HomeCirculationVol. 130, No. 18The Postthrombotic Syndrome: Evidence-Based Prevention, Diagnosis, and Treatment Strategies Free AccessResearch ArticlePDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessResearch ArticlePDF/EPUBThe Postthrombotic Syndrome: Evidence-Based Prevention, Diagnosis, and Treatment StrategiesA Scientific Statement From the American Heart Association Susan R. Kahn, MD, MSc, FRCPC, Anthony J. Comerota, MD, Mary Cushman, MD, MSc, FAHA, Natalie S. Evans, MD, MS, Jeffrey S. Ginsberg, MD, FRCPC, Neil A. Goldenberg, MD, PhD, Deepak K. Gupta, MD, Paolo Prandoni, MD, PhD, Suresh Vedantham, MD, M. Eileen Walsh, PhD, APN, RN-BC, FAHA and Jeffrey I. Weitz, MD, FAHAon behalf of the American Heart Association Council on Peripheral Vascular Disease, Council on Clinical Cardiology, and Council on Cardiovascular and Stroke Nursing Susan R. KahnSusan R. Kahn Search for more papers by this author , Anthony J. ComerotaAnthony J. Comerota Search for more papers by this author , Mary CushmanMary Cushman Search for more papers by this author , Natalie S. EvansNatalie S. Evans Search for more papers by this author , Jeffrey S. GinsbergJeffrey S. Ginsberg Search for more papers by this author , Neil A. GoldenbergNeil A. Goldenberg Search for more papers by this author , Deepak K. GuptaDeepak K. Gupta Search for more papers by this author , Paolo PrandoniPaolo Prandoni Search for more papers by this author , Suresh VedanthamSuresh Vedantham Search for more papers by this author , M. Eileen WalshM. Eileen Walsh Search for more papers by this author and Jeffrey I. WeitzJeffrey I. Weitz Search for more papers by this author and on behalf of the American Heart Association Council on Peripheral Vascular Disease, Council on Clinical Cardiology, and Council on Cardiovascular and Stroke Nursing Originally published22 Sep 2014https://doi.org/10.1161/CIR.0000000000000130Circulation. 2014;130:1636–1661is corrected byCorrectionOther version(s) of this articleYou are viewing the most recent version of this article. Previous versions: January 1, 2014: Previous Version 1 The purpose of this scientific statement is to provide an up-to-date overview of the postthrombotic syndrome (PTS), a frequent, chronic complication of deep venous thrombosis (DVT), and to provide practical recommendations for its optimal prevention, diagnosis, and management. The intended audience for this scientific statement includes clinicians and other healthcare professionals caring for patients with DVT.MethodsMembers of the writing panel were invited by the American Heart Association Scientific Council leadership because of their multidisciplinary expertise in PTS. Writing Group members have disclosed all relationships with industry and other entities relevant to the subject. The Writing Group was subdivided into smaller groups that were assigned areas of statement focus according to their particular expertise. After systematic review of relevant literature on PTS (in most cases, published in the past 10 years) until December 2012, the Writing Group incorporated this information into this scientific statement, which provides evidence-based recommendations. The American Heart Association Class of Recommendation and Levels of Evidence grading algorithm (Table 1) was used to rate the evidence and was subsequently applied to the draft recommendations provided by the writing group. After the draft statement was approved by the panel, it underwent external peer review and final approval by the American Heart Association Science Advisory and Coordinating Committee. External reviewers were invited by the American Heart Association. The final document reflects the consensus opinion of the entire committee. Disclosure of relationships to industry is included with this document (Writing Group Disclosure Table).Table 1. Classification of Recommendations and Levels of EvidenceTable 1. Classification of Recommendations and Levels of EvidenceIntroductionBackgroundDVT refers to the formation of blood clots in ≥1 deep veins, usually of the lower or upper extremities. PTS, the most common long-term complication of DVT, occurs in a limb previously affected by DVT. PTS, sometimes referred to as postphlebitic