Positive D-dimer results in a private hospital emergency department : an audit of patient management and outcomes (posed study)
Date
2013-01-25
Authors
Rudolph, Adriana Josina
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Abstract
Background: The D-dimer test is commonly requested in an emergency
department to confirm or exclude clinically suspected venous thrombosis. In
this setting, the D-dimer is used in conjunction with the Wells clinical score
and other investigation such as duplex doppler, V/Q scan or CT scan to make
a definitive thrombosis diagnosis. In a typical South African private hospital
setting, such as Flora Clinic, it has not yet been established as to how many
of the requested D-dimers are positive, what the impact and contribution of
this result is on patient management and outcome in an emergency
department. In the era of diagnostic test cost cutting and evidence based
practice, this knowledge is important in informing rational decision making by
emergency practitioners and also as part of auditing and improving the
implementation of diagnostic pathways. The aim of this study was to establish
the prevalence of D-dimer positivity in an emergency department, to
determine in how many patients venous thrombosis was part of the
documented differential diagnosis and if patients with a positive D-dimer test
were managed in accordance with published clinical management
recommendations.
Materials and methods: This study is a retrospective cross-sectional
analysis. All D-dimer tests requested at Flora Clinic emergency department
from 1 November 2008 to 31 May 2009 were reviewed. The percentage of
positive results was calculated from the total D-dimer tests conducted by the
laboratory, as requested from the emergency department during the defined study period. Clinical notes and records of those patients with positive results
were de-anonymised and de-identified, using a data capture sheet. The
clinical notes of the patients with a positive D-dimer were reviewed to see
what impact the D-dimer result had in the management and outcome of these
patients in the emergency department.
Results: There were 365 D-dimer tests conducted in the Flora Clinic
emergency department, within the study period. Out of these 145 patients
had a positive D-dimer test, of which 144 met further inclusion criteria. The
study population had a mean age of 62 years with 53% men in the study
sample. Twenty two patients‟ patient records were missing. They still formed
part of the intent-to-treat analysis, although the data were not available
beyond demographic data collection. The prevalence of a positive D-dimer
test, out of all D-dimer tests conducted, between 1 November 2008 and 30
May 2009 within the Flora Clinic emergency department was 39%. The
diagnosis of venous thrombosis was considered in 25% of patient records.
The higher the D-dimer level the more likely the emergency practitioner was
to admit the patient to hospital. No association could be found between age
or sex and D-dimer value. No patient record had a formal pre-test probability
evaluation recorded, although some elements of the Wells Score were
recorded in all the clinical notes. Among the special investigations requested
in the emergency department, 11% were in accordance with published
treatment protocol. Out of these 3% involved chest imaging. In 10% of the
patient records the management initiated in the emergency department was
according to recognised treatment protocol. Conclusion: The study results suggest that the assessment of pre-test
probability is not done in a formalised manner and that positive D-dimer tests
are either misinterpreted or that the emergency practitioners do not have
sufficient knowledge regarding the correct management of a positive D-dimer
test. The study identified the current trend of practice among emergency
practitioners in the South African environment. Further studies evaluating the
reasons for and methods to improve the under-utilisation of both clinical
prediction rules and established treatment protocols will be useful.