Background
Lower extremity deep venous thrombosis (DVT) is a relatively common disease encountered both in hospital patients and outpatients. It has an annual incidence of 1.2–1.6 per 1000 inhabitants [
1,
2]. The most serious complication of DVT is pulmonary embolism (PE) which is often considered as one pole of a continuum of the same disease. In addition to the risk of death associated with PE, DVT frequently causes a post-thrombotic syndrome leading to an impaired quality of life [
3,
4]. Hence it is important to correctly diagnose DVT.
Acute DVT is challenging to diagnose due to its non-specific symptoms including sub-febrile fever, pain, swelling and impaired function, which are often associated with other causes. Hence, it is impossible to make the diagnosis on only a clinical basis. The standard method in DVT diagnostics is compression ultrasound (US) with or without Doppler. Venography, computed tomography (CT) and magnetic resonance imaging (MRI) are used only in rare special cases. The sensitivity and specificity of US in diagnosing a proximal DVT are good, 93.8% and 97.8%, respectively, but the sensitivity decreases to 56.8% below the popliteal vein. The use of Doppler seems to lower the specificity to 94% but increases the sensitivity to 96.5% in proximal and 71.2% in distal veins [
5]. A single negative US is considered safe in excluding a DVT since only 0.5% of these patients experience a thromboembolic complication during the 3 month follow-up [
6]. If the initial US is negative and the symptoms become worse, or the US is technically inadequate, a repetitive US after 5–7 days is recommended [
7].
The US examination is traditionally performed by a radiologist and often that requires that the patient needs to be referred to a hospital emergency department (ED). As the symptoms of a DVT are non-specific, the need for US and a hospital visit are frequently expensive, consuming both public and private resources including a loss of working time. By incorporating serum D-dimer testing into the clinical risk assessment based on symptoms and the patient’s history, namely (modified) Wells’ criteria, then the need for a US examination can be reduced by 23% [
8]. This can be safely reduced by a further 15% using an age-adjusted D-dimer cut-off point [
9].
An alternative method to whole-leg compression US is a limited compression ultrasound (LCUS) examination where only common femoral, proximal superficial femoral and popliteal veins are evaluated. In this approach, LCUS is considered positive if either the thrombus is clearly visualized or the vein is not fully compressible [
10‐
12]. LCUS should be combined with a clinical risk assessment [(modified) Wells’ criteria] and D-dimer [
13]. Although the accuracy of LCUS is lower than that of a radiologist performed US [
14], when the negative LCUS is repeated after 1 week, it has been shown to be safe to withhold anticoagulation treatment if no thrombosis has been identified. The risk of a thromboembolic complication after two negative LCUS examinations parallels that of a single whole-leg ultrasound, being 0.6% during the 3-month follow-up [
6,
14,
15]. It has been shown that using LCUS in primary health care can reduce the number of patients referred to hospital significantly, by 73% [
16].
Even though the risk assessment and D-dimer measurement is widely used, approximately 2% of all ED patients undergo a venous ultrasound (Central Finland Central Hospital and Tampere University Hospital statistics). Since the number of patients is large, this is extremely expensive. In a recent review on cost-effectiveness of ultrasound in emergency care setting, point-of-care ultrasound (POCUS) was found to allow for more cost-effective care, although the existing evidence is limited [
17]. Otherwise, the data regarding the costs of diagnosing a DVT is scarce. A cost-effectiveness analysis on multiple different diagnostic strategies in a hospital has been previously performed [
18,
19]. Verma et al. conducted a cost-minimization analysis and found that incorporating a D-dimer assessment into the diagnostic protocol in hospital setting instead of referring every DVT patient to US saved 24% of costs [
20]. We are not aware of any studies which have estimated the overall costs of the LCUS protocol.
