Inappropriate use of venous duplex scans: an analysis of indications and results

The clinical application of venous ultrasound in diagnosis and follow-up of lower extremity deep vein thrombosis (DVT): a case-based discussion

Current clinical practice guidelines lack explicit guidance on the indications and appropriate timing of venous ultrasound (US) in lower extremity deep vein thrombosis (DVT) follow-up. Moreover, abnormal findings reported on venous US in DVT follow-up or suspected recurrent DVT may be difficult for clinicians to interpret, which carries risk of harm from inappropriate use of anti- coagulation and increased healthcare resource utilization. Due to the above factors, over-use of ultrasound in diagnosis and follow-up of lower extremity DVT has been reported in western health systems. We have undertaken a case-based discussion and a scoping review of existing guidelines on the use of venousUS following prior diagnosis of DVT, to guide appropriate interpretation of commonly reported US abnormalities and provide our suggestions in the light of best available evidence on appropriate timing to perform follow-up US in management of lower extremity DVT.

A Survey of Physicians' Knowledge and Management of Venous Thromboembolism

A review of all patients diagnosed with venous thromboembolism (VTE) at an academic medical center from 1996 to 1998 revealed a wide variation in management and subsequent patient outcomes and a 30% increase in utilization of the vascular laboratory from the previous 2-year period. The purpose of this study was to determine physicians' knowledge and management strategies before the implementation of integrated care pathways for VIE. Mail surveys were sent to 650 physicians covering 3 academic medical centers. The disciplines targeted were from those physicians who had previously referred patients for any VTE screening examination. One-hundred and twenty-eight physicians (20%) completed the survey. Only 12% of the physicians were able to correctly identify all of the veins routinely imaged as either deep or superficial veins. Fifty-nine percent of the physicians incorrectly identified the superficial femoral vein of the thigh as a superficial vein, and 23% believed the popliteal vein to be a superficial vein. Only 17% of the respondents correctly classified the tibial-peroneal veins as deep veins. Approximately 70% of the physicians stated that they would not treat symptomatic isolated calf vein thrombosis, and, of those, only 42% said that they would obtain serial duplex scans to monitor for proximal propagation. Physicians underestimated the charges for all diagnostic screening tests, and only 14% were able to correctly identify the range of charges for a venous duplex scan. This survey of physicians demonstrated a lack of basic knowledge regarding lower extremity venous anatomy, charges for the different diagnostic tests used to diagnose VIE, and, most importantly, current treatment standards for VTE.

Duplex Ultrasonography Has Limited Utility in Detection of Postoperative DVT After Primary Total Joint Arthroplasty

BACKGROUND

Duplex ultrasound is routinely used to evaluate suspected deep venous thrombosis after total joint arthroplasty. When there is a clinical suspicion for a pulmonary embolism, a chest angiogram (chest CTA) is concomitantly obtained.

QUESTIONS/PURPOSES

Two questions were addressed: First, for the population of patients who receive duplex ultrasound after total joint arthroplasty, what is the rate of positive results? Second, for these patients, how many of these also undergo chest CTA for clinical suspicion of pulmonary embolus and how many of these tests are positive? Furthermore, what is the correlation between duplex ultrasound results and chest CTA results?

METHODS

A retrospective chart review was conducted of total joint replacement patients in 2011 at a single institution. Inclusion criteria were adult patients who underwent a postoperative duplex ultrasonography for clinical suspicion of deep venous thrombosis (DVT). Demographic data, result of duplex scan, clinical indications for obtaining the duplex scan, and DVT prophylaxis used were recorded. Additionally, if a chest CTA was obtained for clinical suspicion for pulmonary embolus, results and clinical indication for obtaining the test were recorded. The rate of positive results for duplex ultrasonography and chest CTA was computed and correlated based on clinical indications.

RESULTS

Two hundred ninety-five patients underwent duplex ultrasonography of which only 0.7% were positive for a DVT. One hundred three patients underwent a chest CTA for clinical suspicion of a pulmonary embolism (PE) of which 26 revealed a pulmonary embolus, none of which had a positive duplex ultrasound.

CONCLUSION

Postoperative duplex scans have a low rate of positive results. A substantial number of patients with negative duplex results subsequently underwent chest CTA for clinical suspicion for which a pulmonary embolus was found, presumably resulting from a DVT despite negative duplex ultrasound result. A negative duplex ultrasonography should not rule out the presence of a DVT which can embolize to the lungs and thus should not preclude further workup when clinical suspicion exists for a pulmonary embolus.

