***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 
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    Input: BACKGROUND Compression ultrasonography is the mainstay of diagnosis of deep-vein thrombosis ( DVT ) of the legs .  Compression ultrasonography can be extended to the entire deep venous system ( whole-leg ) or restricted to the proximal veins only ( limited ) , and the two approaches are clinical ly equivalent . We aim ed to assess the diagnostic value of an algorithm combining whole-leg and limited compression ultrasonography . METHODS We did a prospect i ve , multicentre , cohort study at eight centres in five countries . Consecutive out patients aged 18 years or older with suspected DVT underwent D-dimer measurement and pretest clinical probability assessment .  DVT was ruled out without further testing if pretest probability was unlikely and D-dimer was negative ( group 1 ) . Patients in whom either pretest probability was likely or who were positive for D-dimer underwent limited compression ultrasonography only ( group 2 ) . Finally , patients in whom pretest probability was likely and who had a positive measurement for D-dimer underwent extended whole-leg compression ultrasonography ( group 3 ) . All patients in whom DVT was ruled out were followed up for 3 months . The primary outcome was the incidence of objective ly recorded venous thromboembolism . The primary analysis included all patients managed according to the study protocol . This study is registered with Clinical Trials.gov , number NCT01412242 . The final results are reported here . FINDINGS Between March 1 , 2011 , and July 31 , 2014 , 1348 consecutive out patients were referred for this study , of whom 1162 were eligible to participate . After pretest probability assessment and D-dimer testing , 351 were in group 1 , 401 in group 2 , and 410 in group 3 . Limited compression ultrasonography was positive in 12 ( 3 % ) patients in group 2 and extended whole-leg compression ultrasonography was positive in 200 ( 49 % ) patients in group 3 . 82 ( 39 % ) of all DVT diagnosed at baseline were isolated distal thromboses . 26 protocol violations were reported . Thus , 351 patients from group 1 , 371 patients in group 2 , and 202 patients in group 3 who had been excluded for DVT by the algorithm were included in the primary analysis at 3 months . One , four , and three DVTs were reported , respectively . Thus , the 3-month incidence of venous thromboembolism in untreated patients after a negative diagnostic strategy was 0·87 % ( 95 % CI 0·44 - 1·70 ) . INTERPRETATION An algorithm combining limited and whole-leg compression ultrasonography could be a reliable , safe , and convenient method for diagnostic management of out patients with clinical ly suspected DVT . FUNDING None BACKGROUND It remains unclear whether a single complete ultrasound examination , which detects calf vein thrombosis , is as safe as a baseline rapid ultrasound examination , repeated after 1 week when negative , which examines the veins in the groin and the knee . Therefore , we compared the safety and feasibility of two diagnostic ultrasound strategies , involving rapid and complete compression ultrasound ( CUS ) examination . METHODS Consecutive patients with suspected deep vein thrombosis ( DVT ) underwent clinical probability assessment . In patients with an unlikely clinical probability and a normal D-dimer finding , DVT was considered to be excluded . All others were r and omized to undergo a rapid or a single complete CUS examination . Patients in whom DVT was excluded were followed for 3 months to assess the incidence of venous thromboembolism ( VTE ) . RESULTS A total of 1002 patients were included . A clinical decision rule indicating DVT to be unlikely and a normal D-dimer finding occurred in 481 patients ( 48 % ) , with a VTE incidence of 0.4 % [ 95 % confidence interval ( CI ) 0.05 - 1.5 % ] during follow-up . DVT was confirmed in 59 of the 257 patients ( 23 % ) who underwent rapid CUS examination , and in 99 of the 264 patients ( 38 % ) who underwent complete CUS examination . VTE during follow-up occurred in four patients ( 2.0 % ; 95 % CI 0.6 - 5.1 % ) in the rapid CUS arm , and in two patients ( 1.2 % ; 95 % CI 0.2 - 4.3 % ) in the complete CUS arm . CONCLUSIONS A diagnostic strategy with a clinical decision