***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: We explore the potential of Bayesian hierarchical modelling for the analysis of cluster r and omized trials with binary outcome data , and apply the methods to a trial r and omized by general practice . An approximate relationship is derived between the intracluster correlation coefficient ( ICC ) and the between-cluster variance used in a hierarchical logistic regression model . By constructing an informative prior for the ICC on the basis of available information , we are thus able implicitly to specify an informative prior for the between-cluster variance . The approach also provides us with a credible interval for the ICC for binary outcome data . Several approaches to constructing informative priors from empirical ICC values are described . We investigate the sensitivity of results to the prior specified and find that the estimate of intervention effect changes very little in this data set , while its interval estimate is more sensitive . The Bayesian approach allows us to assume distributions other than normality for the r and om effects used to model the clustering . This enables us to gain insight into the robustness of our parameter estimates to the classical normality assumption . In a model with a more complex variance structure , Bayesian methods can provide credible intervals for a difference between two variance components , in order for example to investigate whether the effect of intervention varies across clusters . We compare our results with those obtained from classical estimation , discuss the relative merits of the Bayesian framework , and conclude that the flexibility of the Bayesian approach offers some substantial advantages , although selection of prior distributions is not straightforward Reports of cluster r and omised trials require additional information to allow readers to interpret them accurately The effective reporting of r and omised controlled trials has received useful attention in recent years . Many journals now require that reports conform to the guidelines in the Consoli date d St and ards of Reporting Trials ( CONSORT ) statement , first published in 1996 and revised in 2001 . The statement includes a checklist of items that should be included in the trial report . These items are evidence based whenever possible and are regularly review ed . The statement also recommends including a flow diagram to show the flow of participants from group assignment through to the final analysis . The CONSORT statement focused on reporting parallel group r and omised trials in which individual participants are r and omly assigned to study groups . However , in some situations it is preferable to r and omly assign groups of individuals ( such as families or medical practice s ) rather than individuals . Reasons include the threat of contamination of some interventions ( such as dietary interventions ) if individual r and omisation is used . 5 Also , in certain setting s r and omisation by group may be the only feasible method of conducting a trial . Trials with this design are variously known as field trials , community based trials , place based trials , or ( as in this paper ) cluster r and omised trials . In an earlier discussion paper we considered the implication s of the CONSORT statement for the reporting of cluster r and omised trials . Here we present up date d guidance , based on the 2001 revision of the CONSORT statement OBJECTIVES A community trial was undertaken to evaluate the effectiveness of the North Carolina Breast Cancer Screening Program , a lay health advisor network intervention intended to increase screening among rural African American women 50 years and older . METHODS A stratified r and om sample of 801 African American women completed baseline ( 1993 - 1994 ) and follow-up ( 1996 - 1997 ) surveys . The primary outcome was self-reported mammography use in the previous 2 years . RESULTS The intervention was associated with an overall 6 percentage point increase ( 95 % confidence interval [ CI ] = -1 , 14 ) in community-wide mammography use .  Low-income women in intervention counties showed an 11 percentage point increase ( 95 % CI = 2 , 21 ) in use above that exhibited by low-income women in comparison counties . Adjustment for potentially confounding characteristics did not change the results . CONCLUSIONS A lay health advisor intervention appears to be an effective public health approach to increasing use of screening mammography among low-income , rural population OBJECTIVES This study assessed the effectiveness of telephone counseling in a church-based mammography promotion intervention trial . METHODS Thirty churches were r and omized to telephone counseling and control conditions ; telephone interview data were used in assessing intervention effects on mammography adherence . Separate analyses were conducted for baseline-adherent participants ( maintaining adherence ) and baseline-nonadherent participants ( conversion to adherence ) . RESULTS Year 1 follow-up data indicated that the telephone counseling intervention  maintained mammography adherence among baseline-adherent participants