The prevalence of and predictors to indicate bilateral venous duplex ultrasound testing to detect contralateral asymptomatic lower extremity deep venous thrombosis in patients with acute symptomatic lower extremity deep venous thrombosis

OBJECTIVE

The goal of this study was to determine the prevalence of and predictors to indicate bilateral venous duplex ultrasound (DU) to detect contralateral asymptomatic deep venous thrombosis (DVT) in patients with acute symptomatic lower extremity DVT.

METHODS

Venous DU reports along with medical records of the patients were collected from February 2005 to April 2012 in a tertiary university hospital in Botucatu, Brazil. All patients with DVT detected in one lower extremity routinely underwent contralateral limb venous DU examination. Exclusion criteria were previous DVT in the contralateral asymptomatic limb, thrombophlebitis, workup for pulmonary embolism, and bilateral symptomatic lower extremities.

RESULTS

Scans were done in 579 patients to rule out contralateral lower extremity DVT whenever DVT was confirmed in the ipsilateral lower extremity; of these, 108 patients (18.6%) had an abnormal finding on DU examination for DVT in the contralateral limb, which was proximal DVT in 71.5%. Age >60 years (odds ratio [OR], 3.33; 95% confidence interval [CI], 1.447-7.670), malignant disease (OR, 5.21; 95% CI, 1.943-14.015), and the association of trauma plus malignant disease (OR, 7.11; 95% CI, 1.640-30.863) were the main predictors.

CONCLUSIONS

Age >60 years, malignant disease, lower extremity trauma, inpatient status, and recent hospitalization are risk factors associated with a high incidence of asymptomatic contralateral lower extremity DVT in patients with ipsilateral lower extremity DVT. Therefore, we recommend routine performance of a venous DU examination on the contralateral lower extremity whenever these risk factors are present in patients with ipsilateral lower extremity DVT.

Elimination of medically unnecessary duplex venous scanning based on an established algorithm can result in significant cost savings under Medicare for the institution and the taxpayer

OBJECTIVE

The utility of duplex venous scanning (DVS) for suspected deep venous thrombosis in the emergency department (ED) remains controversial. We aimed to measure potential cost savings and economic impact in our institution and nationally for unnecessary DVS in Medicare patients seen in the ED.

METHODS

We have previously calculated that 15.3% of DVS studies can safely be avoided in patients with suspected deep venous thrombosis in our ED with adherence to our protocol. The Medicare database was queried for the number of DVS studies performed in the ED and charges/payments made in 2011. Cost savings at our institution and nationally by Medicare were computed with the 15.3% number.

RESULTS

In the study period, 2087 DVS studies were performed in our ED across all payers; 572 Medicare patients had 249 (43%) bilateral and 323 (57%) unilateral studies. Annual savings at our institution, with use of our protocol, were estimated at $113,778. Eliminating unnecessary after-hours DVS for 306,307 Medicare beneficiaries would result in $5,285,090 savings annually.

CONCLUSIONS

Increasing pressure for cost containment under a value-based payment model necessitates critical evaluation of resource utilization. Applying this schema for all noninvasive vascular tests is an opportunity for responsible management of finite resources, reducing wasteful care, and significant cost containment.

The current state of practice in the diagnosis of venous thromboembolism at an academic medical center

Evidence-based guidelines for the diagnosis of venous thromboembolism (VTE) have been recommended, yet the adoption of such guidelines into daily practice is unknown. The purpose of this study was to describe the current practices in the diagnosis of VTE. Medical records of 1161 adult patients who underwent lower extremity venous duplex scans (VDS), chest computerized tomographic (CT) angiography, or ventilation and perfusion (V/Q) scans during a 6-month period were retrospectively reviewed in an academic medical center. Patients who were first diagnosed by CT or V/Q scan still underwent a VDS. Nine patients at high risk had incomplete CT scans, yet no further tests were performed. Five pregnant patients had CT scans as the initial test instead of being screened with VDS or V/Q scanning. Inappropriate use of imaging tests was documented. The recommended guidelines of using clinical probability and D-dimer as the initial screening tests for VTE diagnosis were underused.

The impact of a systemwide policy for emergent off-hours venous duplex ultrasound studies

BACKGROUND

We evaluated the impact of an after-hours policy regulating venous duplex ultrasound (VDU) for deep vein thrombosis (DVT) diagnosis on resource utilization and patient care.

METHODS

On July 1, 2007, we altered the approach to emergent VDU of patients with potential DVT during off-hours (defined as 5:00 p.m. to 7:00 a.m. weekdays, after 3:30 p.m. Saturdays and Sundays). Instead of 24 hr access, we permitted a venous duplex study in the noninvasive vascular laboratory (NIVL) only after meeting set criteria developed collaboratively across services. In the emergency department (ED), we based all VDU requests on a preset modified Wells score (MWS) as determined by the ED physician. Those patients with MWS 0 or 1 and those above 1 who could receive empiric single-dose low-molecular weight heparin (LMWH) received next-morning imaging unless consultation with a vascular surgeon created an emergent imaging plan. In parallel, inpatient emergent VDU was permitted only after contact with an attending vascular surgeon and where empiric short-term anticoagulation could not occur safely. We tracked NIVL utilization, patient morbidity, sonographer retention, and satisfaction.

