Results of the National Pilot Screening Program for Venous Disease by the American Venous Forum

Article Outline

• Abstract
• Methods
• Results
• Discussion
• Conclusion
• Author contributions
• Acknowledgment
• Appendix
• Appendix II (online only)
• References
• Copyright

Objective

This report describes the pilot of a free comprehensive national screening program for venous disease.

Methods

The screening process consisted of a venous thromboembolism (VTE) risk assessment, abbreviated duplex examination for venous obstruction and reflux, inspection for signs of chronic venous insufficiency (CVI), and an exit interview. Physicians coordinating the screenings were members of the American Venous Forum.

Results

Seventeen institutions screened 476 people (mean, 28 per site; range, 6 to 71). Mean age was 60 years (range, 40 to 91 years), with 78% women and 68% with a body mass index of ≥25. If placed in a situation conducive for VTE, 22 participants (5%) were low risk, 87 (18%) were moderate risk, 186 (39%) were high risk, and 179 (38%) were at very high risk. In 26 people (6%), one or more segments had venous obstruction, and 190 (40%) had one or more segments of venous reflux in the lower extremities. Varicose veins were present in 32%, edema without skin changes in 11%, skin changes attributable to venous disease in 8%, and healed or active venous stasis ulcer in 1.3% (CEAP classification 2, 3, 4, 5, and 6, respectively). Increasing age and increasing deep venous thrombosis risk score significantly correlated with increasing clinical classification, r = 0.09, P = .04, and r = 0.16, P = .0004, respectively. Those participants with reflux in one or more segments were significantly more likely to have a higher clinical classification compared with those with no reflux (P = .0001).

Conclusion

The first comprehensive national screening for venous disease was performed. Participants were informed of their risk for VTE if placed in a situation conducive to VTE, screened for evidence of obstruction, reflux, and CVI, and empowered to share their results with their primary care provider.

The two most common manifestations of venous disease include venous thromboembolism (VTE) and chronic venous insufficiency (CVI). Statistics are staggering when evaluating the consequences of VTE: 1 in 20 people will be diagnosed with VTE over a lifetime.¹, ², ³ VTE is responsible for >600,000 hospital admissions per year, and pulmonary embolism is the third most common cause of hospital death. Similarly, >6 million individuals in the United States have severe symptoms from CVI that range from skin changes to recalcitrant ulcers in the gaiter area. Other less morbid but clinically relevant manifestations of CVI, such as varicose veins, are estimated to afflict >24 million Americans.⁴, ⁵

Considering the scope of venous disease, public awareness remains paramount to the possibility of improving outcomes of prevention, identification, and treatment. In addition, all specialties of clinical medicine may benefit from improvements in VTE and CVI education. Previous reports have documented difficulties by physicians in providing adequate VTE prophylaxis during high-risk situations as well as early diagnosis and proper treatment for CVI.⁶, ⁷, ⁸

Many public screening programs have been implemented with the goal of early disease detection.⁹, ¹⁰, ¹¹ Enhanced public awareness and education of physicians may be further improved by these programs. In this article, the American Venous Forum reports on the mission of providing a free comprehensive national screening program that educates about VTE, varicose veins, and CVI; identifies those at risk for VTE; examines for venous obstruction or reflux, or both; inspects for the presence of CVI; and empowers those screened to inform their physician of their risk or presence of venous disease.

Back to Article Outline

Methods 

The decision to embark on a public screening program for venous disease was made by the Executive Council of the American Venous Forum during a retreat Washington, DC, in September 2004. An Ad hoc Venous Screening Committee was formed to develop a preliminary screening instrument and begin dialogue with the Arterial Screening Program of the American Vascular Association. During the Seventeenth Annual Meeting of the American Venous Forum in February 2005, representatives from the Ad hoc Venous Screening Committee and the American Vascular Association refined the screening instrument using the model of the American Vascular Association Arterial Screening Program.¹² The American Venous Forum Executive Council voted unanimously to move forward with the screening program and formed a National Venous Screening Committee. Funding for the program was overseen by the American Venous Forum, while the development of the screening program moved in partnership with the American Vascular Association.

National Venous Screening Week was designated to be from November 7 to 12, 2005, approximately 6 months after the national American Vascular Association Arterial Screening Program. Before the screening in November, tasks completed to develop the program included:

The screening process included self-completion of the demographic questionnaire and VTE risk assessment, an abbreviated duplex examination for venous reflux and obstruction of the lower extremities, inspection by a trained professional or physician to classify the lower extremities using the CEAP classification system,¹³ and an exit interview with a venous report card given to the person being screened (Appendix I, A and I, B, online only). Participants were also asked to sign a release form.

The VTE risk assessment was designed to evaluate a person’s risk of developing VTE if put into a high-risk situation. A high-risk situation was defined on the report card as a surgical procedure, major injury or other hospitalizations, malignancy, or prolonged immobility. The VTE risk assessment, developed by Caprini et al,¹⁴ has been based on retrospective incidence data and is beyond the scope of this report. Briefly, point scores based on the severity of the VTE risk factor are assigned and totaled for a final score. VTE risk if placed in a high-risk situation was then categorized as low risk (0% to 0.4%), moderate risk (0.5% to 4%), high risk (5% to 10%), and very high risk (10% to 20%). Total points needed for each risk category were 0 to 1, 2, 3 to 4, and >4, respectively.

The abbreviated duplex ultrasound examination consisted of bilateral insonation of the common femoral vein (CFV), saphenofemoral junction (SFJ), and the above knee popliteal vein. With the person in the supine position and the head of bed elevated 30°, Valsalva was performed at each vein location to evaluate for reversal of flow >0.5 seconds. B-mode was used to evaluate compression of the vein segments in the same locations for any signs of obstruction. Obstruction was defined as inability to oppose the walls of the insonated segments by manual compression of the probe owing to an acute or chronic deep venous thrombosis (DVT).

The AVF screening committee recommended that all sonographers at screening sites be registered vascular technologists and that screening sites be accredited with Inter-societal Committee for the Accreditation of Vascular Laboratories. The recommended technique to perform duplex scanning was outlined in the National Venous Screening Tool Kit that was provided to all sites.

Lower extremities were inspected in the standing position by a trained professional or physician to assess for severity of class in the CEAP system.¹³ After inspection, participants had an exit interview to briefly discuss the findings of their screening and receive a report card with a summary of the results. They were encouraged to share the results with their primary care physicians or family doctors. Each person screened also received three educational brochures with information in laymen’s language about DVT, CVI, and varicose veins. Data collected remained anonymous and were forwarded to the American Vascular Association. All data were entered into a database created by Access (Microsoft Corp, Redmond, Wash).

Members of the American Venous Forum were notified by e-mail of the opportunity to participate in the national pilot screening program. Volunteer sites were notified that November 7 to 12, 2005, would be designated as National Venous Screening Week. Sites were allowed leeway to screen after this week. All sites received a National Venous Screening Tool Kit giving detailed instructions about marketing, preparation, and completing the screening process. Individuals to be targeted for the screening were at the discretion of the screening site. A general recommendation was made to target the general public who were aged ≥40 years.

The statistical software SAS 9.1 (SAS Institute Inc, Cary, NC) was used for all analyses. Independent groups t tests were used to compare groups of patients by the presence or absence of obstruction or reflux. Variables compared included age, body mass index (BMI), and risk score. Fisher’s exact test or χ² tests of independence, as appropriate, were used to examine the relationship of the presence or absence of these findings with the demographic and medical history variables. The χ² tests of independence were also used to examine the relationship of risk category with the previously mentioned variables.

