Quality indicators of preventable adverse drug events in patients with type 2 diabetes: application of a new register-based model
Research output: Book/Report › Ph.D. thesis › Research
Linda Aagaard Thomsen
Background: Preventable adverse drug events are caused by errors in the medication usePreventable adverse drug events are caused by errors in the medication use
process, and are of particular interest when designing interventions to improve the quality
of medication therapy. Type 2 diabetes became the case because a large proportion of
patients are undertreated and not monitored as recommended; yet, the epidemiology of
preventable adverse drug events in type 2 diabetes is largely unknown. The aims of the
studies were to develop quality indicators for preventable adverse drug events in patients
with type 2 diabetes, and apply a new register-based model with the ability to assess the
epidemiology and economic impact of preventable adverse drug events in patients with
type 2 diabetes, in order to give health care decision makers a clinical and health economic
rationale for prioritizing interventions against medication errors.
Methods: A systematic literature review of the available literature on preventable adverseA systematic literature review of the available literature on preventable adverse
drug events was conducted to describe the incidence and characteristics of preventable
adverse drug events in the primary care setting (Article 1).
Construction of the preventable adverse drug events assessment model required four steps.
The first step consisted of the development, validation, and feasibility of preventable
adverse drug event indicators for type 2 diabetes (Articles 2 and 3). Preventable adverse
drug event scenarios were identified through a literature review. Face, content and construct
validity was assessed using a Delphi consensus study. The feasibility of a computerised
search for indicator positives within Danish health care registers was determined by
assessing the operationalisability of the indicators, and the availability of the required data.
The second step in the model consisted of the identification of preventable adverse drug
events. To identify the most frequent preventable adverse drug events, a database
containing health care data for a random 10% of the Danish population receiving oral
antihyperglycaemic treatment (9,791 persons) was set up, and indicator positives identified
(Articles no. 2 and 3). The third step in the model consisted of a risk assessment of
preventable adverse drug events, including an assessment of clinical areas that need quality
improvement. One study concerned the four indicators on inadequate preventive treatment
after acute myocardial infarction (AMI) (Article 4), and another study concerned the four
indicators on inadequate monitoring of HbA1c resulting in admission with hyper- or
hypoglycemia (Article 5). In the AMI study, a register-based study of the total Danish
population (8,275 persons) receiving oral antihyperglycaemic treatment and surviving an
AMI was conducted. The study period was 1 January 2001 to 31 December 2004. Patients
were followed until their first recurrent AMI. The proportion of patients in inadequate
treatment, and the risk of recurrent AMI associated with inadequate treatment were
determined. Statistical analysis was performed using a Cox regression model and a casecrossover
design. In the HbA1c study, a register-based study of the total population in the
Danish county of Århus receiving oral antihyperglycaemic treatment (18,922 persons) was
conducted. The study period was 1 January 2000 to 31 December 2004. The rate of
indicator positives; the status of HbA1c monitoring; stratification between treatment
settings; and high risk patient groups were assessed. The risk of diabetes-related hospital
admission associated with HbA1c monitoring and treatment was determined using logistic
The fourth step in the model was a health economic evaluation of the cost-effectiveness of
shifting patients from inadequate to adequate medical treatment. The database used for the
AMI indicator study formed the database for this study. Five post AMI treatment scenarios
were analysed, and incremental cost-effectiveness ratios calculated.
Results: The systematic literature review (Article 1) revealed that preventable adverse drugThe systematic literature review (Article 1) revealed that preventable adverse drug
events are common in primary care, with many resulting in hospitalisation. Projected to a
Danish setting, 216,000 patients will experience a preventable adverse drug event each
year, and 162,000 of these patients will need hospital admission. Quality improvement
interventions should target errors in prescribing and monitoring, especially for patients
using cardiovascular drugs, analgesics and antihyperglycaemic agents.
The indicator development study resulted in 27 preliminary preventable adverse drug
events indicators for type 2 diabetes, of which 18 (67%) achieved consensus (Article 2). All
indicators were operationalisable, but incomplete information on laboratory data and overthe-
counter medicine caused inaccurate incidence estimates. Therefore, the two risk
assessment studies relied on indicators where laboratory data were not required, or relied on
a diabetes specific database containing the necessary laboratory data.
The screening study (Article 3) revealed that most cases of preventable adverse drug events
concern admissions with hyperglycemia, reduced renal function and recurrent AMI, related
to inadequate treatment or monitoring.
The AMI indicator study (Article 4) revealed that 77% of type 2 diabetes patients do not
receive recommended treatment after an AMI and 19% experience a recurrent AMI after a
median follow-up time of only 1.75 years. Inadequate preventive treatment increases the
risk of recurrent AMI up to five times. Even though underdosed or absent antiplatelet
treatment doubles the risk of recurrent AMI, 29% do not receive such treatment. Also, the
risk of recurrent AMI decreases as the number of recommended medications or the doses
increase; yet, beta-blockers and lipid-lowering agents were underdosed.
The economic evaluation based on the AMI study (Article 6) revealed, that from a public
health care systems' point of view, providing intensive cardioprotective treatment
according to already accepted guidelines to type 2 diabetes patients is cost-effective.
The HbA1c study demonstrated how diabetes-related hospital admissions are frequent, and
how preventable adverse drug events are particularly frequent in insulin users. Important
target groups for future quality improvement initiatives are the small group of unmonitored
patients (3.3 %); the 20 % of the population being hyperglycaemic, particularly those who
do not receive antihyperglycaemic treatment; patients receiving cardiovascular but no
Implications: The developed model for assessment of the epidemiology of preventableThe developed model for assessment of the epidemiology of preventable
adverse drug events may be used at the system level, health care practitioner level, and
patient level. At the system level, the model may assist the tailoring of interventions aimed
at preventing the most frequent medication errors and such which may have serious
consequences, and eventually assist in restructuring the medication use system to achieve a
system less sensitive to errors and safer for patients.
At the health care practitioner level, patient databases may be screened for indicator
positives to provide an assessment of the quality of provided health care. At the patient
level, the indicators may be used to identify medication errors in order to prospectively
avoid the manifestation of adverse outcomes.
|Place of Publication||København|
|Number of pages||30|
|Publication status||Published - 2009|
- The Faculty of Pharmaceutical Sciences