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

Elevated hemoglobin glycation index identify non-diabetic individuals at increased risk of kidney dysfunction

Hemoglobin glycation index (HGI), calculated as the difference between the observed value of HbA1 and the predicted HbA1c based on plasma glucose concentration, is a measure of the individual tendency toward non-enzymatic hemoglobin glycation which has been found to be positively associated with nephropathy in subjects with diabetes. In this cross-sectional study we aimed to evaluate whether higher HGI levels are associated with impaired kidney function also among nondiabetic individuals.

The study group comprised 1505 White nondiabetic individuals stratified in quartiles according to HGI levels. Estimated glomerular filtration rate (eGFR) was calculated by using the MDRD equation.

Individuals in the intermediate and high HGI groups exhibited a worse metabolic phenotype with increased levels of visceral obesity, total cholesterol, triglycerides, inflammatory biomarkers such as hsCRP and white blood cells count and lower values of HDL and insulin sensitivity assessed by Matsuda index in comparison to the lowest quartile of HGI. Subjects in the intermediate and high HGI groups displayed a graded decrease of eGFR levels in comparison with the lowest quartile of HGI. In a logistic regression analysis individuals in the highest quartile of HGI exhibited a significantly 3.6-fold increased risk of having chronic kidney disease (95% CI: 1.13–11.24, P = 0.03) and a significantly 1.6-fold increased risk of having a mildly reduced kidney function (95% CI: 1.19–2.28, P = 0.003) in comparison to individuals in the lowest HGI group.

In conclusion HGI may be a useful tool to identify nondiabetic individuals with an increased risk of having kidney dysfunction.

Methods needed to measure predictive accuracy: A study of diabetic patients

Diabetes is one of the leading causes of morbidity and mortality and it can result in several complications such as kidney failure, heart failure, stroke, and blindness making it a major medical and public health concern in the United States. Statistical methods are important to detect risk factors and identify the best sampling plan to determine predictive bounds for diabetic patients' data. The main objective of this paper is to identify the best fit bootstrapping sampling method and to draw the predictive bound considering diabetes patient data. A random sample was used from the National Health and Nutritional Examination Survey (NHANES) for this study. We found that there were significant relationships between age, marital status, and race/ethnicity with diabetes status (p<0.001) and no relationship was observed between gender and diabetes status. We ran the logistic regression to identify the risk factors from the data. We identified that the significant risk factors are age (p<0.001), total protein (p<0.001), fast food (p<0.0339), and direct HDL (p<0.001). This study provides evidence that the parametric bootstrapping method is the best fit method compared with other methods to estimate the predictive error bounds. These findings will be of great significance for identifying the best sampling methods, which can increase the statistical accuracy of laboratory clinical research of diabetes. This will also allow for the determination of precise risk factors that will best represent the data by detecting mild and extreme outliers from disease observations. Therefore, these results will be useful for researchers and clinicians to select the best sampling methods to study diabetes and other diseases in order to maximize the accuracy of their results. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

Metrics Beyond Hemoglobin A1C in Diabetes Management: Time in Range, Hypoglycemia, and Other Parameters

We review clinical instances in which A1C should not be used and reflect on the use of other glucose metrics that can be used, in substitution of or in combination with A1C and SMBG, to tailor an individualized approach that will result in better outcomes and patient empowerment.

Commentary: In the Rising Era of Big Data, Small Steps are Key

Big Data may be useful to identify and perhaps ameliorate health disparities. However, over reliance on the power on Big Data can potentially cause harm. When assessing health disparities, the use of Big Data should be limited to hypothesis generation.

Association between hemoglobin glycation index with insulin resistance and carotid atherosclerosis in non-diabetic individuals

Hemoglobin glycation index (HGI), defined as the difference between the observed HbA1c value and the value of HbA1c predicted from plasma glucose levels, represents a measure of the degree of non-enzymatic glycation of hemoglobin and it has been found to be positively associated with micro- and macro-vascular complications in subjects with type 2 diabetes. To investigate the pathophysiological abnormalities responsible for the increased cardiovascular risk of patients with higher HGI, we evaluated the association of HGI with cardio-metabolic characteristics in nondiabetic offspring of type 2 diabetic individuals. Insulin sensitivity, measured by a hyperinsulinemic-euglycemic clamp, cardio-metabolic risk factors including lipid profile, uric acid and inflammatory factors, and ultrasound measurement of carotid intima-media thickness (IMT) were assessed in 387 nondiabetic individuals. Participants were stratified in tertiles according to HGI (high, moderate and low). As compared with subjects with low HGI, those with high HGI displayed an unfavorable cardio-metabolic risk profile having significantly higher values of BMI, waist circumference, triglycerides, uric acid, fasting insulin, inflammatory markers, such as high sensitivity C reactive protein, erythrocytes sedimentation rate, complement C3, fibrinogen, and white blood cell count, and carotid IMT, and lower HDL and insulin-stimulated glucose disposal. In a linear regression analysis model including several atherosclerotic risk factors such as gender, age, BMI, inflammatory factors, lipid profile, insulin-stimulated glucose disposal, fasting insulin, uric acid, and blood pressure, HGI was the major predictor of IMT (β = 0.35; P = 0.001). In a logistic regression analysis adjusted for confounders, individuals with high HGI showed a 2.7-fold increased risk of vascular atherosclerosis (OR 2.72, 95%CI 1.01-7.37) as compared with subjects with low HGI. The present findings support the notion that HGI may be a useful tool to identify a subset of nondiabetic individuals conceivably harboring a higher risk of cardiovascular disease.

Impact of demographics and disease progression on the relationship between glucose and HbA1c

CONTEXT

Several studies have shown that the relationship between mean plasma glucose (MPG) and glycated haemoglobin (HbA1c) may vary across populations. Especially race has previously been referred to shift the regression line that links MPG to HbA1c at steady-state (Herman & Cohen, 2012).

OBJECTIVE

To assess the influence of demographic and disease progression-related covariates on the intercept of the estimated linear MPG-HbA1c relationship in a longitudinal model.

DATA

Longitudinal patient-level data from 16 late-phase trials in type 2 diabetes with a total of 8927 subjects was used to study covariates for the relationship between MPG and HbA1c. The analysed covariates included age group, BMI, gender, race, diabetes duration, and pre-trial treatment. Differences between trials were taken into account by estimating a trial-to-trial variability component.

PARTICIPANTS

Participants included 47% females and 20% above 65years. 77% were Caucasian, 9% were Asian, 5% were Black and the remaining 9% were analysed together as other races.

ANALYSIS

Estimates of the change in the intercept of the MPG-HbA1c relationship due to the mentioned covariates were determined using a longitudinal model.

RESULTS

The analysis showed that pre-trial treatment with insulin had the most pronounced impact associated with a 0.34% higher HbA1c at a given MPG. However, race, diabetes duration and age group also had an impact on the MPG-HbA1c relationship.

CONCLUSION

Our analysis shows that the relationship between MPG and HbA1c is relatively insensitive to covariates, but shows small variations across populations, which may be relevant to take into account when predicting HbA1c response based on MPG measurements in clinical trials.

HbA1c screening for new onset diabetes following acute coronary syndrome: is it a worthwhile test in clinical practice?

Background

Diabetes and pre-diabetes are prevalent in acute coronary syndrome (ACS) and relate to adverse outcomes. This study used HbA_1c to screen for degrees of glucose intolerance amongst patients without known diabetes presenting with ACS.

Methods

Over a 1-year period (June 2014–2015) consecutive patients admitted to a single centre cardiology unit with an initial diagnosis of ACS without prior diabetes diagnosis were electronically referred to our diabetes team. Patients were screened for the presence of diabetes by use of an initial HbA_1c blood test on day 2 or 3 post admission. If abnormal (≥42 mmol/mol; ≥6.0%), patients were invited for a repeat HbA_1c at 2 weeks, and if an intermediate result (42–47 mmol/mol; 6.0–6.4%), for an oral glucose tolerance test (OGTT) at 3 months. Patients were diagnosed with Type 2 diabetes if the repeat HbA_1c result was high (≥48 mmol/mol; ≥6.5%) or the OGTT at 3 months confirmed the diagnosis. Other data collected included baseline demographics, risk factors and any history of cardiovascular disease. All patients with ACS were stratified according to the diagnosis and subsequent management.

