future, we can be optimistic that new blood and tissue-based biomarkers will enable the detection, prevention, and treatment of diabetes and its complications long before overt disease develops.

Diabetes mellitus in centenarians

OBJECTIVES

To describe the prevalence of diabetes mellitus (DM) in centenarians.

DESIGN

Cross-sectional, population-based.

SETTING

Forty-four counties in northern Georgia.

PARTICIPANTS

Two hundred forty-four centenarians (aged 98-108, 15.8% male, 20.5% African American, 38.0% community dwelling) from the Georgia Centenarian Study (2001-2009).

MEASUREMENTS

Nonfasting blood samples assessed glycosylated hemoglobin (HbA(1c)) and relevant clinical parameters. Demographic, diagnosis, and DM complication covariates were assessed.

RESULTS

12.5% of centenarians were known to have DM. DM was more prevalent in African Americans (27.7%) than whites (8.6%, P < .001). There were no differences between men (16.7%) and women (11.7%, P = .41) or between centenarians living in the community (10.2%) and in facilities (13.9%, P = .54). DM was more prevalent in overweight and obese (23.1%) than nonoverweight (7.1%, P = .002) centenarians. Anemia (78.6% vs 48.3%, P = .004) and hypertension (79.3% vs 58.6%, P = .04) were more prevalent in centenarians with DM than in those without, and centenarians with DM took more nonhypoglycemic medications (8.6 vs 7.0, P = .02). No centenarians with HbA(1c) of less than 6.5% had random serum glucose levels greater than 200 mg/dL. DM was not associated with 12-month all-cause mortality, visual impairment, amputations, cardiovascular disease, or neuropathy. Thirty-seven percent of centenarians reported onset before age 80 (survivors), 47% between age 80 and 97 (delayers), and 15% aged 98 and older (escapers).

CONCLUSION

Diabetes mellitus is a risk factor for cardiovascular disease and mortality but is seen in persons who live into very old age. Aside from higher rates of anemia and use of more medications, few clinical correlates of DM were observed in centenarians.

Validity of glycated hemoglobin in screening and diagnosing type 2 diabetes mellitus in Chinese subjects

BACKGROUND/AIMS

The application of glycated hemoglobin (HbA(1c)) for the diagnosis of diabetes is currently under extensive discussion. In this study, we explored the validity of using HbA(1c) as a screening and diagnostic test in Chinese subjects recruited in Nanjing, China.

METHODS

In total, 497 subjects (361 men and 136 women) with fasting plasma glucose (PG) ≥ 5.6 mmol/L were recruited to undergo the oral glucose tolerance test (OGTT) and HbA(1c) test. Plasma lipid, uric acid, and blood pressure were also measured.

RESULTS

Using a receiver operating characteristic curve, the optimal cutoff point of HbA(1c) related to diabetes diagnosed by the OGTT was 6.3%, with a sensitivity and specificity of 79.6% and 82.2%, respectively, and the area under the curve was 0.87 (95% confidence interval, 0.83 to 0.92). A HbA(1c) level of 6.5% had a sensitivity and specificity of 62.7% and 93.5%, respectively. When comparing the HbA(1c) ≥ 6.5% or OGTT methods for diagnosing diabetes, the former group had significantly higher HbA(1c) levels and lower levels of fasting and 2-hour PG than the latter group. No significant difference was observed in the other metabolism indexes between the two groups.

CONCLUSIONS

Our results suggest that HbA(1c) ≥ 6.5% has reasonably good specificity for diagnosing diabetes in Chinese subjects, which is in concordance with the American Diabetes Association recommendations.

A Single A1C >= 6.5% Accurately Identifies Type 2 Diabetes/Impaired Glucose Tolerance in African Americans

OBJECTIVE

In 2010, the American Diabetes Association revised its criteria for the diagnosis of diabetes to include A1C ≥ 6.5%; however, this has remained controversial, particularly for African Americans. The objective of this pilot study was to examine the usefulness of a single A1C determination in comparison with a same day 2-hour oral glucose tolerance test to diagnose type 2 diabetes in African Americans.

METHODS

In sum, 195 oral glucose tolerance tests and A1Cs were obtained on the same day from 77 overweight and obese African American women and 6 men over a period of 15 months.

