Usefulness of stable HbA(1c) for supportive marker to diagnose diabetes mellitus in Japanese subjects

Glycated hemoglobin (HbA1c) as diagnostic criteria for diabetes: the optimal cut-off points values for the Pakistani population; a study from second National Diabetes Survey of Pakistan (NDSP) 2016-2017

AIM

Glycated hemoglobin (HbA1c) cut-off values as diagnostic tool in diabetes and prediabetes with its concordance to oral glucose tolerance test (OGTT) in Pakistani population.

METHODOLOGY

Data for this substudy was obtained from second National Diabetes Survey of Pakistan (NDSP) 2016-2017. With this survey, 10 834 individuals were recruited and after excluding known subjects with diabetes, 6836 participants fulfilled inclusion criteria for this study. Demographic, anthropometric and biochemical parameters were obtained. OGTT was used as standard diagnostic tool to screen population and HbA1c for optimal cut-off values. Participants were categorized into normal glucose tolerance (NGT), newly diagnosed diabetes (NDD) and prediabetes.

RESULTS

Out of 6836 participants, 4690 (68.6%) had NGT, 1333 (19.5%) had prediabetes and 813 (11.9%) had NDD by OGTT criteria with median (IQR) age of 40 (31-50) years. Optimal HbA1c cut-off point for identification of diabetes and prediabetes was observed as 5.7% ((AUC (95% CI)=0.776 (0.757 to 0.795), p<0.0001)) and 5.1% ((AUC (95% CI)=0.607 (0.590 to 0.624), p<0.0001)), respectively. However, out of 68.6% NGT subjects identified through OGTT, 24.1% and 9.3% participants were found to have prediabetes and NDD, respectively by using HbA1c criteria. By using both OGTT and HbA1c criteria, only 7.9% and 7.3% were observed as prediabetes and diabetes, respectively.

CONCLUSION

Findings from second NDSP demonstrated disagreement between findings of OGTT and HbA1c as diagnostic tool for Pakistani population. As compared with international guidelines, HbA1c threshold for prediabetes and NDD were lower in this part of world. HbA1c as diagnostic tool might require ethnic or regional-based modification in cut-off points, validated by relevant community-based epidemiological surveys.

Optimal Glycated Hemoglobin Cutoff Point for Diagnosis of Type 2 Diabetes in Iranian Adults

OBJECTIVES

The aim of this study was to evaluate the capability of glycated hemoglobin (A1C) levels to be a tool for identifying Iranian adults with diabetes and prediabetes.

METHODS

In a cross-sectional population-based study, 1,813 adults, men and women 35 to 75 years of age and without a history of diabetes and hemoglobinopathies, were included. Fasting blood glucose and A1C levels were obtained. According to the criteria of the American Diabetes Association, participants were categorized into 3 groups: newly diagnosed diabetes, prediabetes and healthy subjects. The optimal cutoff point for A1C in diabetes and prediabetes diagnosis was determined by studying the sensitivity and specificity of different cutoff points for A1C, while using different levels of fasting blood glucose as the gold standard.

RESULTS

Participants with newly diagnosed diabetes were significantly older than subjects with prediabetes and healthy subjects (mean [± SD] 47.3±12.9, 44.6±13.0 and 39.2±14.1 years, respectively) and also had higher body mass indexes. As expected, the levels of fasting blood glucose (8.79±2.24, 6.01±0.38 and 4.97±0.4 mmol/L) and A1C (6.55±1.4%, 5.61±0.61% and 5.28±0.59%) were significantly different in the groups (p<0.001). The optimal cutoff point for A1C to predict prediabetes was 5.5% (sensitivity of 60.5% and specificity of 63.1%) and for diabetes was 5.9% (sensitivity of 66.7% and specificity of 81.2%). ADA cutoff points for prediabetes and diabetes detection yielded a sensitivity of 45.2% and 39.8%, respectively.

CONCLUSIONS

The findings suggest the necessity of determining the A1C cutoffs for detecting diabetes or prediabetes in each region's population. They also suggest that the combination of these A1C cutoffs with fasting blood glucose levels are required to determine diabetes and prediabetes more accurately.