syndrome or secondary venous stasis syndrome, is considered a syndrome because it manifests as a spectrum of symptoms and signs of chronic venous insufficiency, which vary from patient to patient.1 These can range from minor leg swelling at the end of the day to severe complications such as chronic debilitating lower-limb pain, intractable edema, and leg ulceration,2 which may require intensive nursing and medical care. PTS increases healthcare costs and reduces quality of life (QoL).3,4 The purposes of this scientific statement are to provide current best practice guidelines pertaining to PTS and to serve as an additional resource to healthcare professionals who manage patients with DVT and PTS.Epidemiology and Burden of PTSIncidence and Prevalence of PTSDespite advances in the primary and secondary prevention of DVT, DVT affects 1 to 3 of 1000 people in the general population annually.5,6 Well-designed prospective studies with long-term follow-up (ie, ≥12 months) report that 20% to 50% of patients with DVT develop PTS sequelae. In most cases, PTS develops within a few months to a few years after symptomatic DVT.7–12 However, some studies have reported that the cumulative incidence of PTS continues to increase, even 10 to 20 years after DVT diagnosis.11,12 About 5% to 10% of patients develop severe PTS, which may include venous ulcers.7,8,11,13 Schulman et al11 have shown that the probability of developing a venous ulcer over 10 years after DVT was almost 5%. It is projected that the number of adults in the United States with venous thromboembolism (of which DVT is the predominant form) will double from 0.95 million in 2006 to 1.82 million in 205014; therefore, improved prevention and treatment of DVT are critical in decreasing the incidence of PTS.Impact on Healthcare Costs and QoLPTS adversely affects QoL and reduces productivity,3 leading to substantial burden to patients and the healthcare system.4,15,16 In a Canadian study that assessed the economic consequences of DVT over a 2-year period, the total per-patient cost of PTS was Canadian $4527, a cost that was almost 50% higher than for patients with DVT without PTS.4 This cost increase was largely attributable to greater use of healthcare visits and prescription medications. The average annual cost of PTS treatment in the United States was estimated at ≈$7000 per patient per year.15 Caprini et al17 provided cost analyses of mild to moderate and severe PTS over time. During the first year of diagnosis, the annual cost of mild to moderate PTS was $839 compared with $341 in subsequent years, whereas severe PTS cost $3817 per patient in the first year (all had open ulcers) compared with $3295 (open ulcers) and $933 (healed ulcers) per year in subsequent years. The high cost of treating venous ulcers is due largely to surgery, lost workdays, and loss of employment. It is estimated that 2 million workdays are lost annually in the United States as a result of leg ulcers.18In the assessment of burden of illness for chronic conditions such as PTS, QoL is an important consideration. Ideally, both generic QoL (ie, overall health state) and disease-specific QoL should be assessed. Studies have shown that compared with DVT patients without PTS, patients with PTS have poorer venous disease–specific QoL,3,19–22 and scores worsen significantly with increasing severity of PTS.19 It is notable that generic physical QoL for patients with PTS is worse than that for people with chronic diseases such as osteoarthritis, angina, and chronic lung disease.3Clinical Manifestations and PathophysiologyCharacteristic Symptoms and Signs of PTSPTS, a form of secondary venous insufficiency, is characterized by a range of symptoms and signs (Table 2). Typical symptoms of lower-extremity PTS include pain, swelling, heaviness, fatigue, itching, and cramping (often at night) in the affected limb (upper-extremity PTS is discussed later in Upper-Extremity PTS). Symptoms differ from patient to patient, may be intermittent or persistent, usually worsen by the end of the day or with prolonged standing or walking, and improve with rest or limb elevation. Venous symptoms associated with the initial DVT can persist for several months and