RESULTS

A1C ≥ 6.5% was present in 31 of 195 patients, with 15 of these having type 2 diabetes by oral glucose tolerance test, another 12 having impaired glucose tolerance, and 4 having normal glucose tolerance. This gives a sensitivity of 50% and a specificity of 90%, with a positive predictive value of 48% and a negative predictive value of 91%. A1C ≤ 5.6%, proposed by the American Diabetes Association to indicate normal glucose tolerance, was present in only 28 patients, 10 (35.7%) of whom had normal glucose tolerance, whereas 18 (64.3%) had either impaired glucose tolerance (15 patients) or type 2 diabetes (3 patients). Fasting plasma glucose ≥ 126 mg/dL was present in 5 of 29 patients with type 2 diabetes (sensitivity, 17.2%; specificity, 100%).

CONCLUSIONS

First, A1C ≥ 6.5% was a good "rule in" value to identify impaired glucose tolerance and type 2 diabetes (ie, patients at high risk for micro- and macrovascular complications). Second, A1C ≤ 5.6% did not rule out impaired glucose tolerance or type 2 diabetes. Last, fasting plasma glucose ≥ 126 mg/dL detected less than 1 in 5 cases with type 2 diabetes.

Impact of introducing HbA1c into the diagnostic criteria on prevalence and cardiovascular risk profiles of individuals with newly diagnosed diabetes in Japan: the Toranomon Hospital Health Management Center Study 2 (TOPICS 2)

OBJECTIVE

To evaluate the impact of HbA1c for diagnosis of diabetes and investigate whether cardiovascular risks profiles differ among individuals with diabetes diagnosed by HbA1c or fasting plasma glucose (FPG).

METHODS

This cross-sectional study involved 26,884 participants (30.6% women; aged 20-91 years) without known diabetes. Subjects were categorized into 4 groups according to the presence or absence of FPG ≥7.0 mmol/L and/or HbA1c ≥6.5%, which were American Diabetes Association criteria. Oral glucose tolerance test data were not available.

RESULTS

Prevalence of undiagnosed diabetes was 3.6%. Of those individuals, 47.5% fulfilled both two criteria and 26.0% fulfilled only HbA1c criterion. Individuals with diabetes according to FPG ≥7.0 mmol/L alone were characterized as having poorly controlled hypertension while those with HbA1c ≥6.5% alone were characterized as older, female, and having lower blood pressure and γ-glutamyltransferase values. Persons with newly diagnosed diabetes by HbA1c had low HDL cholesterol and high LDL or non-HDL cholesterol levels.

CONCLUSIONS

Introducing HbA1c into the diagnosis allowed detection of many previously undiagnosed cases of diabetes in Japanese individuals. Those diagnosed by FPG were characterized by hypertension and those diagnosed by HbA1c had unfavorable lipid profiles, reflecting an atherosclerotic trait.

Role of HbA1c in the Screening of Diabetes Mellitus in a Korean Rural Community

BACKGROUND

Recently, the measurement of glycated hemoglobin (HbA1c) was recommended as an alternative to fasting plasma glucose or oral glucose tolerance tests for diagnosing diabetes mellitus (DM). In this study, we analyzed HbA1c levels for diabetes mellitus screening in a Korean rural population.

METHODS

We analyzed data from 10,111 subjects from a Korean Rural Genomic Cohort study and generated a receiver operating characteristic curve to determine an appropriate HbA1c cutoff value for diabetes.

RESULTS

The mean age of the subjects was 56.3±8.1 years. Fasting plasma glucose and 2-hour plasma glucose after 75 g oral glucose tolerance tests were 97.5±25.6 and 138.3±67.1 mg/dL, respectively. The mean HbA1c level of the subjects was 5.7±0.9%. There were 8,809 non-DM patients (87.1%) and 1,302 DM patients (12.9%). A positive relationship between HbA1c and plasma glucose levels and between HbA1c and 2-hour plasma glucose levels after oral glucose tolerance tests was found in a scatter plot of the data. Using Youden's index, the proper cutoff level of HbA1c for diabetes mellitus screening was 5.95% (sensitivity, 77%; specificity, 89.4%).

CONCLUSION

Our results suggest that the optimal HbA1c level for DM screening is 5.95%.

HbA1c in pregnancy

During pregnancy, the glucose levels vary according to the hormonal changes and the metabolic needs necessary to maintain fetal nutrition but strict glycemic control is essential to minimize the maternal and fetal morbidity and mortality of pregnancies complicated by diabetes. Although considered the "gold standard" for diagnosis, measurement of glucose in the blood is subject to several limitations, many of which are not widely appreciated. Measurement of A1c for diagnosis is appealing as with one number, a total, integrated view of glycemia over time is derived though it has some inherent limitations. Thus, supplementation with HbA1c, as is common outside pregnancy, seems appropriate. Before pregnancy, the target for metabolic control in women with diabetes is HbA1c values near the normal range. However, the upper normal range of HbA1c during normal pregnancy is only sparsely investigated with different methods though recently a number of papers have been published regarding the determination of reference ranges for HbA1c in pregnancy. These changes may have clinical implications for the assessment and management of glycemic control in diabetic pregnancy and calls for establishment of separate reference limits of HbA1c levels in different trimesters as compared to general population.

