***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Acute deep venous thrombosis ( DVT ) causes leg pain .  Elastic compression stockings ( ECS ) have potential to relieve DVT-related leg pain by diminishing the diameter of distended veins and increasing venous blood flow . It was our objective to determine whether ECS reduce leg pain in patients with acute DVT . We performed a secondary analysis of the SOX Trial , a multicentre r and omised placebo controlled trial of active ECS versus placebo ECS to prevent the post-thrombotic syndrome . The study was performed in 24 hospital centres in Canada and the U.S. and included 803 patients with a first episode of acute proximal DVT . Patients were r and omised to receive active ECS ( knee length , 30 - 40 mm Hg graduated pressure ) or placebo ECS ( manufactured to look identical to active ECS , but lacking therapeutic compression ) . Study outcome was leg pain severity assessed on an 11-point numerical pain rating scale ( 0 , no pain ; 10 , worst possible pain ) at baseline , 14 , 30 and 60 days after r and omisation . Mean age was 55 years and 60 % were male . In active ECS patients ( n=409 ) , mean ( SD ) pain severity at baseline and at 60 days were 5.18 ( 3.29 ) and 1.39 ( 2.19 ) , respectively , and in placebo ECS patients ( n=394 ) were 5.38 ( 3.29 ) and 1.13 ( 1.86 ) , respectively . There were no significant differences in pain scores between groups at any assessment point , and no evidence for subgroup interaction by age , sex or anatomical extent of DVT . Results were similar in an analysis restricted to patients who reported wearing stockings every day . In conclusion , ECS do not reduce leg pain in patients with acute proximal DVT Objective The purpose of this r and omized study was to evaluate the influence of immediate multilayer compression b and ages before application of elastic stockings in the acute phase of deep-vein thrombosis ( DVT ) on development of the post-thrombotic syndrome ( PTS ) . Methods Sixty-nine patients with acute symptomatic DVT were r and omized to immediate b and aging ( n = 34 ) or no b and aging ( n = 35 ) . After reduction of edema sized-to-fit elastic stockings were applied in all patients after 7–14 days . Follow-up visits and non-invasive examinations were planned after 7 , 30 and 90 days and 1 year . Venous outflow resistance ( VOR ) was measured by strain gauge plethysmography . Thrombosis score ( TS ) and reflux were measured by duplex scanning . After one year patients were evaluated for clinical PTS using both the clinical scale of the CEAP classification and the Villalta score . Results Improvement of clinical symptoms and decrease of leg circumference was better on day 7 in the b and aging group , but after 1 and 3 months clinical symptoms had improved equally in both groups . In 7 patients in the no-b and aging group a b and age was applied after all because of persistent edema after 10 days . There were no differences in VOR , TS and reflux . Using the CEAP classification the incidence of PTS was 39 % in patients with b and ages and 42 % in patients without b and ages ( RR 0.91 , 95 % CI 0.50–1.66 ) . Using the Villalta score the incidence of PTS was resp . 29 and 33 % ( RR 0.87 , 95 % CI 0.41–1.8 ) . There was no difference in severity of PTS . Conclusion Immediate multilayer compression b and aging in the acute phase of DVT is effective in reducing edema and complaints in the first week , but has no effect on thrombus regression , valve incompetence and the development of clinical PTS after 1 year OBJECTIVE The purpose of this r and omized controlled trial was to evaluate the benefits of compression and walking exercises in comparison with bed rest in the acute stage of proximal deep venous thrombosis ( DVT ) . METHODS Forty-five patients with proximal DVT that was proved with compression ultrasound scan or phlebography were r and omized into three groups . Group A consisted of 15 patients who received  inelastic compression b and ages ( Unna boots on the lower leg , adhesive b and ages on the thigh ) , and group B consisted of 15 patients who received thigh-length compression stockings , class II . Group C consisted of 15 patients who underwent bed rest and no compression . All patients received dalteparin , 200 IU/kg per body weight , subcutaneously every 24 hours . The clinical characteristics of the three groups were comparable . Primary end points were the reduction of pain assessed daily with the Visual