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Josie M M Evans a Medicines Monitoring Unit, Department of Clinical
Pharmacology, Ninewells Hospital and Medical School, Dundee DD1 9SY, b Diabetes Centre,
Ninewells Hospital and Medical School, c Department of Epidemiology
and Public Health, Ninewells Hospital and Medical School, d Department of Medicine,
Ninewells Hospital and Medical School
Correspondence to: J M M Evans
josie{at}memo.dundee.ac.uk
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Abstract |
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Objectives:
To investigate patterns of self monitoring of blood glucose concentration in diabetic patients who use insulin and
to determine whether frequency of self monitoring is related to
glycaemic control.
Setting:
Diabetes database, Tayside, Scotland.
Subjects:
Patients resident in Tayside in 1993-5 who were using insulin and were registered on the database and diagnosed with insulin dependent (type 1) or non-insulin dependent
(type 2) diabetes before 1993.
Main outcome measures:
Number of glucose monitoring
reagent strips dispensed (reagent strip uptake) derived from records of
prescriptions. First recorded haemoglobin A1c concentration
in the study period, and reagent strips dispensed in the previous 6 months.
Results:
Among 807 patients with type 1 diabetes,
128 (16%) did not redeem any prescriptions for glucose monitoring reagent strips in the 3 year study period. Only 161 (20%) redeemed prescriptions for enough reagent strips to test glucose daily. The
corresponding figures for the 790 patients with type 2 diabetes who used insulin were 162 (21%; no strips) and 131 (17%; daily tests). Reagent strip uptake was influenced both by age and by deprivation category. There was a direct relation between uptake and
glycaemic control for 258 patients (with recorded haemoglobin A1c concentrations) with type 1 diabetes. In a linear
regression model the decrease in haemoglobin A1c
concentration for every extra 180 reagent strips dispensed was 0.7%.
For the 290 patients with type 2 diabetes who used insulin there was no
such relation.
Conclusions:
Self monitoring of blood glucose
concentration is associated with improved glycaemic control in patients
with type 1 diabetes. Regular self monitoring in patients with
type 1 and type 2 diabetes is uncommon.
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Key messages
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Introduction |
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The importance of normoglycaemia for the subsequent prevention of diabetic complications is now recognised. 1 2 Self monitoring of blood glucose has been recommended as a technique for improving control of blood glucose concentrations,3 and a common view is that it should form part of an integrated treatment programme.4 An American study in 1993, however, showed that over two thirds of diabetic patients carried out no self monitoring at all.5
In 1995 £42.6 million was spent on self monitoring of glucose
concentrations in the United Kingdom,6 despite increasing doubt about its benefits. Studies carried out in selected clinic populations (children,7 young people,8
elderly people9) or under experimental trial
conditions,10-13 or both, have shown that tests can be
inaccurate and unreliable, may not be interpreted by patients
correctly, and can cause psychological harm.6 We studied
patterns of self monitoring and its effect on glycaemic control in an
unselected population of diabetic patients who use insulin in Tayside,
Scotland, using data available through the DARTS/MEMO
collaboration.
14 15
This was an observational outcomes study, enabling the non-interventional investigation of the
effectiveness of glucose monitoring under real life, non-experimental conditions.
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Methods |
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The DARTS/MEMO collaboration has pioneered the record linkage of healthcare data in the population of Tayside, Scotland (estimated mid-year resident population of 395 600 in 199516). By record linking independent data sources with the community health index number (a unique patient identifier used for healthcare activity in Tayside) a population based register of patients with diabetes in Tayside, known as DARTS (diabetes audit and research in Tayside),15 has been created and validated.17-19
This study was carried out among people who were resident in Tayside (or who died) during the study period (January 1993 to December 1995). Patients who were diagnosed with type 1 diabetes before January 1993 were identified from the register, as were those with type 2 diabetes who were using insulin during the first 6 months of 1993 (and were presumed to be using insulin thereafter).
Self monitoring of blood glucose
The number of blood glucose monitoring reagent strips dispensed to
patients during the study period was determined from the MEMO dispensed
prescribing database, a computerised record of all prescriptions
dispensed in community pharmacies in Tayside since 1993.14
Patterns of use were investigated by sex, age, and duration of
diabetes. The Carstairs social deprivation categories of the study
patients, ranging from category 1 (most affluent) to category 7 (least
affluent) and based on four census variables, were also determined from
details of the patients' postcodes.20
Blood glucose control
Patients who had at least one glycated haemoglobin (A1c) concentration recorded between July 1993 and December
1995 were identified. The numbers of reagent strips that were dispensed to these patients during a 6 month period before their first
haemoglobin A1c measurements were calculated. Linear
regression models for patients with type 1 and type 2 diabetes were constructed separately, with haemoglobin A1c
as the outcome and age, sex, duration of diabetes, and deprivation
category as covariates. The effect of body mass index (available for
70% and 75% of patients with type 1 and type 2 diabetes,
respectively) was also investigated. The analyses were repeated in
subgroups of patients who obtained at least one pack of strips.