Results

We screened 399 patients in total. The mean age was 65 ± 14 years, 268 (67%) were men, 290 (73%) were Caucasian, 95 (24%) were South Asian and 14 (4%) were Afro-Caribbean ethnicity. Of all patients, 57 (14.3%) were diagnosed as pre-diabetes and 43 (10.8%) newly diagnosed diabetes. During the study 28 (7%) patients could not be classified; 6 (1.5%) patients died during the study and 22 (5.5%) patients were missing either initial or repeat HbA_1c and were subsequently lost to follow up. Of the baseline variables assessed, there were significantly more patients of South Asian ethnicity in the diabetes group compared to the normal group (42 vs 20%; p = 0.003). There was no difference in detection rates in patients with more severe ACS requiring percutaneous or cardiac surgical intervention.

Conclusions

The use of a simple HbA_1c screening method in clinical practice can detect new onset diabetes in approximately 1 in 10 high-risk post ACS patients.

Effect of ethnicity on HbA1c levels in individuals without diabetes: Systematic review and meta-analysis

Aims/Hypothesis

Disparities in HbA1c levels have been observed among ethnic groups. Most studies were performed in patients with diabetes mellitus (DM), which may interfere with results due to the high variability of glucose levels. We conducted a systematic review and meta-analysis to investigate the effect of ethnicity on HbA1c levels in individuals without DM.

Methods

This is a systematic review with meta-analysis. We searched MEDLINE and EMBASE up to September 2016. Studies published after 1996, performed in adults without DM, reporting HbA1c results measured by certified/standardized methods were included. A random effects model was used and the effect size was presented as weighted HbA1c mean difference (95% CI) between different ethnicities as compared to White ethnicity.

Results

Twelve studies met the inclusion criteria, totalling data from 49,238 individuals. There were significant differences between HbA1c levels in Blacks [0.26% (2.8 mmol/mol); 95% CI 0.18 to 0.33 (2.0 to 3.6), p <0.001; I² = 90%, p <0.001], Asians [0.24% (2.6 mmol/mol); 95% CI 0.16 to 0.33 (1.7 to 3.6), p <0.001; I² = 80%, p = 0.0006] and Latinos [0.08% (0.9 mmol/mol); IC 95% 0.06 to 0.10 (0.7 to 1.1); p <0.001; I² = 0%; p = 0.72] when compared to Whites.

Conclusions/Interpretation

This meta-analysis shows that, in individuals without DM, HbA1c values are higher in Blacks, Asians, and Latinos when compared to White persons. Although small, these differences might have impact on the use of a sole HbA1c point to diagnose DM in all ethnic populations.

The haemoglobin glycation index as predictor of diabetes-related complications in the AleCardio trial

The haemoglobin glycation index (HGI) quantifies the interindividual variation in the propensity for glycation and is a predictor of diabetes complications and adverse effects of intensive glucose lowering. We investigated the relevance of HGI as independent predictor of complications by using data of the AleCardio trial. The AleCardio trial randomized 7226 type 2 diabetes patients with an acute coronary syndrome to aleglitazar or placebo. From 6458 patients with baseline glycated haemoglobin (HbA_1c) and fasting plasma glucose (FPG), a linear regression equation, HbA_1c (%) = 5.45 + 0.0158 * FPG (mg/dl), was used to calculate predicted HbA_1c and derive HGI (= observed - predicted HbA_1c). With multivariate Cox regression we examined the association with major adverse cardiac events, cardiovascular mortality, total mortality and hypoglycaemia, irrespective of treatment allocation, using HGI subgroups (low, intermediate and high) and HGI as continuous variable. Patients with high HGI were younger, more often non-Caucasian, had a longer duration of diabetes, showed more retinopathy and used insulin more often. Hypoglycaemia occurred less often in the low HGI subgroup, but this difference disappeared after adjustment for duration of diabetes, insulin and sulphonylurea use. Low HGI patients were at lower risk for cardiovascular mortality (hazard ratio 0.64; 95% confidence interval 0.44-0.93, p = 0.020) and total mortality (hazard ratio 0.69; 95% confidence interval 0.50-0.95, p = 0.025), as compared with high HGI patients. Every percentage increase in HGI was associated with a 16% increase in the risk for cardiovascular mortality ( p = 0.005). The association between HGI and mortality disappeared with additional adjustment for HbA_1c. HGI predicts mortality in diabetes patients with acute coronary syndromes, but no better than HbA_1c.

Diagnostic performance of HbA1c for diabetes in Arab vs. European populations: a systematic review and meta-analysis

AIM

To examine differences in the performance of HbA_1c for diagnosing diabetes in Arabs compared with Europeans.

METHODS

The PubMed, Embase and Cochrane library databases were searched for records published between 1998 and 2015. Estimates of sensitivity, specificity and log diagnostic odds ratios for an HbA_1c cut-point of 48 mmol/mol (6.5%) were compared between Arabs and Europeans, using a bivariate linear mixed-model approach. For studies reporting multiple cut-points, population-specific summary receiver operating characteristic (SROC) curves were constructed. In addition, sensitivity, specificity and Youden Index were estimated for strata defined by HbA_1c cut-point and population type. Database searches yielded 1912 unique records; 618 full-text articles were reviewed. Fourteen studies met the inclusion criteria; hand-searching yielded three additional eligible studies. Three Arab (N = 2880) and 16 European populations (N = 49 127) were included in the analysis.

RESULTS

Summary sensitivity and specificity for a HbA_1c cut-point of 48 mmol/mol (6.5%) in both populations were 42% (33-51%), and 97% (95-98%). There was no difference in area under SROC curves between Arab and European populations (0.844 vs. 0.847; P = 0.867), suggesting no difference in HbA_1c diagnostic accuracy between populations. Multiple cut-point summary estimates stratified by population suggest that Arabs have lower sensitivity and higher specificity at a HbA_1c cut-point of 44 mmol/mol (6.2%) compared with European populations. Estimates also suggest similar test performance at cut-points of 44 mmol/mol (6.2%) and 48 mmol/mol (6.5%) for Arabs.

CONCLUSIONS

Given the low sensitivity of HbA_1c in the high-risk Arab American population, we recommend a combination of glucose-based and HbA_1c testing to ensure an accurate and timely diagnosis of diabetes.

Detecting prediabetes among Hispanics/Latinos from diverse heritage groups: Does the test matter? Findings from the Hispanic Community Health Study/Study of Latinos

The objectives of this analysis were to compare the ability of fasting plasma glucose (FPG), post oral load plasma glucose (2hPG), and hemoglobin A1c (HbA1c) to identify U.S. Hispanic/Latino individuals with prediabetes, and to assess its cardiovascular risk factor correlates. This is a cross-sectional analysis of baseline data from 15,507 adults without self-reported diabetes mellitus from six Hispanic/Latino heritage groups, enrolled in the Hispanic Community Health Study/Study of Latinos, which takes place in four U.S. communities. The prevalence of prediabetes was determined according to individual or combinations of ADA-defined cut points: FPG=5.6-7.0mmol/L, 2hPG=7.8-11.1mmol/L, and HbA1c=5.7%-6.4% (39-46mmol/mol). The sensitivity of these criteria to detect prediabetes was estimated. The prevalence ratios (PRs) for selected cardiovascular risk factors were compared among alternative categories of prediabetes versus normoglycemia [FPG<5.6mmol/L and 2hPG<7.8mmol/L and HbA1c<5.7% (39mmol/mol)]. Approximately 36% of individuals met any of the ADA prediabetes criteria. Using 2hPG as the gold standard, the sensitivity of FPG was 40.1%, HbA1c was 45.6%, and that of HbA1c+FPG was 62.2%. The number of significant PRs for cardiovascular risk factors was higher among individuals with isolated 2hPG=7.8-11.1mmol/L, FPG=5.6-7.0mmol/L+HbA1c=5.7%-6.4%, or those who met the three prediabetes criteria. Assessing FPG, HbA1c, and cardiovascular risk factors in Hispanics/Latinos at risk might enhance the early prevention of diabetes mellitus and cardiovascular complications in this young and growing population, independent of their heritage group.

Novel biomarkers for prediabetes, diabetes, and associated complications

The number of individuals with prediabetes is expected to grow substantially and estimated to globally affect 482 million people by 2040. Therefore, effective methods for diagnosing prediabetes will be required to reduce the risk of progressing to diabetes and its complications. The current biomarkers, glycated hemoglobin (HbA1c), fructosamine, and glycated albumin have limitations including moderate sensitivity and specificity and are inaccurate in certain clinical conditions. Therefore, identification of additional biomarkers is being explored recognizing that any single biomarker will also likely have inherent limitations. Therefore, combining several biomarkers may more precisely identify those at high risk for developing prediabetes and subsequent progression to diabetes. This review describes recently identified biomarkers and their potential utility for addressing the burgeoning epidemic of dysglycemic disorders.