Wilcoxon rank sum tests were performed to compare maximum clinical classification by gender, race, diabetes, high blood pressure, heart failure, smoking status (ever vs never), use of blood thinner, use of aspirin, presence or absence of obstruction in either leg, reflux in either leg, and reflux in either leg of the CFV, SFJ and popliteal veins. Spearman correlation coefficients were used to examine the relationship between maximum clinical classification and age, BMI, and DVT risk score. Multivariate analysis was not performed owing to low numbers of significant findings in the univariate analyses for each major group comparisons. Major group comparisons included VTE risk factors, duplex examination for obstruction and reflux in venous segments, and CEAP classification in each lower limb. P < .05 was considered statistically significant.

Back to Article Outline

Results 

Seventeen institutions screened 476 people (mean, 28 per site; range, 6 to 71 per site). Fig 1 shows the geographic distribution of the screening sites. Appendix II (online only) lists each screening institution, location, and primary designate. Table I lists basic demographic data and medical information of the screened population. Forty-five percent of participants indicated their doctor was a family practitioner, 40% indicated an internist, and 12% indicated another specialty. Reasons for coming to be screened included 43%, varicose veins; 36%, free screening; 13%, swollen leg; 3%, “blood clot”; 2%, cosmetic problem; and 1%, other reason.

• 
  • View Large Image
  • Download to PowerPoint

• Fig 1. 

  Geographic distribution of 17 centers participating in the National Pilot Screening Program for Venous Disease.

Table I. Demographic and medical information on 476 people participating in the National Pilot Screening Program in Venous Disease

Variable	Mean (range)
Age (years)	60(26-91)
Body mass index	28(16-51)
	Number (%)
Female	373(78)
Male	100(22)
Caucasian	392(84)
African American	36(8)
Diabetes mellitus	33(7)
Hypertension	153(31)
Congestive heart failure	12(2)
Nonsmoker	249(57)
Smoker	24(5)
Past smoker	168(38)
Aspirin	103(21)
Clopidogrel	8(2)
Warfarin	25(5)

Table II lists data showing the number of participants who gave affirmative answers for each risk factor for DVT. Fig 2 shows the distribution of total point scores for the population screened. When considering the DVT risk if placed in a high-risk situation, 22 participants (5%) were low risk, 87 (18%) were moderate risk, 186 (39%) were high risk, and 179 (38%) were at very high risk.

Table II. Number (percent) of people giving affirmative answers to questions assessing venous thromboembolism risk^⁎

	Number (%)
1. Have you ever had a blood clot in your legs or lungs? (3)	59(12)
2. Do you have a family history of blood clots in the veins? (3)	105(22)
3. Do you currently or have you ever had swollen legs? (1)	128(27)
4. Do you have visible varicose veins other than spider veins? (1)	395(82)
5. Do you have ileitis, Crohn’s, or inflammatory bowel disease? (1)	33(7)
6. Do you have serious lung disease or emphysema? (1)	16(3)
7. Within the last month, have you had >3 days of continuous bed rest due to injury or illness? (1)	15(3)
8. Within the last month, have you had a pelvic fracture or a plaster leg cast? (1)	0(0)
9. Do you have or have you had a malignant disease (cancer)? (2)	48(10)
10. Do you weigh >250 pounds? (1)	30(6)
11. Age between 40 to 59? (1)	223(47)
12. Age between 60 to 69? (2)	113(24)
13. Age ≥70? (3)	120(25)
Women only
14. Do you take birth control pills or estrogen (hormone) replacement therapy? (1)	66(14)
15. Are you pregnant or given birth within the last month? (1)	1(0.2)

• 
  • View Large Image
  • Download to PowerPoint

• Fig 2. 

  Percentage of participants having each point total in the score calculation of risk of deep venous thrombosis if placed in a high-risk situation such as surgical procedure, major injury or other hospitalizations, malignancy, or prolonged immobility.

Table III shows the distribution of obstruction and reflux discovered in the CFV, SFJ, and popliteal vein of each leg. In 26 people (6%), one or more segments of obstruction were present, and 190 (40%) people had one or more segments of reflux.