Diabetes screening in overweight and obese children and adolescents: choosing the right test

Type 2 diabetes can occur without any symptoms, and health problems associated with the disease are serious. Screening tests allowing an early diagnosis are desirable. However, optimal screening tests for diabetes in obese youth are discussed controversially. We performed an observational multicenter analysis including 4848 (2668 female) overweight and obese children aged 7 to 17 years without previously known diabetes. Using HbA1c and OGTT as diagnostic criteria, 2.4% (n = 115, 55 female) could be classified as having diabetes. Within this group, 68.7% had HbA1c levels ≥48 mmol/mol (≥6.5%). FPG ≥126 mg/dl (≥7.0 mmol/l) and/or 2-h glucose levels ≥200 mg/dl (≥11.1 mmol/l) were found in 46.1%. Out of the 115 cases fulfilling the OGTT and/or HbA1c criteria for diabetes, diabetes was confirmed in 43.5%. For FPG, the ROC analysis revealed an optimal threshold of 98 mg/dl (5.4 mmol/l) (sensitivity 70%, specificity 88%). For HbA1c, the best cut-off value was 42 mmol/mol (6.0%) (sensitivity 94%, specificity 93%).

CONCLUSIONS

HbA1c seems to be more reliable than OGTT for diabetes screening in overweight and obese children and adolescents. The optimal HbA1c threshold for identifying patients with diabetes was found to be 42 mmol/mol (6.0%). What is Known: • The prevalence of obesity is increasing and health problems related to type 2 DM can be serious. However, an optimal screening test for diabetes in obese youth seems to be controversial in the literature. What is New: • In our study, the ROC analysis revealed for FPG an optimal threshold of 98 mg/dl (5.4 mmol/l, sensitivity 70%, specificity 88%) and for HbA1c a best cut-off value of 42 mmol/mol (6.0%, sensitivity 94%, specificity 93%) to detect diabetes. Thus, in overweight and obese children and adolescents, HbA1c seems to be a more reliable screening tool than OGTT.

Glycated hemoglobin for the diagnosis of diabetes and prediabetes: Diagnostic impact on obese and lean subjects, and phenotypic characterization

Aims/Introduction

Measurement of glycated hemoglobin (HbA1c) has been recommended for the diagnosis of diabetes and prediabetes. However, epidemiological studies have shown significant discordance between HbA1c and glucose-based tests. Of the factors that could influence agreement between HbA1c and the oral glucose tolerance test (OGTT), bodyweight has not been fully evaluated. The aims of the present study were to evaluate the impact of HbA1c criteria to diagnose diabetes and prediabetes compared with OGTT, and to examine HbA1c in relation to body mass index.

Materials and Methods

Two cohorts were studied, one from an obesity clinic (n = 592) and one from subjects undergoing screening for diabetes (n = 462). All underwent OGTT and HbA1c measurement.

Results

In the obese cohort, HbA1c ≥6.5% (≥48 mmol/mol) showed a sensitivity of 69.3% for diabetes, whereas HbA1c 5.7–6.4% (39–46 mmol/mol) did not identify prediabetes well (sensitivity 39.1%). In the diabetes screening cohort, HbA1c had low sensitivities for both diabetes (39.2%) and prediabetes (53.3%). When participants were stratified according to body mass index class I–III, HbA1c agreement with the OGTT for diabetes was much higher (80%, P < 0.005) in class I obesity compared with class II–III obesity; whereas for prediabetes, HbA1c had a low sensitivity in all obesity classes.

Conclusions

The agreement between HbA1c, fasting plasma glucose and 2-h glucose post-OGTT for the diagnosis of prediabetes was poor in our Italian population; whereas HbA1c ≥6.5% showed a relatively good agreement with OGTT for the diagnosis of diabetes. For the first time, we have shown that obesity class influences the diagnostic performance of HbA1c.

Diagnostic accuracy of HbA1c in diabetes between Eastern and Western

BACKGROUND

In 2010, the American Diabetes Association recommended the use of HbA1c as a diagnostic criterion for diabetes. However, HbA1c is not an accepted diagnostic tool for diabetes in Eastern Asia, because genetic differences compromise the standardization of the diagnostic cut-off point.

OBJECTIVES

This study evaluated differences in the use of HbA1c for diagnosing diabetes in Eastern and Western populations and investigated whether HbA1c cut-off point of ≥ 6.5% is diagnostic of diabetes in patients from Eastern Asia.

