title: Derivation & validation of glycosylated haemoglobin (HbA1c) cut-off value as a diagnostic test for type 2 diabetes in south Indian population.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Department of Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: Alladi
authors.initials: A
authors.lastname: Mohan
authors.affiliation: Department of Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: S Aparna
authors.initials: SA
authors.lastname: Reddy
authors.affiliation: Department of Endocrinology and Metabolism, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: Alok
authors.initials: A
authors.lastname: Sachan
authors.affiliation: Department of Statistics, Sri Venkateswara University, Tirupati, India.
authors.forename: Kvs
authors.initials: K
authors.lastname: Sarma
authors.affiliation: Department of Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: D Prabath
authors.initials: DP
authors.lastname: Kumar
authors.affiliation: Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai, India.
authors.forename: Mahesh V
authors.initials: MV
authors.lastname: Panchagnula
authors.affiliation: Department of Biochemistry, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: Pvln Srinivasa
authors.initials: PS
authors.lastname: Rao
authors.affiliation: Department of Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, India.
authors.forename: B Siddhartha
authors.initials: BS
authors.lastname: Kumar
authors.affiliation: Department of General Medicine, Harshitha Hospital, Tirupati, India.
authors.forename: P
authors.initials: P
authors.lastname: Krishnaprasanthi
mesh_terms: D000328:Adult; D001786:Blood Glucose; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000473:pathology; D005006:Ethnicity; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin