Assessment of glycaemic control

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Assessment of glycaemic control:

Assessment and monitoring of glycaemic status is a cornerstone of diabetes care and self-management.
The term “diabetic control” refers to how well the blood glucose levels are maintained in the person with diabetes.

* Diabetes mellitus is unique among the endocrine disorders in that the level of blood glucose is monitored rather than the hormone (ie insulin) as in other endocrine disorders where the hormone blood levels are measured (eg thyroid) to monitor therapeutic effects.

Urine testing:
use of reagent impregnated strips to measure pre-prandial glucose levels in urine
diabetes can not be diagnosed if glycosuria is present – but is a valuable pointer (not sensitive or specific enough for diagnosis)
has major limitations (due to raised renal threshold for glucose – mostly in type 1) – tests are also influenced by fluid intake, the concentration of the urine and the use of some drugs
can be used by some with type 2 who have stable glucose levels and are controlled by diet
eg Clinitest, Diastix
largely been replaced by self monitoring of blood glucose, but has a role for detection of ketone levels, especially during pregnancy or acute illness

Blood testing:
Capillary blood glucose levels/self monitoring of blood glucose (SMBG):
should be performed regularly at home so achievement of specific glycaemic goals can be achieved and maintained; essential component of management
testing of capillary blood from finger prick. Single use, sterile and disposable finger prick devices are available.
enzyme impregnated reagent strips are read visually or a glucose meter is used to electronically determined blood glucose levels
information is available immediately  well informed decisions and helps motivation
provide information for day to day management, but is not an indicator of longer term glycaemic levels
those with Type 1 should generally test before breakfast, before lunch, before evening meal and before bed. Regular use is associated with improved glycaemic control
those with Type 2 and not using insulin usually only need to test every few days

Glycated haemoglobin:
measure of control over previous 90-120 days (average life span of red blood cell), as opposed to one instant of time
ration of glycated haemoglobin to total haemoglobin is normally 4-6%; consensus is that targets for good control in those with diabetes is 7-8% (could depend on individual factors)
HbA1c – stable minor haemoglobin component that form slowly from the non-enzymatic combination of haemoglobin and glucose. The rate of formation is directly proportional to the glucose concentration
blood is assayed by a number of different methods – some variability between laboratories
has become the ‘standard’ for assessing glycaemic control – shown to be predictive of many chronic complications
often recommended that it be done every 6 months
several studies have shown that HbA1c levels are related to the development and progression of the microvascular complications
Can be misleading in presence of conditions that affect red blood cell turn over (eg iron deficiency; pregnancy; blood loss; etc)

Oral glucose tolerance test (OGTT):
not a first line test; indicated if unequivocal diagnosis can not be made from fasting or random glucose tests.
time consuming and labour intensive
3 days of adequate carbohydrate intake and normal activity
fasting or 10-16 hours prior to text
oral glucose load of 75gms in 250-350mls of water (for adults)
blood sample are taken at before glucose load and at 1 and 2 hours after

• results of glycation of plasma proteins (mainly albumin)
• measurement reflects average glycaemia over preceding 2-3 weeks

Continuous Glucose Monitoring:
Ideal method, specially linked to insulin delivery technology.

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