rule , a D-dimer test and a CUS examination is safe and efficient . Both the rapid and the complete CUS test are comparable and efficient strategies , with differing advantages and disadvantages BACKGROUND Several diagnostic strategies using ultrasound imaging , measurement of D-dimer , and assessment of clinical probability of disease have proved safe in patients with suspected deep-vein thrombosis , but they have not been compared in r and omized trials . METHODS Out patients presenting with suspected lower-extremity deep-vein thrombosis were potentially eligible . Using a clinical model , physicians evaluated the patients and categorized them as likely or unlikely to have deep-vein thrombosis . The patients were then r and omly assigned to undergo ultrasound imaging alone ( control group ) or to undergo D-dimer testing ( D-dimer group ) followed by ultrasound imaging unless the D-dimer test was negative and the patient was considered clinical ly unlikely to have deep-vein thrombosis , in which case ultrasound imaging was not performed . RESULTS Five hundred thirty patients were r and omly assigned to the control group , and 566 to the D-dimer group . The overall prevalence of deep-vein thrombosis or pulmonary embolism was 15.7 percent . Among patients for whom deep-vein thrombosis had been ruled out by the initial diagnostic strategy , there were two confirmed venous thromboembolic events in the D-dimer group ( 0.4 percent ; 95 percent confidence interval , 0.05 to 1.5 percent ) and six events in the control group ( 1.4 percent ; 95 percent confidence interval , 0.5 to 2.9 percent ; P=0.16 ) during three months of follow-up . The use of D-dimer testing result ed in a significant reduction in the use of ultrasonography , from a mean of 1.34 tests per patient in the control group to 0.78 in the D-dimer group ( P=0.008 ) . Two hundred eighteen patients ( 39 percent ) in the D-dimer group did not require ultrasound imaging . CONCLUSIONS Deep-vein thrombosis can be ruled out in a patient who is judged clinical ly unlikely to have deep-vein thrombosis and who has a negative D-dimer test . Ultrasound testing can be safely omitted in such patients Objective To assess the safety of using single complete compression ultrasonography in pregnant and postpartum women to rule out deep vein thrombosis . Design Prospect i ve outcome study . Setting Two tertiary care centres and 18 private practice s specialising in vascular medicine in France and Switzerl and . Participants 226 pregnant and postpartum women referred for suspected deep vein thrombosis . Methods A single proximal and distal compression ultrasonography was performed . All women with a negative complete compression ultrasonography result did not receive anticoagulant therapy and were followed up for a three month period . Main outcome measures Symptoms of venous thromboembolism , second compression ultrasonography or chest imaging , a thromboembolic event , and anticoagulant treatment . Results 16 women were excluded , mainly because of associated suspected pulmonary embolism .  Deep vein thrombosis was diagnosed in 22 out of the 210 included women ( 10.5 % ) . 10 patients received full dose anticoagulation despite a negative test result during follow-up . Of the 177 patients without deep vein thrombosis and who did not receive full dose anticoagulant therapy , two ( 1.1 % , 95 % confidence interval 0.3 % to 4.0 % ) had an objective ly confirmed deep vein thrombosis during follow-up . Conclusions The rate of venous thromboembolic events after single complete compression ultrasonography in pregnant and postpartum women seems to be within the range of that observed in studies in the non-pregnant population . These data suggest that a negative single complete compression ultrasonography result may safely exclude the diagnosis of deep vein thrombosis in this setting . Trial registration clinical trials.gov NCT00740454 Background —Serial ultrasonography is reliable for the diagnosis of deep venous thrombosis in symptomatic patients , but the low prevalence of thrombosis in this group renders the approach costly and inconvenient to patients . We studied the clinical validity of the combination of a pretest clinical probability score and a D-dimer test in the initial evaluation of patients suspected of deep venous thrombosis . Methods and Results — Patients with a normal D-dimer concentration ( < 500 fibrin equivalent units [ FEU ] & mgr;g/L ) and a non-high probability score ( <3 ) had no further testing . Patients with a normal D-dimer concentration and a high probability score ( ≥3 ) underwent one ultrasonogram . Serial ultrasonography was performed in patients with an abnormal D-dimer concentration . Patients were followed for 3 months . A total of 812 patients were evaluable for efficacy . Only 1 of 176 patients ( 0.6 % ; 95 % CI , 0.02 % to 3.1 % ) with a normal D-dimer concentration and a non-high probability score developed thrombosis during follow-up . A normal D-dimer concentration and a high probability score were found in 39 patients ; 3 of them ( 7.7 % ; 95 % CI , 1.6 % to 20.9 % ) had thrombosis at presentation , and one ( 2.8 % ; 95 % CI , 0.07 % to 14 . 5 % ) developed pulmonary embolism during follow-up . In 306 of 597 patients ( 51.3 % ) with an abnormal D-dimer concentration , thrombosis was detected by serial ultrasonography . Six patients ( 2.1 % ; 95 % CI , 0.8 % to 4 . 4 % ) developed thrombosis during follow-up . No deaths due to thromboembolism occurred during follow-up . The total need for ultrasonography  was reduced by 29 % . Conclusion —The combination of a non-high pretest clinical probability score and a normal D-dimer concentration is a safe strategy to rule out deep venous thrombosis and to withhold anticoagulation In a prospect i ve study 90 patients with clinical ly suggested lower limb deep venous thrombosis ( DVT ) were examined with duplex ultrasonography ( US ) prior to venography . No attempts were made to examine the calf veins . Five ultrasound examinations were inconclusive . Thirty-four patients had DVT diagnosed at US with a sensitivity of 97 per cent and a specificity of 96 per cent . Compressibility of the vein as assessed by the real-time image was in the acute phase an easy and fast test for DVT , whereas the Doppler data failed to add to the diagnostic accuracy . Twenty-seven patients with DVT were followed during anticoagulant treatment , but only 16 regained fully compressible veins within the observation period of 3 to 6 months . Duplex sonography was useful in monitoring the changes in vein patency during anticoagulant treatment Background : Compression ultrasonography performed serially over a 7-day period is recommended for the diagnosis of deep vein thrombosis in symptomatic pregnant women , but whether this approach is safe is unknown . We evaluated the safety of withholding anticoagulation from pregnant women with suspected deep vein thrombosis following negative serial compression ultrasonography and iliac vein imaging . Methods : Consecutive pregnant women who presented with suspected deep vein thrombosis underwent compression ultrasonography and Doppler imaging of the iliac vein of the symptomatic leg(s ) . Women whose initial test results were negative underwent serial testing on 2 occasions over the next 7 days . Women not diagnosed with deep vein thrombosis were followed for a minimum of 3 months for the development of symptomatic deep vein thrombosis or pulmonary embolism . Results : In total , 221 pregnant women presented with suspected deep vein thrombosis .  Deep vein thrombosis was diagnosed in 16 ( 7.2 % ) women by initial compression ultrasonography and Doppler studies ; none were identified as having deep vein thrombosis on serial testing . One patient with normal serial testing had a pulmonary embolism diagnosed 7 weeks later . The overall prevalence of deep vein thrombosis was 7.7 % ( 17/221 ) ; of these , 65 % ( 11/17 ) of cases were isolated to the iliofemoral veins and 12 % ( 2/17 ) were isolated iliac deep vein thromboses . The incidence of venous thromboembolism during follow-up was 0.49 % ( 95 % confidence interval [ CI ] 0.09%–2.71 % ) . The sensitivity of serial compression ultrasonography with Doppler imaging was 94.1 % ( 95 % CI 69.2%–99.7 % ) , the negative predictive value was 99.5 % ( 95 % CI 96.9%–100 % ) , and the negative likelihood ratio was 0.068 ( 95 % CI 0.01–0.39 ) . Interpret 
    Output:
    
The relative failure rate of single limited CUS remains uncertain , as the DVT prevalence was lower in these studies .
Therefore , this CUS strategy may only be safe in a selected group of low-risk patients .