RESULTS

The number of overall off-hours emergent VDUs decreased from 59 to 19/month after implementation. Testing was deferred in 52 ED patients: 15 stayed in the ED for testing in the morning and 37 were discharged to be tested the following day. Thirty-one of 37 patients returned for testing as outpatient follow-up. Twenty-eight received ED LMWH while awaiting testing. No adverse events were noted with the delay. The mean MWS for ED after-hours studies was 2.9+/-1.6 and that for deferred ER studies was 2.4+/-1.3 (p=0.005). Incidentally, overall off-hours inpatient and ED VDU requests decreased 64% with no clinical adverse events in the first year. The rate of overall positive studies done off-hours increased from 6.7% to 20% (p<0.0001). Sonographer satisfaction was maintained with regulation of call.

CONCLUSION

Our collaborative approach allowed off-hour VDU utilization to decrease without any measurable negative care impact.

Venous thrombosis in an outpatient oncologic center: distribution, type, and comorbidities

PURPOSE

To examine outpatient oncologic patients with venous thrombosis (VT) and correlate ultrasound findings with clinical characteristics and outcome.

MATERIALS AND METHODS

A retrospective study of 76 patients who had upper- and lower-extremity ultrasound examinations positive for VT formed the population, drawn from a total of 509 patients who presented over a 24-month period for non-invasive imaging. Clinical indication, demographics, sonographic findings, comorbidities, and development of pulmonary embolism in these patients were recorded. The Fisher-Freeman-Halton exact test was used to determine if test characteristics varied according to the location of VT (upper or lower extremity), the level of lower-extremity thrombosis (above the knee, below the knee, or both), the presence of active disease or remission, the chronicity or acuteness of thrombosis, and the presence of a central venous catheter (CVC).

RESULTS

In the study group, 64 patients had deep VT, and 12 had superficial VT. The most prevalent tumors in our study population were lymphoma and breast and lung cancers. The most common symptoms were swelling, pain, and erythema. Whereas 61 patients had active disease, 18 patients were in remission at the time of examination. Among 30 patients with upper-extremity VT, 18 had CVCs. Venous thrombosis involved the vessel containing the central venous line in 66% of studies. Pulmonary embolism developed in 8 patients who had lower-extremity VT despite an initiation of anticoagulation therapy. Patients with thrombus in the lower extremity had higher chance to develop pulmonary embolism, but there was no significant statistical difference in the level of lower-extremity thrombosis (above the knee, below the knee, or both), disease activity, and chronicity of thrombosis.

CONCLUSIONS

Venous thrombosis is most commonly acute and involves the lower extremity and the deep venous system above the knee. When VT involves the upper extremity, it is usually associated with a CVC. Pulmonary embolism is almost exclusively associated with lower-extremity VT and can occur despite anticoagulation therapy.

Do not forget the distal lower limb veins in screening patients with spinal cord injuries for deep venous thromboses

In this prospective study, we aimed to document the rate and localization of deep venous thromboses in patients with spinal cord injuries. Patients with paraplegia or tetraplegia were screened by a serial color duplex sonography protocol for deep venous thrombosis within the first 36 hours after admission, at day 7, and at day 21. Sonography was performed by a complete scan including the veins below the knee. A total of 139 patients were included (19-90 years, 63.5% male). Cumulative rate of deep venous thrombosis after 3 duplex scans was 45.3% (n = 63). In 71.4% (n = 45), thromboses were localized below the knee. Because of the relevant number of distal vein thromboses, inclusion of the calf veins during screening scans is suggested. Further studies are needed to analyze the clinical benefit of diagnosing and treating distal vein thromboses.

Use of D-dimer to aid in excluding deep venous thrombosis in ambulatory patients

BACKGROUND

Duplex imaging is currently the gold standard for diagnosing deep venous thrombosis (DVT), but its nonselective use overburdens vasuclar laboratories, particularly during off hours. It is the purpose of this study to determine if a new D-dimer assay could be used as an aid in determing whether duplex imaging could be performed on an elective or emergent basis in patients with suspected DVT.

METHODS

D-dimer levels were measured and venous duplex examinations were obtained in all patients. D-dimer assays were performed using the Tina-quant latex agglutination test (Roche Diagnostics, Mannheim, Germany). Venous duplex examinations were performed using colorflow doppler.