Analogue Scale and the Lowenberg test , the reduction of leg circumference at the ankle and calf levels , and the improvement of clinical scores . The daily walking distance was measured with a pedometer . Safety parameters were ventilation-perfusion scans and duplex ultrasound scans performed on days 0 and 9 . RESULTS The daily walking distance was between 600 and 12,000 m in the compression groups and averaged 66 m in the bed rest group . The pain level showed a statistically significant reduction starting after the second day in the compression groups ( A and B ) and after 9 days in the bed rest group C ( P < .05 ) . The same was true for the measurement of leg circumference . Improvement of the clinical scores was significantly better in the compression groups compared with the bed rest group ( P < .01 ) . There was no significant difference concerning the occurrence of new pulmonary emboli and regression of thrombus diameter . Progression of thrombi in the femoral vein was greater and occurred more frequently in the bed rest group than in the other two groups ( P = not significant ) . CONCLUSION Mobile patients with acute proximal DVT treated with low molecular weight heparin should be encouraged to walk with compression b and ages or medical compression stockings . The rate of resolution of pain and swelling is significantly faster when the patient ambulates with compression . The risk of pulmonary embolism is not significantly increased by this approach BACKGROUND Graduated elastic compression ( GEC ) stockings have been demonstrated to reduce the morbidity associated with post-thrombotic syndrome . The ideal length or compression strength required to achieve this is speculative and related to physician preference and patient compliance . The aim of this study was to evaluate the hemodynamic performance of four different stockings and determine the patient 's preference . METHODS Thirty-four consecutive patients ( 40 legs , 34 male ) with post-thrombotic syndrome were tested with four different stockings ( Mediven plus open toe , Bayreuth , Germany ) of their size in r and om order : class 1 ( 18 - 21 mm Hg ) and class II ( 23 - 32 mm Hg ) , below-knee ( BK ) and above-knee thigh-length ( AK ) . The median age , Venous Clinical Severity Score , Venous Segmental Disease Score , and Villalta scale were 62 years ( range , 31 - 81 years ) , 8 ( range , 1 - 21 ) , 5 ( range , 2 - 10 ) , and 10 ( range , 2 - 22 ) , respectively . The C of C0 - 6EsAs , d , pPr , o was C0 = 2 , C2 = 1 , C3 = 3 , C4a = 12 , C4b = 7 , C5 = 12 , C6 = 3 . Obstruction and reflux was observed on duplex in 47.5 % legs , with deep venous reflux alone in 45 % . Air plethysmography was used to measure the venous filling index ( VFI ) , venous volume , and time to fill 90 % of the venous volume . Direct pressure measurements were obtained while lying and st and ing using the PicoPress device ( Microlab Elettronica , Nicolò , Italy ) . The pressure sensor was placed underneath the test stocking 5 cm above and 2 cm posterior to the medial malleolus . At the end of the study session , patients stated their preferred stocking based on comfort . RESULTS The VFI , venous volume , and time to fill 90 % of the venous volume improved significantly with all types of stocking versus no compression . In class I , the VFI ( mL/s ) improved from a median of 4.9 ( range , 1.7 - 16.3 ) without compression to 3.7 ( range , 0 - 14 ) BK ( 24.5 % ) and 3.6 ( range , 0.6 - 14.5 ) AK ( 26.5 % ) . With class II , the corresponding improvement was to 4.0 ( range , 0.3 - 16.2 ) BK ( 18.8 % ) and 3.7 ( range , 0.5 - 14.2 ) AK ( 24.5 % ) . Median stocking pressure ( mm Hg ) as measured with the PicoPress in class I was 23 ( range , 12 - 33 ) lying and 27 ( range , 19 - 39 ) st and ing ( P < .0005 ) and in class II was 28 ( range , 21 - 40 ) lying and 32 ( range , 23 - 46 ) st and ing ( P < .0005 ) . There was a significant but weak correlation ( Spearman ) between stocking interface pressure measured directly with the PicoPress and the VFI improvement ( baseline VFI-compression VFI ) at r = .237 ; P = .005 . Twenty-one patients ( legs ) changed their preference of  compression  and 38 % of these ( 8/21 patients , 9/21 legs ) preferred an AK-GEC stocking . CONCLUSIONS Compression significantly improved all hemodynamic parameters on air plethysmography . However , the hemodynamic benefit did not significantly change with the class or length of stocking . These results support