The cutoffs and performance of glycated hemoglobin for diagnosing diabetes and prediabetes in a young and middle-aged population and in an elderly population.

The aims were to compare the appropriate cutoffs of glycated hemoglobin (HbA1c) in a population of varying ages and to evaluate the performance of HbA1c for diagnosing diabetes and prediabetes. A total of 1064 participants in the young and middle-aged group and 1671 in the elderly group were included and underwent HbA1c testing and an oral glucose tolerance test (OGTT). Sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the optimal HbA1c cutoffs. Kappa coefficients were used to test for agreement between HbA1c categorization and OGTT-based diagnoses. The optimal HbA1c cutoffs for diagnosing diabetes were 5.7% (39 mmol/mol) in the young and middle-aged group with a sensitivity of 66.7%, specificity of 86.7%, and AUC of 0.821 (95% CI: 0.686, 0.955) and 5.9% (41 mmol/mol) in the elderly group with a sensitivity of 80.4%, specificity of 73.3%, and AUC of 0.831 (0.801, 0.861). The optimal cutoffs for diagnosing prediabetes were 5.6% (38 mmol/mol) and 5.7% (39 mmol/mol) in the young and middle-aged group and in the elderly group, respectively. Agreement between the OGTT-based diagnosis of diabetes or prediabetes and the optimal HbA1c cutoff was low (all kappa coefficients <0.4). The combination of HbA1c and fasting plasma glucose increased diagnostic sensitivities or specificities. In conclusion, age-specific HbA1c cutoffs for diagnosing diabetes or prediabetes were appropriate. Furthermore, the performance of HbA1c for diagnosing diabetes and prediabetes was poor. HbA1c should be used in combination with traditional glucose criteria when detecting and diagnosing diabetes or prediabetes.

Yan ST ，Xiao HY ，Tian H ，Li CL ，Fang FS ，Li XY ，Cheng XL ，Li N ，Miao XY ，Yang Y ，Wang LC ，Zou XM ，Ma FL ，He Y ，Sai XY ... -  《-》

HbA1c Cutoff for Prediabetes and Diabetes Based on Oral Glucose Tolerance Test in Obese Children and Adolescents.

Oral glucose tolerance test (OGTT) is a traditional diagnostic tool for diabetes. Hemoglobin A1c (HbA1c) is an alternative method used in adults; however, its application in youths has been controversial. We evaluated the diagnostic performance of HbA1c and determined optimal cutoff points for detecting prediabetes and diabetes in youth. This retrospective study included 389 obese children (217 boys, 55.8%) who had undergone simultaneous OGTT and HbA1c testing at six hospitals, Korea, between 2010 and 2016. Subjects were diagnosed with diabetes (fasting glucose ≥ 7.0 mmol/L; 2-hour glucose ≥ 11.1 mmol/L) or prediabetes (fasting glucose 5.6-6.9 mmol/L; 2-hour glucose 7.8-11.0 mmol/L). The diagnostic performance of HbA1c for prediabetes and diabetes was determined using the area under the receiver operating characteristic curve (AUC). At diagnosis, 197 (50.6%) subjects had normoglycemia, 121 (31.1%) had prediabetes, and 71 (18.3%) had diabetes. The kappa coefficient for agreement between OGTT and HbA1c was 0.464. The optimal HbA1c cutoff points were 5.8% (AUC, 0.795; a sensitivity of 64.1% and a specificity of 83.8%) for prediabetes and 6.2% (AUC, 0.972; a sensitivity of 91.5% and a specificity of 93.7%) for diabetes. When HbA1c (≥ 6.2%) and 2-hour glucose level were used to diagnose diabetes, 100% were detected. Pediatric criteria for HbA1c remain unclear, therefore, we recommend the combination of fasting and 2-hour glucose levels, in addition to HbA1c, in the diagnosis of childhood prediabetes and diabetes.

Nam HK ，Cho WK ，Kim JH ，Rhie YJ ，Chung S ，Lee KH ，Suh BK ... -  《-》

HbA1c and the diagnosis of diabetes and prediabetes in a middle-aged and elderly Han population from northwest China (HbA1c).