High Prevalence of Diabetes and Prediabetes and Their Coexistence with Cardiovascular Risk Factors in a Hispanic Community

This study examined the prevalence and association of diabetes mellitus (DM) and prediabetes with cardiovascular risk factors among Puerto Ricans adults. Data from a household survey of 857 adults aged 21-79 years who underwent interviews, physical exams, and blood draws were analyzed. Prevalence of total DM and prediabetes was estimated using American Diabetes Association diagnostic criteria of fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c). Poisson regression models were used to estimate the prevalence ratio for each cardiovascular risk factor under study. Age-standardized prevalence of total DM and prediabetes, detected by FPG and/or HbA1c, was 25.5 and 47.4 %, respectively. Compared with participants with normoglycemia, those with previously diagnosed DM, undiagnosed DM, and prediabetes had more adverse cardiovascular risk factor profiles, characterized by a higher prevalence of general and abdominal obesity, hypertension, low HDL cholesterol, elevated LDL cholesterol, elevated triglycerides, and elevated plasminogen activator inhibitor 1 (p < 0.05). The high prevalence of DM and prediabetes calls for public health actions to plan and implement lifestyle interventions to prevent or delay the onset of DM and cardiovascular disease.

Derivation & validation of glycosylated haemoglobin (HbA 1c ) cut-off value as a diagnostic test for type 2 diabetes in south Indian population

Background & Objectives:

Glycosylated haemoglobin (HbA_1c) has been in use for more than a decade, as a diagnostic test for type 2 diabetes. Validity of HbA_1c needs to be established in the ethnic population in which it is intended to be used. The objective of this study was to derive and validate a HbA_1c cut-off value for the diagnosis of type 2 diabetes in the ethnic population of Rayalaseema area of south India.

Methods:

In this cross-sectional study, consecutive patients suspected to have type 2 diabetes underwent fasting plasma glucose (FPG) and 2 h post-load plasma glucose (2 h-PG) measurements after a 75 g glucose load and HbA_1c estimation. They were classified as having diabetes as per the American Diabetes Association criteria [(FPG ≥7 mmol/l (≥126 mg/dl) and/or 2 h-PG ≥11.1 mmol/l (≥200 mg/dl)]. In the training data set (n = 342), optimum cut-off value of HbA_1c for defining type 2 diabetes was derived by receiver-operator characteristic (ROC) curve method using oral glucose tolerance test results as gold standard. This cut-off was validated in a validation data set (n = 341).

Results:

On applying HbA_1c cut-off value of >6.3 per cent (45 mmol/mol) to the training data set, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for diagnosing type 2 diabetes were calculated to be 90.6, 85.2, 80.8 and 93.0 per cent, respectively. When the same cut-off value was applied to the validation data set, sensitivity, specificity, PPV and NPV were 88.8, 81.9, 74.0 and 92.7 per cent, respectively, although the latter were consistently smaller than the proportions for the training data set, the differences being not significant.

Interpretation & conclusions:

HbA_1c >6.3 per cent (45 mmol/mol) appears to be the optimal cut-off value for the diagnosis of type 2 diabetes applicable to the ethnic population of Rayalaseema area of Andhra Pradesh state in south India.

Association between Alcohol Intake and Hemoglobin A1c in the Korean Adults: The 2011-2013 Korea National Health and Nutrition Examination Survey

BACKGROUND

Although alcohol consumption is commonly encountered in clinical practice, few studies have investigated the clinical significance of alcohol intake on the use of the hemoglobin A1c (HbA1c) level.

OBJECTIVES

This study was performed to investigate the association between alcohol intake and HbA1c level in the general population.

METHODS

Among the 24,594 participants who participated in the 2011-2013 Korea National Health and Nutrition Examination Survey (KNHANES), 12,923 participants were analyzed in this study. We excluded diabetic patients currently taking antidiabetes medication. We compared the HbA1c level and proportions of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% according to the fasting plasma glucose (FPG) concentration range and the amount of alcohol intake. The average amounts of daily alcohol intake were categorized into three groups: 0 g/day, <30 g/day, ≥30 g/day.

RESULTS

The mean HbA1c level was 5.65%, and the mean FPG concentration was 95.3 mg/dl. The percentages of patients with an HbA1c level of ≥5.7%, ≥6.1%, and ≥6.5% were 42.6%, 13.4%, and 4.5%, respectively. The average amount of alcohol intake was 12.3 g/day. The percentages of subjects with alcohol intake 0, <30, and ≥ 30 g/day were 16.5%, 69.7%, and 13.8%, respectively. There was a significant positive relationship between alcohol intake and FPG concentration (P < 0.001), the prevalence of impaired fasting glucose (P < 0.001), and the prevalence of diabetes (P < 0.001). However, there was no significant relationship between the alcohol intake and HbA1c level. Overall, the adjusted HbA1c levels decreased across alcohol intake (5.70% ± 0.01%, 5.66% ± 0.01%, and 5.55% ± 0.01%) after adjustment for confounding factors such as age, sex, FPG concentration, college graduation, smoking history, presence of hypertension, waist circumference, serum total cholesterol concentration, serum high-density lipoprotein cholesterol concentration, serum triglyceride concentration, presence of anemia, serum white blood cell count, and serum alanine aminotransferase concentration (P < 0.001). The adjusted proportions (%) of patients with an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001) showed significant negative trends across alcohol intake after adjustment for confounders. Logistic regression analyses showed that, when using the group that abstained as the control, the group that consumed ≥ 30g/day was negatively associated with the risk of an HbA1c level of ≥5.7% (P < 0.001), ≥6.1% (P < 0.001), and ≥6.5% (P < 0.001), using the above-mentioned variables as covariates.

CONCLUSIONS

Higher alcohol intake was associated with lower HbA1c levels, even after adjusting for confounding factors, including the FPG concentration, in this nationally representative sample of Korean adults. These results suggest that excessive drinking shifts the HbA1c level downward, which might complicate use of the HbA1c level for the diagnosis of diabetes or prediabetes.

PERFORMANCE OF A1C VERSUS OGTT FOR THE DIAGNOSIS OF PREDIABETES IN A COMMUNITY-BASED SCREENING

OBJECTIVE

Reliable identification of individuals at risk for developing diabetes is critical to instituting preventative strategies. Studies suggest that the accuracy of using hemoglobin A1c as a sole diagnostic criterion for diabetes may be variable across different ethnic groups. We postulate that there will be lack of concordance between A1c and the oral glucose tolerance test (OGTT) for diagnosing prediabetes across Hispanic and non-Hispanic white (NHW) populations.

METHODS

A total of 218 asymptomatic adults at risk for type 2 diabetes (T2D) were assessed with A1c and OGTT for the diagnosis of prediabetes. Glucose homeostasis status was assigned as no diabetes (A1c <5.7% [39 mmol/mol]), prediabetes (A1c 5.7 to 6.4% [46 mmol/mol]), and T2D (A1c >6.4% [46 mmol/mol]). Inclusion criteria were age >18 years and at least one of the following: a family history of diabetes, a history of gestational diabetes, Hispanic ethnicity, non-Caucasian race, or obesity. Subjects received a fasting 75-g OGTT and A1c on the same day. Bowker's test of symmetry was employed to determine agreement between the tests.

RESULTS

Data from 99 Hispanic patients and 79 NHW patients were analyzed. There was no concordance between A1c and OGTT for Hispanic (P = .002) or NHW individuals (P = .003) with prediabetes.

CONCLUSION

A1c is discordant with OGTT among Hispanic and NHW subjects for the diagnosis of prediabetes. Sole use of A1c to designate glycemic status will result in a greater prevalence of prediabetes among Hispanic and NHW New Mexicans.

ABBREVIATIONS

A1c = hemoglobin A1c BMI = body mass index CDC = Centers for Disease Control CI = confidence interval FPG = fasting plasma glucose NHW = non-Hispanic white OGTT = oral glucose tolerance test T2D = type 2 diabetes WHO = World Health Organization.

Diagnostic performance of glycated hemoglobin for diabetic retinopathy in non-diabetic older overweight/obese African-Americans

OBJECTIVES

Although clinicians do not routinely screen for diabetic retinopathy in non-diabetic patients, previous studies have shown that diabetic retinopathy can occur in patients with prediabetes. However, due to the limitations of glycated hemoglobin (HbA1c) in overweight/obese subjects, African-Americans and older adults, little is known about the correlation between HbA1c and diabetic retinopathy in non-diabetic older overweight/obese African-Americans. The aims of this study were to determine the association between HbA1c and diabetic retinopathy, and the optimal diagnostic threshold of HbA1c that predicts diabetic retinopathy in non-diabetic older overweight/obese African-Americans.

