Mohan Alladi, Reddy S Aparna, Sachan Alok, Sarma Kvs, Kumar D Prabath, Panchagnula Mahesh V, Rao Pvln Srinivasa, Kumar B Siddhartha, Krishnaprasanthi P
Department of Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
Department of Endocrinology and Metabolism, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
Indian J Med Res. 2016 Aug;144(2):220-228. doi: 10.4103/0971-5916.195035.
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.
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).
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.
糖化血红蛋白（HbA1c）作为2型糖尿病的诊断检测方法已应用十余年。HbA1c在目标使用的种族人群中的有效性需要确立。本研究的目的是得出并验证印度南部雷雅拉西马地区种族人群中用于诊断2型糖尿病的HbA1c临界值。
在这项横断面研究中，连续入选的疑似2型糖尿病患者在口服75克葡萄糖后接受空腹血糖（FPG）和负荷后2小时血糖（2h-PG）测定以及HbA1c检测。根据美国糖尿病协会标准[FPG≥7 mmol/l（≥126 mg/dl）和/或2h-PG≥11.1 mmol/l（≥200 mg/dl）]将他们分类为患有糖尿病。在训练数据集（n = 342）中，以口服葡萄糖耐量试验结果作为金标准，采用受试者操作特征（ROC）曲线法得出定义2型糖尿病的HbA1c最佳临界值。该临界值在验证数据集（n = 341）中进行验证。
将HbA1c临界值>6.3%（45 mmol/mol）应用于训练数据集时，诊断2型糖尿病的敏感性、特异性、阳性预测值（PPV）和阴性预测值（NPV）分别计算为90.6%、85.2%、80.8%和93.0%。当将相同的临界值应用于验证数据集时，敏感性、特异性、PPV和NPV分别为88.8%、81.9%、74.0%和92.7%，尽管后者始终小于训练数据集的比例，但差异无统计学意义。
HbA1c>6.3%（45 mmol/mol）似乎是适用于印度南部安得拉邦雷雅拉西马地区种族人群诊断2型糖尿病的最佳临界值。