the liberal selection of a GEC stocking based on patient preference BACKGROUND Selection bias arises in clinical trials by reason of selective assignment of patients to treatment groups . Even in r and omized clinical trials with allocation concealment this phenomenon can occur if future assignments can be predicted due to knowledge of former allocations . OBJECTIVES Considering  unmasked r and omized clinical trials  with allocation concealment the impact of selection bias on type I error rate under permuted block r and omization is investigated . We aim ed to extend the existing research into this topic by including practical assumptions concerning misclassification of patient characteristics to get an estimate of type I error close to clinical routine . To establish an upper bound for the type I error rate different biasing strategies of the investigator are compared first . In addition , the aspect of patient availability is considered . METHODS To evaluate the influence of selection bias on type I error rate under several practical situations , different block sizes , selection effects , biasing strategies and success rates of patient classification were simulated using SAS . RESULTS Type I error rate exceeds 5 percent significance level ; it reaches values up to 21 percent . More cautious biasing strategies and misclassification of patient characteristics may diminish but can not eliminate selection bias . The number of screened patients  is about three times larger than the needed number for the trial . CONCLUSIONS Even in unmasked r and omized clinical trials using permuted block r and omization with allocation concealment the influence of selection bias must not be disregarded evaluating the test decision . It should be incorporated when design ing and reporting a clinical trial BACKGROUND AND OBJECTIVE In contrast to the extensive documentation on the short-term outcome of patients with acute deep vein thrombosis ( DVT ) of the lower extremities , little is known about the long-term clinical course of this disease . To determine the clinical course of patients with a first episode of symptomatic DVTn over an 8-year follow-up period . The primary aims were to assess the long-term incidence of recurrent venous thromboembolism and that of the post-thrombotic syndrome . In addition , we determined mortality and evaluated potential risk factors for all these outcomes . METHODS This was design ed as a prospect i ve cohort follow-up study . Consecutive symptomatic out patients with a first episode of venography proven DVT were treated with an initial course of full-dose ( low molecular weight ) heparin , followed by at least three months of oral anticoagulants . After discharge , they were instructed to wear compression elastic stockings for at least two years . Follow-up assessment s were scheduled at three and six months , and then every six months up to eight years . Diagnosis of recurrent venous thromboembolism was made according to st and ard criteria . The presence of post-thrombotic syndrome was evaluated using a st and ardized scale . RESULTS A total of 528 consecutive patients with a first episode of venography confirmed DVT were included in the study . The cumulative incidence of recurrent venous thromboembolism after two , five and eight years was 17.2 , 24.3 and 29.7 % , respectively . Malignancy and impaired coagulation inhibition increased the risk of recurrent venous thromboembolism ( RR = 1.48 and 2.0 , respectively ) . In contrast , surgery and recent trauma or fracture were associated with a diminished risk of recurrent venous thromboembolism ( RR = 0.65 and 0.39 , respectively ) . The cumulative incidence of post-thrombotic syndrome after two , five and eight years was 24.5 , 29.6 and 29.8 % , respectively . The development of ipsilateral recurrent DVT was strongly associated with the risk for post-thrombotic syndrome ( risk ratio , 2.4 ) . Survival after eight years was 69 % . The presence of malignancy increased the risk of death remarkably ( risk ratio , 7.1 ) . INTERPRETATION AND CONCLUSIONS Symptomatic DVT car 
    Output:
    
Moderate- quality evidence from one large RCT does not suggest effect on acute pain after deep vein thrombosis .
The highest- quality evidence available suggests no effect of elastic compression stockings on postthrombotic syndrome or pain relief , from a single large RCT .
Elastic compression stockings are unlikely to prevent death or recurrent venous thromboembolism