Predictive value of HbA1c for incident diabetes among subjects with impaired glucose tolerance--analysis of the Indian Diabetes Prevention Programmes

AIMS

The objectives of the study were to assess the predictive value of baseline HbA(1c) for incident diabetes among the participants with impaired glucose tolerance in the Indian Diabetes Prevention Programmes 1 and 2.

METHODS

Data at baseline and at 3-year follow-up were analysed in combined cohorts of the Indian Diabetes Prevention Programmes 1 and 2. Within the 3 years, 324 of the 845 participants developed diabetes (World Health Organization criteria). The predictive value of baseline HbA(1c) for incident diabetes was determined by logistic regression analysis.

RESULTS

Baseline HbA(1c) values had heterogenous distribution. The distribution was similar in isolated impaired glucose tolerance or in impaired glucose tolerance in combination with impaired fasting glucose. A progressive increase in diabetes occurred with increasing HbA(1c). HbA(1c) showed the strongest association with incident diabetes in the multiple logistic regression analysis (odds ratio 3.548, P < 0.0001). The cut-off HbA(1c) of 43 mmol/mol (6.05%) had 67% sensitivity and 60% specificity to predict future diabetes. The diagnostic sensitivity of HbA(1c) of ≥ 48 mmol/mol (≥ 6.5%) was only 51%, with a specificity of 87%, when compared with the oral glucose tolerance glucose values.

CONCLUSIONS

Baseline HbA(1c) was highly predictive of future diabetes in Asian Indian subjects with impaired glucose tolerance and nearly 60% of the incidence occurred with values ≥ 42 mmol/mol (≥ 6.0). Diagnostic sensitivity of HbA(1c) ≥ 48 mmol/mol (≥ 6.5%) for new diabetes was only 51% using the oral glucose tolerance test as the standard for comparison.

Usefulness of HbA1c to diagnose diabetes among Japanese children detected by a urine glucose screening program in the Tokyo Metropolitan Area

We examined the correlation between plasma glucose (PG) and hemoglobin A1c (HbA1c) to evaluate the usefulness and limitations of applying the new diagnostic criteria for diabetes to Japanese pediatric patients. Data were collected from 298 school children who took an oral glucose tolerance test (OGTT) at a school-based urinary glucose screening program in the Tokyo Metropolitan Area between 1988 and 2009. Mean (SD) age of the children was 11.9 (2.5) years. Male-to-female ratio was 1:1.1. Children were diagnosed with renal glucosuria (n=146), diabetes mellitus (n=133), or the Japan Diabetes Society (JDS) "borderline type" (n=19). Median (range) values of fasting plasma glucose (FPG), 2-h plasma glucose in an OGTT (OGTT-2h), and HbA1c were 101 (76-378) mg/dL, 146.5 (57-563) mg/dL, and 6.05 (4.7-14.1) %. The correlation between PG and HbA1c was analyzed using least squares regression, and HbA1c was found to highly correlate with PG. From estimated regression equations, mean values of FPG and OGTT-2h corresponding to an HbA1c of 6.5% were calculated to be 111.4 mg/dL and 170.4 mg/dL. The mean values of HbA1c corresponding to an FPG of 126 mg/dL and OGTT-2h of 200 mg/dL were calculated to be 7.5% and 7.8%. The mean values of PG corresponding to HbA1c of 6.5% were lower than found in adults as analyzed by JDS. The mean values of HbA1c corresponding to diabetic type PG were higher than found in adults.

Evaluation of hemoglobin A1c criteria to assess preoperative diabetes risk in cardiac surgery patients

OBJECTIVE

Hemoglobin A1c (A1C) has recently been recommended for diagnosing diabetes mellitus and diabetes risk (prediabetes). Its performance compared with fasting plasma glucose (FPG) and 2-h post-glucose load (2HPG) is not well delineated. We compared the performance of A1C with that of FPG and 2HPG in preoperative cardiac surgery patients.