METHODS

Literature was obtained from MEDLINE, EMBASE and Cochrane databases. The pooled sensitivity and specificity of each HbA1c cut-off point were extracted and compared between Western and Eastern populations. Differences in the cut-off point for diagnosing diabetes in each region were compared by examining differences in the area under summary receiver operating characteristic (SROC) curves.

RESULTS

Twelve publications from Eastern countries (n = 59,735) and 13 from Western countries (n = 22,954) were included in the analysis. Areas under SROC curves in the Eastern and Western groups were 0.9331 and 0.9120, respectively (P = 0.98). The cut-off point of the highest Youden index was 6.0%. At the HbA1c cut-off point of 6.5%, the pooled sensitivity and specificity were 58.7% and 98.4% for Eastern countries and 65.5% and 98.1% for Western countries, respectively.

CONCLUSIONS

HbA1c exhibits the same diagnostic value for diabetes in Eastern and Western populations. In both populations, HbA1c levels > 6.0% identify the population at high risk of diabetes, and HbA1c > 6.5% is diagnostic of clinically established diabetes.

Use of hemoglobin A1C to detect Haitian-Americans with undiagnosed Type 2 diabetes

OBJECTIVE

To evaluate the validity of hemoglobin A1C (A1C) as a diagnostic tool for type 2 diabetes and to determine the most appropriate A1C cutoff point for diagnosis in a sample of Haitian-Americans.

SUBJECTS AND METHODS

Subjects (n = 128) were recruited from Miami-Dade and Broward counties, FL. Receiver operating characteristics (ROC) analysis was run in order to measure sensitivity and specificity of A1C for detecting diabetes at different cutoff points.

RESULTS

The area under the ROC curve was 0.86 using fasting plasma glucose ≥ 7.0 mmol/L as the gold standard. An A1C cutoff point of 6.26% had sensitivity of 80% and specificity of 74%, whereas an A1C cutoff point of 6.50% (recommended by the American Diabetes Association - ADA) had sensitivity of 73% and specificity of 89%.

CONCLUSIONS

A1C is a reliable alternative to fasting plasma glucose in detecting diabetes in this sample of Haitian-Americans. A cutoff point of 6.26% was the optimum value to detect type 2 diabetes.

Cloning and characterization of fructosamine-6-kinase from Arthrobacter aurescens

Fructosamine-6-kinases (FN6Ks) that catalyze phosphorylation of glycated amino acids, i.e., fructosyl amino acids (FAs), have been shown as a potential recognition element for glycated protein detection. However, there are only two available FN6Ks: those from Escherichia coli which is specific for ε-fructosyl lysine (ε-FK) and Bacillus subtilis which recognizes both ε-FK and α-FA as substrates. In this study, we characterized an FN6K homologue isolated from Arthrobacter, some of whose species are reported to assimilate FA. The BLAST searches of Arthrobacter genomic database, using the bacterial FN6K primary structure information, revealed the presence of an FN6K homologue in Arthrobacter aurescens TC1 strain. Indeed, enzymatic assays confirmed that the putative FN6K from A. aurescens is an FN6K that is specific for ε-FK, although the primary sequence alignments showed similarity of A. aurescens FN6Ks with FN6Ks from B. subtilis and E. coli at the same level. In this study, we describe for the first time the presence of FN6K in Arthrobacter spp. and ε-FK-specific degradation pathway from Gram-positive bacteria, providing important information for the development of FA-recognizing molecules as well as for the FA assimilation system in bacteria.

Risk factors for primary open-angle glaucoma in Japanese subjects attending community health screenings

Background/aims

To describe risk factors associated with primary open-angle glaucoma (POAG) in Japanese subjects who participated in community health screenings.

Methods

Residents of Akita, Japan, participating in a community health checkup were selected to undergo a comprehensive ophthalmic examination. Glaucoma was diagnosed based on optic disk appearance, perimetric results, and other ocular findings. Systemic blood pressure and intraocular pressure were measured and ocular perfusion pressure was calculated. Logistic regression analysis was performed to determine risk factors for POAG patients.