may transition to chronic symptoms without a symptom-free period.8 PTS may also present as venous claudication, likely caused by persistent venous obstruction of a major venous confluence (iliofemoral or popliteal veins). Such patients report bursting leg pain during exercise that can resemble arterial claudication.23Table 2. Clinical Characteristics of PTSSymptomsClinical SignsPainEdemaSensation of swellingTelangiectasiaCrampsVenous dilatation/ectasiaHeavinessVaricose veinsFatigueRednessItchingCyanosisPruritisHyperpigmentationParesthesiaEczemaBursting painPain during calf compressionVenous claudicationLipodermatosclerosisAtrophie blancheOpen or healed ulcersPTS indicates postthrombotic syndrome.Typical signs of PTS are similar to those of other chronic venous diseases. These range from perimalleolar (or more extensive) telangiectasia, pitting edema, brownish hyperpigmentation of the skin, venous eczema, and secondary varicose veins to signs of more severe PTS such as atrophie blanche (white scar tissue), lipodermatosclerosis (fibrosis of subcutaneous tissues of the medial lower limb), and leg ulceration (Figure 1).Download figureDownload PowerPointFigure 1. Clinical manifestations and spectrum of postthrombotic syndrome (PTS). A and B, Edema and hyperpigmentation. C, PTS 3 months after the onset of iliofemoral deep venous thrombosis (DVT; treated with anticoagulation alone). The patient has venous claudication, swelling, bluish discoloration, and pigment changes of the left lower extremity. CEAP (clinical, etiological, anatomic, pathophysiological) classification is C4a. His Villalta score is 16. D, Lower extremity of a patient with PTS 6 years after acute DVT showing edema, hyperpigmentation, and lipodermatosclerosis. His CEAP classification is C4b and Villalta score is 15. E, Edema, redness, hyperpigmentation, and lipodermatosclerosis. F, Hyperpigmentation and a healed venous ulcer.Pathophysiology of PTSAlthough the pathogenesis of PTS is complex and has not been fully characterized, venous hypertension appears to play a central role (Figure 2). Venous pressure is dependent on the weight of the blood column between the right atrium and the foot (hydrostatic pressure). Normally, when an individual is at rest in the supine position, venous pressure is low because dynamic pressure derived from the pumping action of the heart maintains movement of the blood through arteries and veins.24 When an individual is upright (sitting or standing) but motionless, venous pressure is highest, increasing to up to 80 to 90 mm Hg. While an individual is walking at a rate of 1.7 mph, venous pressure is incrementally reduced to a mean of 22 mm Hg.25 Blood is ejected by contraction of the leg muscles, which are assisted by competent venous valves working to return blood proximally from the distal leg to the heart after exercise, thus preventing reflux and limiting accumulation of blood in the lower-extremity veins.24 Therefore, any damage to the venous valves impedes venous return to the heart, leading to venous hypertension and consequent leg pain and swelling.Download figureDownload PowerPointFigure 2. Proposed pathophysiology of postthrombotic syndrome.In the case of PTS, ambulatory venous hypertension can occur from outflow obstruction as a result of the thrombus or valvular incompetence (reflux). After DVT, recanalization of the thrombosed veins, which occurs through a combination of fibrinolysis, thrombus organization, and neovascularization,26 is often incomplete, resulting in residual venous obstruction, which may interfere with calf muscle pump function and cause damage to venous valves, ultimately leading to venous valvular incompetence. In this situation, there is insufficient reduction in venous pressure with walking, resulting in ambulatory hypertension.24The literature on whether PTS development is predominantly the consequence of outflow obstruction, venous valvular reflux, or both is conflicting, which may reflect, in part, the limited ability to quantify venous obstruction and reflux. Prandoni et al27 found that PTS developed more frequently in patients who had persistent venous obstruction within the first 6 months after an episode of acute proximal DVT (relative risk [RR], 1.6; 95% confidence interval [CI], 1.0–2.4), a result that was replicated by the same group in a second study.28 Similarly, Roumen-Klappe et al29 reported that persistent venous obstruction was an important predictor of PTS 3 months after DVT (RR, 1.7; 95% CI, 1.0–2.2). In the Catheter-Directed Venous Thrombolysis Trial (CaVenT), which assessed the efficacy of catheter-directed thrombolysis (CDT) using alteplase in patients with acute DVT extending above the popliteal vein, the absolute risk of PTS was reduced by 14.4% (95% CI, 0.2–27.9) in the CDT group.30 Iliofemoral patency was noted in 65.9% of patients randomized to CDT compared with 47.4% of those who received conventional anticoagulant therapy,30 but the prevalence of valvular reflux was similar in the 2 groups.31 In contrast, Haenen et al32 reported a significant positive correlation between increasing severity of PTS and prevalence of reflux in the proximal femoral vein (P<0.001), distal femoral vein (P<0.05), and popliteal vein (P<0.05). These investigators also noted that venous obstruction alone or in combination with reflux had no relation to the presence of severe PTS. Yamaki et al33 and Asbeutah et al34 have similarly reported that reflux appears to be more important than persistent obstruction in the pathophysiology of PTS.Other models focus on vein wall damage and acute and chronic inflammation as potential drivers of PTS.18,35 Sustained venous hypertension can cause structural and biochemical abnormalities of the vein wall, resulting in pathological effects in the skin and subcutaneous tissues such as edema, hyperpigmentation, varicose veins, and ulceration.24 Several studies have reported associations between elevated levels of various inflammation markers and PTS development35,36 (see Role of Biomarkers to Predict PTS).Although the pathogenesis of PTS remains incompletely elucidated, there is mounting interest in the early use of pharmacomechanical therapy in patients with iliofemoral DVT to restore venous blood flow and to preserve valve function with the expectation that such treatment will reduce the risk of PTS (see Treatment of PTS). Further understanding of the pathophysiology of PTS will lead to more optimal prevention and management of the syndrome.Diagnosis of PTSThere is no single gold standard test to diagnose PTS. PTS is diagnosed primarily on clinical grounds when characteristic symptoms and signs (Table 2) occur in a patient with prior DVT. Because PTS is a chronic condition that often demonstrates a waxing-and-waning pattern, the recommendation is to wait at least 3 months for the initial pain and swelling associated with acute DVT to resolve; therefore, a diagnosis of PTS should generally be deferred until after the acute phase (up to 6 months) has passed.Clinical Tools to Diagnose PTSA number of clinical tools or scales have been used to help diagnose and define PTS. Of these, 3 were developed specifically to diagnose PTS after objectively diagnosed DVT: the Villalta scale,37 Ginsberg measure,9 and Brandjes scale.38 The others, developed for chronic venous disease in general, include the CEAP (clinical, etiological, anatomic, pathophysiological) classification,39 Venous Clinical Severity Score (VCSS),40 and Widmer scale.41 The general characteristics of each clinical scale are described below. Tables 3–5 show the individual components and scoring of the various scales.Villalta ScaleThe Villalta scale is a clinical measure that incorporates the assessment of 5 subjective (patient-rated) venous symptoms (pain, cramps, heaviness, paresthesia, and pruritus) and 6 objective (clinician-rated) venous signs (pretibial edema, skin induration, hyperpigmentation, redness, venous ectasia, and pain on calf compression), as well as the presence or absence of ulcer, in the DVT-affected leg13,37 (Table 3). The Villalta scale shows good correlation with generic and disease-specific QoL scores,3,19 as well as anatomic and physiological markers of PTS.27,44 A potential shortcoming of the Villalta scale (which also applies to other scales discussed below) is its relative nonspecificity; symptoms and signs could be due, at least in part, to nonvenous conditions or