METHODS

The 2005-2012 data from the U.S. National Health and Nutrition Examination Surveys (NHANES) were utilized for this study. Prevalence odds ratios from logistic regression analyses were used to estimate risks of diabetic retinopathy across HbA1c categories, adjusting for age, sex, and hypertension. Receiver operating characteristic curve was used to determine diagnostic cutoff point of HbA1c for prevalent diabetic retinopathy.

RESULTS

There were gradients of increasing prevalence and odds of diabetic retinopathy with increasing HbA1c in non-diabetic overweight/obese African-Americans 50years of age and older. HbA1c cut-off point of 5.2% (AUC=.726, 95% CI=0.696-0.756) was found to maximize sensitivity [93.5%; 95% CI: 83.2-95.7] for diabetic retinopathy, though specificity [22.1%; 95% CI 19.9-32.8] was low.

CONCLUSION

Current criteria for diagnosis of prediabetes are effective in identifying many older overweight/obese African Americans with diabetic retinopathy. Based on our analysis, a lower HbA1c of 5.2% could serve as a more sensitive cutoff point for defining prediabetes in this population subgroup.

Distribution of Glycated Haemoglobin According to Early-Life and Contemporary Characteristics in Adolescents and Adults without Diabetes: The 1982 and 1993 Pelotas Birth Cohorts

Aim

Glycated haemoglobin (HbA_1c), a marker of glucose control in individuals with diabetes mellitus, is also related with the incidence of cardiometabolic risk in populations free of disease. The aim of this study was to describe the distribution of HbA_1c levels according to early-life and contemporary factors in adolescents and adults without diabetes mellitus.

Methods

HbA_1c was measured in adults aged 30 years and adolescents aged 18 years who are participants in the 1982 and 1993 Pelotas Birth Cohorts, respectively. Bivariate and multivariate analyses were performed to describe the HbA_1c mean values according to early-life and contemporary characteristics collected prospectively since birth.

Results

The distribution of the HbA_1c was approximately normal in both cohorts, with a mean (SD) 5.10% (0.43) in the 1982 cohort, and 4.89% (0.50) in the 1993 cohort. HbA_1c mean levels were significantly higher in individuals self-reported as black/brown skin color compared to those self-reported as white in both cohorts. Parental history of diabetes was associated with higher HbA_1c mean in adults, while stunting at one year old presented an inverse relation with the outcome in adolescents. No other early and contemporary factors were associated with HbA_1c levels in adults or adolescents.

Conclusions

We found a consistent relationship between HbA_1c and skin color in both cohorts. Further research is needed to understand the role of genomic ancestry on levels of HbA_1c concentrations which may inform policies and preventive actions for diabetes mellitus and cardiometabolic risk.

Factors Affecting Hemoglobin A1C in the Diagnosis of Diabetes and Prediabetes in Youth

We sought to examine the correlation between variables and A1C levels to determine if prediction modeling could be used in the screening and diagnosis of diabetes and prediabetes in youth. We also sought to test relationships between A1C levels to insulin sensitivity indices and β-cell function indices.

DESIGN AND METHODS

We performed a retrospective review of 904 medical records from youth deemed at-risk for the disease. We performed Pearson correlation, multiple regression, and simple regression testing to determine the relationship between variables and A1C levels. In addition, we performed Pearson correlation testing on insulin sensitivity indices and β-cell function indices to determine the strength of correlation to A1C levels.

RESULTS

Statistical analysis did not show a strong relationship between the variables tested and the A1C. When racial and ethnic groups were tested together, the results from African American participants resulted in bias estimates, and as a result, a statistical model for the entire sample could not be performed. Results indicate that A1C is correlated with all β-cell function proxy measurements and correlated to the corrected insulin level at 30minutes, but not the fasting insulin or insulinogenic index.

DISCUSSION

The results from this study underline the multi-dimensional causes of diabetes and prediabetes and further stress the difficulties in predicting the diseases. The causes of diabetes and prediabetes are multifaceted, often individualized, and often difficult to ascertain.

PRACTICE IMPLICATIONS

Clinicians should continue to examine a variety of variables prior to determining the need for diabetes diagnostic testing.

Efficacy and Safety of Linagliptin in Black/African American Patients with Type 2 Diabetes: A 6-month, Randomized, Double-blind, Placebo-controlled Study

OBJECTIVE

Although black/African American individuals are disproportionately affected by type 2 diabetes, there is scant clinical trial information available on antidiabetes therapies in this group. We compared linagliptin with placebo in black/African American adults who were treatment-naïve or receiving one oral antidiabetes drug.

METHODS

Of 226 patients randomized to 24 weeks' linagliptin 5 mg/day or placebo, 208 had baseline and at least one on-treatment glycated hemoglobin (HbA1c) measurement. Mean baseline HbA1c was 8.6% in the linagliptin group (n = 98) and 8.68% in the placebo group (n = 110). The primary outcome was change in HbA1c from baseline to week 24.

RESULTS

By week 24, mean HbA1c changes were -0.84% with linagliptin and -0.25% with placebo (treatment difference, -0.58%; P<.001), and more patients in the linagliptin group achieved HbA1c <7.0% (26.8% vs. 8.3%; P = .001) or an HbA1c reduction ≥0.5% (54.1% vs. 30.0%; P<.001). Mean weight loss was -1.1 kg in both groups. During the treatment period, 8 of 98 linagliptin-group patients and 17 of 110 placebo-group patients required rescue therapy (odds ratio, 0.5; P = .14). For postprandial glucose, values were available for few patients (11 placebo, 10 linagliptin), and thus the between-group difference was associated with wide confidence intervals (CIs) (difference, -1.97 mg/dL; 95% CI, -53.80 to 49.86; P = .94). In the overall study population, a similar proportion of patients in both groups had adverse events (58.5% vs. 61.7%); most events were mild or moderate and considered unrelated to study drug. Investigator-defined hypoglycemia was rare (3 linagliptin-group patients and 1 placebo-group patient), with no severe events (requiring external assistance).

CONCLUSION

This study confirms that linagliptin is efficacious and well tolerated in black/African American patients with type 2 diabetes.

Racial/Ethnic Disparities in Primary Care Quality Among Type 2 Diabetes Patients, Medical Expenditure Panel Survey, 2012

INTRODUCTION

Racial and ethnic disparities exist in diabetes prevalence, access to diabetes care, diabetes-related complications and mortality rates, and the quality of diabetes care among Americans. We explored racial and ethnic disparities in primary care quality among Americans with type 2 diabetes.

METHODS

We analyzed data on adults with type 2 diabetes derived from the household component of the 2012 Medical Expenditure Panel Survey. Multiple regression and multivariate logistic regressions were used to examine the association between race/ethnicity and primary care attributes related to first contact, longitudinality, comprehensiveness, and coordination, and clusters of confounding factors were added sequentially.

RESULTS

Preliminary findings indicated differences in primary care quality between racial/ethnic minorities and whites across measures of first contact, longitudinality, comprehensiveness, and coordination. After controlling for confounding factors, these differences were no longer apparent; all racial/ethnic categories showed similar rates of primary care quality according to the 4 primary care domains of interest in the study.

CONCLUSION

Results indicate equitable primary care quality for type 2 diabetes patients across 4 key domains of primary care after controlling for socioeconomic characteristics. Additional research is necessary to support these findings, particularly when considering smaller racial/ethnic groups and investigating outcomes related to diabetes.

Are There Clinical Implications of Racial Differences in HbA1c? A Difference, to Be a Difference, Must Make a Difference

Studies that have compared HbA1c levels by race have consistently demonstrated higher HbA1c levels in African Americans than in whites. These racial differences in HbA1c have not been explained by measured differences in glycemia, sociodemographic factors, clinical factors, access to care, or quality of care. Recently, a number of nonglycemic factors and several genetic polymorphisms that operate through nonglycemic mechanisms have been associated with HbA1c Their distributions across racial groups and their impact on hemoglobin glycation need to be systematically explored. Thus, on the basis of evidence for racial differences in HbA1c, current clinical guidelines from the American Diabetes Association state: "It is important to take…race/ethnicity…into consideration when using the A1C to diagnose diabetes." However, it is not clear from the guidelines how this recommendation might be actualized. So, the critical question is not whether racial differences in HbA1c exist between African Americans and whites; the important question is whether the observed differences in HbA1c level are clinically meaningful. Therefore, given the current controversy, we provide a Point-Counterpoint debate on this issue. In the preceding point narrative, Dr. Herman provides his argument that the failure to acknowledge that HbA1c might be a biased measure of average glycemia and an unwillingness to rigorously investigate this hypothesis will slow scientific progress and has the potential to do great harm. In the counterpoint narrative below, Dr. Selvin argues that there is no compelling evidence for racial differences in the validity of HbA1c as a measure of hyperglycemia and that race is a poor surrogate for differences in underlying causes of disease risk.-William T. CefaluEditor in Chief, Diabetes Care.