and reduced the nonadherence rate from 23 % to 16 % . CONCLUSIONS Partnerships between the public health and faith communities are potentially effective conduits to promote maintenance of widely endorsed health behaviors such as regular cancer screening INTRODUCTION We evaluated an intervention program for Mexican-American women to increase Pap smear and mammography screening . METHODS The three-year intervention included the presentation of role models in the media and reinforcement by peer volunteers . We used a two-community ( intervention and comparison ) pre-post test design . Activities were targeted to a mainly Spanish-speaking , poverty-level , immigrant population . Pre- and postintervention screening rates were based on independent r and om sample s of Mexican-American women 40 years and older . RESULTS Women reported a 6 % absolute increase in Pap smear use similar to the 7 % increase in the comparison community . Both communities experienced large but similar increases in recent mammography use ( 17 % and 19 % ) . Adjusting for differences in demographic factors , intervention and comparison changes remained identical . CONCLUSIONS Our peer intervention failed to accelerate the secular trend in cancer screening low-income Mexican-American women . Likely , promotional activities were too diffuse and the comparison community was contaminated with similar interventions . Strong social and market forces make it difficult to measure the effect of a specialized intervention on cancer screening rates BACKGROUND A r and omized trial was conducted to evaluate the impact of a community-based intervention on mammography use among low-income women living in public housing . METHODS All 41 public housing high-rise buildings were r and omized to treatment and delayed treatment ( control ) conditions . After a cross-sectional baseline survey , an intervention called Friend to Friend was conducted in the treatment buildings by American Cancer Society and building resident volunteers . The intervention consisted of a health professional talk , small group discussion s , and an opportunity to request assistance in obtaining a mammogram or mammogram reminder . A second cross-sectional survey was conducted to measure differences in screening rates between the study groups . RESULTS Participation in the intervention averaged 27 % . The study groups were equivalent at baseline . At follow-up , the proportion of women age 50 - 79 years who reported mammography screening in the previous 15 months was significantly higher in the treatment group ( 64 % ) than in the control group ( 52 % ) . Breast cancer knowledge , attitudes , and beliefs did not differ between groups . CONCLUSIONS These findings suggest that a multidimensional intervention which reaches women within their social environment and uses community volunteers can increase mammography utilization among women in public housing Introduction The Tepeyac Project is a church-based health promotion project that was conducted from 1999 through 2005 to increase breast cancer screening rates among Latinas in Colorado . Previous reports evaluated the project among Medicare and Medicaid enrollees in the state . In this report , we evaluate the program among enrollees in the state 's five major insurance plans . Methods We compared the Tepeyac Project 's two interventions : the Printed Intervention and the Promotora Intervention . In the first , we mailed culturally tailored education packages to 209 Colorado Catholic churches for their use . In the second , promotoras ( peer counselors ) in four Catholic churches delivered breast-health education messages personally . We compared biennial mammogram cl aims from the five insurance plans in the analysis at baseline ( 1998–1999 ) and during follow-up ( 2000–2001 ) for Latinas who had received the interventions . We used generalized estimating equations ( GEE ) analysis to adjust rates for confounders . Results The mammogram rate for Latinas in the Printed Intervention remained the same from baseline to follow-up ( 58 % [ 2979/5130 ] vs 58 % [ 3338/5708 ] ) . In the Promotora Intervention , the rate was 59 % ( 316/536 ) at baseline and 61 % ( 359/590 ) at follow-up . Rates increased modestly over time and varied widely by insurance type . After adjusting for age , income , urban versus rural location , disability , and insurance type , we found that women exposed to the Promotora Intervention had a significantly higher increase in biennial mammograms than did women exposed to the Printed Intervention ( GEE parameter estimate = .24 [ ±.11 ] , P = .03 ) . Conclusion For insured Latinas , personally delivering church-based education through peer counselors appears to be a better breast-health promotion method than mailing printed educational material s to churches INTRODUCTION Mammography is underused by certain groups of women , in particular poor and minority women . We developed a lay health advisor ( LHA ) intervention based on behavioral theories and tested whether it improved mammography attendance in Robeson County , NC , a rural , low-income , triracial ( white , Native American , African American ) population . METHODS A total of 851 women who had not had a mammogram within the past year were r and omly assigned to the LHA intervention ( n = 433 ) or to a comparison arm ( n = 418 ) during 1998 - 2002 .  