We read with interest the work of Fancher et al. on the combined use
of rapid D-dimer testing and estimation of clinical probability in the
diagnosis of deep venous thrombosis (DVT) (1). We are enthusiastic about
the implications of this work for the diagnosis of DVT in an outpatient
setting, as it may allow an economical, safe and prompt exclusion of the
diagnosis in low risk patients.
When used in combination with clinical assessment, a rapid D-dimer
test may be a simpler clinical pathway that reduces the need for Doppler
ultrasound. It has been established that of the available options, use of
rapid D-dimer and clinical assessment in combination with a single
ultrasound is highly cost-effective, more so than the use of serial
ultrasonography (2). Yet even a single use of venous ultrasound imaging
may not be readily available in areas with limited resources, and
unnecessary use of the tool imposes a significant burden on the community,
in terms of cost and accessibility of ultrasonography. SimpliRED D-dimer
tests are already widely available; hence using them to refine clinical
assessment will allow maximal utilisation of existing resources.
As to the clinical application of the assessment combination proposed
by Fancher et al., we are unsure how specific this is as a test for
exclusion of DVT in the general population. It is well recognized that
the D-dimer level may increase with myocardial infarction, recent surgery,
trauma or any systemic illness (3). A patient presenting with symptoms and
signs suspicious of DVT may well have underlying pathology causing a high
D-dimer. It would be fair to question the practical usefulness and
significance of such a test if a high proportion of patients have an
elevated D-dimer. The paper did not specify the proportion of patients
included in this review with a high D-dimer assay, making judgment on this
issue difficult.
Furthermore, in a clinical setting where different practitioner
approaches interplay with patient factors and an increasingly litigious
environment, it is difficult to determine whether the added subjective
benefits of a venous ultrasound would incline practitioners to order the
investigation despite the review findings. As the authors pointed out,
these findings may not be applicable once the new Wells probability tool
classification scheme is adopted.
Therefore, despite the development of novel combined clinical
classifications and laboratory approaches to diagnosis, it is important to
emphasise the necessity of traditional clinical acumen in determining the
pre-test probability that the patient has a condition before potentially
unnecessary testing is undertaken (4).
In conclusion, this systematic review highlights the potential of an
economical, accessible and rapid D-dimer test to exclude DVT in low risk
patients. The findings are promising for use in the field of outpatient
care. They are particularly relevant for health services with limited
resources and those without ready access to pathology services or where
there are geographical considerations in referring patients. There is also
a potential for use in the long-term observation settings of ambulatory
care and general practice follow-up.
Rapid Response:
Clotting Screen?
Clotting screen?
Dear Sir,
We read with interest the work of Fancher et al. on the combined use
of rapid D-dimer testing and estimation of clinical probability in the
diagnosis of deep venous thrombosis (DVT) (1). We are enthusiastic about
the implications of this work for the diagnosis of DVT in an outpatient
setting, as it may allow an economical, safe and prompt exclusion of the
diagnosis in low risk patients.
When used in combination with clinical assessment, a rapid D-dimer
test may be a simpler clinical pathway that reduces the need for Doppler
ultrasound. It has been established that of the available options, use of
rapid D-dimer and clinical assessment in combination with a single
ultrasound is highly cost-effective, more so than the use of serial
ultrasonography (2). Yet even a single use of venous ultrasound imaging
may not be readily available in areas with limited resources, and
unnecessary use of the tool imposes a significant burden on the community,
in terms of cost and accessibility of ultrasonography. SimpliRED D-dimer
tests are already widely available; hence using them to refine clinical
assessment will allow maximal utilisation of existing resources.
As to the clinical application of the assessment combination proposed
by Fancher et al., we are unsure how specific this is as a test for
exclusion of DVT in the general population. It is well recognized that
the D-dimer level may increase with myocardial infarction, recent surgery,
trauma or any systemic illness (3). A patient presenting with symptoms and
signs suspicious of DVT may well have underlying pathology causing a high
D-dimer. It would be fair to question the practical usefulness and
significance of such a test if a high proportion of patients have an
elevated D-dimer. The paper did not specify the proportion of patients
included in this review with a high D-dimer assay, making judgment on this
issue difficult.
Furthermore, in a clinical setting where different practitioner
approaches interplay with patient factors and an increasingly litigious
environment, it is difficult to determine whether the added subjective
benefits of a venous ultrasound would incline practitioners to order the
investigation despite the review findings. As the authors pointed out,
these findings may not be applicable once the new Wells probability tool
classification scheme is adopted.
Therefore, despite the development of novel combined clinical
classifications and laboratory approaches to diagnosis, it is important to
emphasise the necessity of traditional clinical acumen in determining the
pre-test probability that the patient has a condition before potentially
unnecessary testing is undertaken (4).
In conclusion, this systematic review highlights the potential of an
economical, accessible and rapid D-dimer test to exclude DVT in low risk
patients. The findings are promising for use in the field of outpatient
care. They are particularly relevant for health services with limited
resources and those without ready access to pathology services or where
there are geographical considerations in referring patients. There is also
a potential for use in the long-term observation settings of ambulatory
care and general practice follow-up.
Sincerely,
Kate Crossley and Kenny Sze
4th year Medical Students
Macarthur Ambulatory Care Service
Competing interests:
None declared
Competing interests: No competing interests