Investigations to diagnose diabetes mellitus
1- Blood Glucose Testing:
normal fasting whole blood glucose varies from :60-100 mg/dl
normal fasting plasma blood glucose levels are 10-15% higher beacause the structural components of blood cells are absent, so that more glucose is present per unit volume
Aplasma glucose measurement is more frequently used clinically beacause : they are independent of hematocrit
blood samples may be:
Venous: venous blood samples should be collected in tubes containing sodium fluoride which prevents glycolysis in blood samples that would lower the measured glucose level
capillary: capillary blood samples measure capillary whole blood glucose it is performed using glucometer and it is rapid,easy and reliable method
diagnostic values:
Fasting plasma glucose level more than 120 mg/dl on two or more separate dayes after an overnight fast
random plasma glucose level more than 200 mg/dl
Oral glucose tolerance test: it is rarely used except for questionable cases: if fasting plasma glucose level is between 110-126mg/dl in suspected cases, fasred overnight
2-Urine Testing
testing of the urine for glucose is performed using sensitive glucose-specific dipstick method
advantage: rapid,convenientand glucose-specific
disadvantage: it is rough guide as rental threshold for glucose more than 180 mg/dl is widely changed and increase whith age