Are There Clinical Implications of Racial Differences in HbA1c? Yes, to Not Consider Can Do Great Harm!

Studies that have compared HbA1c levels by race have consistently demonstrated higher HbA1c levels in African Americans than in whites. These racial differences in HbA1c have not been explained by measured differences in glycemia, sociodemographic factors, clinical factors, access to care, or quality of care. Recently, a number of nonglycemic factors and several genetic polymorphisms that operate through nonglycemic mechanisms have been associated with HbA1c Their distributions across racial groups and their impact on hemoglobin glycation need to be systematically explored. Thus, on the basis of evidence for racial differences in HbA1c, current clinical guidelines from the American Diabetes Association state: "It is important to take…race/ethnicity…into consideration when using the A1C to diagnose diabetes." However, it is not clear from the guidelines how this recommendation might be actualized. So, the critical question is not whether racial differences in HbA1c exist between African Americans and whites; the important question is whether the observed differences in HbA1c level are clinically meaningful. Therefore, given the current controversy, we provide a Point-Counterpoint debate on this issue. In the point narrative below, Dr. Herman provides his argument that the failure to acknowledge that HbA1c might be a biased measure of average glycemia and an unwillingness to rigorously investigate this hypothesis will slow scientific progress and has the potential to do great harm. In the counterpoint narrative that follows Dr. Herman's contribution, Dr. Selvin argues that there is no compelling evidence for racial differences in the validity of HbA1c as a measure of hyperglycemia and that race is a poor surrogate for differences in underlying causes of disease risk.-William T. CefaluEditor in Chief, Diabetes Care.

Risk of progression to diabetes from prediabetes defined by HbA1c or fasting plasma glucose criteria in Koreans

AIMS

To examine the abilities of HbA1c and fasting plasma glucose (FPG) criteria predicting 5-year progression rate to diabetes in Korean adults with prediabetes.

METHODS

Participants included 17,971 Koreans (aged 20-79years) who underwent routine medical check-ups at a mean interval of 5.2years (3.1-6.7years). Prediabetes was defined as FPG 5.6-6.9mmol/l or HbA1c 5.7-6.4% (39-46mmol/mol). Incident diabetes was defined as FPG⩾7.0mmol/l, HbA1c⩾6.5% (48mmol/mol), or initiation of antidiabetic medications.

RESULTS

At baseline, the prevalence of prediabetes was 30.6% (n=5495) by FPG and 20.4% (n=3664) by HbA1c criteria. The 5-year progression rate to diabetes was significantly higher in prediabetes identified by HbA1c than by FPG tests (14.7% vs. 10.4%, P<0.001). Of individuals diagnosed with prediabetes by only one test, those by HbA1c alone had a higher risk of progression to diabetes than those diagnosed by FPG alone (6.0% vs. 3.9%, P<0.001). Receiver operating characteristic curve analysis showed that area under the curve was greater for HbA1c (0.855, 95% CI 0.840-0.870) than for FPG (0.830, 0.813-0.846) (P=0.016). After adjustment for conventional risk factors, the odds ratio (OR) of developing diabetes was higher in participants with prediabetes identified by HbA1c (OR 9.91, 8.24-11.9) than by FPG (OR 7.29, 5.97-8.89) (P=0.026).

CONCLUSIONS

Although fewer individuals with prediabetes were identified by HbA1c than by FPG criteria, the ability to predict progression to diabetes was stronger for HbA1c than for FPG in Koreans.

Prognosis of Ischemic Stroke With Newly Diagnosed Diabetes Mellitus According to Hemoglobin A1c Criteria in Chinese Population

Background and Purpose—

Hemoglobin A1c (HbA1c) was recommended to diagnose diabetes mellitus, but whether newly diagnosed diabetes mellitus (NDDM) according to the new criteria was associated with stroke prognosis was unclear. We aimed to investigate the prognosis of ischemic stroke with NDDM according to the new criteria.

Methods—

Ischemic stroke without a diabetes mellitus history in the survey on Abnormal Glucose Regulation in Patients With Acute Stroke Across China were included in the analysis. NDDM was defined as fasting plasma glucose ≥7.0 mmol/L, 2-hour oral glucose tolerance test ≥11.1 mmol/L, or HbA1c ≥6.5%, and NDDM was divided into group 1, diagnosed by glucose criteria (fasting plasma glucose ≥7.0 mmol/L or 2-hour oral glucose tolerance test ≥11.1 mmol/L with/without HbA1c ≥6.5%), or group 2, diagnosed by single high HbA1c (fasting plasma glucose <7.0 mmol/L, 2-hour oral glucose tolerance test <11.1 mmol/L, and HbA1c ≥6.5%). The association between NDDM and 1-year prognosis (mortality, stroke recurrence, and poor functional outcome [modified Rankin scale score 3–6]) was estimated.

Results—

Among 1251 ischemic stroke patients, 539 were NDDM and 141 of NDDM with single high HbA1c. NDDM was an independent risk factor for 1-year mortality (hazard ratio, 1.12; 95% confidence interval, 1.001–1.26), stroke recurrence (hazard ratio, 1.14; 95% confidence interval, 1.01–1.28), and poor functional outcome (odds ratio, 2.58; 95% confidence interval, 1.95–3.43) compared with non–diabetes mellitus. Nevertheless, NDDM with single high HbA1c was not significantly associated with 1-year prognosis for all end points ( P >0.05 for all).

Conclusions—

NDDM by new criteria was associated with poor prognosis at 1 year after ischemic stroke; however, NDDM with single high HbA1c did not predict a poor prognosis.

IDENTIFYING PROBABLE DIABETES MELLITUS AMONG HISPANICS/LATINOS FROM FOUR U.S. CITIES: FINDINGS FROM THE HISPANIC COMMUNITY HEALTH STUDY/STUDY OF LATINOS

OBJECTIVE

The aim of this study was to compare the ability of American Diabetes Association (ADA) diagnostic criteria to identify U.S. Hispanics/Latinos from diverse heritage groups with probable diabetes mellitus and assess cardiovascular risk factor correlates of those criteria.

METHODS

Cross-sectional analysis of data from 15,507 adults from 6 Hispanic/Latino heritage groups, enrolled in the Hispanic Community Health Study/Study of Latinos. The prevalence of probable diabetes mellitus was estimated using individual or combinations of ADA-defined cut points. The sensitivity and specificity of these criteria at identifying diabetes mellitus from ADA-defined prediabetes and normoglycemia were evaluated. Prevalence ratios of hypertension, abnormal lipids, and elevated urinary albumin-creatinine ratio for unrecognized diabetes mellitus-versus prediabetes and normoglycemia-were calculated.

RESULTS

Among Hispanics/Latinos (mean age, 43 years) with diabetes mellitus, 39.4% met laboratory test criteria for probable diabetes, and the prevalence varied by heritage group. Using the oral glucose tolerance test as the gold standard, the sensitivity of fasting plasma glucose (FPG) and hemoglobin A1c-alone or in combination-was low (18, 23, and 33%, respectively) at identifying probable diabetes mellitus. Individuals who met any criterion for probable diabetes mellitus had significantly higher (P<.05) prevalence of most cardiovascular risk factors than those with normoglycemia or prediabetes, and this association was not modified by Hispanic/Latino heritage group.

CONCLUSION

FPG and hemoglobin A1c are not sensitive (but are highly specific) at detecting probable diabetes mellitus among Hispanics/Latinos, independent of heritage group. Assessing cardiovascular risk factors at diagnosis might prompt multitarget interventions and reduce health complications in this young population.

ABBREVIATIONS

2hPG = 2-hour post-glucose load plasma glucose ADA = American Diabetes Association BMI = body mass index CV = cardiovascular FPG = fasting plasma glucose HbA1c = hemoglobin A1c HCHS/SOL = Hispanic Community Health Study/Study of Latinos HDL-C = high-density-lipoprotein cholesterol NGT = normal glucose tolerance NHANES = National Health and Nutrition Examination Survey OGTT = oral glucose tolerance test TG = triglyceride UACR = urine albumin-creatinine ratio.

