Cost-minimization analysis of venous thromboembolism diagnosis: Comparison of standalone imaging with a strategy incorporating D-dimer for exclusion of venous thromboembolism

Optimizing resource allocation: Cost-effectiveness of specified D-dimer cut-offs in cancer patients with suspected venous thromboembolism

An accurate diagnosis of venous thromboembolism (VTE) is crucial, given the potential for high mortality in undetected cases. Strategic D-dimer testing may aid in identifying low-risk patients, preventing overdiagnosis and reducing imaging costs. We conducted a retrospective, comparative analysis to assess the potential cost savings that could be achieved by adopting different approaches to determine the most effective D-dimer cut-off value in cancer patients with suspected VTE, compared to the commonly used rule-out cut-off level of 0.5 mg/L. The study included 526 patients (median age 65, IQR 55-75) with a confirmed cancer diagnosis who underwent D-dimer testing. Among these patients, the VTE prevalence was 29% (n = 152). Each diagnostic strategy's sensitivity, specificity, negative likelihood ratio (NLR), as well as positive likelihood ratio (PLR), and the proportion of patients exhibiting a negative D-dimer test result, were calculated. The diagnostic strategy that demonstrated the best balance between specificity, sensitivity, NLR, and PLR, utilized an inverse age-specific cut-off level for D-dimer [0.5 + (66-age) × 0.01 mg/L]. This method yielded a PLR of 2.9 at a very low NLR for the exclusion of VTE. We observed a significant cost reduction of 4.6% and 1.0% for PE and DVT, respectively. The utilization of an age-adjusted cut-off [patient's age × 0.01 mg/L] resulted in the highest cost savings, reaching 8.1% for PE and 3.4% for DVT. Using specified D-dimer cut-offs in the diagnosis of VTE could improve economics, considering the limited occurrence of confirmed cases among patients with suspected VTE.

Age-adjusted D-Dimer Thresholds Combined with the Modified Wells Score as a Predictor of Lower Extremity Deep Venous Thrombosis

BACKGROUND

Neurosurgical patients are at an increased risk of deep venous thrombosis (DVT), which, if not properly managed, can lead to pulmonary embolism. This study aimed to investigate the accuracy of age-adjusted D-dimer thresholds combined with the modified Wells score as a predictor for lower extremity DVT diagnosis.

METHODS

We conducted a study among patients aged >50 years with suspected lower extremity DVT in the neurosurgery intensive care unit between December 2019 and December 2020. Receiver operating characteristic curve analysis was performed to examine the diagnostic capacity of age-adjusted D-dimer combined with the modified Wells score.

RESULTS

A total of 233 participants, with an average age of 71.81 ± 12.59 years, were enrolled in the study. The mean D-dimer levels were 0.73 ± 0.39 mg/L. Among the participants, 57 (57.9%, 33 males) were diagnosed with DVT. The age-adjusted D-dimer combined with the modified Wells score had the highest area under the curve for diagnosing lower extremity DVT compared to D-dimer and age-adjusted D-dimer alone, with an AUC of 0.858. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the age-adjusted D-dimer combined with the modified Wells score for DVT diagnosis were 78.95%, 80.68%, 57%, 92.2%, and 80.26%, respectively. When analyzing subgroups, the accuracy was 79.55% for participants with cerebral hemorrhage, 81.69% for those with craniocerebral injury, 74.99% for participants with intracranial infection, and 88.89% for those with craniocerebral tumor.

CONCLUSION

The combination of the age-adjusted D-dimer thresholds with the modified Wells score might effectively predict lower extremity DVT.

Performance Evaluation of the Quantitative Point-of-Care LumiraDx D-Dimer Test

INTRODUCTION

Fibrin degradation product D-dimer can be a valuable indicator for venous thromboembolism (VTE). The use of D-dimer testing in primary care settings can be limited by restricted access to laboratory services. This performance evaluation compares a quantitative, point-of-care (POC) D-dimer assay (LumiraDx D-Dimer Test) with a reference laboratory-based D-dimer assay.

METHODS

Plasma samples from patients presenting to secondary care in the UK, USA, and Germany were analyzed centrally using the LumiraDx D-Dimer Test and the reference test (bioMérieux VIDAS D-Dimer Exclusion II immunoassay). Method comparison used Passing-Bablok regression analysis with pre-specified equivalence criteria of r ≥ 0.9 and slope of 0.9-1.1. The NOVEL-3 study (NCT04375982) compared equivalency of fingerstick, venous blood (VB), and plasma samples from the same patient, tested at US primary care clinics next to the patient using the POC LumiraDx D-Dimer device. Measurements obtained from fingerstick and VB samples were compared with results from plasma samples, using Deming regression. The healthy reference range was determined using plasma samples of healthy volunteers, collected by commercial suppliers in Germany and the USA, which were analyzed centrally using the LumiraDx D-Dimer Test and the reference test.

