Key points & background
Self monitoring of blood glucose is an important component of diabetes management for some people. But, which people?
Any component of a treatment plan that is both invasive and expensive needs to result in an improved clinical outcome.
information about blood glucose levels is only useful when it can be used to improve clinical outcomes.
Clinical outcomes in diabetes are improved when glycaemic control is improved. Measurement of the concentration of glycated
haemoglobin (HbA1c) is the most appropriate and accurate way to monitor glycaemic control. When then, does self monitoring
of blood glucose provide additional benefit?
Type 1 Diabetes
Self monitoring of blood glucose (SMBG) is mandatory for people with type 1 diabetes. The information gained is essential
for patients to adjust the type and amount of food and exercise, document hypo and hyperglycaemia and select appropriate
dosages of insulin. People with type 1 diabetes usually test three to four times a day and are educated to act on the
result to bring about improved control (i.e. a lower HbA1c result).
Type 2 Diabetes
Self monitoring is required for people with type 2 diabetes on insulin
Advice regarding the use of SMBG for people with type 2 diabetes treated with insulin is essentially the same as for
people with type 1 diabetes. These people however, may be on insulin regimens with less frequent dosing, and so may only
need to test twice a day.
Advice for people with type 2 diabetes who are not using insulin needs individual consideration (includes those on
There is no doubt that for the vast majority of people with diabetes, measurement of the concentration of glycated haemoglobin
(HbA1c) remains the most appropriate and accurate way to monitor glycaemic control.
Evidence of benefit for SMBG in non-insulin treated type 2 diabetes
There is now an abundance of published research in this area. However the designs of the studies, the outcomes and ultimately
the conclusions reached, have varied widely.2 There is still a lack of consensus.3,4 A
conclusion reached in a recent commentary article was that for people with non-insulin treated type 2 diabetes, SMBG �is
an expensive and popular procedure without an evidence base�.5 The author suggests that
the only way to answer the question of whether to advocate routine SBMG would be through �properly designed, randomised
Do the guidelines help us?
The current New Zealand guideline states that �self-monitoring of blood glucose is well-established in clinical practice,
but the literature in this area is limited and difficult to assess�.6 The recommendation
is that SMBG �should be considered in conjunction with appropriate therapy as a part of integrated self-care. The purpose
of blood glucose self-monitoring should be clear and agreed with the person with diabetes.� A similar recommendation is
included in the NICE guideline.7 However, a new draft of this guideline is under consultation
When does SMBG produce benefit for people with non-insulin type 2 diabetes?
The key message is that the aim of using SMBG is to improve glycaemic control, i.e. a lower HbA1c, and to ultimately
reduce long term complications. Measuring blood glucose gives immediate information for the patient, but to give any benefit,
this information must be acted upon.9
If HbA1c is already satisfactory without SMBG, adding it may not be associated with any further improvement.2
Therapeutic benefit is more likely to be obtained when:
- There are special circumstances such as new diagnosis, starting or changing medication, illness, pregnancy and frequent
- The patient knows how and when to test and how to interpret or act on the results2
- Patient education is individually tailored and ongoing11
- Patients are �sufficiently literate and numerate�10
- Patients are motivated to make changes to diet or lifestyle2,10
- A clear goal is negotiated and agreed with patients11
- There is an understanding of the relationship between SMBG and HbA1c results11
When used appropriately, SMBG can increase disease awareness and compliance10, it can
empower9,12 and reassure.11
Conversely, the continual reminder of less than ideal control can lead to uncertainty, frustration, guilt and high levels
of anxiety.9,11 If GPs and practice nurses take little notice of self monitoring results
and don�t use the readings as a chance for further education, it tends to reinforce the idea that test results are not
important.11 The patient will often become discouraged and lose motivation. GPs can end
up spending a lot of time dealing with the anxiety arising from unexpected or poor results.
In patients who are receiving no benefit from SMBG, it is appropriate to stop.
The recent Diabetes Glycaemic Education and Monitoring (DiGEM) trial has concluded that �routine self monitoring of
blood glucose for patients with reasonably controlled non-insulin treated type 2 diabetes seems to offer, at best, small
advantages, is not well accepted, and the cost, effort and time involved in the procedures may be better directed to supporting
other health related behaviours.�13 It is thought that studies such as this may encourage
clinicians to talk to their patients about the usefulness of SMBG and give them �confidence to discontinue it if it is
providing no benefit.�14
A pragmatic approach to the use of SMBG is recommended
If we are faced then with contradictory evidence and very broad recommendations, how do we make choices that will benefit
our patients? The decision comes down to an individual patient level and relies upon the doctor and patient reaching agreement
on the best course of action.