RESULTS

Between September 1, 2002 and April 30, 2003, 148 patients were seen in the emergency department for suspected DVT. Nineteen patients (12.8%) had positive venous duplex examinations and 129 (87.2%) duplex examinations were negative. None of the 19 patients with positive venous duplex studies had D-dimer levels within of the normal range (0 to 0.49). The sensitivity, specificity, positive predictive value, and negative predictive value of the D-dimer test were 100%, 48.8%, 22.4%, and 100%, respectively.

CONCLUSION

The D-dimer test can effectively used without adjuncting risk stratification as an aid in excluding the diagnosis of DVT in ambulatory patients. Its routine use could significantly reduce the need for the performance of emergent venous duplex examinations.

Evaluation of a screening protocol to exclude the diagnosis of deep venous thrombosis among emergency department patients

OBJECTIVE

The purpose of this study was to evaluate the efficacy and cost effectiveness of a deep venous thrombosis (DVT) screening protocol incorporating DVT pretest probability (PTP), selective D-dimer assay, and venous duplex imaging (VDI) to exclude the diagnosis of DVT among emergency department (ED) patients.

METHODS

A prospective study of all patients evaluated in the ED for suspected DVT during 1 year was undertaken. Patients were classified into PTP risk category by ED physicians before VDI. Correlation studies were completed using VDI as the gold standard. Charges associated with the protocol were calculated.

RESULTS

One hundred fourteen patients were included. The incidence of DVT was 9.6% (11). Thirty-six (55%) patients were classified as high risk, 23 (35%) as moderate, and 7 (10%) as low risk. All patients diagnosed with DVT were in the high-risk group (incidence, 16.7%). The sensitivity and negative predictive value were both 100% when PTP and D-dimer were used, but fell to 80% and 95%, respectively, when only D-dimer was considered. The true negative rates were 23% and 37%, respectively. Based on this study, we propose the following screening: for high-risk patients, use direct VDI (no D-dimer); for low-risk or moderate-risk patients, obtain D-dimer, and if it is positive, use VDI, and if it is negative, no further action is required. The average charge associated with the protocol was 170.50 dollars as opposed to 202.00 dollars for global VDI.

CONCLUSION

A screening protocol using PTP along with selective D-dimer and VDI to exclude the diagnosis of DVT among ED patients is efficacious and cost efficient. This screening approach establishes criteria to satisfy billing requirements, can eliminate unnecessary VDI in 23% of ED referrals, and can reduce charges by 16%.

Is bilateral ultrasound scanning of the legs necessary for patients with unilateral symptoms of deep vein thrombosis?

PURPOSE

The purpose of this study was to determine the necessity of bilateral lower-extremity venous duplex ultrasound scanning in patients with unilateral symptoms of deep vein thrombosis (DVT).

PATIENTS AND METHODS

A retrospective review of 1080 bilateral venous duplex scans was performed. Patients were randomly selected from a total of 7922 studied between May 1998 and May 2000. Data on patient age, sex, comorbidity, and the reason for ultrasound scan were compiled. Forty percent (435/1080) of patients presented with unilateral symptoms of lower-extremity DVT. This group was further analyzed according to their status as inpatients or outpatients.

RESULTS

DVT was diagnosed in 26.9% (117/435) of the patients. Of the inpatients found to have DVT, the thrombus was confined to the symptomatic leg in 23.8% (38/159), thrombus was present just in the asymptomatic leg in 8/159 (5.0%), and thrombus was found in both legs in 8/159 (5.0%). In the outpatient group, thrombus was confined to the symptomatic leg in 21.0% (58/276) and found in both legs in 1.8% (5/276). None of the 276 outpatients had DVT isolated in the asymptomatic leg.

CONCLUSION

Routine bilateral lower-extremity venous duplex studies are not necessary in outpatients presenting with unilateral symptoms. In many outpatients, a single-limb study will suffice. If a patient is found to have a DVT on the symptomatic side, then we believe that a bilateral study is indicated. We do believe that routine bilateral scanning of inpatients remains justified. This algorithm may save technician time and increase vascular laboratory efficiency.

Enoxaparin treatment in high-risk trauma patients limits the utility of surveillance venous duplex scanning

OBJECTIVE

The value of surveillance venous duplex scanning for detecting unsuspected deep venous thrombosis (DVT) in trauma patients who are receiving enoxaparin prophylaxis is open to question. This study was undertaken to determine whether enoxaparin reduced the clinical utility of surveillance scanning and whether management of these patients was altered by findings of the scans.