Results and conclusion

Of the 710 subjects examined, 26 had POAG. The estimated prevalence of POAG was 3.7%. After adjusting for age, the prevalence of POAG was similar to that found in the Tajimi Study of Japanese subjects. Multivariate logistic regression analysis demonstrated that older age (≥60 years, odds ratio [OR]: 3.49), lower diastolic blood pressure (≤58 mmHg, OR: 2.11), higher intraocular pressure (≥19 mmHg, OR: 4.12), and lower ocular perfusion pressure (≤34 mmHg, OR: 5.78) were associated with increased risk of having POAG. These findings may be relevant for identifying high risk groups.

HbA(1c) measurement for the diagnosis of diabetes: is it enough?

AIM

To analyse the performance of HbA(1c) in diagnosing Type 2 diabetes based on fasting plasma glucose and/or 2-h plasma glucose measurements after a 75-g oral glucose tolerance test.

METHODS

This is a study of diagnostic test accuracy in individuals referred to the Clinical Pathology Department for oral glucose tolerance testing. After fasting overnight, HbA(1c), fasting plasma glucose and 2-h plasma glucose were measured. The receiver operating characteristic curve was used to evaluate the diagnostic performance of HbA(1c).

RESULTS

Four hundred and ninety-eight subjects (195 male, mean age 56 years) were enrolled and 115 (23.1%) were diagnosed with diabetes according to glucose-based methods and only 56 (11.2%) individuals were identified by HbA(1c) ≥ 6.5% (48 mmol/mol) (sensitivity 20.9%, specificity 95.3%). There is poor agreement between the newly recommended criterion and the current glucose-based diagnostic criteria (κ = 0.217; P < 0.001), probably because the diagnostic methods identify different populations of patients. Adding a glucose-based method into an algorithm, as proposed by the UK Department of Health, improved HbA(1c) performance.

CONCLUSIONS

HbA(1c) ≥ 6.5% (48 mmol/mol) showed limited sensitivity to diabetes diagnosis, although with high specificity. The results suggest that this cut-off point would not be enough to diagnose diabetes. Its use as the sole diabetes diagnostic test should be interpreted with caution to assure the correct classification of diabetic individuals.

Diabetes, prediabetes and cancer mortality

AIMS/HYPOTHESIS

We aimed to investigate the risk of cancer mortality in relation to the glucose tolerance status classified according to the 2 h OGTT.

METHODS

Data from 17 European population-based or occupational cohorts involved in the DECODE study comprising 26,460 men and 18,195 women aged 25-90 years were collaboratively analysed. The cohorts were recruited between 1966 and 2004 and followed for 5.9 to 36.8 years. Cox proportional hazards analysis with adjustment for cohort, age, BMI, total cholesterol, blood pressure and smoking status was used to estimate HRs for cancer mortality.

RESULTS

Compared with people in the normal glucose category, multivariable adjusted HRs (95% CI) for cancer mortality were 1.13 (1.00, 1.28), 1.27 (1.02, 1.57) and 1.71 (1.35, 2.17) in men with prediabetes, previously undiagnosed diabetes and known diabetes, respectively; in women they were 1.11 (0.94, 1.30), 1.31 (1.00, 1.70) and 1.43 (1.01, 2.02), respectively. Significant increases in deaths from cancer of the stomach, colon-rectum and liver in men with prediabetes and diabetes, and deaths from cancers of the liver and pancreas in women with diabetes were also observed. In individuals without known diabetes, the HR (95% CI) for cancer mortality corresponding to a one standard deviation increase in fasting plasma glucose was 1.06 (1.02, 1.09) and in 2 h plasma glucose was 1.07 (1.03, 1.11).

CONCLUSIONS/INTERPRETATION

Diabetes and prediabetes were associated with an increased risk of cancer death, particularly death from liver cancer. Mortality from all cancers rose linearly with increasing glucose concentrations.

