Effective self-monitoring of blood glucose

Back in 2005, Owens et al outlined a guide to the frequency of self-monitoring of blood glucose (SMBG) according to therapy use. Few published works improve on the advice therein and it  remains a useful guide. NICE has provided its own, simpler, algorithm (summarised in Figure  1), but this does not describe frequency of testing. Another aspect of SMBG that must be considered is the recent changes to driving regulations, which will also be discussed in the article. There is little debate on the need for people with type 1 diabetes to self-monitor their blood glucose, as the majority of them use the information to alter their insulin doses and to detect potential hypoglycaemic episodes and treat them accordingly. NICE (2009) acknowledges that, and furthermore advises that, SMBG is an essential element of self-care if backed by education.

However, NHS Diabetes (2010) points out that “there is increasing concern that health service managers and GPs are using published evidence to prevent even individuals who find blood glucose monitoring useful from checking their blood glucose whenever they feel they need to.”

The Scottish Intercollegiate Guidelines Network (SIGN; 2010) advises that the impact of SMBG on management of glycaemic control is positive but small for patients with type 2 diabetes who are not on insulin, and slightly larger, but based on poorer evidence, for those using insulin. It is difficult to use the evidence base to define those patients with type 2 diabetes who will gain most benefit from SMBG. Extrapolation from the evidence would suggest that specific subgroups of patients may benefit. These include those who are at increased risk of hypoglycaemia or its consequences, and those who are supported by health professionals in acting on glucose readings to change health behaviours including appropriate alterations in insulin dose. Further research is needed to define more clearly which subgroups are most likely to benefit (SIGN, 2010).

Effectiveness of SMBG
Controversy exists regarding the effectiveness of SMBG in type 2 diabetes. On the one hand it is seen as an expensive option with little evidence to support it; on the other it is seen as a vital tool in engaging people with diabetes in their own care. The paragraphs that follow illustrate these differences of opinion.

Martin et al (2006) found that SMBG was associated with decreased diabetes-related morbidity and all-cause mortality in people with type 2 diabetes. The association was also observed in a subgroup of participants who were not receiving insulin. The authors’ opinion was that SMBG may be associated with a healthier lifestyle and better disease management.

Peel and Lawton (2007) found that clinical uncertainty about the efficacy and role of SMBG in people with type 2 diabetes was mirrored in individuals’ accounts. People tended not to act on their self-monitoring results, in part because of a lack of education about the appropriate response to readings – a fact well recognised by healthcare professionals working with people with diabetes. The authors stressed that healthcare professionals should be explicit about whether and when such patients should self-monitor and how they should interpret and act upon the results, especially high readings. This may be seen as an argument for improved education rather than for restrictions in SMBG and is reflected in the latest guidance from NICE (Figure 1).

Simon et al (2008), on behalf of the DiGEM (Diabetes Glycaemic Education and Monitoring) study group, found that SMBG – with or without additional training in incorporating the results into self-care – was associated with higher costs and lower quality of life in people with non-insulin-treated type 2 diabetes. The authors felt that SMBG was unlikely to be cost-effective in addition to standardised, usual care. 

Furthermore, Farmer et al (2009), again on behalf of the DiGEM study group, found no convincing evidence to recommend routine use of SMBG by reasonably well-controlled, non-insulin-treated people with type 2 diabetes. However, the authors did consider that clinical judgement is required to identify those who would benefit, including people at high risk of hypoglycaemia and those motivated to make alterations to behaviour that lead to consistent changes in blood glucose levels, and where there is strong patient preference. The authors stated that if HbA_1c levels remain >64 mmol/mol (8%), then self-monitoring may provide motivation for medication adherence and lifestyle measures, as insulin therapy may be required in this group.

A small study from Ireland (O’Kane et al, 2008), comprising 96 participants in the monitoring group, is frequently quoted as a reason for restricting access to SMBG testing strips. The authors concluded that people with newly diagnosed type 2 diabetes had no beneficial effects from SMBG, but that it was associated with higher scores on a depression sub-scale. The size of the study (among other things), however, leads others to argue with its validity in the larger population (see BMJ rapid responses; available at: http://bit.ly/PCBVu6 [accessed 23.08.12]).

The authors of the STeP (Structured TEsting Protocol) study recognise that while some studies have questioned the value and utility of SMBG, specifically in non-insulin-treated patients, more recent studies have shown that appropriate use of structured SMBG, combined with education and goal-setting, facilitates and reinforces adoption of healthy behaviours and promotes timely and persistent therapy adjustments, resulting in improved clinical and behavioural outcomes (Parkin, 2011). Further details on the STeP study tools and resources are available at http://bit.ly/SLJMIJ (accessed 23.08.12).

Hypoglycaemia
People with type 2 diabetes treated with sulphonylureas or insulin may also be subject to hypoglycaemia, and SMBG may be seen as a key component of self-management in this population. This has become even more relevant in view of the updated guidance from the Driver and Vehicle Licensing Agency (DVLA; 2012).

In its guidance, the DVLA states that those treated with insulin must: 

• Have awareness of hypoglycaemia.
• Not have had more than one episode of hypoglycaemia requiring the assistance of another person in the preceding 12 months.
• Have appropriate blood glucose monitoring.