Do glycemic marker levels vary by race? Differing results from a cross-sectional analysis of individuals with and without diagnosed diabetes

OBJECTIVE

It is well known that A1c varies by race. However, racial differences in other biomarkers of hyperglycemia are less well characterized. The objective of this study was to determine whether average levels of glycemic markers differ by race in adults with and without diagnosed diabetes, before and after accounting for postchallenge glucose.

RESEARCH DESIGN AND METHODS

This cross-sectional study included 2692 middle-aged men and women (5.5% with diagnosed diabetes; 44% African-American; and 56% white) from the Coronary Artery Risk Development in Young Adults Study (2005-2006) who had fasting glucose, 2-hour postchallenge glucose, A1c, glycated albumin, fructosamine, and 1,5-anhydroglucitol (1,5-AG) measured. Multiple linear regression was used to evaluate racial differences in mean levels of each glycemic marker stratified by the diabetes status and adjusted for sociodemographics, cardiovascular factors, and postchallenge glucose.

RESULTS

Among those with diagnosed diabetes, racial differences were not observed for any of the glycemic markers. In contrast, among those without diagnosed diabetes, African-Americans had higher mean levels than whites of A1c (β=0.19% points; 95% CI 0.14 to 0.24), glycated albumin (β=0.82% points; 95% CI 0.68 to 0.97), fructosamine (β=8.68 μmol/L; 95% CI 6.68 to 10.68), and 2-hour glucose (β=3.50 mg/dL; 95% CI 0.10 to 6.90) after multivariable adjustment, whereas there were no statistically significant racial difference in 1,5-AG. The racial differences observed for A1c, glycated albumin, and fructosamine persisted after further adjustment for fasting and 2-hour glucose and were of similar magnitude (SD units).

CONCLUSIONS

Racial differences in glycemic marker levels were evident among middle-aged adults without diagnosed diabetes even after adjustment for postchallenge glucose. Whether these racial differences in biomarkers of hyperglycemia affect the risk of complications warrants additional study.

Differences in Hemoglobin A1c Between Hispanics/Latinos and Non-Hispanic Whites: An Analysis of the Hispanic Community Health Study/Study of Latinos and the 2007-2012 National Health and Nutrition Examination Survey

OBJECTIVE

To determine whether, after adjustment for glycemia and other selected covariates, hemoglobin A1c (HbA1c) differed among adults from six Hispanic/Latino heritage groups (Central American, Cuban, Dominican, Mexican, Puerto Rican, and South American) and between Hispanic/Latino and non-Hispanic white adults without self-reported diabetes.

RESEARCH DESIGN AND METHODS

We performed a cross-sectional analysis of data from 13,083 individuals without self-reported diabetes from six Hispanic/Latino heritage groups, enrolled from 2008 to 2011 in the Hispanic Community Health Study/Study of Latinos, and 2,242 non-Hispanic white adults enrolled during the 2007-2012 cycles of the National Health and Nutrition Examination Survey. We compared HbA1c levels among Hispanics/Latinos and between Hispanics/Latinos and non-Hispanic whites before and after adjustment for age, sex, fasting (FPG) and 2-h post-oral glucose tolerance test (2hPG) glucose, anthropometric measurements, and selected biochemical and hematologic variables and after stratification by diabetes status: unrecognized diabetes (FPG ≥7.1 mmol/L or 2hPG ≥11.2 mmol/L), prediabetes (FPG 5.6-7.0 mmol/L or 2hPG 7.8-11.1 mmol/L), and normal glucose tolerance (FPG <5.6 mmol/L and 2hPG <7.8 mmol/L).

RESULTS

Adjusted mean HbA1c differed significantly across all seven groups (P < 0.001). Non-Hispanic whites had significantly lower HbA1c (P < 0.05) than each individual Hispanic/Latino heritage group. Upon stratification by diabetes status, statistically significant differences (P < 0.001) in adjusted mean HbA1c persisted across all seven groups.

CONCLUSIONS

HbA1c differs among Hispanics/Latinos of diverse heritage groups and between non-Hispanic whites and Hispanics/Latinos after adjustment for glycemia and other covariates. The clinical significance of these differences is unknown.

Association of HbA1c with hospitalization and mortality among patients with heart failure and diabetes

Background

Comorbid diabetes is common in heart failure and associated with increased hospitalization and mortality. Nonetheless, the association between glycemic control and outcomes among patients with heart failure and diabetes remains poorly characterized, particularly among low income and minority patients.

Methods

We performed a retrospective cohort study of outpatients with heart failure and diabetes in the New York City Health and Hospitals Corporation, the largest municipal health care system in the United States. Cox proportional hazard models were used to measure the association between HbA1c levels and outcomes of all-cause hospitalization, heart failure hospitalization, and mortality.

Results

Of 4723 patients with heart failure and diabetes, 42.6 % were black, 30.5 % were Hispanic/Latino, 31.4 % were Medicaid beneficiaries and 22.9 % were uninsured. As compared to patients with an HbA1c of 8.0–8.9 %, patients with an HbA1c of <6.5, 6.5–6.9, 7.0–7.9, and ≥9.0 % had an adjusted hazard ratio (aHR) (95 % CI) for all-cause hospitalization of 1.03 (0.90–1.17), 1.05 (0.91–1.22), 1.03 (0.90–1.17), and 1.13 (1.00–1.28), respectively. An HbA1c ≥ 9.0 % was also associated with an increased risk of heart failure hospitalization (aHR 1.33; 95 % CI 1.11–1.59) and a non-significant increased risk in mortality (aHR 1.20; 95 % CI 0.99–1.45) when compared to HbA1c of 8.0–8.9 %.

Conclusions

Among a cohort of primarily minority and low income patients with heart failure and diabetes, an increased risk of hospitalization was observed only for an HbA1c greater than 9 %.

Relationship between glycated albumin and glycated hemoglobin according to glucose tolerance status: A multicenter study

AIMS

To determine the relationship between glycated albumin (GA) and glycated hemoglobin (HbA1c) and to explore the association of glycated albumin/glycated hemoglobin (GA/HbA1c) ratio with glucose indices in Chinese subjects with varying glucose tolerance status.

METHODS

This hospital-based, cross-sectional study involved 953 participants without known diabetes from 11 centers in China. Oral glucose tolerance test (OGTT) was used to identify three groups of subjects: normal glucose regulation (n=194), impaired glucose regulation (n=303) and newly diagnosed type 2 diabetes group (n=456). The GA, HbA1c and GA/HbA1c ratio were tested.

RESULTS

GA was positively correlated with HbA1c (r=0.832, P<0.001). After correcting for age, sex and BMI, the correlations remained significant (r=0.824, P<0.001). Linear regression analysis estimated that a 1% increase of HbA1c was associated with a 2.84% increase of GA (GA=2.843×HbA1c-0.203; R(2)=0.692, P<0.001). GA would be 18.3 (16.7-19.9)% and 19.7 (18.0-21.4)% with HbA1c of 6.5% (48mmol/mol) and 7.0% (53mmol/mol). The mean GA/HbA1c ratio was 2.81±0.38, and it significantly increased with the presence of glucose intolerance (all, P<0.05). In the total study population, GA/HbA1c was correlated with BMI, glucose levels and 30-min insulin during OGTT, the homeostatic model assessment of β-cell function (HOMA-β), and ΔI30/ΔG30 (all, P<0.05). Increased glucose at 30min (standardized β=0.221, P<0.001), and decreased BMI (standardized β=-0.114, P=0.008) were associated with elevated GA/HbA1c ratio by multiple linear regression (adjusted R(2)=0.045).

CONCLUSIONS

The relationship between GA and HbA1c was strong. The GA/HbA1c ratio was related to acute postprandial glucose fluctuation and BMI level.

Decreased Glycemic Difference Between Diabetes and Nondiabetes in the Elderly Leads to the Reduced Diagnostic Accuracy of Hemoglobin A1c for Diabetes Screening in an Aged Chinese Population

BACKGROUND

This study investigated the impact of age on the accuracy of glycated hemoglobin (HbA1c) for diabetes screening and explored the possible cause(s).

MATERIALS AND METHODS

Data from 3,050 Chinese participants 25-75 years of age without known diabetes in a population-based cross-sectional survey were analyzed. Diabetes was diagnosed by the oral glucose tolerance test (OGTT). The performance of HbA1c for detecting OGTT-defined diabetes in tertile groups (divided by age) was evaluated by the area under the curve (AUC) of the receiver operating characteristic curve (ROC). The effect of age on the difference in glucose levels between participants with and without diabetes and the impact of this difference on the performance of HbA1c were evaluated.