Table III. Number (percent) of abnormal findings of obstruction or reflux in the common femoral vein, saphenofemoral junction, and popliteal vein of each extremity

Obstruction	Right n (%)	Left n (%)
Common femoral vein	5(1)	1(0.2)
Saphenofemoral junction	4(1)	1(0.2)
Popliteal vein	9(2)	2(0.4)
Reflux
Common femoral vein	56(12)	54(11)
Saphenofemoral junction	78(16)	83(17)
Popliteal vein	34(7)	49(10)

Table IV shows the distribution of clinical class for CVI for each extremity. When individuals were examined for signs of CVI as opposed to left or right limb, varicose veins were present in 32%, edema without skin changes in 11%, skin changes attributable to venous disease in 8%, and healed or active venous stasis ulcer in 1.3%.

Table IV. Number (percent) of extremities in each clinical class of chronic venous insufficiency

		Right n (%)	Left n (%)
Class 0	No visible or palpable signs of venous disease	87(19)	91(20)
Class 1	Telangiectases, reticular veins, malleolar flare	171(37)	170(37)
Class 2	Varicose veins	129(28)	122(26)
Class 3	Edema without skin changes	45(10)	48(10)
Class 4⁎	Skin changes ascribed to venous disease	30(6)	29(6)
Class 5	Skin changes† with healed ulceration	3(0.6)	3(0.6)
Class 6	Skin changes† with active ulceration	1(0.2)	1(0.2)

When the demographic data (eg, male vs female), medical information (eg, hypertension vs no hypertension), and DVT risk score (eg, low risk vs high risk) of screening participants with or without obstruction was compared, no significant differences were noted. The only significant difference when making similar comparisons with the presence or absence of valvular reflux demonstrated that smokers were significantly more likely to have no reflux in one or both legs compared with nonsmokers (P = .03).

Several significant differences were noted when comparisons were made among different cohort groups for reflux vs no reflux in individual venous segments. Participants with hypertension were significantly less likely to have CFV reflux compared with nonhypertensive individuals (P = .03). Those participants with reflux of the SFJ had a significantly higher risk factor point score (mean, 4.7) compared with those without reflux (mean, 4.0; P = .01). Similarly, those participants with reflux of the popliteal vein had a significantly higher risk factor point score (mean, 4.9) compared with those without reflux (mean, 4.1; P = .02). Men were significantly more likely than women to have popliteal vein reflux (P = .002).

When comparing different cohort groups with the DVT risk score grouped as low/moderate risk vs high/very high risk, African Americans were significantly less likely to be in the high/very high risk group compared with Caucasians (P = .02). Participants with hypertension were significantly more likely to be in the high/very high risk for DVT compared with those without hypertension (P = .03).

An examination of differences in cohort groups with respect to clinical classification of CVI demonstrated that clinical class was significantly lower in African Americans compared with all others (P = .02). Similarly, increasing age and increasing DVT risk score significantly correlated with increasing clinical classification, r = 0.09, P = .04 and r = 0.16, P = .0004, respectively. Those participants with reflux in one or more segments were significantly more likely to have a higher clinical classification compared with those with no reflux, P = .0001.

Back to Article Outline

Discussion 

The mission of the first National Screening Program for Venous Disease created by the American Venous Forum in concert with the American Vascular Association was to educate, identify, and empower people with knowledge about common venous problems affecting themselves and others. In doing so, a major goal of the study was to develop a program that was comprehensive yet streamlined. The four parts of the screening process included completion of a DVT risk factor assessment, abbreviated duplex examination, inspection of the legs for signs of CVI, and an exit interview with a physician or trained allied health professional. Participants received a report card that they were encouraged to share with their primary care providers. Additional education materials about DVT, varicose veins, and CVI were given to those being screened at no charge.

Although free venous screenings for varicose veins and telangiectasias are relatively common among specialty vein centers, the National Screening Program for Venous Disease sought to be as complete as possible in covering the spectrum of venous disease while at the same time remaining consistent and streamlined. Considering the scope of venous disease, designing an ideal screening program remains difficult. As outlined in the “Methods” section, much deliberation from experts in venous disease from the American Venous Forum led to a process that would address VTE and CVI. The major focus of the process, modeled after the arterial screening process from the American Vascular Association, was to increase public education and awareness. The risk assessment, abbreviated duplex ultrasound examination, clinical inspection, and exit interview with report card all contribute to the educational experience of the participant.