primary venous insufficiency.45 In addition, although the presence of ulcer is noted, ulcer size and number are not. Nonetheless, the Villalta scale has been widely and successfully used to diagnose PTS,21,35,46,47 to classify its severity, and to evaluate treatment,48–50 including in randomized, controlled trials (RCTs).30,51 In an effort to standardize the definition of PTS for research purposes, the International Society on Thrombosis and Haemostasis Subcommittee on Control of Anticoagulation recommended the Villalta scale as the most appropriate measure to diagnose and rate the severity of PTS,13 as has a recent systematic review.52 Kahn et al13 provide a more detailed description of the Villalta scale and recommendations on how to administer it.Table 3. Villalta ScaleNoneMildModerateSevere5 Symptoms Pain0 Points1 Point2 Points3 Points Cramps0 Points1 Point2 Points3 Points Heaviness0 Points1 Point2 Points3 Points Paresthesias0 Points1 Point2 Points3 Points Pruritus0 Points1 Point2 Points3 Points6 Clinical Signs Pretibial edema0 Points1 Point2 Points3 Points Hyperpigmentation0 Points1 Point2 Points3 Points Venous ectasia (venules or varicose veins)0 Points1 Point2 Points3 Points Redness0 Points1 Point2 Points3 Points Skin induration0 Points1 Point2 Points3 Points Pain on calf compression0 Points1 Point2 Points3 PointsVenous ulcerAbsentPresentTotal score of 0 to 4 indicates no postthrombotic syndrome (PTS); score of ≥5 indicates PTS. PTS severity: total score of 5 to 9, mild PTS; score of 10 to 14, moderate PTS; and score of ≥15 or venous ulcer present, severe PTS.Adapted from Guanella et al42 with permission from Informa Health Care. Copyright © 2012, Informa Health Care. Authorization for this adaptation has been obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation.Ginsberg MeasureThe Ginsberg measure9 defines PTS by the presence of daily leg pain and swelling that persists for at least 1 month, is typical in character (worse with standing or walking and relieved by rest or leg elevation), and occurs at least 6 months after acute DVT. This measure was used as the primary PTS outcome measure in the recently published Compression Stockings to Prevent the Post-Thrombotic Syndrome (SOX) trial.53 Although the measure does not rate the severity of PTS, it correlates well with QoL scores and identifies more severe PTS than the Villalta scale.52,54 Potential shortcomings include a lack of sensitivity for milder forms of PTS and the fact that it is not quantitative.Brandjes ScaleThe Brandjes scale, similar to the Villalta scale, assesses a number of subjective and objective criteria, including leg circumference.38 On the basis of scores determined in 2 consecutive visits 3 months apart, patients are classified as having no PTS, mild to moderate PTS, or severe PTS. This scale was used to assess PTS in 1 study.38CEAP ClassificationThe CEAP classification was developed to diagnose and compare treatment outcomes in patients with chronic venous disorders.43 CEAP categorizes venous disease according to clinical, etiologic, anatomic, and pathophysiologic attributes. There are 7 clinical classes, which correspond with objective clinical signs (Table 4). Although CEAP has been used to diagnose PTS,12,29,35,55 there is no agreed-on cutoff that defines the diagnosis,52 it has a limited ability to monitor change over time, and it does not incorporate assessment of PTS symptom severity. Therefore, CEAP is not an ideal scoring system to diagnose and follow up the course of PTS.Table 4. Clinical Component of CEAP ClassificationClassClinical Signs0No visible or palpable signs of venous disease1Telangiectasiae or reticular veins2Varicose veins; distinguished from reticular veins by a diameter of ≥3 mm3Edema4Changes in skin and subcutaneous tissue secondary to CVD, now divided into 2 classes to better define the differing severity of venous disease:4aPigmentation or eczema4bLipodermatosclerosis or atrophie blanche5Healed venous ulcer6Active venous ulcerCEAP indicates clinical, etiological, anatomic, pathophysiological; and CVD, cardiovascular disease.Adapted from Porter et al43 with permission from The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. Copyright © 