METHODS

Data from 92 patients without a history of diabetes were analyzed. Patients were classified with diabetes or prediabetes using established cutoffs for FPG, 2HPG, and A1C. Sensitivity and specificity of the new A1C criteria were evaluated.

RESULTS

All patients diagnosed with diabetes by A1C also had impaired fasting glucose, impaired glucose tolerance, or diabetes by other criteria. Using FPG as the reference, sensitivity and specificity of A1C for diagnosing diabetes were 50% and 96%, and using 2HPG as the reference they were 25% and 95%. Sensitivity and specificity for identifying prediabetes with FPG as the reference were 51% and 51%, respectively, and with 2HPG were 53% and 51%, respectively. One-third each of patients with prediabetes was identified using FPG, A1C, or both. When testing A1C and FPG concurrently, the sensitivity of diagnosing dysglycemia increased to 93% stipulating one or both tests are abnormal; specificity increased to 100% if both tests were required to be abnormal.

CONCLUSIONS

In patients before cardiac surgery, A1C criteria identified the largest number of patients with diabetes and prediabetes. For diagnosing prediabetes, A1C and FPG were discordant and characterized different groups of patients, therefore altering the distribution of diabetes risk. Simultaneous measurement of FGP and A1C may be a more sensitive and specific tool for identifying high-risk individuals with diabetes and prediabetes.

Is there a relationship between mean blood glucose and glycated hemoglobin?

Measurement of hemoglobin A1c (HbA1c) is considered the gold standard for monitoring chronic glycemia of diabetes patients. Hemoglobin A1c indicates an average of blood glucose levels over the past 3 months. Its close association with the risk for the development of long-term complications is well established. However, HbA1c does not inform patients about blood glucose values on a daily basis; therefore, frequent measurements of blood glucose levels are necessary for the day-to-day management of diabetes. Clinicians understand what HbA1c means and how it relates to glucose, but this is not the case with patients. Therefore, the translation of the HbA1c results into something more familiar to patients seemed a necessity. The scope of this article is to review the literature to search for enough scientific evidence to support the idea of a close relationship between HbA1c and mean blood glucose (MBG), and to justify the translation of HbA1c into something that reflects the MBG. Most studies confirm a close relationship between HbA1c and MBG, although different studies result in different linear equations. Factors affecting this relationship may limit the usefulness and applicability of a unique mathematical equation to all diabetes populations.

Defining obesity cut-off points for migrant South Asians

BACKGROUND

Body mass index (BMI) and waist circumference (WC) are used to define cardiovascular and type 2 diabetes risk. We aimed to derive appropriate BMI and WC obesity cut-off points in a migrant South Asian population.

METHODS

4688 White Europeans and 1333 South Asians resident in the UK aged 40-75 years inclusive were screened for type 2 diabetes. Principal components analysis was used to derive a glycaemia, lipid, and a blood pressure factor. Regression models for each factor, adjusted for age and stratified by sex, were used to identify BMI and WC cut-off points in South Asians that correspond to those defined for White Europeans.

FINDINGS

For South Asian males, derived BMI obesity cut-off points equivalent to 30.0 kg/m(2) in White Europeans were 22.6 kg/m(2) (95% Confidence Interval (95% CI) 20.7 kg/m(2) to 24.5 kg/m(2)) for the glycaemia factor, 26.0 kg/m(2) (95% CI 24.7 kg/m(2) to 27.3 kg/m(2)) for the lipid factor, and 28.4 kg/m(2) (95% CI 26.5 kg/m(2) to 30.4 kg/m(2)) for the blood pressure factor. For WC, derived cut-off points for South Asian males equivalent to 102 cm in White Europeans were 83.8 cm (95% CI 79.3 cm to 88.2 cm) for the glycaemia factor, 91.4 cm (95% CI 86.9 cm to 95.8 cm) for the lipid factor, and 99.3 cm (95% CI 93.3 cm to 105.2 cm) for the blood pressure factor. Lower ethnicity cut-off points were seen for females for both BMI and WC.

CONCLUSIONS

Substantially lower obesity cut-off points are needed in South Asians to detect an equivalent level of dysglycemia and dyslipidemia as observed in White Europeans. South Asian ethnicity could be considered as a similar level of risk as obesity (in White Europeans) for the development of type 2 diabetes.

Comparison of hemoglobin A1c with fasting plasma glucose and 2-h postchallenge glucose for risk stratification among women with recent gestational diabetes mellitus

OBJECTIVE

Postpartum testing with a 75-g 2-h oral glucose tolerance test or fasting plasma glucose (FPG) alone is often not performed among women with histories of gestational diabetes mellitus (GDM). Use of hemoglobin A(1c) (A1C) might increase testing. The association between A1C and glucose has not been examined in women with histories of GDM.