Costs and analysis
The total cost of the blood glucose test strips dispensed was
calculated with 1998 tariffs obtained from the British National Formulary (number 35)21 (including the
pharmacist's dispensing fee). All statistical analyses were carried
out with SPSS.
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Results |
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Self monitoring of blood glucose
Among 367 051 Tayside residents there were 807 (0.2%) patients
with type 1 diabetes and 5601 (1.5%) with type 2 diabetes,
790 of whom were included in the study (table 1). In total, 13 382
prescriptions for blood glucose monitoring reagent strips were
dispensed to 1307 of these patients during the 3 year
period.
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Blood glucose control
There were 258 patients with type 1 diabetes who had at least
one valid haemoglobin A1c concentration recorded (ranging
from 4.2% to 17.4% of total haemoglobin), of whom 152 had obtained at
least one pack of reagent strips in the previous 6 months. In a linear
regression model the total number of reagent strips dispensed was a
predictor of haemoglobin A1c concentration (P<0.001; table
3), with a decrease in haemoglobin A1c concentration for
every extra 180 test strips dispensed (equivalent to one a day) of
0.7%. Sex was the only other independent predictor of haemoglobin
A1c concentration (P=0.002), with higher values in female
patients (table 3). In the subgroup of 152 patients (those who obtained
at least one pack of strips in the 6 month period) the relation between
strip uptake and haemoglobin A1c concentration was still
strong (regression coefficient
0.672, P<0.001).
Cost
The total cost of the 7002 prescriptions for glucose
monitoring test strips dispensed to patients with type 1 diabetes
was £155 912 (an average of £64.40 per patient per year). The 6381 prescriptions for reagent strips dispensed to patients with
type 2 diabetes who used insulin cost £134 907 (£56.92 per
patient per year).
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Discussion |
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Self monitoring of blood glucose
This study provides an insight into blood glucose monitoring
habits in all diabetic patients in Tayside who used insulin and shows
that many patients with either type of diabetes did no testing at all.
Less than one fifth tested daily.
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Blood glucose control
The regression analysis suggested a direct association between
haemoglobin A1c concentration and the number of strips
obtained in a previous 6 month period in patients with type 1 diabetes. This result indicates either that self monitoring is
important for maintaining good diabetic control or that it is a proxy
measure of good health behaviour and practice that is associated with
good control. In other words, patients who self monitor are also likely
to be compliant with their diabetic regimen, with confounding by
factors such as diet and exercise. When the analysis was restricted to
patients who obtained at least some strips and could be regarded as
partially compliant (providing some control for confounding), however,
the association was still evident. Even if it is non-causal, self
monitoring might improve quality of life by giving patients more
control over their disease.4
cell reserve. An alternative explanation for
the study findings is that self monitoring may be recommended
particularly in those patients who are the most difficult to control.
Cost
The average cost of glucose monitoring per patient was relatively
low when compared with other costs associated with diabetes
care.24 Even for a patient who is self monitoring four
times daily, the approximate cost per year is only £409. We therefore
suggest that self monitoring of blood glucose should be further
encouraged, particularly in those subgroups of patients who do not
monitor their blood glucose concentrations regularly
for example,
young deprived men with type 1 diabetes.
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Acknowledgments |
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MEMO is part of the MRC Health Services Research Collaboration.
We thank the members of the DARTS/MEMO collaboration who made this work
possible
notably, Mr DIR Boyle, computer programmer for DARTS. We also
thank members of the DARTS steering group for their support: Ms Kim
Boyle, Dr Alan Connacher, Ms Pauline Clark, Ms Alison Cowie, Dr Derek
Dunbar, Dr Alisdair Dutton, Dr Alistair Emslie-Smith, Professor Roland
Jung, Dr Margaret Kenicer, Dr Brian Kilgallon, Dr Graham Leese, Dr
Rebecca Locke, Dr Sandy McKendrick, Dr Peter Slane, and Dr Sandy Young.
Contributors: JMME was the principal investigator in this study. She designed the study, analysed the data, and wrote the first draft of the paper. RWN, DAR, TMMacD, and ADM all appraised the study design, contributed to interpretation of the study results, and made revisions to the draft paper. ADM had the original idea for the study. RJS carried out a pilot study and collected some of the original data. All the authors were involved in approval of the final version to be published. JMME is the guarantor.
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Footnotes |
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Funding: Dr Evans holds a Wellcome Trust Training Fellowship in Health Services Research (Ref 050212).
Competing interests: None declared.
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References |
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(Accepted 19 April 1999)
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