Tuesday, March 17, 2009

Glucose Monitoring

Introduction

Glucose can be monitored in blood and urine and techniques for doing so are widely employed in clinical practice. However optimal use of home glucose monitoring requires more research and better evaluation of available techniques.1

Self monitoring of blood glucose costs the NHS more than £100 million every year, and the cost is rising. Although blood glucose monitoring is an essential tool in type 1 diabetes (for example in confirminghypoglycaemia and taking corrective action) a recent study found no effect of blood glucose home monitoring on glycaemic control in type 2 diabetics.2,3

Currently the evidence supports use of regular HbA1c estimation to monitor blood glucose control in diabetic patients.1,4
However there is widespread use of methods of home monitoring. This is supported by Diabetes UK5 and should be supported by appropriate advice from health professionals. Many different methods and devices are available for home use by patients. It is important that the use of such devices should be safe.

Good advice and information on the use of such devices may allow improved management of diabetes mellitus. Inappropriate use can confuse and impede good diabetic control. Treatments for diabetes have become more sophisticated in recent years and there is a growing need for support and education of patients when undertaking home monitoring and the subsequent interpretation of results.

Blood glucose monitoring

See article: Blood Glucose Monitoring in Diabetes Mellitus.
Methods are available to allow rapid blood glucose estimation. These allow detection of hypoglycaemia and hyperglycaemia. Diabetes UK has produced a statement on home monitoring of blood glucose levels.5Guidance on the use of home monitoring has been disseminated by some Primary Care Trusts aimed at reducing excessive use of testing strips. The costs of regular blood glucose monitoring are significant. It is important that patients have:

  • Training in the use of the particular method and device
  • Full instructions on how to manage different results and readings
  • Full understanding of the significance of readings and normal fluctuations

NICE4 has further recommended that:

  • Self-monitoring should not be considered as a stand alone intervention.
  • Self-monitoring should be taught if the need/purpose is clear and agreed with the patient.
  • Self-monitoring can be used in conjunction with appropriate therapy as part of integrated self-care.

Evidence statements made by NICE include:

  • Blood or urine testing alone does not improve HbA1c, reduce weight, reduce episodes of hypoglycaemia or improve health related quality of life.
  • Self-monitoring may have a role as part of an integrated self-care package in Type 2 diabetes.
  • There is no evidence that blood glucose monitoring is more effective than urine testing as part of an integrated self-care package in improving blood glucose control.
  • Urine testing is cheaper than blood glucose testing.
  • Urine testing is preferred by some patients.
  • Insulin doses can only be adjusted appropriately on the basis of self-monitored blood glucose levels at different times of day.

However it should be remembered that:

  • The studies reviewed by NICE were poorly conducted and clinically relevant effects might not have been detectable.
  • Patients perceptions of monitoring were incompletely studied and further work was called for.

Indications

Home glucose monitoring in both type 1 and type 2 diabetes mellitus can be part of good self management of patients diabetes.5

  • It is widely used in type 1 and type 2 diabetes mellitus (particularly those on sulphonylureas).
  • Patients with type 2 diabetes who do not need to regularly self-test blood glucose are those:
    • Controlled with diet and exercise
    • On metformin with or without a glitazone
    Blood glucose testing can be limited to periods of illness, changes in medication etc. At these times once or twice daily testing may be needed.
  • There is a lack of evidence to show that blood or urine glucose self-monitoring improves blood glucose control or any other outcomes.2,3,1
  • It can usefully be used to measure peaks and troughs in blood glucose levels over 24 hours.
  • It is important particularly when there is intercurrent illness.
  • It may be important in pregnancy although there is lack of evidence on the value of this.1
  • It is helpful when making small adjustments to diabetic treatment or changes of diabetic treatment.
  • It may be helpful when other drugs are used which may affect blood glucose.
  • It may be helpful for improved control with more extreme changes in activity (for example sport and exercise).

Specific advice on how monitoring is employed should be given with full advice and information tailored to the individual patient. In one study of diabetics not treated with insulin self-monitoring was associated with higher HbAic levels and greater psychological burden.6

Methods

Blood sampling

This should be done using a method which is convenient, hygienic and comfortable. Techniques which may help achieve this include:

  • Washing the hand to be used in warm water
  • Shaking the hand before sampling
  • Using side of finger rather than sensitive fleshy pulp of finger
  • Use of lancing devices, especially those allowing use of less sensitive sites such as upper arm or thigh (for example the Freestyle device by Abbott and the Ascencia Vacculance by Bayer)
  • Use of a less painful but expensive (£400-£500) laser device (for example the Lasette device)

Test strips

A variety of test strips are available. Visual colour comparison can be used but is less reliable.

Test meters

The test strips are best read using a meter. The meters are more accurate and they overcome visual impairments (such as colour blindness and poor acuity). It should always be checked that the correct strips for the particular meter are prescribed.7

Blood glucose targets

Diabetes UK recommends that diabetics aim for:

  • Preprandial levels of 4-6 mmol/l
  • Postprandial levels below 10 mmol/l 2 hours after meals

However these targets should be set as part of an individual and integrated care package to ensure that they are appropriate and effective.

Urinary glucose monitoring

See article: Urine Glucose Monitoring in Diabetes Mellitus.
Urine testing is cheaper than blood glucose monitoring and preferred by some patients with type 2 diabetes. It is not recommended for use in type 1 diabetes or when there is a risk of hypoglycaemia as it cannot identify hypoglycaemia.

Indications

Type 2 diabetes mellitus.

Methods

Available methods can detect:

  • Glucose specifically with reagent strips:
    • Clinistix are suitable for screening purposes only
    • Diabur-Test 5000
    • Diastix
    • Medi-Test Glucose
  • Reducing sugars with reagent tablets:
    • Clinitest kits (test tube and dropper packs available) are seldom used
  • Ketones

Patients are instructed as follows:

  • Test in the morning before breakfast
  • Empty bladder
  • Test urine passed 30 minutes later
  • Hold a test strip under the stream of urine for a few seconds and compare the colour change of the strip with the chart on the container after a set amount of time
  • The reading is usually given as a percentage figure where 0 is ideal
  • Tests can be performed 2-3 hours after a meal (postprandial/ peak level)
  • Urine is less accurate than blood glucose and cannot identify hypoglycaemia
  • Some people with low renal threshold for glucose may show positive results at blood levels below 10mmol/l
  • High renal threshold may occur in older patients

Document references
  1. Coster S, Gulliford MC, Seed PT, et al; Monitoring blood glucose control in diabetes mellitus: a systematic review. Health Technol Assess. 2000;4(12):i-iv, 1-93.
  2. Farmer A, Wade A, Goyder E, et al; Impact of self monitoring of blood glucose in the management of patients with non-insulin treated diabetes: open parallel group randomised trial. BMJ. 2007 Jul 21;335(7611):132. Epub 2007 Jun 25. [abstract]
  3. Farmer A, Wade A, French DP, et al; The DiGEM trial protocol--a randomised controlled trial to determine the effect on glycaemic control of different strategies of blood glucose self-monitoring in people with type 2 diabetes . BMC Fam Pract. 2005 Jun 16;6:25. [abstract]
  4. Management of Type 2 Diabetes - blood glucose, NICE (2002)
  5. Diabetes UK: Position statement on home monitoring of blood glucose levels
  6. Franciosi M, Pellegrini F, De Berardis G, et al; The impact of blood glucose self-monitoring on metabolic control and quality of life in type 2 diabetic patients: an urgent need for better educational strategies. Diabetes Care. 2001 Nov;24(11):1870-7. [abstract]
  7. Diabetes UK: Guide to meters and test strips
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