Are the same clinical risk factors relevant for incident diabetes defined by treatment, fasting plasma glucose, and HbA1c?

Global variation in diabetes diagnosis and prevalence based on fasting glucose and hemoglobin A1c

Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) are both used to diagnose diabetes, but these measurements can identify different people as having diabetes. We used data from 117 population-based studies and quantified, in different world regions, the prevalence of diagnosed diabetes, and whether those who were previously undiagnosed and detected as having diabetes in survey screening, had elevated FPG, HbA1c or both. We developed prediction equations for estimating the probability that a person without previously diagnosed diabetes, and at a specific level of FPG, had elevated HbA1c, and vice versa. The age-standardized proportion of diabetes that was previously undiagnosed and detected in survey screening ranged from 30% in the high-income western region to 66% in south Asia. Among those with screen-detected diabetes with either test, the age-standardized proportion who had elevated levels of both FPG and HbA1c was 29-39% across regions; the remainder had discordant elevation of FPG or HbA1c. In most low- and middle-income regions, isolated elevated HbA1c was more common than isolated elevated FPG. In these regions, the use of FPG alone may delay diabetes diagnosis and underestimate diabetes prevalence. Our prediction equations help allocate finite resources for measuring HbA1c to reduce the global shortfall in diabetes diagnosis and surveillance.

Association of mean arterial pressure with 5-year risk of incident diabetes in Chinese adults：a secondary population-based cohort study

OBJECTIVE

Hypertension predicts the development of diabetes. However, there are still lacking high-quality studies on the correlation between mean arterial pressure (MAP) and incident diabetes. We aimed to explore the relationship between MAP and diabetes in Chinese adults.

DESIGN

This is a secondary retrospective cohort study and the data were downloaded from the 'DATADRYAD' database (www.Datadryad.org).

PARTICIPANTS

The study included 210 418 adults without diabetes at baseline between 2010 and 2016 across 32 sites and 11 cities in China.

SETTING

The target-independent and dependent variables were MAP measured at baseline and diabetes occurred during follow-up. Cox proportional hazards regression was used to explore the relationship between MAP and diabetes.

PRIMARY OUTCOME MEASURES

The outcome was incident diabetes, which was defined as fasting blood glucose ≥7.00 mmol/L and/or self-reported diabetes during follow-up. Patients were censored either at the time of the diagnosis or at the last visit, whichever comes first.

RESULTS

3927 participants developed diabetes during a 5-year follow-up. After adjusting covariates, MAP positively correlated with diabetes (HR=1.008, 95% CI 1.005 to 1.011, p<0.001), and the absolute risk difference was 0.02%. E-value analysis and multiple imputations were used to explore the robustness of the results. The relationship between MAP and diabetes was also non-linear, and the inflection point of MAP was 100.333 mm Hg. Subgroup analysis revealed a stronger association between MAP and diabetes in people with age (≥30,<50 years old), fasting plasma glucose <6.1 mmol/L and drinking. Additionally, receiver operating characteristic (ROC) curves showed the predictive performance of MAP for diabetes was similar to systolic blood pressure (SBP) (area under the curve (AUC)=0.694 with MAP vs AUC=0.698 with SBP).

CONCLUSIONS

MAP is an independent predictor for a 5-year risk of incident diabetes among Chinese adults. The relationship between MAP and diabetes is also non-linear. When MAP is below 100.333 mm Hg, MAP is closely positively related to diabetes.

Enhanced Predictive Capability of a 1-Hour Oral Glucose Tolerance Test: A Prospective Population-Based Cohort Study

OBJECTIVE

To examine whether the 1-h blood glucose measurement would be a more suitable screening tool for assessing the risk of diabetes and its complications than the 2-h measurement.

RESEARCH DESIGN AND METHODS

We conducted a prospective population-based cohort study of 4,867 men, randomly selected from prespecified birth cohorts between 1921 and 1949, who underwent an oral glucose tolerance test with blood glucose measurements at 0, 1, and 2 h. Subjects were followed for up to 39 years, with registry-based recording of events. Discriminative abilities of elevated 1-h (≥8.6 mmol/L) versus 2-h (≥7.8 mmol/L) glucose for predicting incident type 2 diabetes, vascular complications, and mortality were compared using Kaplan-Meier analysis, Cox proportional hazards regression, and net reclassification improvement.

RESULTS

Median age was 48 years (interquartile range [IQR] 48-49). During follow-up (median 33 years [IQR 24-37]), 636 (13%) developed type 2 diabetes. Elevated 1-h glucose was associated with incident diabetes (hazard ratio 3.40 [95% CI 2.90-3.98], P < 0.001) and provided better risk assessment than impaired glucose tolerance (Harrell concordance index 0.637 vs. 0.511, P < 0.001). Addition of a 1-h measurement in subjects stratified by fasting glucose provided greater net reclassification improvement than the addition of a 2-h measurement (0.214 vs. 0.016, respectively). Finally, the 1-h glucose was significantly associated with vascular complications and mortality.