For the purposes of the present study, two different diagnostic strategies were created. The first strategy (later “standard strategy”) involves a clinical risk assessment to a D-dimer measurement and if DVT cannot be ruled-out, the patient is referred to the hospital to undergo a radiologist performed US. In the second strategy (later “LCUS strategy”), if DVT cannot be ruled out after the clinical risk assessment and D-dimer assay, an LCUS is performed. If a DVT is found, a treatment is initiated. If the clinical risk is low (Wells 0 or less), a negative LCUS rules out DVT. If the clinical risk is moderate to high (Wells 1 or more), and D-dimer positive, a repeated LCUS is performed after 1 week. If the repeated LCUS is still negative, DVT is ruled out. Both strategies are consistent with national guidelines [
21]. The goal of this study was to compare the total costs of these different diagnostic strategies of a suspected DVT using a cost-minimization modeling.
Results
The total costs of LCUS strategy were shown to be significantly lower than those of the standard pathway therapy (Table
3). Considering the real-life scenario, in which a part of the patients receive the standard strategy, and training LCUS causes expenses, the difference in expenses remains considerable (Table
4).
Table 3
Cost calculator demonstrating the cost-minimization modeling on different diagnostic pathways
Primary health care visit (time, monetized) | 9.35 | 16.86 | − 7.51 (− 8.46 to− 6.55) | < 0.001 |
Primary health care visit price (paid by municipalities) | 96.00 | 139.64 | − 43.64 (− 58.34 to – 28.94) | < 0.001 |
Primary health care visit price (paid by patient) | 28.30 | 41.16 | − 12.86 (− 17.20 to − 8.53) | < 0.001 |
Travel (time, monetized) | 45.43 | 11.08 | 34.35 (30.32 to 38.38) | < 0.001 |
Travel expenses | 361.73 | 93.21 | 268.53 (234.37 to 302.68) | < 0.001 |
Hospital visit (time, monetized) | 66.07 | 0 | 66.07 (55.11 to 77.03) | < 0.001 |
Hospital visit price (paid by municipalities) | 503.45 | 0 | 503.45 (503.45 to 503.45) | 0.001 |
Hospital visit price (paid by patient) | 41.20 | 0 | 41.20 (41.20 to 41.20) | 0.000 |
Total costs | 1151.53 | 301.94 | 849.59 (800.21 to 898.97) | < 0.001 |
Total costs assuming 60 patients per year | 69,091.80 | 18,116.40 | 50,975.40 | |
Table 4
Cost calculator demonstrating the cost-minimization modeling in real-life including educational costs
Primary health care visit (time, monetized) | 9.35 | 14.86 | − 5.51 (− 6.61 to − 4.40) | < 0.001 |
Primary health care visit price (paid by municipalities) | 96.00 | 128.00 | − 32.00 (− 43.79 to − 20.21) | < 0.001 |
Primary health care visit price (paid by patient) | 28.3 | 37.73 | − 9.43 (− 12.91 to − 5.96) | < 0.001 |
Travel (time, monetized) | 45.43 | 17.92 | 27.51 (22.30 to 32.72) | < 0.001 |
Travel expenses | 361.73 | 148.83 | 212.90 (169.53 to 256.27) | < 0.001 |
Hospital visit (time, monetized) | 66.07 | 16.11 | 49.96 (36.80 to 63.12) | < 0.001 |
Hospital visit price (paid by municipalities) | 503.45 | 134.25 | 369.20 (311.20 to 427.19) | < 0.001 |
Hospital visit price (paid by patient) | 41.20 | 10.99 | 30.21 (25.47 to 34.96) | < 0.001 |
Total costs | 1151.53 | 508.69 | 642.84 (541.85 to 743.82) | < 0.001 |
Total costs assuming 60 patients per year | 69,091.80 | 30,521.40 | 38,570.40 | |
Price of education | 0 | 3500 | | |
Salary of GPs participating in training | 0 | 3753 | | |
Total education cost | 0 | 7253 | | |
Total costs for the first year assuming 60 patients per year including one-time training costs | 69,091.80 | 37,774.40 | 31,317.40 | |
Ruling-in or ruling-out lower extremity DVT in primary health care proved to save a significant amount of private and public expenditures. In this study, the costs of the standard diagnostic and LCUS pathways were 1119.45€ and 261.20€, respectively, i.e., a difference of 790.52€ or 75%. Since most likely some patients with suspected DVT are always referred to hospital, another analysis simulating a real-life scenario was performed. In this approach, the cost of the LCUS pathway was 500.19€, with a 619.26€ or 55% reduction in costs per patient. The one-time educational cost of 7253€ is less than the savings made during the first year.