Andrew Moore, the editor of Bandolier, has been involved in a systematic review of the current evidence.10 He
�It is sobering to remember that where doctors make their own decisions, the results have been terrific, especially
in clinical outcomes with major consequence. They did it by deciding which patients with type 2 diabetes would benefit
from self-monitoring and prescribing self-monitoring in those patients. Simple, really�.16
The issue of cost
Healthcare providers worldwide are struggling with the difficulties of who should get the healthcare dollars. A huge
multi-billion dollar industry has developed to supply meters and strips and there is ongoing spending, with companies
trying to produce increasingly fast and easy to use devices.15
The largest group of people using SMBG are those with non-insulin treated type 2 diabetes. The routine use of SMBG in
this group can have a major cost impact and the expense can be justified only if it leads to savings in the future.15
Who to test and why to test have become major issues. In the United Kingdom, some primary care organisations now restrict
access to blood testing strips causing debate between doctors, patients and suppliers. Diabetes UK (a charity for people
with diabetes) has launched a national online campaign to try and reintroduce unrestricted access to home blood glucose
testing equipment.3 Similar financial dilemmas face those working in primary health care
in New Zealand.
Glucose Meters � different meters, different results
The way that blood glucose results are presented varies depending on the type of meter used. There is a danger that
these variations could be falsely attributed to poor control.
Whole blood versus plasma glucose
Plasma glucose results measure approximately 15% higher than whole blood glucose results. This is often called the �matrix
effect� and is due to the higher protein and lipid content of red cells than the liquid portion of the blood. This results
in glucose (which is water soluble) being unequally distributed between the intracellular and the extracellular space.
Variation in the way blood glucose meters report results
The difference is significant because glucose meters currently available in New Zealand report results as either whole
blood or as a �plasma equivalent� while laboratory results are reported as plasma results.
The �plasma equivalent� result is calculated from the whole blood glucose reading using an equation built into the glucose
meter. This allows GPs and patients to easily compare laboratory test results with glucose results obtained at home. The
International Federation of Clinical Chemistry and the American Diabetes Association has also recommended home glucose
analysers should report results as �plasma equivalent�.
If however, the meter is reporting results as �whole blood equivalent�, both GP and patient have to know that
the whole blood equivalent result is approximately 15% lower than the plasma result, and is therefore not directly
comparable with results obtained from the laboratory.
Table 1 indicates the method of reporting for glucose meters currently available in New Zealand.
As of the 1 July 2008, PHARMAC will no longer be funding test strips for Accu-chek Advantage, therefore patients currently
using these meters will need to change to either the Abbott Optium Xceed or the Roche Accu-Chek Performa system. Following
this change results throughout New Zealand will be consistently reported as �plasma equivalent�.
Table 1: methods of reporting for glucose meters currently available in New Zealand.
|Abbott Optium Xceed
|Roche Accu-Chek Advantage
||Whole blood equivalent
|Roche Accu-Chek Performa
Glucose Meters � common problems
Probably the greatest concern when using glucose meters is false results. All users should be educated about factors
contributing to false results.
The Office of In Vitro Diagnostics (OIVD), a service of the FDA, evaluates glucose meters. They evaluate long term safety
and effectiveness of the analysers and how devices are used. OIVD, in consultation with manufacturers and users, have
produced a table of common problems encountered when using glucose meters (Table 2).
Causes of false results may be patient/sample based or user/device based. Probably the most important advice for any
user of a blood glucose meter is to question any result not consistent with the clinical picture. This needs to be investigated
and, at a minimum, the test repeated.
Table 2: Common problems with glucose meter results.
|Falsely low results
||Sensor strips not fully inserted into meter
||Always be sure strip is fully inserted in meter
|Not enough blood applied to strip
||Repeat test with a new sample
|Patient in shock
||Treat appropriately. Venous sample should be sent immediately to a laboratory
|Squeezing fingertip too hard because blood is not flowing
||Repeat test with a new sample from a new stick
||Venous sample should be sent to a laboratory
|Falsely high results
||Patient sample site (for example the fingertip) is contaminated with
||Always clean test site before sampling
|Patient is dehydrated
||Treat appropriately. Venous sample should be sent immediately to a
||Venous sample should be sent to a laboratory
||Test strips/controls stored at temperature extremes
||Store kit according to directions
|Sites other than fingertips
||Results from alternative sites may not match finger stick results
|Test strips/controls damaged
||Always inspect package for cracks, leaks, etc.
||Even small amounts of blood, grease, or dirt on a meter�s lens can
alter the reading
||Batteries low on power
||Change batteries and repeat sample collection
|Test will not complete
||Check package details, calibration code, and expiry dates are all