CONCLUSIONS

The 1-h blood glucose level is a stronger predictor of future type 2 diabetes than the 2-h level and is associated with diabetes complications and mortality.

Follow-up duration influences the relative importance of OGTT and optimal timing of glucose measurements for predicting future type 2 diabetes

OBJECTIVE

To examine the impact of follow-up duration on the incremental prognostic yield of a baseline oral glucose tolerance test (OGTT) for predicting type 2 diabetes and to assess the discrimination ability of blood glucose (BG) obtained at different time points during OGTT.

DESIGN

A prospective, population-based cohort study (Malmö Preventive Project) with inclusion of subjects from 1974 to 1992.

METHODS

A total of 5256 men without diabetes, who had BG measured at 0, 20, 40, 60, 90, and 120 min during OGTT (30 g/m2 glucose), were followed for 30 years. Incident type 2 diabetes was recorded using registries. The performance of OGTT added to a clinical prediction model (age, body mass index (BMI), diastolic blood pressure, fasting BG, triglycerides, and family history of diabetes) was assessed using Harrell's concordance index (C-index) and integrated discrimination improvement (IDI).

RESULTS

Median age was 48 years, mean BMI 24.9 kg/m2, and mean fasting BG 4.7 mmol/L. Models with added post-load BG performed better than the clinical model (C-index: P = 0.08 for BG at 120 min at 5 years, otherwise P ≤ 0.045; IDI: P ≥ 0.06 for BG at 60 and 90 min at 5 years, otherwise P ≤ 0.01). With a longer follow-up duration, C-index decreased, and the C-index increase associated with OGTT was attenuated. Models including BG at 60 or 90 min performed significantly better than the model with BG at 120 min, evident beyond follow-up of 10 and 5 years, respectively.

CONCLUSIONS

OGTT provided incremental prognostic yield for type 2 diabetes prediction. BG measured at 60 or 90 min provided better discrimination than BG at 120 min.

Effects of diabetes definition on global surveillance of diabetes prevalence and diagnosis: a pooled analysis of 96 population-based studies with 331,288 participants

BACKGROUND

Diabetes has been defined on the basis of different biomarkers, including fasting plasma glucose (FPG), 2-h plasma glucose in an oral glucose tolerance test (2hOGTT), and HbA1c. We assessed the effect of different diagnostic definitions on both the population prevalence of diabetes and the classification of previously undiagnosed individuals as having diabetes versus not having diabetes in a pooled analysis of data from population-based health examination surveys in different regions.

METHODS

We used data from 96 population-based health examination surveys that had measured at least two of the biomarkers used for defining diabetes. Diabetes was defined using HbA1c (HbA1c ≥6·5% or history of diabetes diagnosis or using insulin or oral hypoglycaemic drugs) compared with either FPG only or FPG-or-2hOGTT definitions (FPG ≥7·0 mmol/L or 2hOGTT ≥11·1 mmol/L or history of diabetes or using insulin or oral hypoglycaemic drugs). We calculated diabetes prevalence, taking into account complex survey design and survey sample weights. We compared the prevalences of diabetes using different definitions graphically and by regression analyses. We calculated sensitivity and specificity of diabetes diagnosis based on HbA1c compared with diagnosis based on glucose among previously undiagnosed individuals (ie, excluding those with history of diabetes or using insulin or oral hypoglycaemic drugs). We calculated sensitivity and specificity in each survey, and then pooled results using a random-effects model. We assessed the sources of heterogeneity of sensitivity by meta-regressions for study characteristics selected a priori.

FINDINGS

Population prevalence of diabetes based on FPG-or-2hOGTT was correlated with prevalence based on FPG alone (r=0·98), but was higher by 2-6 percentage points at different prevalence levels. Prevalence based on HbA1c was lower than prevalence based on FPG in 42·8% of age-sex-survey groups and higher in another 41·6%; in the other 15·6%, the two definitions provided similar prevalence estimates. The variation across studies in the relation between glucose-based and HbA1c-based prevalences was partly related to participants' age, followed by natural logarithm of per person gross domestic product, the year of survey, mean BMI, and whether the survey population was national, subnational, or from specific communities. Diabetes defined as HbA1c 6·5% or more had a pooled sensitivity of 52·8% (95% CI 51·3-54·3%) and a pooled specificity of 99·74% (99·71-99·78%) compared with FPG 7·0 mmol/L or more for diagnosing previously undiagnosed participants; sensitivity compared with diabetes defined based on FPG-or-2hOGTT was 30·5% (28·7-32·3%). None of the preselected study-level characteristics explained the heterogeneity in the sensitivity of HbA1c versus FPG.