Motif-based search for a novel fructosyl peptide oxidase from genome databases

The measurement of glycated hemoglobin A1c (HbA1c) has important implications for diagnosis of diabetes and assessment of treatment effectiveness. We proposed specific sequence motifs to identify enzymes that oxidize glycated compounds from genome database searches. The gene encoding a putative fructosyl amino acid oxidase was found in the Phaeosphaeria nodorum SN15 genome and successfully expressed in Escherichia coli. The recombinant protein (XP_001798711) was confirmed to be a novel fructosyl peptide oxidase (FPOX) with high specificity for alpha-glycated compounds, such as HbA1c model compounds fructosyl-(alpha)N-valine (f-(alpha)Val) and fructosyl-(alpha)N-valyl-histidine (f-(alpha)Val-His). Unlike previously reported FPOXs, the P. nodorum FPOX has a K(m) value for f-(alpha)Val-His (0.185 mM) that is considerably lower than that for f-(alpha)Val (0.458 mM). Based on amino acid sequence alignment, three dimensional structural modeling, and site-directed mutagenesis, Gly60 was found to be a determining residue for the activity towards f-(alpha)Val-His. A flexible surface loop region was also found to likely play an important role in accepting f-(alpha)Val-His.

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

CONTEXT

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

OBJECTIVE

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

DESIGN AND SETTING

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

SUBJECTS

Subjects included 1972 subjects aged 20 yr or older.

INTERVENTION

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSION

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

Inverse associations of serum bilirubin with high sensitivity C-reactive protein, glycated hemoglobin, and prevalence of type 2 diabetes in middle-aged and elderly Japanese men and women

AIM

The aim of this study was to examine the association of serum bilirubin, an endogenous antioxidant, with serum high sensitivity C-reactive protein (hs-CRP) level, HbA(1c), and the prevalence of type 2 diabetes in middle-aged and elderly Japanese men and women (n=12,400).

METHODS

Analysis of covariance and logistic regression analysis were used to estimate geometric means of hs-CRP and HbA(1c) and odds ratios of prevalent diabetes according to bilirubin concentrations, respectively, with statistical adjustment for behavioral factors and liver enzymes.

RESULTS

Geometric means of hs-CRP and HbA(1c) were progressively lower with increasing concentrations of serum bilirubin in men and women each. An inverse association between serum bilirubin and HbA(1c) was slightly attenuated after adjustment for hs-CRP, but still remained highly significant (trend P=0.0004 in men and trend P=10(-5) in women). Multivariate-adjusted odds ratios of prevalent diabetes for the lowest to highest quintiles of serum total bilirubin were 1.00, 1.00, 0.73, 0.80, and 0.73 (trend P=0.002), without adjustment for hs-CRP, and 1.00, 1.04, 0.76, 0.86, and 0.79 (trend P=0.01), with adjustment for hs-CRP.

CONCLUSIONS

Higher concentrations of serum bilirubin probably confer protection against the development of type 2 diabetes.

Performance of HbA(1c) for detecting newly diagnosed diabetes and pre-diabetes in Chinese communities living in Beijing

AIM

To determine the performance of glycated haemoglobin (HbA(1c)) as a screening tool for detecting newly diagnosed diabetes (NDM) and pre-diabetes.

METHODS

A diabetes survey was conducted in Beijing among community dwellers who were willing to participate in the survey. Included in the survey were 903 individuals aged 21-79 years without previously diagnosed diabetes and in whom HbA(1c) and other required covariates had been measured. NDM and pre-diabetes (impaired glucose tolerance + impaired fasting glucose) were defined according to the World Health Organization 1999 criteria based on 75-g oral glucose tolerance test. Receiver operating characteristic curve (ROC) was plotted to determine the performance of HbA(1c).

RESULTS

The prevalence of NDM and pre-diabetes was 11.1% and 22.4%, respectively. At an optimal HbA(1c) cut-off point of > or = 6.0%, the test gave a sensitivity of 80.0% and a specificity of 89.8% for diagnosing NDM; at an optimal cut-off point of > or = 5.7%, the sensitivity was 59.4% and specificity 73.9% for diagnosing pre-diabetes. Individuals with HbA(1c)> or = 6.0% tended to be more obese than those with HbA(1c) < 6.0%, but blood pressure and lipid profiles did not differ between the two groups.

CONCLUSIONS

HbA(1c) as a single screening test is adequate to detect newly diagnosed diabetes but is not able to identify pre-diabetes in this obese Chinese population.

