Laboratory Testing in Diabetes
Sample GP Report
Full colour PDF of ‘Laboratory Testing in Diabetes Sample GP Report’ June 2007.
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The complications of diabetes are well known. Management includes not only aiming for good glycaemic control, but also monitoring for and managing risk factors for cardiovascular, renal, nerve and eye disease. This report focuses on laboratory testing in the monitoring of ‘your patients’ with diabetes.
How we define people with diabetes
For the purposes of this report, a person with diabetes is one who was dispensed an anti‑diabetic medication or a diabetes testing strip at least once in 2005 and at least once in 2006, or a blood test for HbA1C levels at least once in 2005 and at least once in 2006.
Women taking metformin for polycystic ovary syndrome (PCO) will therefore be included and this will affect the results. However, numbers are likely to be small. It is a timely reminder that women with PCO are at higher risk of metabolic syndrome and diabetes.
Although HbA1C is not recommended as a screening test for diabetes, we are aware that some clinicians do use it. People who are screened for diabetes with HbA1C will be included in this report only if they have had an HbA1C test in both 2005 and 2006. We do not expect this inclusion criterion will significantly skew national figures but if you use HbA1C for screening for diabetes, your personal figures may be skewed.
How we defined people with diabetes as ‘your patient’
We have included an eligible person as ‘your patient’ if you provided any of the following for the patient:
- A prescription for either an anti-diabetic agent or a testing strip in the 2006 calendar year or
- Any of the following tests in the 2006 calendar year:
- HbA1C - Glucose - Microalbumin - Serum creatinine - Lipids
This means that people you have seen casually for any aspect of their diabetes care will be included as ‘your patient’. Some clinicians may feel that this distorts their figures. The figures should not be seen as a scorecard for your individual practice but more an opportunity for reflection on the monitoring of people with diabetes in your wider community.
Data presented in this report is sourced from the NZHIS laboratory and pharmaceutical claims databases. There is a potential for data entry errors at the pharmacy, laboratory, HealthPAC or NZHIS. All laboratory tests and prescriptions associated with an NZMC number will be presented regardless of where they were generated e.g. an after-hours clinic, rest home or on a practitioner supply order.
Data has been excluded where the NZMC number or the NHI number of the patient was not recorded.
Total Diabetes related tests requested for the 2006 calendar year
|Diabetes Related Tests||You||National
Using our criteria, we identified XXX patients with whom you were involved in their diabetic care in 2006.The following graphs represent tests performed on these patients. They may not have been ordered by you.
HbA1C is the best test for monitoring glycaemic control in diabetes. When a patient is undergoing changes in treatment it is worth testing HbA1C three monthly. More frequent testing is not necessary because HbA1C assesses glycaemic control over the lifespan of red blood cells (approximately 120 days). Once the HbA1C is stable the testing interval can be extended to six months. The target range for this report is two to four tests of HbA1C per year.
|HbA1C tests for ‘your patients’ with diabetes|
People who take insulin for diabetes management should regularly self-monitor blood glucose to guide insulin doses and detect and avoid hypoglycaemia. Self-monitoring of blood glucose can also be useful as part of a structured education programme for people with diabetes not on insulin, especially around times of change in diet or treatment. There is seldom an indication for laboratory glucose testing in people with known diabetes. The target range for this report is less than three laboratory tests of glucose per year.
|Glucose tests for ‘your patients’ with diabetes|
Monitoring and management of lipid levels is central to the management of cardiovascular risk for people with diabetes. It is recommended that fasting lipid levels are performed three monthly until levels are satisfactory and stable. More frequent testing is not recommended. Thereafter, the testing period can be extended to 6 to 12 monthly. The target range for this report is therefore, one to four tests of fasting lipids per year.
|Lipid tests for ‘your patients’ with diabetes|
Prevention of diabetic renal disease includes monitoring for early signs of failing renal function and microalbuminuria. It is recommended that people with diabetes have a serum creatinine test and a urinary microalbumin (albumin:creatinine ratio) at least once per year. The target range for this report is therefore at least one test of serum creatinine and microalbumin per year.
|Creatinine tests for ‘your patients’ with diabetes|
|Microalbumin tests for ‘your patients’ with diabetes|
- For patients with normal glucose metabolism - test every 5 years (or 3 years for those at risk*).
- For patients with impaired glucose tolerance or impaired fasting glucose - test annually. Early identification is important because lifestyle interventions can delay and prevent the onset of diabetes.
Testing for diabetes should be performed as part of a cardiovascular risk assessment.
NZGG recommends this should begin at the following ages:
|Age to start testing|
|Asymptomatic people without known risk factors||45 years||55 years|
|Maori, Pacific peoples and people from the Indian subcontinent||35 years||45 years|
|People with cardiovascular risk factors or at high risk* of developing diabetes||35 years||45 years|
- Equivocal fasting glucose results, should be followed with a glucose tolerance test.
- Urine glucose and HbA1C are not appropriate for diagnosis.
- A fasting glucose ≥ 7.0 mmol/L or a random glucose ≥ 11.0 mmol/L on two separate occasions is diagnostic of diabetes.
- A random glucose of between 7.0 mmol/L and 11.0 mmol/L should be followed up with fasting glucose or OGTT.
Interpretation of fasting blood glucose
|Fasting glucose||< 5.5||5.5 – 6.0||6.1 – 6.9||≥ 7.0|
|Interpretation||Normal||Borderline||Impaired fasting glucose||Diabetic|
||Retest in five years or three years for those at risk.||OGTT for those at increased risk of diabetes.
Re-test annually those with IFG or IGT.
|Assess with OGTT.
|Two results>7.0 on two different days are diagnostic of diabetes.
OGTT is not required.
Interpretation of glucose tolerance test
|2 hours post load
|Normal||< 5.5||AND||< 7.8|
|IFG||6.1 – 6.9||AND||< 7.8|
|IGT||< 7.0||AND||7.8 – 11.0|
|Diabetes mellitus||≥ 7.0||AND/OR||≥ 11.1|
|GDM||≥ 5.5||AND/OR||≥ 9.0|