To identify the optimal threshold of HbA1c and to evaluate the predictive performance of HbA1c levels in diagnosing diabetes and prediabetes in a middle-aged and elderly Han Chinese population from northwest China. In all, 3354 participants aged ≥ 40 years with no history of diabetes from northwest China were enrolled in the present cross-sectional study. All subjects underwent a 75-g oral glucose tolerance test (OGTT), as well as HbA1c testing. HbA1c thresholds for diagnosing diabetes and prediabetes were identified by the highest sum of sensitivity and specificity of each cut-off point, and the receiver operating characteristic (ROC) curve was used to evaluate the diagnostic accuracy of the HbA1c threshold. The mean (± SD) age of the participants was 57 ± 8 years, and 70.75% were women. Based on results of the OGTT, 1347 (40.16%) subjects had impaired fasting glucose and/or impaired glucose tolerance, and 725 (21.62%) had diabetes. The area under the ROC curve for detecting undiagnosed diabetes and prediabetes by HbA1c levels was 0.810 (95% confidence interval [CI] 0.796-0.823) and 0.732 (95% CI 0.717-0.747), respectively. HbA1c threshold of 6.4% and 6.1% produced the highest sum of sensitivity (60.00% and 61.49%) and specificity (87.33% and 73.24%) for diagnosing diabetes and prediabetes, respectively. HbA1c is an effective and convenient method for diagnosing diabetes and prediabetes. HbA1c thresholds of 6.4% and 6.1% may be used as diagnostic criteria for diabetes and prediabetes, respectively, in the Han Chinese population living in northwest China.

Wu S ，Yi F ，Zhou C ，Zhang M ，Zhu Y ，Tuniyazi Y ，Huang L ，Huang X ，Wang F ，Bi Y ，Ning G ... -  《-》

Erythrocytosis and Performance of HbA1c in Detecting Diabetes on an Oxygen-Deficient Plateau: A Population-based Study.

The hemoglobin A1c (HbA1c) test is a standard test for diabetes screening and diagnosis. To evaluate A1c performance for diabetes screening in high-altitude polycythemia compared to a population with a high proportion of people living in an oxygen-deficient environment. A population-based epidemiological survey was conducted. The cities Lhasa and Shigatse were selected. Volunteers were recruited through educational advertisements about diabetes. A total of 1401 Tibetan adults without known diabetes. Oral glucose tolerance test (OGTT), HbA1c, and complete blood cell count were performed. Hemoglobin A1c was evaluated using high-performance liquid chromatography, and serum glucose level, using the hexokinase method. World Health Organization criteria were used to define diabetes and prediabetes. Hemoglobin A1c test performance was evaluated using receiver operating characteristic analysis. The participants' mean age was 44.3 ± 15.0 years; 33.3% of the participants were men and 38.6% lived in urban areas. The prediabetes and diabetes prevalence rates were 7.5% and 3.6%, respectively. The optimal HbA1c cutoff for detecting diabetes was 46 mmol/mol (6.4%), with a sensitivity and specificity of 60.8% and 93.6%, respectively. The cutoff for detecting diabetes was 6.7% (50 mmol/mol) in subjects with high-altitude polycythemia (HAPC). The relationship between red blood cell (RBC) counts and HbA1c was significant (P < 0.001), while there was no correlation between hemoglobin (Hb) and HbA1c (P = 0.085). Multiple linear regression analysis showed that after adjusting for age and fasting serum glucose or 2-hour OGTT (OGTT2h) serum glucose, RBC count and not Hb level was an independent risk factor for HbA1c (β = 0.140, P < 0.001). The optimal HbA1c cutoff for detecting diabetes was 46 mmol/mol (6.4%) in Tibet. Red blood cell count was an independent risk factor for elevated HbA1c, and HAPC may affect the predictive ability of HbA1c.

Ren Q ，Lv X ，Yang L ，Yue J ，Luo Y ，Zhou L ，Meng S ，Yang S ，Puchi B ，Zhou X ，Ji L ... -  《-》

Use of HbA1c for diagnoses of diabetes and prediabetes: comparison with diagnoses based on fasting and 2-hr glucose values and effects of gender, race, and age.

Guo F ，Moellering DR ，Garvey WT 《-》