Use of glycated hemoglobin (HbA(1C)) and impaired glucose tolerance in the screening of undiagnosed diabetes in the Malaysian population

Although HbA(1C) is widely accepted as a useful index of mean blood glucose in type 2 diabetic patients its usefulness as screening test for diabetes has been controversial. The present study was undertaken to determine whether the level of HbA(1C) predicted diabetes in a prediabetic group of subjects. Plasma lipids, oral glucose tolerance, HbA(1C) was determined in 90 normal control subjects, 57 offspring of one type 2 diabetes mellitus parent and 11 diagnosed type 2 diabetes mellitus individuals. The mean age of participants was 44.5 yrs (not significantly different amongst the three groups) and the mean body mass index was 26.8 (not significantly different amongst the three groups). Two hours after a 75 g glucose challenge, the offspring had a significantly higher plasma glucose level (mean = 7.1 mmol/L, p value = 0.002) than the normals. Similarly the HbA(1C) values were higher in the offspring than in the normals (mean = 5.78%, p value = 0.016). Besides the significantly higher values for oral glucose tolerance test and HbA(1C), the diabetics also were significantly higher for triglycerides (mean = 2.25mmol/L), total cholesterol (mean = 6.24mmol/L) and systolic blood pressure (mean = 138.45mm Hg) than the offspring (P value = 0.031, 0.006, 0.010) and the normals (P value = 0.026, 0.018, 0.002) respectively. The mean values of diastolic blood pressure, LDL cholesterol and HDL cholesterol were not significantly different amongst the three groups.

Does HbA1C predict isolated impaired fasting glycaemia in the oral glucose tolerance test in subjects with impaired fasting glycaemia?

Background

To assess the usefulness of erythrocyte glycated haemoglobin (HbA1C) as a screening tool to identify those subjects with impaired fasting glycaemia (IFG) who do not have impaired glucose tolerance (IGT) or diabetes mellitus (DM) on a 75 g oral glucose tolerance test (OGTT).

Design and methods

All subjects undergoing an OGTT had HbA1C measured at baseline. Receiver operator characteristics analysis was used to identify optimal HbA1C cut-off values for diagnosing and excluding IGT and DM.

Results

We studied 140 subjects (69 women) with IFG (fasting capillary plasma glucose between 6.1–6.9 mmol/L). Using World Health Organisation criteria, 27 had isolated IFG, 56 had IGT and 57 had DM. HbA1C was higher ( P < 0.001) in patients with DM (6.8 ± 0.93%) when compared with those with IGT (6.3 ± 0.68%) and isolated IFG (6.2 ± 0.30%), but HbA1C was similar in those with IGT and isolated IFG. There was no HbA1C cut-off value differentiating isolated IFG from IGT or DM. None of the subjects with isolated IFG had HbA1C concentration of >6.8%, but 76% and 54% subjects with IGT and DM, respectively, had HbA1C of ≤6.8%.

Conclusions

HbA1C measurement is of limited value in differentiating isolated IFG, IGT and DM in subjects with IFG. It cannot be used to identify which subjects with IFG do not require an OGTT.

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

AIM

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

METHODS

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

Relationship between HbA(1)c and mortality in a Japanese population

AIM/HYPOTHESIS

HbA(1)c concentrations are known to be associated with all-cause excess mortality risk in Caucasians. However, the relationship has not been clarified well in the Japanese. In addition, studies of the relationship between HbA(1)c and mortality from malignant neoplasms are scarce.

METHODS

HbA(1)c was measured for 3,710 people of a cohort composed of A-bomb survivors and controls. At baseline they were divided into five groups: a normal HbA(1)c group of 1,143 individuals with HbA(1)c of <5.5%, a slightly high but normal HbA(1)c group of 1,341 individuals with HbA(1)c > or =5.5% to <6.0%, a slightly high HbA(1)c group of 589 individuals with HbA(1)c > or =6.0% to <6.5%, a high HbA(1)c group of 259 individuals with HbA(1)c > or =6.5%, and a group of 378 individuals known to have type 2 diabetes. Using a Cox proportional hazards model, hazard ratios based on comparisons with the normal HbA(1)c group were obtained.

RESULTS

During the observation period there were 754 deaths. For all-cause and cardiovascular disease mortality, a significant increase of the hazard ratio was observed for the slightly high HbA(1)c group. A similar increase in malignant neoplasm-related mortality was observed for both the high HbA(1)c group and the diabetes group.

CONCLUSIONS/INTERPRETATION

Our results suggest that individuals in the Japanese population with HbA(1)c levels of 6% or more might have increased mortality risk. The results indicate that HbA(1)c measurements should be sought even for people who have not been diagnosed with diabetes.