METHODS

The medical records of trauma patients who met defined criteria for high DVT risk, admitted during 30 consecutive months, were reviewed. These patients received enoxaparin 30 mg every 12 hours for the duration of their admissions. Per protocol, surveillance lower extremity venous duplex scans were performed within 72 hours of enoxaparin administration and then weekly until patients were discharged from the hospital. The records were reviewed for thromboembolic events (DVT or pulmonary embolism [PE]), patient location and ambulatory status, therapeutic interventions (systemic anticoagulation, vena cava filter), and complications of enoxaparin therapy.

RESULTS

A total 241 patients underwent 513 venous duplex examinations (1-13 per patient). Eight patients had DVT on the initial scan; seven of these patients were asymptomatic. Five were treated with anticoagulation and/or vena cava filter placement. Of the 233 patients with initially negative duplex scan results, five patients (2%) developed clinically unsuspected lower extremity DVT while hospitalized. All of these five patients were in an intensive care unit. Three of the five patients had no change in treatment. Two of the five underwent anticoagulation, and one vena cava filter was placed. PE occurred in two hospitalized patients, one of whom was ambulatory, with negative duplex scan results. After hospital discharge, six other patients had symptomatic DVT or PE despite in-hospital scans with negative results. Complications associated with enoxaparin included hemorrhage (2) and thrombocytopenia (8).

CONCLUSIONS

After initial negative scan results, repeat surveillance duplex scanning during hospitalization detected a low incidence (2%) of DVT in high-risk patients. Furthermore, the detection of unsuspected DVT altered the clinical management of less than 1% of the patients tested. Thus, after a venous duplex scan with negative results and initiation of enoxaparin prophylaxis, subsequent surveillance duplex examinations are not warranted in asymptomatic trauma patients.

Diagnostic value of the D-dimer test in deep vein thrombosis: improved results by a new assay method and by using discriminate levels

Previous studies have suggested that D-dimer testing reliably selects patients for whom duplex sonography should be performed for diagnosis of deep vein thrombosis (DVT). However, the interassay correlation is poor. Therefore, we tested four D-dimer methods for their ability to rule out DVT, including the Miniquant test, a new D-dimer assay method. Sensitivity, specificity, negative predictive value (NPV) and positive predictive value (PPV) were calculated vs. duplex sonography. Twenty-nine of 108 (27%) patients with suspected DVT were diagnosed as having DVT by sonography. The Vidas enzyme-linked immunoabsorbent assay (ELISA) test, the Miniquant turbidimetric test and the latex agglutination test for D-dimer all provided discriminate values for achieving 100% sensitivity and 100% NPV. D-dimer results demonstrated higher specificity and PPV in the outpatient vs. the inpatient group. This probably reflects the higher proportion of inpatients with comorbid conditions, such as malignancy and postsurgery status, in whom D-dimer results show very poor specificity and PPV. The new Miniquant turbidimetric assay performed as well as the more established ELISA method. We conclude that the D-dimer tests were shown to possess the necessary sensitivity and NPV to be useful in screening patients with suspected DVT. A negative D-dimer test in selected patients could be helpful in reducing the number of sonograms performed for diagnosis of DVT.

Lower extremity venous sonography in the high-risk cancer population: one leg or two?

OBJECTIVE

We correlated the diagnostic yield of unilateral and bilateral lower extremity venous sonograms in a high-risk cancer population with the clinical indication for the examination.

MATERIALS AND METHODS

Reports from 433 bilateral and 619 unilateral lower extremity Doppler sonograms obtained over an 18-month period in patients with cancer were retrospectively reviewed, and clinical indication and findings were determined.

RESULTS

Overall, 228 (22%) of 1052 examinations revealed deep venous thrombosis (DVT): 83 (19%) of 433 bilateral and 145 (23%) of 619 unilateral. Among studies performed for unilateral symptoms (pain, edema, or postorthopedic procedure), 23% (135/581) of unilateral and 27% (44/162) of bilateral studies revealed DVT. Among these 44 bilateral studies with positive findings performed for unilateral symptoms, there were 30 DVT in the symptomatic side, 12 bilaterally, and two in the asymptomatic side alone. Ten percent (11/110) of the bilateral studies performed for bilateral symmetric symptoms revealed DVT. Among studies performed for bilateral asymmetric symptoms, 13% (1/8) of the unilateral and 8% (2/25) of the bilateral studies revealed DVT; both bilateral studies showed positive findings in the more symptomatic side. Among studies performed for suspected or proven pulmonary embolus, 20% (23/113) of bilateral and 54% (7/13) of unilateral studies had positive findings.

CONCLUSION

In a high-risk cancer population, the incidence of DVT in patients with unilateral symptoms is more than twice that of patients with bilateral symptoms. Because DVT isolated to an asymptomatic lower extremity is rare (1%), bilateral sonographic examination is generally unnecessary with unilateral lower extremity symptoms.