A total of 77% of the participants were classified as high risk (5% to 10%) or very high risk (10% to 20%) for developing a DVT if placed in a situation at high risk for thrombosis. At first glance, this finding may appear to be too high when considering the general population. Closer scrutiny shows that this percentage may indeed be accurate considering the population that was screened in this pilot program. The demographic data indicate that our population was older (mean age, 60 years), overweight (68% with BMI of ≥25), and had more comorbidities than would have been observed from a more random selection of people closer to the middle age years.

The medical literature is laden with situations that increase the risk of DVT with no or varying degrees of prophylaxis.¹⁵ Without prophylaxis, the risk of DVT when patients are put in a high-risk situation, such as sustained head injury or total hip replacement, can be even higher than those quoted from our own risk assessment. Furthermore, correct prophylaxis as directed from the American College of Chest Physicians¹⁶ is not guaranteed given the variations in physician compliance and practice habits.¹⁷, ¹⁸ Educating the public about the risk of DVT when in a high-risk situation therefore becomes paramount to providing the necessary step to remind physicians to be more aware of these risks. Additional education about what constitutes a high-risk situation is as equally important in this mission of prevention.

Forty percent of participants had evidence of venous valve reflux of >0.5 seconds. This abbreviated examination is a variation of that previously described by van Bemmelen et al.¹⁹ The method use during the screening process was to put the person in the supine position with the head of the bed elevated 30° to 45°. The segments were identified by duplex imaging, and a Valsalva maneuver was then performed to demonstrate reflux. As stated in the report by van Bemmelen et al, the Valsalva maneuver can be hindered by the presence of iliofemoral valves, and therefore, one could infer from this study that potentially >40% of people could have had venous reflux in one or more segments.

The automated cuff deflation test with the person in the standing position was not practical because of time constraints in providing for an abbreviated streamlined screening process. More work will be needed in the form of an audit to determine variability of the duplex ultrasound screening from site to site. Despite a level of presumed variability, the correspondence of reflux to clinical classification further validates the abbreviated duplex examination performed during screening. Signs of CVI were very common in the population screened. One in three people had varicose veins, and one in five had a clinical classification score of ≥3. Considering the morbidity from CVI, education about measures to help prevent and treat these conditions could have a profound impact on those people at risk.

The National Venous Screening Program is not a program designed to give intricate details about the complex physiology of venous valvular reflux and findings of obstruction. We admonish that individual trends in valvular reflux and a thorough examination for obstruction from a screening examination may not indicate a complete picture. Emphasis should be placed on the fact that the abbreviated screening duplex examination for obstruction and valvular reflux does not relay information about other areas that are insonated during a complete examination, hence screening participants could have positive findings in other areas. The hope of the screening program is to identify in a quick and cohesive way whether a person may have reflux in a limb. The three sites in each limb (CFV, above knee popliteal vein, and SFJ) were chosen because of their importance and their ease of duplex examination by the method previously described.

Despite correlation of the abbreviated screening duplex exam to clinical classification in this screening population, more work is needed to correlate the abbreviated screening duplex examination to the comprehensive examination as described by van Bemmelen et al.¹⁹ Given that the abbreviated screening duplex examination could yield a false-negative examination and the screening participant could have physical signs of venous obstruction or insufficiency, the hope of the National Venous Screening Program is that the screening participant will give the report card to the primary care physician, who will in turn conduct a detailed reflux examination or refer to a specialist who will conduct a more detailed reflux examination performed in the standing position with cuff deflation.

