Hemoglobin which has diagnostic value in diabetes mellitus?
Glycated haemoglobin provides an accurate and objective measure of glycaemic control over a period of weeks to months. In diabetes, the slow non-enzymatic covalent attachment of glucose to haemoglobin (glycation) increases the amount in the HbA1 (HbA1c) fraction relative to non-glycated adult haemoglobin (HbA0). These fractions can be separated by chromatography; laboratories may report glycated haemoglobin as total glycated haemoglobin (GHb), HbA1 or HbA1c. In most countries, HbA1c is the preferred measurement. 
Davidson Ed 23 Pg 726
HbA
HbF
HbA1
HbS
HbA1