Rates of  mammography  use after 12 - 14 months ( as verified by medical record review ) were compared using a chi-square test . Baseline and follow-up ( at 12 - 14 months ) surveys were used to obtain information on demographics , risk factors , and barriers , beliefs , and knowledge about mammography . Linear regression , Mantel-Haenszel statistics , and logistic regression were used to compare barriers , beliefs , and knowledge from baseline to follow-up and to identify baseline factors associated with mammography . RESULTS At follow-up , 42.5 % of the women in the LHA group and 27.3 % of those in the comparison group had had a mammogram in the previous 12 months ( relative risk = 1.56 , 95 % confidence interval [ CI ] = 1.29 to 1.87 ) . Compared with those in the comparison group , women in the LHA group displayed statistically significantly better belief scores ( difference = 0.46 points on a 0 - 10 scale , 95 % CI = 0.15 to 0.77 ) and reduced barriers at follow-up ( difference = -0.77 points , 95 % CI = -1.02 to -0.53 ) , after adjusting for baseline scores . CONCLUSIONS LHA interventions can improve mammography utilization . Future studies are needed to assess strategies to disseminate effective LHA interventions to underserved population Background Cluster r and omization design is increasingly used for the evaluation of health-care , screeening or educational interventions . At the planning stage , sample size calculations usually consider an average cluster size without taking into account any potential imbalance in cluster size . However , there may exist high discrepancies in cluster sizes . Methods We performed simulations to study the impact of an imbalance in cluster size on power . We determined by simulations to which extent four methods proposed to adapt the sample size calculations to a pre-specified imbalance in cluster size could lead to adequately powered trials . Results We showed that an imbalance in cluster size can be of high influence on the power in the case of severe imbalance , particularly if the number of clusters is low and /or the intraclass correlation coefficient is high . In the case of a severe imbalance , our simulations confirmed that the minimum variance weights correction of the variation inflaction factor ( VIF ) used in the sample size calculations has the best properties . Conclusion Publication of cluster sizes is important to assess the real power of the trial which was conducted and to help design ing future trials . We derived an adaptation of the VIF from the minimum variance weights correction to be used in case the imbalance can be a priori formulated such as " a proportion ( γ ) of clusters actually recruit a proportion ( τ ) of subjects to be included ( γ ≤ τ ) " Abstract OBJECTIVE : To determine if women would have higher breast and cervical cancer screening rates  if lay health advisers recommended screening and offered a convenient screening opportunity . DESIGN : Controlled trial . SETTING : Urban county teaching hospital . PARTICIPANTS : Women aged 40 years and over attending appointements in several non- primary -care outpatient clinics . INTERVENTIONS : Lay health advisers assessed the participants ’ breast and cervical cancer screening status and offered women in the intervention group who were due for screening an appointment with a female nurse practitioner . MEASUREMENTS AND MAIN RESULTS : Screening rates at base-line and at follow-up 1 year after the intervention were determined . At follow-up , the mammography rate was 69 % in the intervention group versus 63 % in the usual care group ( p=.009 ) , and the Pap smear rate was 70 % in the intervention group versus 63 % in the usual care group ( p=.02 ) . In women who were due for screening at baseline , the mammography rate was 60 % in the intervention group versus 50 % in the usual care group ( p=.006 ) , and the Pap smear rate was 63 % in the intervention group versus 50 % in the usual care group ( p=.002 ) . The intervention was effective across age and insurance payer strata , and was particularly effective in Native American women . CONCLUSIONS : Breast and cervical cancer screening rates were improved in women attending non- primary -care outpatient clinics by using lay health advisers and a nurse practitioner to perform screening . The effect was strongest in women in greatest need of screening BACKGROUND Screening has become one of our best tools for early detection and prevention of cancer . The group-r and omized trial is the most rigorous experimental design for evaluating multilevel 
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CONCLUSIONS CHW interventions are effective for increasing screening mammography in certain setting s and population s. IMPACT CHW interventions are especially associated with improvements in rate of screening mammography in medical setting s , urban setting s , and in participants who are racially or ethnically concordant with the CHW