RESULTS

The LumiraDx D-Dimer Test demonstrated agreement with the bioMérieux VIDAS D-Dimer Exclusion II immunoassay for plasma samples (r = 0.923, slope of 1.016, n = 1767). There was good agreement between fingerstick/VB samples and plasma samples (r = 0.980-0.986, n = 93) measured using the LumiraDx D-Dimer Test. Overall error rates were 1.8%. The healthy reference range 90% percentile for D-dimer was calculated as 533 µg/l fibrinogen equivalent units (FEU).

CONCLUSIONS

The quantitative LumiraDx D-Dimer Test is easy to use and can accurately measure D-dimer levels in a range of blood sample types, including fingerstick samples, which could improve assessment of VTE cases in community and hospital near-patient settings.

Cost-minimization modeling of venous thromboembolism diagnostics: performing limited compression ultrasound in primary health care reduces costs compared to referring patients to a hospital

Background

The aim of this retrospective study was to determine whether diagnosing a deep venous thrombosis (DVT) in primary health care using limited compression ultrasound (LCUS) can save resources compared to referring these patients to hospital. According to the current literature, LCUS is as safe as a standard protocol based on a whole-leg ultrasound (US).

Methods

We created a standardized patient for this cost-analysis model based on 76 patients that were referred to hospital for a suspected DVT. Travel distance to the health care centre and hospital was calculated based on the home address. Hospital costs were acquired from the hospital price list and Finnish legislation. Time spent in the hospital was retrieved from hospital statistics. Time spent in the health care centre and travelling were estimated and monetized based on average salary. The cost of participating physicians attending a US training course was estimated based on the national average salary of a general practitioner as well as the course participation fee. A cost-minimization modeling was performed for this standardized patient comparing the total costs, including private and public costs, of standard and LCUS strategies.

Results

The total costs per patient of standard and LCUS pathways were 1151.52€ and 301.94€ [difference 849.59€ (95% CI 800.21€–898.97€, p < 0.001)], respectively. The real-life costs of these strategies, considering that some patients are probably referred to hospital every year and including training costs, are 1151.53€ and 508.69€ [difference 642.84€ (95% CI 541.85€–743.82€)], respectively.

Conclusion

Using LCUS in diagnosing DVT in primary health care instead of referring these patients to the hospital is shown to save a significant amount of public and private resources.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13089-021-00227-5.

Age-adjusted D-dimer cut-off levels to rule out venous thromboembolism in patients with non-high pre-test probability: Clinical performance and cost-effectiveness analysis

BACKGROUND

As aging was found to be associated with increased D-dimer levels, the question arose whether D-dimer measurement was useful in the diagnostic strategy of venous thromboembolism (VTE) in elderly patients.

AIM OF THE STUDY

To compare retrospectively the performance of six diagnostic strategies based on the three-level Wells scores and various cut-off levels for D-dimer, evaluated using the HemosIL D-Dimer HS 500 assay, in a derivation cohort of 644 outpatients with non-high pretest probability (PTP) of VTE. The clinical usefulness of the best-performing strategy was then confirmed in a multicenter validation study involving 1255 consecutive outpatients with non-high PTP.

RESULTS

The diagnostic strategy based on the age-adjusted cut-off level calculated by multiplying the patient's age by 10 above 50 years was found to perform the best in the derivation study with a better sensitivity-to-specificity ratio than the conventional strategy based on the fixed cut-off level (500 ng/ml), a higher specificity and a negative predictive value (NPV) above 99%. Such an increase in test specificity was confirmed in the validation cohort, with the NPV remaining above 99%. Taking into account the local reimbursement rates of diagnostic tests, using this strategy led to a 6.9% reduction of diagnostic costs for pulmonary embolism and a 5.1% reduction for deep vein thrombosis, as imaging tests would be avoided in a higher percentage of patients.

CONCLUSION

The diagnostic strategy of VTE based on the age-adjusted cut-off level for D-dimer in patients over 50 years was found to be safe, with NPV above 99%, and cost-effective.

PURL: A better approach to the diagnosis of PE

A simple diagnostic algorithm is all that's needed to safely and effectively reduce our reliance on CT pulmonary angiography to diagnose PE.