1995, The Society for Vascular Surgery and International Society for Cardiovascular Surgery, North American Chapter. Authorization for this adaptation has been obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation.The VCSSThe VCSS (Table 5),56 recently revised by Vasquez et al,40 combines key elements of CEAP with additional criteria such as use of compression therapy and number and duration of ulcers, thus allowing assessment of change with treatment. The VCSS scoring system assesses the severity of 9 clinical signs of chronic venous disease. VCSS elements are weighted toward more severe manifestations, and only 1 symptom (pain) is assessed; hence, this measure has not been used in many studies to diagnose incident PTS.Table 5. Revised VCSSAttributeNone=0Mild=1Moderate=2Severe=3Pain or other discomfort(ie, aching, heaviness, fatigue, soreness, burning): presumes venous originOccasional pain or other discomfort (ie, not restricting regular activity)Daily pain or other discomfort (ie, interfering with but not preventing regular daily activities)Daily pain or other discomfort (ie, limits most regular activities)Varicose veins(>4 mm in diameter):varicose veins must be ≥3 mm in diameter to qualify in the standing positionFew: scattered (ie, isolated branch varicosities or clusters); also includes corona phlebectatica (ankle flare)Confined to calf or thighInvolves calf and thighVenous edema: presumes venous originLimited to foot and ankle areaExtends above ankle but below kneeExtends to knee and aboveSkin pigmentation: presumes venous origin; does not include focal pigmentation resulting from other chronic diseasesNone or focalLimited to perimalleolar areaDiffuse over lower third of calfWider distribution (above lower third) and recent pigmentationInflammation: more than just recent pigmentation (ie, erythema, cellulitis, venous eczema, dermatitis)Limited to perimalleolar areaDiffuse over lower third of calfSevere cellulitis (lower third and above) or significant venous eczemaInduration: presumes venous origin of secondary skin and subcutaneous changes (ie, chronic edema with fibrosis, hyperdermitis); includes white atrophy and lipodermatosclerosis)Limited to perimalleolar areaDiffuse over lower third of calfEntire lower third of leg or moreActive ulcer number012>2Active ulcer duration(longest active)N/A<3 mo>3 mo but <1 yNot healed for >1 yActive ulcer size(largest active)N/ADiameter <2 cmDiameter 2–6 cmDiameter >6 cmUse of compression therapyNot usedIntermittent use of stockingsWears stockings most daysFull compliance with stockingsAbsence of venous disease is defined by a score of ≤3; a score of ≥8 defines severe disease. VCSS indicates Venous Clinical Severity Score.Adapted from Vasquez et al40 with permission from the Society for Vascular Surgery. Copyright © 2010, the Society for Vascular Surgery. Authorization for this adaptation has been obtained both from the owner of the copyright in the original work and from the owner of copyright in the translation or adaptation.Widmer ClassificationThe Widmer classification, developed to grade chronic venous disease into classes I, II, and III according to the presence of clinical signs, has also been used to diagnose PTS41 and to assess the effectiveness of compression therapy in patients with stage I and II PTS.57A comparison of the various PTS classifications and their relationships with invasive venous pressure measurement was performed by Kolbach et al.44 In general, agreement among the different clinical measures is modest. For example, there is poor to moderate agreement between the Villalta scale and CEAP, and VCSS shows poor correlation with other scoring systems.44 A study by Kahn et al54 found that the proportion of patients classified as having PTS according to the Villalta scale was almost 5 times higher than that classified by the Ginsberg measure (37% versus 8.1%, respectively), with the Ginsberg measure tending to be less sensitive for mild PTS. Jayaraj and Meissner58 recently reported good correlation between the Villalta scale and VCSS for mild and moderate PTS but not for severe PTS.The variability in the measures used to define PTS has limited the ability to compare results across