The selection of participants in this first national venous screening pilot project was not random and, overall, they represented a small cohort. Sites were advised to screen adults aged ≥40 years, and those who finally responded to advertising to participate in the screening were a select group. Not surprisingly, this screening process revealed a very high rate of positive findings for venous disease. In contrast, although the public may be aware of venous disease, they may not be generally privy to the devastating risks of VTE and the potential morbidity of CVI. Thus, the screening further verifies the commonality of DVT risk, varicose veins, and CVI by the findings herein. Critically needed in this commonality is public awareness and fostering public responsibility in prevention of these potentially serious problems. The exit interview with a physician or allied health professional in combination with a report card to share with the participants’ primary care provider begin the foundation for building a national paradigm of improved health through public education and empowerment.

More work is needed, and the National Venous Screening program hopes to expand to more centers in the future. Balance is required in improving the National Venous Screening program, and the effectiveness of screening is often at odds with mechanics and feasibility of screening. Nevertheless, adding a venous disability score or an abbreviated quality-of-life questionnaire may improve the screening process and further validate the instrument. Other goals include providing participants with more educational materials, linking screenings with awareness campaigns directed to physicians, continuing to build sponsorship, and performing a cost-effectiveness analysis. This first pilot program was feasible due to a generous grant from the Juzo Company (Aichach, Germany); however, all screening materials were void of any link to industry sponsors.

Back to Article Outline

Conclusion 

Physicians and allied health professionals who are capable of meeting the requirements of performing a venous screening are encouraged to participate and offer this public health service to their community. A single day of free screening to the public for venous disease seems little to ask when one considers the scope of venous disease and the sorely needed beginning of preventative medicine in the United States.

Back to Article Outline

Author contributions 

Back to Article Outline

We thank Michele Lentz for her tireless commitment to the National Venous Screening Program.

Back to Article Outline

Appendix 

Additional material for this article may be found online at www.jvascsurg.org.

Back to Article Outline

Appendix II (online only) 

List of centers participating in the National Pilot Screening Program for Venous Disease by state and their coordinators

Arizona: Morrison Vein Institute, Tempe, Valerie Killip

Florida: Anchor Vascular Surgery, Naples, Hiranya Rajasinghe, MD

Illinois: SIU School of Medicine, Springfield, Robert McLafferty, MD

Indiana: IU Vascular Diagnostic Center, Indianapolis, Debra Hinchman, BS, RVT

Michigan: University of Michigan Health System, Ann Arbor, Sandy Brown; Comprehensive Vascular Care, Southfield, Linda Myers; University of Michigan Medical Center, Ann Arbor, Thomas Wakefield, MD; Vein and Vascular Clinic of Lansing, Lansing, Graham Kelly, MD

Mississippi: River Oaks Health System, Jackson, Emily Myers

North Carolina: Vein Clinic of NC/Forsyth Medical Center, Winston-Salem, Susan Martin

New York: University Hospital at Stony Brook, Stony Brook, Antonios Gasparis, MD; Vascular Institute of New York, Brooklyn, Natalie Marks

Ohio: The Cleveland Clinic Foundation, Cleveland, Matthew Eagleton, MD; Good Samaritan Hospital, Cincinnati, Sue Polaski

South Carolina: Carolina Vascular Surgery, Rock Hill, Tracie Dauplaise, RVT

Tennessee: Vascular Center/Vanderbilt University Medical Center, Nashville, Marc Passman, MD

