***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: To establish the cost effectiveness of community leg ulcer clinics using four-layer compression b and aging and the care provided by district nurses , a r and omised controlled trial was set up in eight community-based research clinics in four trusts , funded by Trent Regional Health Authority . The main outcomes monitored were the amount of time needed to complete ulcer healing , patient health status , and recurrence . Satisfaction with care , use of services and personal costs were also monitored We performed a Monte Carlo study to evaluate the effect of the number of events per variable ( EPV ) analyzed in logistic regression analysis . The simulations were based on data from a cardiac trial of 673 patients in which 252 deaths occurred and seven variables were cogent predictors of mortality ; the number of events per predictive variable was ( 252/7 =) 36 for the full sample . For the simulations , at values of EPV = 2 , 5 , 10 , 15 , 20 , and 25 , we r and omly generated 500 sample s of the 673 patients , chosen with replacement , according to a logistic model derived from the full sample . Simulation results for the regression coefficients for each variable in each group of 500 sample s were compared for bias , precision , and significance testing against the results of the model fitted to the original sample . For EPV values of 10 or greater , no major problems occurred . For EPV values less than 10 , however , the regression coefficients were biased in both positive and negative directions ; the large sample variance estimates from the logistic model both overestimated and underestimated the sample variance of the regression coefficients ; the 90 % confidence limits about the estimated values did not have proper coverage ; the Wald statistic was conservative under the null hypothesis ; and paradoxical associations ( significance in the wrong direction ) were increased . Although other factors ( such as the total number of events , or sample size ) may influence the validity of the logistic model , our findings indicate that low EPV can lead to major problems Twenty-one patients with stasis leg ulcers  were r and omly assigned to two groups . The first group was treated with Unna 's boots , while the second was treated with elastic support stockings with grade d compression from 24 mm/Hg pressure at the ankle to 16 mm/Hg pressure at the calf . The ulcers on seven of ten legs ( 70 % ) treated with Unna 's boots and on 10 of 14 legs ( 71 % ) treated with elastic support stocking healed . Although the two groups were small , there was no statistically significant difference between their success rate in healing stasis leg ulcers ( p = 0.9394 ) . Both treatment groups showed significant changes in lower limb volume , calf circumference , and ankle circumference , although there was no statistically significant difference between the two groups . If healing times are calculated , however , the average healing time in the Unna boot-treated group was 7.3 weeks , while patients treated with support stockings took an average of 18.4 weeks . If one patient whose ulcerations almost encircled her calves and took 78 weeks to heal is excluded , patients treated with support stockings had an average healing time of 11.8 weeks OBJECTIVE To test the safety , efficacy , and immunological impact of a cultured allogeneic human skin equivalent ( HSE ) in the treatment of venous ulcers . DESIGN Prospect i ve , r and omized study . SETTING Multicenter study in the outpatient setting . INTERVENTION Each patient with a venous ulcer received either compression therapy alone or compression therapy and treatment with HSE . The patients were evaluated for  HSE safety , complete ( 100 % ) ulcer healing , time to wound closure , wound recurrence , and immune response to the HSE .  OUTCOME The study was completed as planned in 293 r and omized patients . RESULTS Treatment with HSE was more effective than compression therapy in the percentage of patients healed by 6 months ( 63 % vs 49 % ; P=.02 , Fisher exact test , 2-tailed ) and the median time to complete wound closure ( 61 days vs 181 days ; P=.003 , log-rank test ) . Treatment with HSE was superior to compression therapy in healing larger ( > 1000 mm2 ; P=.02 ) and deeper ulcers ( P=.003 ) and ulcers of more than 6 months ' duration ( P=.001 ) . Occurrence of adverse events was similar in both groups . No symptoms or signs of rejection occurred in response to treatment with HSE , and no  HSE-specific immune responses were detected in vitro to bovine collagen or to alloantigens expressed on keratinocytes or fibroblasts . CONCLUSIONS Treatment with HSE healed venous ulcers more rapidly and in more patients than compression therapy alone . There was no clinical or laboratory evidence of rejection or sensitization in response to HSE application . These data suggest that HSE represents a significant advance in the treatment of venous ulcers , particularly those that are difficult to heal This study compared the rate of leg ulcer recurrence using two types of compression stockings  and examined the factors underlying This r and omised controlled study compares the healing rates , complications and patient and staff acceptability of three  four-layer b and age regimens for leg ulcers .  