Driving
Drivers with insulin-treated diabetes are advised by the DVLA to take the following precautions:

• You must always carry your glucose meter and blood glucose strips with you. You must check your blood glucose before the first journey and every 2 hours whilst you are driving.
• In each case if your blood glucose is 5.0 mmol/L or less, take a snack. If it is <4.0 mmol/L or you feel hypoglycaemic, do not drive.
• If hypoglycaemia develops while driving, stop the vehicle as soon as possible.
• You must switch off the engine, remove the keys from the ignition and move from the driver’s seat.
• You must not start driving until 45 minutes after blood glucose has returned to normal. It takes up to 45 minutes for the brain to recover fully.

The DVLA provides further guidelines for those wishing to drive Group 2 vehicles.

Those treated with tablets which may induce hypoglycaemia (sulphonylureas and glinides):

• Must not have had more than one episode of hypoglycaemia requiring the assistance of another person within the preceding 12 months.
• It may be appropriate to monitor blood glucose regularly and at times relevant to driving to enable the detection of hypoglycaemia.
• Must be under regular medical review.

When to test
Although SMBG is a vital part of the management of glycaemia in people with type 1 diabetes, many people do not routinely monitor glucose levels either postprandially or overnight, which may leave undetected episodes of hyperglycaemia and hypoglycaemia respectively.

Fasting levels, pre-meal levels or both are a good indication of effectiveness of therapy but post-meal spikes can be an indicator of future cardiovascular risk. The International Diabetes Federation (2011) has published guidance on post-meal testing. If HbA_1c remains above target but pre-meal self-monitoring levels remain well controlled
(<7.0 mmol/L), consider self-monitoring to detect postprandial hyperglycaemia (>8.5 mmol/L), and manage to below this level if detected.

Reliance on HbA_1c as a marker of long-term glycaemic control is an accepted practice, but self-monitoring data and patient history should also be taken into consideration as frequent hypoglycaemic events may result in a low HbA_1c level, while adversely affecting quality of life. Systems using continuous monitoring of glucose by means of subcutaneous sensors which measure interstitial glucose levels have been developed. These systems are generally only considered for use by patients who experience particular difficulties in maintaining normal glucose levels or who have been transferred to continuous subcutaneous insulin infusion therapy (SIGN, 2010).

Involving the person with diabetes in setting self-monitoring goals and targets should be the norm. They should recognise that SMBG is an educational tool that is available to them and to use it wisely. It should not simply be a paper record that they bring into clinic for interpretation. Three questions to consider asking to aid effective use of strips are:

1. Why did you do that test?
2. What did you learn from the result?
3. What action did you take?

If they cannot answer these questions perhaps they need to be more involved in education and meaningful goal-setting, or perhaps they are gaining little from self-monitoring.

Who should monitor?
NICE guidance states that self-monitoring of blood glucose should only be offered as an integral part of diabetes self-management education and to specific groups (Box 2; NICE, 2009).

Costs
In 2011/12 this area of prescribing represented 14.9% of total items and 20.8% of the  total cost of prescribing for the treatment of diabetes. It was second only in cost to the prescribing of analogue insulins (The Information Centre, 2012).

Quality Control
The Medicines and Healthcare Products Regulatory Agency (MHRA; 2010) has published updated guidance for healthcare professionals to ensure accuracy on blood glucose meters including where to report any adverse incidents. It also issues alerts on problems with meters. 

Standard Operating Procedure (SOP)
There must be an SOP in place wherever blood glucose testing is performed. SOPs must include the manufacturer’s instructions for use and should be directly available to the user and be kept with the equipment.

Internal Quality Control (IQC)/External Quality Assessment (EQA)
IQC: Appropriate control material must be analysed according to local hospital procedures and manufacturers’ recommendations. It can provide reassurance that the device is working correctly and assure the operator of the reliability of patient results. 
EQA: It is advisable that all sites performing blood glucose analysis also undertake the analysis of EQA samples. EQA is the analysis of samples with an undisclosed value from an external source. Participation in an EQA scheme will establish comparability between sites.

Record keeping
It is essential that accurate records are kept for all aspects of blood glucose testing. This could include test strip lot number, meter maintenance, calibration, quality control, patient results, patient and operator identity and battery change. In the event of an adverse incident or product recall, such information would be essential in performing a risk analysis of the situation, enabling appropriate action to be taken.

Training
Training must be provided for staff who use blood glucose meters and should be refreshed at appropriate intervals. Only staff whose training and competence has been established and recorded should be permitted to carry out blood glucose testing. Staff involved in training and advising people with diabetes should ensure that they inform them of potential sources of error and give advice on how to interpret results. Training should include:

• Basic principles of measurement.
• Expected results in normal and pathological states.
• Demonstration of the proper use of the equipment in accordance with the manufacturer’s specification.
• Demonstration of the consequences of improper use.
• Knowledge of operator-dependent steps.
• Instruction in the collection of appropriate blood samples.
• Health and safety aspects.
• Instruction in the importance of complete documentation of all data produced.
• Appropriate calibration and quality control techniques.
• Practical experience of the procedures, including a series of analyses to satisfy the instructor that the trainee is competent.
• Information regarding contra-indications.
• Information on basic troubleshooting, error messages and potential sources of error. 

Conclusions
Health professionals undertaking blood glucose monitoring must ensure quality control procedures are in place on the meters that they use and remember that HbA_1c does not identify blood glucose highs and lows. SMBG, if combined with education on its use, can be effective and can assist people with diabetes to self-care. The costs to the NHS will continue to fuel the debate as to its effectiveness in type 2 diabetes treated with agents other than insulin or sulphonylureas. Education of people with diabetes and healthcare professionals alike is vital to effective monitoring.

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