Discussion
The key finding in this study was that diagnosing or ruling out DVT in primary health care saves private and public resources. Even considering the cost of training, the savings are still substantial. This finding shows that teaching LCUS to GPs could help with the burden of increasing health care costs. As we are living in a world of scarce resources and rising health care costs, it is important to evaluate scientifically where resources can be saved without compromising the quality of care.
These saved resources can be used for the better of the patient, for example hiring more staff. The savings in a relatively small health centre are approximately the same as the salary of a nurse [
31]. Furthermore, in a busy emergency department, if there were fewer patients, this would reduce the over-crowding and hence one could argue that the remaining patients would receive better care [
32]. Another way of looking at this is that emergency department personnel could concentrate their efforts on those patients that would truly benefit from hospital care.
In addition to the public savings, there are also costs incurred by the individual patient. As the visits to a health care centre consume less time than the visit to the hospital, less working time is lost. The fees paid by the patient are also lower. According to our experience, patient satisfaction is higher when the diagnostics and treatment can be achieved closer to home.
The use of POCUS has been shown to allow for more cost-effective care in emergency care setting [
17]. One previous cost-effectiveness analysis of different diagnostic strategies of DVT has been performed [
19]. However, that analysis only compared the emergency department expenses when the patient was already in that unit. In that analysis, it was shown that the most cost-effective diagnostic strategy incorporated a clinical risk assessment, D-dimer assay, and ultrasound. Depending on the threshold of willingness to pay for an extra quality-adjusted life expectancy, a repeated ultrasound was recommended.
DVT is a common reason for an emergency department visit. These visits incur significant expenses to both the public and private purses. Although there have been some analysis on parts of the diagnostic pathway [
19], no analysis has examined the total expenses including costs to the individual patient. Since the LCUS strategy has been assessed to be as safe as the standard protocol, there was a need for the cost-minimization modeling to demonstrate that it also saves resources.
In this study we performed a cost-minimization modeling of the two strategies that are widely in use. The analysis focused fully on the costs. Since there was no data available on the actual patients diagnosed with the LCUS strategy, we needed to base our analysis on the available data and estimates. The measured data was based on 76 actual patients that had had a suspected DVT. Some data, such as the need for a repeated LCUS, was estimated based on the literature. Since the Finnish guidelines for DVT still use the original Wells’ criteria [
21], although most of the recent studies have applied the modified Wells’ criteria, this might have introduced a minor inaccuracy. In an attempt to make the analysis as accurate as possible, despite the inevitable compromises in the estimates that had to be made, comprehensive data was collected including public and private costs.
There are limitations in this study. Since the sensitivity and specificity of LCUS are less than those of US [
14], some DVTs are missed and it is possible that these could result in an increase in PEs and obviously any additional PEs would cause significant expenses. However, it has been shown that the number of PEs following the LCUS protocol parallels that with the standard protocol [
6,
14,
15]. A possible increase in false positive DVTs would lead to an increase in medical expenses. This increase is assumed to be minor. Since there was no validation by US for the DVTs found to be positive on LCUS, the number of false positives cannot be retrieved from our data and this potential expense has been neglected.
When a DVT is diagnosed, it is often necessary to perform etiologic examinations such as a chest X-ray. The costs of possible additional imaging or laboratory examinations performed during the same visit were not included in the analyses.
This cost-minimization modeling assessed the total costs of traditional and LCUS protocols. The data available for this study was not sufficient for a more patient centered analysis such as cost per life saved or cost per correct diagnosis. An averaged patient was used in the analysis i.e. it was not based on actual individuals, which may introduce some minor inaccuracy. Furthermore, the travel time was estimated using the speed of 80 km/h, which reflects the speed limit of the majority of the roads in the area. Although this might cause a slight underestimate of the travelling time it was considered better than overestimating it. The goal of data collection was to gather as much data as possible and we are confident that the results reflect the actual expenses in Finland fairly well. However, the study was local regarding the organization of the Finnish health care system and the results cannot be straightforward extrapolated to other countries.
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