RESULTS

In young (25-41 years old), middle-aged (41-53 years old), and old (55-72 years old) participants, the ROC AUC (95% confidence interval) of HbA1c for detecting OGTT-defined diabetes was 0.958 (0.915, 1.000), 0.891 (0.852, 0.930), and 0.861 (0.821, 0.901), respectively (P = 0.005). The difference of fasting plasma glucose between participants with diabetes and those without diabetes decreased with increasing age: 3.01 (2.80, 3.22) mmol/L, 2.90 (2.71, 3.09) mmol/L, and 2.33 (2.16, 2.50) mmol/L in the three consecutive age groups, respectively. A similar pattern was found in 2-h postprandial plasma glucose. The impact of age on the diagnostic power of HbA1c diminished after data were rearranged to artificially increase the difference between participants without diabetes and those with diabetes.

CONCLUSIONS

The accuracy of HbA1c for detecting OGTT-defined diabetes declines with age. This is largely due to the decreased separation in glycemic levels between participants with diabetes and without diabetes in the elderly.

Agreement of Point-of-Care Capillary Glycated Hemoglobin Levels with Conventional Screening Tests for Diabetes Mellitus in a Canadian First Nations Population

OBJECTIVES

1) How closely do capillary glycated hemoglobin (A1C) levels agree with venous A1C levels? 2) How well do venous A1C levels agree with plasma glucose for diagnosis of diabetes in this population?

METHODS

The Seabird Island mobile diabetes clinic screened people not known to have diabetes by using finger-prick capillary A1C levels with point-of-care analysis according to the Siemens/Bayer DCA 2000 system. Clients then went to a clinical laboratory for confirmatory testing for venous A1C levels, fasting plasma glucose (FPG) and plasma glucose 2 hours after 75 g oral glucose load (2hPG). A reference laboratory compared the DCA 2000 and the clinical laboratory's Roche Integra 800CTS system to the National Glycohemoglobin Standardization Program Diabetes Control and Complications Trial (DCCT) reference.

RESULTS

1) In the reference laboratory, DCA 2000 and Integra 800CTS both agreed very closely with the DCCT standard. In the field, capillary glycated hemoglobin percent (A1C) % was biased, underestimating venous A1C % by a mean of 0.19 (p<0.001). The margin of error of bias-adjusted capillary A1C % was ±0.36 for 95% of the time, compared to ±0.27 for venous A1C%. 2) By linear regression, we found FPG 7.0 mmol/L and 2hPG 11.1 mmol/L predicted mean venous A1C levels very close to 6.5%, with no significant bias.

CONCLUSIONS

Point-of-care capillary A1C did not perform as well in the field as in the laboratory, but the bias is correctible, and the margin of error is small enough that the test is clinically useful. In this population, venous A1C levels ≥6.5% agree closely with the FPG and 2hPG thresholds to diagnose diabetes; ethnic-specific adjustment of the venous A1C threshold is not necessary.

Superiority of lipoprotein particle number to detect associations with arterial thickness and stiffness in obese youth with and without prediabetes

BACKGROUND

The nuclear magnetic resonance (NMR) lipoprotein profile provides additional cardiovascular risk information beyond traditional lipids in high-risk adults. Similar studies have not been conducted in youth.

OBJECTIVE

To evaluate the relationship between the NMR profile and preclinical vascular measures in youth.

METHODS

We studied 96 obese youth with prediabetes (mean age = 18.1 ± 3.6 years, 63% female, 78% African American) and 118 obese normoglycemic controls (mean age = 18.0 ± 3.1 years, 75% female, 62% African American) cross sectionally. Traditional lipids (triglycerides, total, high-density lipoprotein [HDL], and low-density lipoprotein [LDL] cholesterol), NMR particle size (particle concentration [P] and size) and vascular thickness (carotid IMT) and stiffness (pulse wave velocity [PWV]) were measured. Independent associations between lipoproteins with carotid IMT and PWV after adjustment for group, age, race, sex, BMI z score, blood pressure, HOMA-IR, and A1c were studied.

RESULTS

NMR analysis revealed youth with prediabetes exhibited a more atherogenic profile with higher levels of small LDL-P and HDL-P and lower levels of intermediate and large HDL-P (P < .03). In addition, lower intermediate HDL-P was associated with a higher carotid IMT, whereas higher small HDL-P was associated with a higher PWV (P < .01). Traditional lipids were not significantly different between groups and were not associated with either vascular outcome.

CONCLUSIONS

NMR lipoprotein subclasses have improved sensitivity compared to traditional lipids to detect lipoprotein abnormalities in normoglycemic and prediabetic obese youth and are independently associated with preclinical vascular thickness and stiffness. NMR lipids may enhance cardiovascular risk assessment in youth.

Led Astray by Hemoglobin A1c: A Case of Misdiagnosis of Diabetes by Falsely Elevated Hemoglobin A1c

Hemoglobin A1c (A1c) is used frequently to diagnose and treat diabetes mellitus. Therefore, it is important be aware of factors that may interfere with the accuracy of A1c measurements. This is a case of a rare hemoglobin variant that falsely elevated a nondiabetic patient’s A1c level and led to a misdiagnosis of diabetes. A 67-year-old male presented to endocrine clinic for further management after he was diagnosed with diabetes based on an elevated A1c of 10.7%, which is approximately equivalent to an average blood glucose of 260 mg/dL. Multiple repeat A1c levels remained >10%, but his home fasting and random glucose monitoring ranged from 92 to 130 mg/dL. Hemoglobin electrophoresis and subsequent genetic analysis diagnosed the patient with hemoglobin Wayne, a rare hemoglobin variant. This variant falsely elevates A1c levels when A1c is measured using cation-exchange high-performance liquid chromatography. When the boronate affinity method was applied instead, the patient’s A1c level was actually 4.7%. Though hemoglobin Wayne is clinically silent, this patient was erroneously diagnosed with diabetes and started on an antiglycemic medication. Due to this misdiagnosis, the patient was at risk of escalation in his “diabetes management” and hypoglycemia. Therefore, it is important that providers are aware of factors that may result in hemoglobin A1c inaccuracy including hemoglobin variants.

Medication Adherence Does Not Explain Black-White Differences in Cardiometabolic Risk Factor Control among Insured Patients with Diabetes

BACKGROUND

Among patients with diabetes, racial differences in cardiometabolic risk factor control are common. The extent to which differences in medication adherence contribute to such disparities is not known. We examined whether medication adherence, controlling for treatment intensification, could explain differences in risk factor control between black and white patients with diabetes.

METHODS

We identified three cohorts of black and white patients treated with oral medications and who had poor risk factor control at baseline (2009): those with glycated hemoglobin (HbA1c) >8 % (n = 37,873), low-density lipoprotein cholesterol (LDL-C) >100 mg/dl (n = 27,954), and systolic blood pressure (SBP) >130 mm Hg (n = 63,641). Subjects included insured adults with diabetes who were receiving care in one of nine U.S. integrated health systems comprising the SUrveillance, PREvention, and ManagEment of Diabetes Mellitus (SUPREME-DM) consortium. Baseline and follow-up risk factor control, sociodemographic, and clinical characteristics were obtained from electronic health records. Pharmacy-dispensing data were used to estimate medication adherence (i.e., medication refill adherence [MRA]) and treatment intensification (i.e., dose increase or addition of new medication class) between baseline and follow-up. County-level income and educational attainment were estimated via geocoding. Logistic regression models were used to test the association between race and follow-up risk factor control. Models were specified with and without medication adherence to evaluate its role as a mediator.

RESULTS

We observed poorer medication adherence among black patients than white patients (p < 0.01): 50.6 % of blacks versus 39.7 % of whites were not highly adherent (i.e., MRA <80 %) to HbA1c oral medication(s); 58.4 % of blacks and 46.7 % of whites were not highly adherent to lipid medication(s); and 33.4 % of blacks and 23.7 % of whites were not highly adherent to BP medication(s). Across all cardiometabolic risk factors, blacks were significantly less likely to achieve control (p < 0.01): 41.5 % of blacks and 45.8 % of whites achieved HbA1c <8 %; 52.6 % of blacks and 60.8 % of whites achieved LDL-C <100; and 45.7 % of blacks and 53.6 % of whites achieved SBP <130. Adjusting for medication adherence/treatment intensification did not alter these patterns or model fit statistics.

CONCLUSIONS

Medication adherence failed to explain observed racial differences in the achievement of HbA1c, LDL-C, and SBP control among insured patients with diabetes.

Diagnostic values of glycated haemoglobin and diagnosis of diabetes: Results of a cross-sectional survey among general practitioners in the province of Reggio Emilia, Italy

•

The multilevel analysis showed a strong GP clustering effect.

•

The age was related to the likelihood to be diagnosed as ‘having diabetes’.