Combination of a clinical risk assessment score and rapid whole blood D-dimer testing in the diagnosis of deep vein thrombosis in symptomatic patients

PURPOSE

The clinical diagnosis of deep vein thrombosis (DVT) is unreliable in more than 50% of cases, and, in recent years, plasma D-dimer assays have been used to predict the presence of DVT with high sensitivity and negative predictive values. This study investigated the use of a rapid whole blood test that could be performed and interpreted by the bedside in addition to a clinically derived risk assessment score (RAS) to determine whether a practical and cost-effective clinical model could be developed for the diagnosis and exclusion of DVT in symptomatic patients.

METHODS

Two hundred consecutive patients who were referred to the vascular laboratory with clinically suspected DVT underwent the following procedures: (1) clinical assessment and stratification into low, moderate, or high risk for DVT on the basis of an RAS related to history, symptoms, and physical examination findings; (2) rapid (5-minute) whole blood D-dimer testing with a semi-qualitative agglutination technique on a fingerprick blood sample; and (3) color flow duplex ultrasound scanning with standard criteria for the diagnosis of proximal and calf DVT.

RESULTS

Forty-six patients (23%) had acute DVT on duplex ultrasound scanning. Of these cases, 28 (61%) had proximal DVT and 18 (39%) were confined to the calf. A total of 88 patients were classified as low risk, 67 were classified as moderate, and 45 were classified as high risk on the basis of the RAS method. Of the patients who were classified at low risk, 4.5% (4/88) had DVT, as compared with 17.9% (12/67) in the moderate clinical risk group and 66.7% (30/45) in the high risk group. Isolated calf DVT was found in 30% (9/30), 50% (6/12), and 75% (3/4) of the high, moderate, and low risk groups, respectively. The sensitivity (8.7%, 26.1%, 65.2%), specificity (45.5%, 64.3%, 90.3%), positive predictive value (4.5%, 17.9%, 66.7%), and overall accuracy rate (37%, 55.5%, 84.5%) of the low, moderate, and high risk groups, respectively, in the diagnosis of DVT increased significantly with increasing risk score stratification. The sensitivity, specificity, positive and negative predictive value, and overall accuracy of the rapid D-dimer test for all DVT were 91.3%, 81.9%, 60%, 96.9%, and 84%, respectively, with a 100% sensitivity and negative predictive value for proximal DVT. A combination of the RAS and D-dimer identified a low risk group with a negative D-dimer as having less than a 1% likelihood of DVT and a high risk group with positive D-dimer as having a likelihood of more than 90%.

CONCLUSION

A combination of clinical assessment and rapid D-dimer testing provides an effective means of excluding proximal DVT in symptomatic patients. The application of a clinical diagnostic model on the basis of these parameters has the potential for saving a large proportion of unnecessary duplex scans with the associated time and costs.

The value of rapid D-dimer testing combined with structured clinical evaluation for the diagnosis of deep vein thrombosis

PURPOSE

Large studies have shown that most cases referred for duplex sonography for suspected deep vein thrombosis (DVT) have normal scan results. For medical and economic reasons, a preselection procedure, which allows the detection of true-negative cases before duplex scanning, is required; this procedure should be characterized by a high sensitivity and a high negative predictive value.

METHODS

In 343 patients (398 lower extremities) with suspected DVT, the DVT probability was clinically assessed, and a whole blood D-dimer agglutination test and a duplex scan were performed. The diagnostic sensitivities of the D-dimer test alone, a high clinical DVT probability alone, and the combination of both were evaluated.

RESULTS

The sensitivity values for the D-dimer test to diagnose proximal and distal DVTs were 88.7% and 80.9%, the negative predictive values (NPV) were 96.3% and 97.9%, and the specificity and the positive predictive value (PPV) were 54.8% and 49.6% and 26.6% and 8.2%, respectively. The sensitivities of the clinical DVT probability assessment for the diagnosis of proximal and distal DVTs were 83.9% and 66.7%, respectively; the corresponding NPVs were 94.9% and 96.5%, respectively. The specificity was 56.1% and 50.8%, and the PPVs were 26.1% and 7.0%, respectively. The combined use of the results of the clinical probability assessment and the D-dimer test resulted in sensitivities for proximal and distal DVTs of 98.4% and 90.5%, NPVs of 99.3% and 98.6%, a specificity of 43.4% and 38.4%, and PPVs of 24. 3% and 7.6%, respectively.

CONCLUSION

The combined use of a clinical DVT probability assessment scheme and the D-dimer test largely avoids false negative results, has a high sensitivity and NPV, helps to reduce the costs of DVT diagnosis, and may, in the future, be useful as a preselection procedure before duplex sonography.