studies. Because the Villalta scale was developed specifically for PTS and has undergone assessment of its validity and reliability for PTS diagnosis and PTS severity classification, we endorse its use for this purpose, in line with the recommendations of the International Society on Thrombosis and Haemostasis Subcommittee on Control of Anticoagulation.13Objective Diagnosis of PTSIn patients with a characteristic clinical presentation of PTS but no history of previous DVT, compression ultrasonography can be done to look for evidence of prior DVT such as lack of compressibility of the popliteal or common femoral veins or reflux of venous valves on continuous-wave Doppler.9,59,60 In carefully selected patients in whom iliac vein obstruction is suspected on clinical grounds (eg, chronic severe aching or swelling of the entire limb, lack of respiratory phasicity of the common femoral vein Doppler waveform), imaging of the iliac vein using cross-sectional modalities (computed tomography, magnetic resonance imaging) or contrast venography with or without intravascular ultrasound can be performed. In such patients, the imaging finding of iliac vein thrombosis can confirm the diagnosis of PTS and guide therapeutic options. However, venography is invasive, so it is not routinely recommended for patients with mild symptoms that do not significantly affect daily functioning. It is important to highlight that many patients have demonstrable residual venous abnormalities after DVT (eg, venous reflux, venous hypertension, internal venous trabeculation) yet have no symptoms of PTS. In the absence of characteristic clinical features of PTS, PTS should not be diagnosed.Risk Factors for PTSTo date, known risk factors can generally be divided into 1 of 2 categories: factors apparent at the time of DVT diagnosis and those that manifest during follow-up (Table 6).Table 6. Risk Factors for PTSRisk FactorAuthor, YearRisk EstimateStrength/Consistencyof Risk AssociationPresent at the time of DVT diagnosis Older ageWik et al,61 2012OR, 3.9 (95% CI, 1.8–8.3) if >33 y at time of pregnancy++Tick et al,46 2008RR, 0.6 (95% CI, 0.4–0.9); >60 yKahn et al,8 20080.30 Villalta scale increase per 10 ySchulman et al,11 2006Increased risk if age ≥60 yvan Dongen et al,47 2005RR, 2.56 (95% CI, 1.39–4.71); >65 yPrandoni et al,51 2004RR, 1.36 (95% CI, 1.15–1.60) per 10-y age increase SexTick et al,62 2010RR, 1.4 (95% CI, 0.9–2.2); male+/−Kahn et al,8 20080.79 Villalta scale increase for female vs maleTick et al,46 2008RR, 1.5 (95% CI, 1.3–1.8); femaleStain et al,10 2005OR, 1.6 (95% CI, 1.0–2.3); male Increased BMI/obesityGalanaud et al,45 2013OR, 2.63 (95% CI, 1.47–4.70): BMI ≥30 kg/m2++Kahn et al,8 20080.14 Villalta scale increase per unit BMI increaseTick et al,46 2008RR, 1.5 (95% CI, 1.2–1.9); BMI >30 kg/m2Kahn et al,63 20050.16 Villalta scale increase per unit BMI increasevan Dongen et al,47 2005OR, 1.14 (95% CI, 1.06–1.23); BMI >25 kg/m2Stain et al,10 2005OR, 1.6 (95% CI, 1.0–2.4); BMI >25 kg/m2Ageno et al,64 2003OR, 3.54 (95% CI, 1.07–12.08); BMI >28 kg/m2 DVT localizationWik et al,61 2012OR, 6.3 (95% CI, 2.0–19.8); proximal postnatal thrombosis, up to 3 mo postpartum++Kahn et al,8 20082.23 Villalta scale increase for iliac or CFV vs distalTick et al,46 2008RR, 1.4 (95% CI, 1.1–1.8); iliac or CFV vs poplitealStain et al,10 2005OR, 2.1 (95% CI, 1.3–3.7); proximal vs distal DVTAsbeutah et al,34 2004Increased risk if proximal vs distalGabriel et al,65 2004Increased risk if proximal+distal DVTMohr et al,66 2000RR, 3.0 (95% CI, 1.6–4.7); proximal vs distal DVTPrandoni et al,7 1996No relation between extent of DVT and PTSLabropoulos et al,67 2008Increased risk if DVT was extensive ThrombophiliaSpiezia et al,68 2010HR, 1.23 (95% CI, 0.92–1.64); antithrombin, protein C and S deficiencies, lupus anticoagulant, FVL and prothrombin gene mutation; compared with noncarriers of thrombophilia−Tick et al,46 2008RR, 1.1 (95% CI, 0.9–1.4); FVLRR, 1.2 (95% CI, 0.9–1.4); prothrombin gene mutationKahn et al,63 2005RR, 0.33 (95% CI, 0.2–0.7); FVL or prothrombin gene mutationStain et al,10 2005OR, 0.9 (95% CI, 0.6–1.3); FVLOR, 0.8 (95% CI, 0.4–1.7); prothrombin gene mutationOR, 2.0 (95% CI, 0.8–5.1); FVIII Varicose