•

Need to enhance dissemination on the use of HbA1c test as diagnostic tool.

•

The exchange between GPs and the register could improve the diagnosis timeliness.

Aims

The aim of this study was to investigate whether subjects included in the diabetes register solely because their HbA1c was over the diagnostic threshold received a diagnosis of diabetes from their general practitioner (GP).

Methods

The study included all registered cases in 2009–2010 aged 18 or over that were identified only by the laboratory database because they had one or more HbA1c over the 6.5% threshold and for whom we did not find any information in the search of full electronic clinical records. Multilevel logistic regression was used to examine the influence of GP and patient characteristics.

Results

There were 228 participating GPs (76.3% of those invited) and 832 assessed subjects (68.8% of study population). There was a strong clustering among the GPs (residual intraclass correlation = 0.52, 95% CI 0.40–0.64). About one in two (55.5%) subjects with two or more HbA1c > =6.5% has been diagnosed as diabetic and the percentage declined – unless zeroing – in case the abnormal value was only one (28.3%). The likelihood of being labelled ‘no diabetes’ was greater in subjects aged less than 65 or over 74 with respect to the reference age group (OR 1.89, 95% CI 1.13–3.15; OR 1.55 95% CI 0.94–2.53). The same likelihood consistently decreased when HbA1c test was accompanied by abnormal fasting plasma glucose (FPG) assay (OR 0.20, 95% CI 0.12–0.32).

Conclusions

A permanent exchange of information between the diabetes register and GPs should be maintained to improve the care of patients and the awareness of criteria for diabetes diagnosis among GPs.

Standardising HbA1c-based diabetes diagnosis: opportunities and challenges

Globally, the incidence of diabetes mellitus is rising at an alarming rate and has become a health crisis that threatens the economies of all nations. Therefore, diagnosing diabetes has become an important issue in the management of diabetes. Glycated hemoglobin (HbA1c) is now recommended as a means to diagnose diabetes, but its use still has limitations. In this article, the biology, measurement, standardization, and opportunities and challenges of the use of HbA1c to diagnose diabetes are reviewed. More specifically, its use in China and the Asian region is discussed in detail.

Is There a Role for HbA1c in Pregnancy?

Outside pregnancy, HbA1c analysis is used for monitoring, screening for and diagnosing diabetes and prediabetes. During pregnancy, the role for HbA1c analysis is not yet established. Physiological changes lower HbA1c levels, and pregnancy-specific reference ranges may need to be recognised. Other factors that influence HbA1c are also important to consider, particularly since emerging data suggest that, in early pregnancy, HbA1c elevations close to the reference range may both identify women with underlying hyperglycaemia and be associated with adverse pregnancy outcomes. In later pregnancy, HbA1c analysis is less useful than an oral glucose tolerance test (OGTT) at detecting gestational diabetes. Postpartum, HbA1c analysis detects fewer women with abnormal glucose tolerance than an OGTT, but the ease of testing may improve follow-up rates and combining HbA1c analysis with fasting plasma glucose or waist circumference may improve detection rates. This article discusses the relevance of HbA1c testing at different stages of pregnancy.

Novel Risk Factors for Type 2 Diabetes in African-Americans

In the USA, compared to whites, African-Americans are disproportionately impacted by the diabetes epidemic. Traditional diabetes risk factors, such as obesity, are more common among African-Americans, but these traditional risk factors do not explain all of the disparity in diabetes risk. Recent research has identified novel environmental, lifestyle, physiologic, and genetic risk factors for diabetes, some of which appear to impact African-Americans more than whites. This manuscript reviews the recent literature to highlight some of these novel risk factors that may be contributing to the racial disparity in diabetes risk. Further study is needed of the modifiable risk factors for development of interventions to reduce the risk of diabetes in African-Americans, as well as other high-risk populations.

Performance of HbA1c for the prediction of diabetes in a rural community in Korea

AIM

To investigate the performance of HbA1c in predicting incident diabetes among Korean adults with normal fasting glucose and impaired fasting glucose levels.

METHODS

This study used data from the Korean Genome Epidemiology Study-Kangwha Study. A prospective analysis was carried out on 2079 people (820 men and 1259 women) who completed follow-up examinations up until 2013. Diabetes was defined as fasting blood glucose level ≥ 7.0 mmol/l, HbA1c level ≥ 48 mmol/mol (6.5%), or current treatment for diabetes. Areas under the receiver-operating characteristic curves were used to assess the different performances of HbA1c , glucose and insulin in predicting diabetes.

RESULTS

The median follow-up time was 3.97 years, during which 7.7% of men and 6.3% of women developed incident diabetes. The areas under the receiver-operating curves (95% CI) for diabetes prediction were 0.740 (0.692-0.787) for HbA1c , 0.716 (0.667-0.764) for glucose and 0.598 (0.549-0.648) for insulin. HbA1c showed better predictive power in people with impaired fasting glucose (area under the curve 0.753, 95% CI 0.685-0.821) than in those with normal glucose (area under the curve 0.648, 95% CI 0.577-0.719). An HbA1c threshold of 40 mmol/mol (5.8%) was found to have the highest predictive value for diabetes, with a relative risk of 6.30 (95% CI 3.49-11.35) in men and 3.52 (95% CI 2.06-6.03) in women after adjusting for age, waist circumference, triglycerides, hypertension, family history of diabetes, smoking, alcohol intake, exercise and baseline glucose level.

CONCLUSIONS

HbA1c can be used to identify people at high risk for the development of diabetes, especially in those with impaired fasting glucose levels.

Family Model of Diabetes Education With a Pacific Islander Community

PURPOSE

The purpose of the study was to use a community-based participatory research approach to pilot-test a family model of diabetes education conducted in participants' homes with extended family members.

METHODS

The pilot test included 6 families (27 participants) who took part in a family model of diabetes self-management education (DSME) using an intervention-driven pre- and posttest design with the aim of improving glycemic control as measured by A1C. Questionnaires and additional biometric data were also collected. Researchers systematically documented elements of feasibility using participant observations and research field reports.

RESULTS

More than three-fourths (78%) of participants were retained in the study. Posttest results indicated a 5% reduction in A1C across all participants and a 7% reduction among those with type 2 diabetes. Feasibility of an in-home model with extended family members was documented, along with observations and recommendations for further DSME adaptations related to blood glucose monitoring, physical activity, nutrition, and medication adherence.

CONCLUSIONS

The information gained from this pilot helps to bridge the gap between knowledge of an evidence-based intervention and its actual implementation within a unique minority population with especially high rates of type 2 diabetes and significant health disparities. Building on the emerging literature of family models of DSME, this study shows that the family model delivered in the home had high acceptance and that the intervention was more accessible for this hard-to-reach population.

Improving Detection of Prediabetes in Children and Adults: Using Combinations of Blood Glucose Tests

Highlights

Aim

To determine combinations of blood glucose tests: oral glucose tolerance (OGT), fasting plasma glucose (FPG), and hemoglobin A1C (HbA1C) that are associated with highest diagnostic rates of prediabetes in non-diabetic American children and adults.

Methods

The 2007–2008 U.S. National Health and Nutrition Examination Surveys data were used for this study. Overall and specific prevalence of prediabetes (defined using OGT + FPG, OGT + HbA1C, HbA1C + FPG, and OGT + FPG + HbA1C tests) were determined across age, race/ethnicity, sex, and BMI categories.

Results

FPG + HbA1C test was associated with significantly higher diagnostic rates of prediabetes across age, race/ethnicity, and BMI. Estimates of overall prevalence of prediabetes using OGT + FPG, OGT + HbA1C, HbA1C + FPG, and OGT + FPG + HbA1C tests were 20.3, 24.2, 33, and 34.3%, respectively. Compared to OGT + FPG, the use of HbA1C + FPG test in screening was associated with 44.8, 135, 38.6, and 35.9% increased prevalence of prediabetes in non-Hispanic White, non-Hispanic Black, Mexican-American, and other racial/ethnic men, respectively. The corresponding values in women were 67.8, 140, 37.2, and 42.6%, respectively. Combined use of all blood glucose tests did not improve the overall and gender-specific prediabetes prevalence beyond what was observed using HbA1C + FPG test.

Conclusion

HbA1C criteria were associated with higher diagnosis rates of prediabetes than FPG and OGT tests in non-diabetic American children and adults. Using a combination of HbA1C and FPG test in screening for prediabetes reduces intrinsic systematic bias in using just HbA1C testing and offers the benefits of each test. A well-defined HbA1C that takes into consideration race/ethnicity, gender, age, and body mass index may improve detection of prediabetes in population and clinical settings.