Report of the Committee on the classification and diagnostic criteria of diabetes mellitus

In 1995, the Japan Diabetes Society (JDS) appointed the Committee for the Classification and Diagnosis of Diabetes Mellitus. The Committee presented a final report in May 1999 in Japanese. This is the English version with minor modifications for readers outside Japan.

CONCEPT OF DIABETES MELLITUS

Diabetes mellitus represents a group of diseases of heterogeneous etiology, characterized by chronic hyperglycemia and other metabolic abnormalities, which are due to deficiency of insulin effect. After a long duration of metabolic derangement, specific complications of diabetes (retinopathy, nephropathy, and neuropathy) may occur. Arteriosclerosis is also accelerated. Depending on the severity of the metabolic abnormality, diabetes may be asymptomatic, or may be associated with symptoms (thirst, polyuria, and weight loss), or may progress to ketoacidosis and coma.

CLASSIFICATION

Both etiological classification and staging of pathophysiology by the degree of deficiency of insulin effect need to be considered. The etiological classification of diabetes and related disorders of glycemia includes, (1) type 1; (2) type 2; (3) those due to specific mechanisms and diseases; and (4) gestational diabetes mellitus. Type 1 is characterized by destructive lesions of pancreatic beta cells either by an autoimmune mechanism or of unknown cause. Type 2 diabetes is characterized by combinations of decreased insulin secretion and decreased insulin sensitivity (insulin resistance). Category (3) includes two subgroups; subgroup A is diabetes in which specific mutations have been identified as a cause of genetic susceptibility, while subgroup B is diabetes associated with other pathologic conditions or diseases. The staging of glucose metabolism includes normal, borderline and diabetic stages. The diabetic stage is further classified into three substages; non-insulin requiring, insulin-requiring for glycemic control, and insulin-dependent (ID) for survival. In each individual, these stages may vary according to the deterioration or the improvement of the metabolic state, either spontaneously or by treatment.

DIAGNOSIS

The confirmation of chronic hyperglycemia is a prerequisite for the diagnosis of diabetes mellitus. The state of glycemia may be classified within three categories, diabetic type; borderline type; and normal type. Diabetic type is defined when fasting plasma glucose (FPG) is 7.0 mmol/l (126 mg/dl) or higher, and/or plasma glucose 2 h after 75 g glucose load (2hPG) is 11.1 mmol/l (200 mg/dl) or higher. A casual plasma glucose (PG) > or =11.1 mmol/l (200 mg/dl) also indicates diabetic type. Normal type is defined when FPG is below 6.1 mmol/l (110 mg/dl) and 2hPG below 7.8 mmol/l (140 mg/dl). Borderline type includes those who are neither diabetic nor normal types. These cutoff values are for venous PG measurements. The persistence of 'diabetic type' in a subject indicates that he or she has diabetes. For children, a dose of 1.75 g/kg (maximum, 75 g) is used for oral glucose tolerance test (OGTT). The procedure for clinical diagnosis is as follows. Diabetes mellitus is diagnosed when hyperglycemia meeting the criteria for 'diabetic type' is shown on two or more occasions examined on separate days. Diabetes can be diagnosed by a single PG test of 'diabetic type' if one of the following three conditions co-exists, (1) typical symptoms of diabetes mellitus; (2) HbA1c > or =6.5% by a standardized method; or (3) unequivocal diabetic retinopathy. If the above conditions ((1) or (2)) have been present in the past and well documented, the subject is diagnosed either to have diabetes or to be suspected of diabetes, even if the present level of glycemia does not reach that of 'diabetic type'. If the diagnosis of diabetes cannot be established by these procedures, re-testing of PG is recommended after an appropriate interval. The physician should assess not only the presence or absence of diabetes, but also its etiology and glycemic stage, and the presence and absence of diabetic complications or associated conditions.

EPIDEMIOLOGICAL ASPECTS AND SCREENING

In order to determine the prevalence of diabetes in a population, 'diabetic type' may be regarded as 'diabetes'. The use of 2hPG cutoff level of > or =11.1 mmol/l (200 mg/dl) is recommended. If this is difficult, the FPG cutoff level of > or =7.0 mmol/l (126 mg/dl) can be used, but is likely to lead to under-ascertainment. For screening, the most important point is not to overlook 'diabetes'. In addition to parameters of hyperglycemia, clinical information such as family history, obesity etc., should be regarded as indications for further testing.

