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Glucose meters: what you should know

jim delillo/dreamstime.comBlood glucose meters designed for use by healthcare professionals have been available since the 1970s, and devices suitable for self-monitoring first became available in the UK in 1980.1 Since then, they have improved in speed, accuracy and reliability, and reduced in size — most are now smaller than many mobile telephones, allowing for discreet testing. Supporting patients with diabetes can include giving advice on these machines.

Key points

  • Advances in blood glucose monitoring technology include automatic coding, all in one systems, talking meters, large reading memories, IT compatability, and analysis of patterns.
  • Helping people to choose a blood glucose monitor that best suits their needs may result in better blood glucose control.

Who should use them?

For people with type 1 diabetes, the National Institute for Health and Clinical Excellence advises that self-monitoring of blood glucose should be part of an integrated package that includes appropriate insulin regimens and education to support choice and achievement of optimal diabetes outcomes.2

There continues to be debate, however, over the benefits of glucose testing for those with type 2 diabetes. “There is evidence both for and against home blood glucose monitoring and the advantages and disadvantages will need to be discussed with each individual,” Beverley Bostock-Cox, clinical lead for cardiovascular health at the charity Education for Health, told The Journal.

NICE says that people newly diagnosed with type 2 diabetes should only be offered self-monitoring of blood glucose as part of their self-management education.3 It recommends that healthcare professionals should discuss with patients the purpose of the monitoring and agree how results should be interpreted and acted on. Self-monitoring of plasma glucose should be available to those with type 2 diabetes and on insulin treatment or oral glucose-lowering medicines, to provide information on hypoglycaemia.

NICE also recommends that self-monitoring should be available to patients who need to assess changes in glucose control resulting from changes in medication and lifestyle or to monitor changes during illness or ensure safety during activities, including driving. It says that the continued use of blood glucose self-monitoring should be assessed at least annually and in a structured way.

Most people who need to check their blood glucose levels will receive advice on meters from their diabetes nurse or GP. In fact, Diabetes UK’s clinical adviser Cathy Moulton pointed out that most people with diabetes who need a meter will be given one in a diabetes clinic. “A healthcare professional will then be able to help them with it and provide education about how to use it,” she said. “Pharmacists are more likely to deal with people with type 2 diabetes who are newly diagnosed and who can’t get a meter from their GP, but want to test their blood glucose.”

How blood glucose meters work

Blood glucose meters originally used the reaction of glucose oxidase and peroxidase to produce a colour change corresponding to the level of glucose in a sample of blood. The colour change was then measured by a photoelectric cell. Subsequently, meters using blood glucose biosensor systems became available. These used glucose oxidase and replaced oxygen in the glucose oxidase reaction with the electron transfer mediator ferrocene. Ferrocene is reoxidised at the electrode to generate a current, which a sensor detected. Later meters used glucose dehydrogenase and the co-enzyme pyrroloquinoline quinone. Their reaction is more sensitive than the glucose oxidase reaction but is prone to interference by high concentrations of maltose or galactose, and for this reason may not be suitable for some people with diabetes.7

More recent meters have used dry-reagent test strips, reflectance photometry and biosensors to assess levels of glucose in blood samples. In 2004, meters based on reactions using glucose dehydrogenase and flavin adenine dinucleotide were introduced.

From SF Clarke, JR Foster. A history of blood glucose meters and their role in self-monitoring of diabetes mellitus. British Journal of Biomedical Science 2012;69(2);83–93.

Given that blood glucose testing may not be suitable for all people with diabetes, Ms Moulton said it is important for pharmacists to talk to them about why they might need a meter. Testing among people with type 2 diabetes can be counter-productive, she pointed out. “Some people are testing and testing and getting themselves over-anxious and this can even bring on depression,” she explained. “Healthcare professionals need to talk to people about why they’re testing and why they need to test.”

Ms Moulton added that, if people with type 2 diabetes buy a meter from a pharmacy without advice from a diabetes clinic, advice from the pharmacist about the affect of food and physical activity on blood glucose levels is particularly important.

Choosing a meter

The range of meters available to people with diabetes has increased over the past two decades, with improved functionality and the incorporation of increasingly sophisticated technologies and features. For example, with older meters users had to place the drop of blood on top of the test strip (which could be messy and often resulted in too much blood on the strip) but most devices now only require the edge of the test strip to touch the edge of the drop and the blood is drawn up into the strip.

Coding

Until the 1990s, all patients needed to calibrate (“code”) their meters to ensure different batches of test strips produced accurate results. This would usually involve reading a code from the test strip packaging and entering it into the meter or, later on, inserting a code chip into the machine with each new batch. Since 1992, however, meters using barcoded test strips have eliminated the need for users to code each new batch manually. Examples of meters with automatic coding include FreeStyle Lite and One Touch UltraSmart. Research suggests that meters that do not require manual coding help people with diabetes achieve more accurate results4 — miscoded meters can give false results.

Note that people with diabetes should be aware that they will still need to conduct periodic checks of their meters using a control solution.

Integrated systems

Meters that include lancing devices and collect blood samples in one integral system have also been developed so patients do not have to carry around several separate components. The integration of test strips and lancets into devices also mean that users do not have to handle individual lancets and strips. For example, the Accu-Chek Mobile device has a lancing device attached and is loaded with a drum that contains six lancets and a continuous tape of 50 test strips. (Some lancing devices are now also loaded with drums containing a number of lancets.)

Alternative site testing

Many meters (eg, OneTouch Ultra 2, TRUEone, WaveSense JAZZ) now allow alternative site testing (AST), using the forearm or hand for example. This is designed to cause less pain when sampling — there are fewer nerve endings at these sites compared with fingertips — and so encourage people to test when necessary.