INTERPRETATION

Different biomarkers and definitions for diabetes can provide different estimates of population prevalence of diabetes, and differentially identify people without previous diagnosis as having diabetes. Using an HbA1c-based definition alone in health surveys will not identify a substantial proportion of previously undiagnosed people who would be considered as having diabetes using a glucose-based test.

FUNDING

Wellcome Trust, US National Institutes of Health.

Evaluation of hemoglobin A1c measurement by Capillarys 2 electrophoresis for detection of abnormal glucose tolerance in African immigrants to the United States

BACKGROUND

Hemoglobin A1c (HbA1c) is used to monitor long-term glycemic control in individuals with diabetes, guide therapy, predict the risk of microvascular complications, and more recently to diagnose diabetes. An automated liquid-flow capillary electrophoresis method was recently developed to measure HbA1c using the Capillarys 2 Flex Piercing instrument.

METHODS

Analytical evaluation was performed at 2 clinical centers. A clinical analysis was conducted in 109 African-born individuals, 24% of whom have variant hemoglobin (HbAS or HbAC). Abnormal glucose tolerance (which includes both diabetes and prediabetes) was defined as 2h glucose of ≥ 140 mg/dl (7.8 mmol/l) during an oral glucose tolerance test.

RESULTS

Interlaboratory CVs were ≤ 2.1%. The method showed satisfactory correlation with 2 other analyzers that measure HbA1c by high-performance liquid chromatography. Neither labile HbA1c, carbamylated hemoglobin, uremia, bilirubin nor common hemoglobin variants (HbC/HbS/HbE) interfered. Forty-five individuals (41%) had abnormal glucose tolerance. The sensitivity of HbA1c for diagnosing abnormal glucose tolerance was 38%, 36% and 42% for total, normal and variant hemoglobin groups, respectively.

CONCLUSIONS

The analytical performance of HbA1c on the Capillarys 2 is suitable for clinical application. Variant hemoglobin in Africans did not interfere with the detection of abnormal glucose tolerance by HbA1c measured on the Capillarys 2.

Dental Findings and Identification of Undiagnosed Hyperglycemia

A change in the American Diabetes Association guidelines added hemoglobin A1c (HbA1c) to the assays for diabetes diagnosis, but evidence suggests that glucose vs. HbA1c criteria may identify different segments of the affected population. We previously demonstrated that oral findings offer an opportunity for the detection of undiagnosed abnormal fasting plasma glucose (FPG) among dental patients who present with diabetes risk factors. In this new cross-sectional study, we sought to extend these observations. The first goal, using data from 591 new participants, was to assess our previously identified hyperglycemia detection models when HbA1c is used for case definition. The second goal, using data from our total cohort of 1,097 participants, was to evaluate the models’ performance regardless of whether an FPG or an HbA1c is used for diagnosis. The presence of ≥ 26% teeth with deep pockets or ≥ 4 missing teeth correctly identified 72% of pre-diabetes or diabetes cases in the HbA1c sample and 75% in the total population. The addition of a point-of-care HbA1c ≥ 5.7% increased correct identification to 87% and 90%, respectively. These results demonstrate the validity of our prediction models regardless of the test used for diabetes or pre-diabetes diagnosis in the clinical setting and underscore the contribution dentists can make.

Fasting plasma glucose and HbA1c in cardiovascular risk prediction: a sex-specific comparison in individuals without diabetes mellitus

AIMS/HYPOTHESIS

This study aimed to assess the cardiovascular risk of individuals with fasting plasma glucose (FPG)- and/or HbA(1c)-defined prediabetes (5.6-6.9 mmol/l and 39-47 mmol/mol [5.7-6.4%], respectively) or manifest diabetes mellitus and to evaluate whether FPG or HbA(1c) can improve risk prediction beyond that estimated by the Systematic Coronary Risk Evaluation (SCORE) chart in individuals without diabetes mellitus.

METHODS

Cox regression was employed to estimate HRs for primary incident cardiovascular events (CVEs) in a cohort of 8,365 individuals aged 50-74 years. Furthermore, HbA(1c) and FPG were added individually to the variables of the SCORE and measures of model discrimination and reclassification were assessed.

RESULTS

During 8 years of follow-up, 702 individuals had a primary CVE. After adjusting for conventional cardiovascular risk factors, HRs were attenuated close to one for the prediabetes groups (especially for women), whereas a 1.7- and a 1.9-fold increased risk persisted for men and women with diabetes, respectively. Extension of the SCORE variables by either FPG or HbA(1c) did not improve its predictive abilities in individuals without diabetes. There was a non-significant net reclassification improvement for men when HbA(1c) was added (2.2%, p = 0.16).

CONCLUSIONS/INTERPRETATION

The increased cardiovascular risk of individuals with FPG- or HbA(1c)-defined prediabetes can mainly be explained by other cardiovascular risk factors. Adding FPG or HbA(1c) did not significantly improve CVE risk prediction by the SCORE variables in individuals without diabetes mellitus.

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.