A total of 149 patients were recruited into the study , of whom 50 received the original Charing Cross system ( CX4L ) , 50 a modified Charing Cross system ( Parema ) and 49 a commercially available kit , Robinson Ultra Four ( Robinson ) .  No significant difference was found in the healing rates of the three systems . Overall 12 weeks ' healing was 65 % , while the 20-week healing rates for the individual systems were 87 % ( CX4L ) , 84 % ( Parema ) and 83 % ( Robinson ) . Analysis of known risk factors for delayed healing showed that no b and aging system had an advantage over the others . Staff familiarity result ed in an initial preference for the CX4L but there was no b and age preference by the end of the study . The data suggest that none of the systems has an advantage over the others and that cost savings can be made by pursuing a competitive pricing policy Abstract Objectives : To establish the relative cost effectiveness of community leg ulcer clinics that use four layer compression b and aging versus usual care provided by district nurses . Design : R and omised controlled trial with 1 year of follow up . Setting : Eight community based research clinics in four trusts in Trent . Subjects : 233 patients with venous leg ulcers allocated at r and om to intervention ( 120 ) or control ( 113 ) group . Interventions : Weekly treatment with four layer b and aging in a leg ulcer clinic ( clinic group ) or usual care at home by the district nursing service ( control group ) . Main outcome measures : Time to complete ulcer healing , patient health status , and recurrence of ulcers . Satisfaction with care , use of services , and personal costs were also monitored . Results : The ulcers of patients in the clinic group tended to heal sooner than those in the control group over the whole 12 month follow up ( log rank P=0.03 ) . At 12 weeks , 34 % of patients in the clinic group were healed compared with 24 % in the control . The crude initial healing rate of ulcers in intervention compared with control patients was 1.45 ( 95 % confidence interval 1.04 to 2.03 ) . No significant differences were found between the groups in health status . Mean total NHS costs were £ 878.06 per year for the clinic group and £ 859.34 for the control ( P=0.89 ) . Conclusions : Community based leg ulcer clinics with trained nurses using four layer b and aging is more effective than traditional home based treatment . This benefit is achieved at a small additional cost and could be delivered at reduced cost if certain service configurations were used . Key messages Leg ulcer clinics based in the community using four layer compression b and aging can be more clinical ly effective than usual care provided by the district nursing service Community based leg ulcer clinics could be provided more cost effectively than usual home based care for venous leg ulcers Recurrence of venous leg ulcers is an important variable that should be measured in future trials of venous leg ulcer care It is difficult to measure improvements in health related quality of life among people with venous leg Many venous ulcers are healed by the application of external compression . It has been suggested that b and ages capable of producing greater compression enhance healing . The aim of this study was to compare the time to total healing of venous ulcers  in two groups of patients treated with different compression regimens  in a r and omized prospect i ve trial This evaluation examined the effectiveness of the K-Four ( Parema ) high compression b and age system on 50 patients with recalcitrant ' hard-to-heal ' venous leg ulcers and relates the outcome to an earlier r and omised study which compared three other four-layer b and age systems . Twelve-week healing rates were 53.2 % in the current series , which included patients with poor mobility , large ulcers and long pretreatment ulcer duration , rising to 69.5 % at 20 weeks . When account was taken of known risk factors for delayed ulcer healing , no significant difference could be identified between between either K-Four or the earlier evaluated b and ages , which included the original Charing Cross system , where the overall healing rates were 64.5 % and 80 % , respectively , at 12 and 20 weeks . It would seem more likely that treatment outcome is related to patient risk factors for delayed healing and b and aging expertise than to the b and age system employed OBJECTIVE --To evaluate the prognostic factors in uncomplicated venous leg ulcer healing . DESIGN --R and omised parallel group controlled trial with subjects stratified by initial ulcer diameter and four months ' maximum duration of follow up . SETTING -- Assessment at Northwick Park Hospital vascular unit with community based treatment . PATIENTS --200 patients with clinical and objective evidence of uncomplicated venous leg ulceration and an initial ulcer diameter > 2 cm . MAIN OUTCOME MEASURE -- Time to complete healing of the ulcer . RESULTS --In the presence of graduated compression healing occurred more rapidly in patients with a smaller initial ulcer area ( relative risk of healing 1.92 associated with halving of ulcer area ( 95 % confidence interval 1.58 to 2.33 ) ) , shorter duration of ulceration ( relative risk 1.35 associated with halving duration ( 1.17 to 1.56 ) ) , younger age ( relative risk 1.34 associated with 10 year decrease ( 1.12 to 1.59 ) ) , and no deep vein involvement ( relative risk 1.8 ( 1.19 to 2.78 ) ) . CONCLUSION --These prognostic factors used in a simple scoring system predict time to healing This study aim ed to develop an alternative graduated compression b and age for the treatment of venous leg ulcers . Alternative b and age components were identified and assessed for optimal performance as a graduated multi-layer compression b and age . Subsequently the physical characteristics and clinical efficacy of the optimal b and age combination was prospect ively examined . Ten healthy limbs were used to develop the optimal combination and 20 limbs with venous ulceration to compare the physical properties of the two b and age types . Subsequently 42 consecutive ulcerated limbs were prospect ively treated to examine the efficacy of the new b and age combination . The new combination produced graduated median ( range ) sub-b and age pressures ( mmHg ) as follows : ankle 59 ( 42 - 100 ) , calf 36 ( 27 - 67 ) and knee 35 ( 16 - 67 ) . Over a seven-day period this combination maintained a comparable level of compression with the Charing Cross system , and achieved an overall healing rate at one year of 88 % . The described combination should be brought to the attention of healthcare professionals treating venous ulcers as a possible alternative to other forms of multi-layer graduated compression b and ages pending prospect i ve , r and omised clinical trials Recent reports have suggested that polyurethane foam dressings provide a more rapid and comfortable healing of venous stasis cutaneous ulcerations  than st and ard semirigid impregnated gauze dressings . This multi-institutional study consists of a r and omized , prospect i ve comparison of 36 consecutive patients who were treated with either polyurethane foam dressings ( group 1 , n = 17 ) or Unna 's boot ( group 2 , n = 19 ) for venous ulceration of the lower extremities . Ulcer size ranged from 6.0 to 270 cm2 ( mean , 32.2 cm2 ) for group 1 and 0.2 to 600 cm2 ( mean , 76.0 cm2 ) for group 2 . Nine ( 52.9 % ) of 17 group 1 patients withdrew from the study due to wound odor , while there was 100 % compliance in group 2 . Overall wound healing was superior in group 2 ( 18 [ 94.7 % ] of 19 ) as compared with group 1 ( 7 [ 41.2 % ] of 17 ) ( chi 2 = 8.2 ) . The rate of healing was also better in group 2 ( 0.5 cm2/d ) than in group 1 ( 0.07 cm2/d ) . Contrary to published European trials , impregnated gauze dressings exhibited superior treatment results when compared with polyurethane foam dressings in the current study The aim of the study was to compare the efficacy of two types of compression b and age with different degrees of elasticity on healing of venous leg ulcers . Forty-three patients with venous leg ulcers were included and blindly r and omized to treatment with one of the two types of b and age aim ing at a sub-b and age pressure in the ankle area of 40 mmHg . Forty legs were evaluated .  Healed ulcers after 12 months were observed in 71 % of the long-stretch group and in 30 % of the short-stretch group ( p = 0.06 ) . Using life-table analysis the predicted healing rate in the long-stretch group after 12 months was 
    Output:
    
REVIEW ER 'S CONCLUSIONS Compression increases ulcer healing rates compared with no compression .
Multi-layered systems are more effective than single-layered systems .
High compression is more effective than low compression but there are no clear differences in the effectiveness of different types of high compression