AST can be useful for those who need to monitor frequently, avoiding sore fingers and thickened skin. It should be noted, however, that this sort of testing should only be used when blood sugar is stable (eg, before a meal or when fasting) and fingertip blood should be used if blood sugar may be changing rapidly (eg, after a meal or exercise).

Lancing devices may need to be adjusted to a deeper setting when using alternative sites. Some come with a cap to be added for AST.

Talking meters

Meters that incorporate speech input (eg, SuperCheck2 and Clever Chek) are available for blind and visually impaired people.5 (All Clever Chek devices were recently recalled because the meter did not alert users when insufficient blood had been applied to the test strip, giving the potential for false results.6)

Memory and IT compatability

A particularly significant development in recent years is that most meters now include memories to record test results. Ms Bostock-Cox also believes that having a meter that records all readings is particularly helpful for healthcare professionals as well as patients: “It is really useful for healthcare professionals to be able to cycle through readings, and it means people do not have to keep notes of their readings on a separate piece of paper.” However, Helen Hollern, diabetes specialist nurse facilitator for the Integrated Diabetes Care Team at Cambridgeshire Community Service NHS Trust, noted that health professionals tend not to like meters where patients can delete the results they do not want seen.

Ms Bostock-Cox pointed out that the memory function of a glucose meter is particularly useful for Driving and Vehicle Licensing Agency (DVLA) requirements. This is because it allows people with diabetes to have information on episodes of severe hypoglycaemia easily available when they need it. The DVLA says that people with diabetes should notify the agency if they have more than one episode of severe hypoglycaemia, within 12 months, or if they or their carers feel think they are at high risk of developing severe hypoglycaemia.

Many glucose meters can be connected to computers and other devices so that results can be downloaded and analysed. Many patients like this facility. The newest meters are also compatible with the latest gadgets. For example, the iBGStar device is connected to an iPhone or iPod Touch for testing. Users can then view and analyse the result on their iPhones (or iPods) and can use it to share this information with their healthcare professionals.

Some machines, such as the OneTouch VerioPro, analyse results for low blood glucose patterns and automatically inform users of a risk of hypoglycaemia.

Other factors

Ms Bostock-Cox believes that the simplest machines are often the best. “Ideally you want one that gives a clear indication of the reading and that has a memory,” she says.

Ms Hollern believes portability and display clarity are often the most important aspects for patients. “Most patients like easy-to-use meters that are small enough to carry around but with a large enough screen to enable them to see the results clearly… . They also favour a smaller blood sample,” she said. Sample sizes required by meters generally range from 0.3 to 3.0µl. If not enough blood is placed on a test strip, the user may have to prick his or her finger again. Devices that only require 0.3µl of blood include FreeStyle Freedom Lite, FreeStyle Lite and MyGlucoHealth.

Ms Hollern said that different patient groups may have different needs. For instance, patients with type 1 diabetes have different requirements in a glucose meter and may want a meter that also tests for ketones (eg, Freestyle Optium and GlucoMen LX Plus).

Availability and funding

As well as knowing about the different meters available, pharmacists may need to give advice on the availability of test strips, which may not be funded locally for all patients with diabetes. Ms Hollern says that NHS bodies are now restricting the types of glucose test strip that they are willing to fund. “The tariff price of strips varies massively and many organisations are changing their formulary to encourage the use of meters with cheaper strips that also have a long life,” she said. “As long as this is done in conjunction with the local specialist diabetes team there should be no risk to patients.”

Ms Moulton said that people with diabetes who are buying meters may find it useful to know which strips local NHS bodies are willing to fund. “Staff at a GP practice are likely to be able to hand out meters free of charge, and that is likely to be one that the local NHS organisation is willing to pay for strips for,” she said. “Pharmacists would probably have a good idea which strips are funded on the local NHS because of the prescriptions that come through.”

As well as limitations on the strips available on the NHS locally, people with diabetes can also face problems as a result of local restrictions on which patients NHS bodies are willing to fund the provision of strips to, Ms Moulton said.

People who have bought a meter in a pharmacy and become used to testing can become face difficulties if they are then told they cannot be prescribed test strips, she pointed out. “People who’ve been using test strips can feel real distress if they are not allowed access to them… . They feel they don’t know what’s going on in their blood and can become almost obsessive about the need to test,” she explained.

Support and accuracy

Helping people to choose the blood glucose monitor that best suits their needs and lifestyle means that they are more likely to follow their testing routine and improve their blood glucose control. In addition to advising on which device to use (if glucose monitoring is appropriate) pharmacists will need to talk to people with diabetes about how to ensure the blood glucose results they obtain are as accurate as possible.

Research suggests that blood glucose meters released in the past few years do produce accurate results7 but despite improvements in meter technology, the accuracy of meters designed for patient use has limitations that must be considered.8 For example, problems can arise from applying insufficient blood to the strip, using strips that are out of date or that have been exposed to excess moisture or humidity or, for meters that require coding, failing to enter the correct code.9

Some of the latest machines, (eg, WaveSense JAZZ and BGStar), use “dynamic electrochemistry” in order to achieve more accurate results. According to the manufacturers of BGStar, dynamic electrochemistry involves extracting a spectrum of information from the blood (eg, hematocrit [which can vary due to exercise or smoking] and ascorbic acid) and compensating for these factors that can distort blood glucose results.

There have been so many advances in technology that people with diabetes should not have to struggle with a meter that is not right for them. However, the wide range of meters available also means more for pharmacists to be familiar with.

The chart below compares the features of currently available devices and the latest addition to the PJ Online “See how it should be done” video archive gathers together demonstrations of how to use some of these blood glucose meters.

 

About the author

Tom Moberly is a freelance medical writer

 

 

Citation: The Pharmaceutical Journal URI: 11110106

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