NORMAL TYPE AND BORDERLINE

Only FPG and 2hPG are adopted as cutoff values, but in clinical situations, it is recommended to measure PG also at 30 and 60 min during 75 g OGTT. Among people with normal type, those with 1hPG higher than 10.0 mmol/l (180 mg/dl) are at higher risk to develop diabetes than those with lower 1hPG. When OGTT is performed, the borderline type corresponds to the sum of impaired fasting glycemia (IFG) plus impaired glucose tolerance (IGT) according to the new WHO report. Subjects in this category are at higher risk of developing diabetes than those with 'normal type'. Those with low insulinogenic index (the ratio of increment of plasma insulin to that of PG at 30 min during OGTT) are at particularly high risk to develop diabetes. Microvascular complications are rare but arteriosclerotic complications are fairly frequent in this category.

GESTATIONAL DIABETES MELLITUS (GDM)

The current definition of GDM is ' any glucose intolerance developed or detected during pregnancy'. We adopt the proposal of the Japan Society of Gynecology and Obstetrics for the diagnosis of GDM (1984). GDM is defined when two or more values during a 75 g OGTT are higher than the following cutoff levels; FPG > or =5.5 mmol/l (100 mg/dl), 1hPG > or =10.0 mmol/l (180 mg/dl) and 2hPG > or =8.3 mmol/l (150 mg/dl). As a screening test, subjects with casual PG > or =5.5 mmol/l (100 mg/dl) are recommended for further testing. Patients who have had documented glucose intolerance before pregnancy, and who present as 'diabetic type' should be under closer supervision than those who develop GDM during pregnancy for the first time. HbA1c: There is a large overlap in the distribution of HbA1c between groups with 'normal type' and 'borderline type' and mild 'diabetic type'. Therefore, HbA1c is not a suitable parameter to detect mild glucose intolerance. HbA1c higher than 6.5% suggests diabetes, but HbA1c below 6.5% alone should not be taken as evidence against the diagnosis of diabetes. COMPARISON WITH REPORTS OF AMERICAN DIABETES ASSOCIATION (ADA) IN 1997 AND WHO IN 1999: The present report is unique in the following points when compared with those of the ADA 'Diabetes Care 20 (1997) 1183' and WHO 'Report of a WHO Consultation (1999)'. (1) Diabetes due to specific mechanisms and diseases is divided into two subgroups; diabetes in which genetic susceptibility is clarified at the DNA level and diabetes associated with other diseases or conditions. (2) Cutoff PG levels are the same as those of ADA and WHO, but a term 'type' is added to each glycemic category, because a single coding of 'diabetic type' hyperglycemia does not define diabetes. Diabetes is diagnosed when 'diabetic type' hyperglycemia is shown on two or more occasions. (3) A single 'diabetic type' hyperglycemia is considered sufficient for the diagnosis of diabetes, if the patient has typical symptoms, HbA1c > or =6.5%, or diabetic retinopathy. (4) OGTT is recommended for those with mild hyperglycemia, because FPG criteria alone would overlook many subjects with 'diabetic type' in Japan. High 1hPG without elevation of FPG and 2hPG is also considered to be a risk factor for future diabetes. (5) Borderline type in the present report corresponds to the sum of IFG and IGT by WHO when OGTT is performed. (6) New criteria for GDM by OGTT are proposed.

Current literature in diabetes

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of diabetes/metabolism. Each bibliography is divided into 17 sections: 1 Books, Reviews & Symposia; 2 General; 3 Genetics; 4 Epidemiology; 5 Immunology; 6 Prediction; 7 Prevention; 8 INTERVENTION: a&rpar General; b&rpar Pharmacology; 9 Pathology: a&rpar General; b&rpar Cardiovascular; c&rpar Neurological; d&rpar Renal; 10 Endocrinology & Metabolism; 11 Nutrition; 12 Animal Studies; 13 Techniques. Within each section, articles are listed in alphabetical order with respect to author (9 Weeks journals - Search completed at 1st Aug 2001)