Virginia: Rockingham Memorial Hospital, Harrisonburg, Helen Simmons

Back to Article Outline

References 

1. Hirsch DR, Ingenito EP, Goldhaber SZ. Prevalence of deep venous thrombosis among patients in the medical intensive care. JAMA. 1995;274:335–337
   • View In Article
   • MEDLINE
2. Christiansen SC, Cannegieter SC, Koster T, Vandenbroucke JP, Rosendaal FR. Thrombophilia, clinical factors, and recurrent venous thrombotic events. JAMA. 2005;293:2352–2361
   • View In Article
   • CrossRef
3. Lopez JA, Kearon C, Lee AY. Deep venous thrombosis. Hematology Am Soc Hematol Educ Program. 2004;439–456
   • View In Article
4. Beebe-Dimmer JL, Pfeifer JR, Engle JS, Schottenfeld D. The epidemiology of chronic venous insufficiency and varicose veins. Ann Epidemiol. 2005;15:175–184
   • View In Article
   • Abstract
   • Full Text
   • Full-Text PDF (181 KB)
   • CrossRef
5. Alguire PC, Mathes BM. Chronic venous insufficiency and venous ulceration. J Gen Intern Med. 1997;12:374–383
   • View In Article
   • MEDLINE
   • CrossRef
6. Merli GJ. Prophylaxis for deep venous thrombosis and pulmonary embolism in the surgical patient. Clin Cornerstone. 2000;2:15–28
   • View In Article
   • MEDLINE
   • CrossRef
7. Pieper B, DiNardo E. Reasons for nonattendance for the treatment of venous ulcers in an inner-city clinic. J Wound Ostomy Continence Nurs. 1998;25:180–186
   • View In Article
   • MEDLINE
   • CrossRef
8. Marston WA, Carlin RE, Passman MA, Farber MA, Keagy BA. Healing rates and cost efficacy of outpatient compression treatment for leg ulcers associated with venous insufficiency. J Vas Surg. 1999;30:491–498
   • View In Article
9. Lieberman DA. Targeted colon cancer screening: a concept whose time has almost come. Am J Gastroenterol. 1992;87:1085–1093
   • View In Article
   • MEDLINE
10. Holcomb K, Runowicz CD. Cervical cancer screening. Surg Oncol Clin N Am. 2005;14:777–797
    • View In Article
    • Full Text
    • Full-Text PDF (381 KB)
    • CrossRef
11. Harasymowycz P, Kamdeu Fansi A, Papamatheakis D. Screening for primary open-angle glaucoma in the developed world: are we there yet?. Can J Opthamol. 2005;40:477–486
    • View In Article
12. The American Vascular Association. VascularWeb, Provided by the Society for Vascular Surgery. Available at: http://www.vascularweb.org/_CONTRIBUTION_PAGES/AVA_Screening/index.html. Accessed Apr 17, 2006.
    • View In Article
13. Moneta GM, Porter JM International Consensus Committee on Chronic Venous Disease. Reporting standards in venous disease: an update. In:  Gloviczki P,  Yao JST editor. Handbook of venous disorders. 2nd edition. New York, NY: Chapman and Hall Medical; 2001;p. 509–520
    • View In Article
14. Caprini JA. Thrombosis risk assessment as a guide to quality patient care. Dis Mon. 2005;51:70–78
    • View In Article
    • Full Text
    • Full-Text PDF (325 KB)
    • CrossRef
15. Agnelli G, Sonaglia F. Prevention of venous thromboembolism in high risk patients. Haematologica. 1997;82:496–502
    • View In Article
    • MEDLINE
16. Geerts WH, Pineo GF, Heit JA, Bergqvist D, Lassen MR, Colwell CW, et al. Prevention of venous thromboembolism: the Seventh ACCP conference of antithrombotic and thrombolytic therapy. Chest. 2004;126(3 Suppl):338S–400S
    • View In Article
    • MEDLINE
    • CrossRef
17. Arnold DM, Kahn SR, Shrier I. Missed opportunities for prevention of venous thromboembolism: an evaluation of the use of thromboprophylaxis guidelines. Chest. 2001;120:1964–1971
    • View In Article
    • MEDLINE
    • CrossRef
18. Goldhaber SZ, Dunn K, MacDougall RC. New onset of venous thromboembolism among hospitalized patients at Brigham and Women’s Hospital is caused more often by prophylaxis failure than by withholding treatment. Chest. 2000;118:1680–1684
    • View In Article
    • MEDLINE
    • CrossRef
19. van Bemmelen PS, Bedford G, Beach K, Strandness DE. Quantitative segmental evaluation of venous valvular reflux with duplex ultrasound scanning. J Vasc Surg. 1989;10:425–431
    • View In Article
    • Abstract
    • Full Text
    • Full-Text PDF (1625 KB)
    • CrossRef