A national survey of practice patterns in the noninvasive diagnosis of deep venous thrombosis

PURPOSE

Recent studies have recommended unilateral venous duplex scanning for the diagnosis of deep venous thrombosis (DVT) in patients who are unilaterally symptomatic. Vascular laboratory accreditation standards, however, imply that bilateral leg scanning should be performed. We examined whether actual practice patterns have evolved toward limited unilateral scanning in such patients.

METHODS

A questionnaire was mailed to all 808 vascular laboratories in the United States that were accredited by the Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL). To encourage candid responses, the questionnaires were numerically coded and confidentiality was assured.

RESULTS

A total of 608 questionnaires (75%) were completed and returned. Most of the respondents (442; 73%) were either community-hospital or office-based laboratories, and the remaining 163 (27%) were university or affiliated-hospital laboratories. Most of the laboratories (460; 76%) had been in existence for 9 years or more, and 65% had been ICAVL-accredited in venous studies for 3 years or more. Board-certified vascular surgeons were the medical directors in 54% of the laboratories. Duplex ultrasound scanning was the diagnostic method used by 98% of the laboratories. In patients with unilateral symptoms, 75% of the laboratories did not routinely scan both legs for DVT. A large majority (75%) believe that bilateral scanning is not clinically indicated. Only 57 laboratories (14%) recalled having patients return with a DVT in the previously unscanned leg, with 93% of these laboratories reporting between one and five such patients. This observation correlated with larger volumes of venous studies performed by those laboratories (P <.05). Similarly, only 52 laboratories (12%) recalled having patients return with subsequent pulmonary emboli. Of these laboratories, only five reported proximal DVT in the previously unscanned legs of such patients. Of all these laboratories, therefore, only 1% (5 of 443) have potentially missed the diagnosis of a DVT that caused a preventable pulmonary embolus with such a policy. Among those laboratories that always perform bilateral examinations, 41% do so because of habit. Most (61%) of the laboratories that perform bilateral scanning would do unilateral scanning if it were specifically approved by ICAVL.

CONCLUSION

Three quarters of the ICAVL-accredited vascular laboratories perform limited single-extremity scanning for the diagnosis of DVT in patients with unilateral symptoms. This broad clinical experience suggests that this practice is widespread in selected patients. Clinical protocols should be established to provide guidelines for local laboratory implementation.

Use of Venous Duplex Scans to Evaluate Symptoms of Deep Vein Thrombosis: An Analysis of Ultrasound Usage by Various Medical Specialties

In today's environment of cost-containment and utilization management, duplex ultrasound is often overused to evaluate symptoms of deep venous thrombosis/thrombophlebitis (DVT), reflecting the low diagnostic yield of such studies. We investigated the use of venous duplex scans by various medical specialties to determine whether a tendency exists to overuse this diagnostic tool by one specialty compared with others and to assess the cost-effectiveness of ordering this test for acute venous disease changes. We retrospectively reviewed the results of venous duplex ultrasound studies for 330 consecutive patients with suspected DVT for a 1-year period. Our analysis showed that 51 of 330 (16%) of all duplex scans ordered in our institution were positive for DVT. Internists, as a group, ordered 185 studies of which 26 were positive (14%). The surgeons’ requests for duplex studies resulted in 23 of 137 (17%) confirmed positive studies. The overall positive examination rate was 16 per cent, which is not only suboptimal as a diagnostic tool, but also cumbersome with regard to health care cost-containment.

Improved selection criteria for ordering stat venous ultrasounds from the emergency department

BACKGROUND

The accuracy and convenience of venous ultrasound (VU) to exclude deep vein thrombosis (DVT) has led to indiscriminate use and low positive yield rates.

METHODS

A total of 256 patients were referred from our emergency department (ED) for stat VU during a 2-year period (1995 to 1996). The VUs were interpreted as normal in 198 (77%). Positive findings were discovered in 58 (23%), with DVT accounting for 43 (17%). Retrospective multivariant analysis was used to identify predictive indicators.

RESULTS

Unilateral leg swelling/edema identified 36 of 40 (90%) patients with DVT and 8 of 10 (80%) with other thrombotic disorders (saphenous and/or chronic venous thrombosis). A history of leg pain with prior DVT or recent trauma < or =3 days' duration increased DVT duration to 98% (39 of 40). Using these criteria, a 47% charge reduction would have been recognized.

CONCLUSIONS

Improving ED screening criteria can safely increase yield rate and reduce charges with minimal loss of VU sensitivity.

Diagnosis of deep venous thrombosis and pulmonary embolism

Diagnostic evaluation in the patient with suspected deep vein thrombosis (DVT) and pulmonary embolism (PE) includes a clear correlation between clinical probability, test selection and test interpretation. Real-time B-mode ultrasound with color Doppler remains the imaging technique of choice in suspected DVT. The ventilation/perfusion (V/Q) lung scan is the preferred diagnostic modality in suspected PE. The D-dimer assay may be useful in excluding PA. New diagnostic techniques, including spiral computerized tomography may further modify the diagnostic algorithm.