RESEARCH DESIGN AND METHODS

We assessed the association of A1C ≥5.7% with FPG ≥100 mg/dL and 2-h glucose ≥140 mg/dL among 54 women with histories of GDM between 6 weeks and 36 months postpartum.

RESULTS

A1C ≥5.7% had 65% sensitivity and 68% specificity for identifying elevated FPG or 2-h glucose and 75% sensitivity and 62% specificity for elevated FPG alone. The area under the receiver operating characteristic curve for A1C was 0.76 for elevated FPG or 2-h glucose and 0.77 for elevated FPG alone.

CONCLUSIONS

The agreement between A1C and glucose levels is fair for detection of abnormal glucose tolerance among women with histories of GDM.

Does genetic ancestry explain higher values of glycated hemoglobin in African Americans?

OBJECTIVE

Glycated hemoglobin (HbA(1c)) values are higher in African Americans than whites, raising the question of whether classification of diabetes status by HbA(1c) should differ for African Americans. We investigated the relative contribution of genetic ancestry and nongenetic factors to HbA(1c) values and the effect of genetic ancestry on diabetes classification by HbA(1c) in African Americans.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional analysis of data from the community-based Atherosclerosis Risk in Communities (ARIC) Study. We estimated percentage of European genetic ancestry (PEA) for each of the 2,294 African Americans without known diabetes using 1,350 ancestry-informative markers. HbA(1c) was measured from whole-blood samples and categorized using American Diabetes Association diagnostic cut points (<5.7, 5.7-6.4, and ≥6.5%).

RESULTS

PEA was inversely correlated with HbA(1c) (adjusted r = -0.07; P < 0.001) but explained <1% of its variance. Age and socioeconomic and metabolic factors, including fasting glucose, explained 13.8% of HbA(1c) variability. Eleven percent of participants were classified as having diabetes; adjustment for fasting glucose decreased this to 4.4%. Additional adjustment for PEA did not significantly reclassify diabetes status (net reclassification index = 0.034; P = 0.94) nor did further adjustment for demographic, socioeconomic, and metabolic risk factors.

CONCLUSIONS

The relative contribution of demographic and metabolic factors far outweighs the contribution of genetic ancestry to HbA(1c) values in African Americans. Moreover, the impact of adjusting for genetic ancestry when classifying diabetes by HbA(1c) is minimal after taking into account fasting glucose levels, thus supporting the use of currently recommended HbA(1c) categories for diagnosis of diabetes in African Americans.

Race-ethnicity as an effect modifier of the association between HbAlc and mortality in U.S. adults without diagnosed diabetes

OBJECTIVE

HbAlc is increasingly appreciated as a risk factor for all-cause and cardiovascular disease (CVD) mortality in the non-diabetic population. In this study, we investigated the association between HbAlc and mortality with a particular focus on the impact of race-ethnicity. Design Cohort study.

METHODS

We analyzed the association between HbAlc and all-cause and CVD mortality in 12 698 non-diabetic adults 20 years or older from the Third National Health and Nutrition Examination Survey using separate models for people of different race-ethnicity.

RESULTS

In our stratified analyses, higher non-diabetic HbAlc levels were associated with all-cause and CVD mortality in non-Hispanic whites only. In this group, compared with HbAlc values of 5.0-<5.35%, the multivariable-adjusted estimated hazard ratios (est. HR) with 95% confidence interval (CI) for all-cause mortality were 1.21 (0.92, 1.58), 1.22 (1.03, 1.45), 1.29 (1.14, 1.47), and 1.4 (1.02, 1.87) for HbAlc levels of <5.0, 5.35-<5.7, 5.7-<6.5, and 6.5% or greater respectively. The association did not reach significance in Mexican-Americans (est. HR (95% CI): 1.77 (1.08, 2.91), 0.81 (0.56, 1.19), 1.16 (0.86, 1.57), and 1.4 (0.83, 2.36)). No association was observed in non-Hispanic blacks: 1.13 (0.91, 1.39), 0.81 (0.61, 1.08), 0.84 (0.69, 1.03), and 0.94 (0.67, 1.33). Results were similar for CVD mortality.

CONCLUSIONS

Our data suggest limitations of HbAlc as a risk factor for all-cause and cardiovascular mortality across race-ethnic populations.

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.

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 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.