Noninvasive venous testing in the diagnosis of pulmonary embolism: the impact on decisionmaking

PURPOSE

To characterize the use and utility of lower extremity noninvasive venous testing (NIVT) in the diagnosis of pulmonary embolism (PE).

METHODS

The study is a retrospective case series of consecutive patients in whom PE was suspected who were referred to a large, urban tertiary care center for NIVT. The main outcome measures of the study were the rate of positive results of NIVT, the amount of new information provided by NIVT, and the frequency of management changes that were attributable to NIVT.

RESULTS

Forty-one of 450 patients (9%) had deep venous thrombosis (DVT) by NIVT. The prevalence of DVT by NIVT among patients not evaluated by ventilation/perfusion (V/Q) scanning was 8%. The prevalence of DVT by NIVT among patients with a high-probability V/Q scan result before NIVT was 39%, but no management decisions in this group were based on a positive NIVT result and only two decisions were based on negative NIVT results. The prevalence of DVT according to NIVT among patients who had a negative "diagnostic" (low, or very low probability, or normal) result of V/Q scan before NIVT was 2%. The overall frequency of management changes attributed to NIVT was only 2.5%. In the remaining 97% of patients, management was determined by the result of V/Q scanning or of subsequent pulmonary arteriography.

CONCLUSIONS

In patients in whom PE is suspected, results of NIVT are usually negative for acute DVT. Management decisions are almost always based on V/Q scan or results of pulmonary arteriography and not on NIVT. The utility of NIVT to identify DVT in these patients appears limited, and a more selective approach to its application for the diagnosis of PE should be considered.

Predictive value of clinical criteria for the diagnosis of deep vein thrombosis

BACKGROUND

The widespread use of ultrasonography for the diagnosis of deep vein thrombosis (DVT) has led to the overuse of ultrasonography with low diagnostic yield. We conducted this study to investigate the predictive value of clinical features in the diagnosis of DVT and their potential value as clinical guidelines for the use of ultrasonographic testing in the diagnosis of DVT.

METHODS

The results of lower-extremity duplex ultrasonographic studies and clinical surveys prospectively obtained in 1526 patients suspected of having DVT were analyzed.

RESULTS

There were 916 inpatients and 610 outpatients. Acute DVT was found in 16% of the inpatient duplex scans, and in 12% of the outpatient studies (p < 0.05). The incidence of acute DVT was not different between men and women in inpatient or outpatient populations. Acute DVT was found in the left leg in 60% of the outpatient studies, significantly more often (p < 0.001) than in the inpatients (35%). Bilateral DVT was more common (p < 0.05) in the inpatient population (35%) compared with the outpatient population (20%). No difference in the anatomic distribution of thrombosis was found between inpatients and outpatients. The presence of leg symptoms was associated with a significantly higher rate (p < 0.05) of positive studies compared with those patients without leg symptoms in both the inpatient and the outpatient populations. Individual symptoms, risk factors, and physical findings had low positive predictive value and sensitivity for the presence of acute DVT on duplex scan. A calf circumference discrepancy of less than 2 cm predicted the absence of DVT in 93% of inpatients and 85% of outpatients. The combination of a calf circumference discrepancy of less than 2 cm with the absence of recent operation, trauma, malignancy, previous history of DVT, or hypercoagulable state predicted the absence of DVT in 92% of the inpatients and 97% of the outpatients.

CONCLUSIONS

Clinical symptoms, risk factors, and physical findings are poor predictors of the presence of acute DVT on duplex scan. However, the absence of a combination of objective clinical factors has high predictive value for the absence of acute DVT on duplex scan. These criteria may be used to establish clinical guidelines to reduce the use of duplex scanning for the diagnosis of DVT.

Diagnosis of acute lower limb deep venous thrombosis with ultrasound: trends and controversies

Acute deep venous thrombosis of the lower limb is a common and threatening condition whose clinical diagnosis is known to be unreliable. Sonography has gradually superseded venography as the primary diagnostic procedure. A review of the medical literature shows that sonography offers a high level of sensitivity and specificity in symptomatic patients but suffers from a lack of sensitivity at the calf level and in asymptomatic patients. Technologic progress, as well as increased operator experience, may improve sensitivity. Nevertheless, several critical issues remain unresolved, such as the significance of free-floating thrombi, the usefulness of calf and bilateral examination, the criteria that are essential to the diagnosis, the risk of compression sonography, and sonography's role in the direct detection of venous emboli.