***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: Systematic Review Series Series Editors : Cynthia Mulrow , MD , MSc Deborah Cook , MD , MSc The last article in this series outlined methods with which to search the literature for studies on the clinical question that generates a systematic review [ 1 ] . Herein , we discuss the subsequent steps of selecting and appraising  studies  for a review . Both of these steps involve important judgments that can influence the results of a review . In selecting studies , review ers judge the relevance of the studies to the review question . In appraising studies , review ers judge numerous features of design and analysis . Some of these judgments are easy to make ; others are more difficult and prone to error . To be confident in their decisions , review ers should use methods that are reliable ( the results do not change if the procedure is repeated ) , impartial ( not influenced by the study results ) , and explicit ( unambiguous ) [ 2 ] . These strategies for selection and appraisal are sensible , and they distinguish most systematic review s from most narrative review s. However , evidence to support the importance of some of the methods we suggest is either scant or conflicting ; readers are referred to the original research on these approaches for more details . Selecting Studies for Systematic Review s If review ers perform a comprehensive search of the literature using the methods described previously in this series [ 1 ] , they will probably have assembled a large sample of articles . This sample will include most ( ideally , all ) studies that are relevant to the review question ( that is , the sensitivity of the search will be high ) . Inevitably , because such a wide net is cast , articles not pertinent to the clinical question will be retrieved ( that is , the specificity of the search will be modest ) . Thus , the review ers ' next task is to sort through all of the potentially relevant articles and select those that will be included in the review . To do so , review ers adopt several of the tactics listed in Table 1 and Table 2 for planning and executing the selection process ( in effect , improving the specificity of the search ) ; these tactics are described below . Table 1 . Planning Study Selection Table 2 . Strategies for Selecting and Appraising Studies Begin with a Well-Built Clinical Question Review ers should ensure that the question for review includes the four elements of a well-built clinical question [ 3 , 4 ] : the patients of interest , the main interventions under investigation , the comparison interventions , and the clinical outcomes of interest . By including these four elements , review ers can better focus the selection process . Choose Selection Criteria That Fit the Clinical Question Consider a systematic review of the effectiveness of a drug treatment ( for example , a proton-pump inhibitor ) for patients with a particular disorder ( such as esophageal reflux ) . Review ers need to decide whether to include studies of patients with any symptoms of reflux , only those with classic symptoms , or only those in whom definitive diagnostic tests have confirmed the presence of reflux . In addition , review ers might choose to include studies of patients with different comorbid conditions ; patients from different demographic or geographic or cultural background s ; or patients from different health systems , such as inpatient or community population s. Similarly , review ers should use selection criteria that reflect the main and comparison interventions of interest . In our esophageal reflux example , review ers would need to decide whether to include studies of a particular drug or studies of all agents in that drug 's class and whether to include studies of any dose and regimen or only studies with a specific regimen . For the comparison interventions , the review ers would decide whether to include studies that compare the experimental drug with alternate treatments ( such as antacids or histamine-2-receptor antagonists ) , with placebo , or with both . For the clinical outcomes , review ers have analogous tasks of defining the outcomes and translating them into criteria . In our example , the review ers would start by listing each clinical outcome ( for example , whether the outcome was endoscopic or clinical and whether it focused on cure or persistence ) and then decide whether to include studies that reported any outcome or only those with certain clinical ly important outcomes ( such as improvement in symptoms at 1 year ) . After thoroughly considering each element of the review question , review ers compile a set of explicit selection criteria . When these criteria are not explicit , the results of the review are more prone to error [ 5 , 6 ] . Reporting the selection criteria used in a review is extremely important to readers because the criteria indicate the relevance of the review to the readers ' clinical practice . Specify the Types of Study Design To Be Included After creating selection criteria that appropriately reflect the review question , review ers should consider which study design s to include . Ideally , review ers choose study design s that are most likely to produce valid results . For example , to answer questions about therapy or harm , review ers may want to include r and omized trials [ 7 ] because they provide more accurate estimates of benefit or harm than do cohort studies , casecontrol studies , and case series [ 8 ] . In reality , however , r and omized trials may not be conducted to address questions of harm [ 9 ] . Therefore , review ers need to consider which study design s are likely to be available to answer their question ; this information may necessitate modification of originally conceptualized selection criteria to incorporate observational ( nonexperimental ) studies . Specify Criteria Related to Type and Form of Publication Review ers also need to consider issues related to type and form of publication . Ideally , all of the relevant studies would be published as peer- review ed journal articles . However , some completed studies may be published only as abstract s , in non-peer- review ed form , or not at all . Review ers decide whether to include these incompletely reported studies when planning their literature search . By including all articles in various stages of publication and subjecting them to rigorous critical appraisal , review ers minimize the threat of publication bias ( the preferential reporting of studies with positive results ) [ 10 - 12 ] , which could generate misleading review s. Other studies may be reported more than once . To avoid over-representing duplicate studies in the review , investigators should plan to look for and exclude duplicate publications [ 13 ] . Finally , because studies may be published in different language s and because excluding studies published in different language s may bias the results of review s [ 14 , 15 ] , articles should be included , as appropriate , regardless of the language of publication ( translating as necessary ) . Limited time and re sources , however , may preclude such an approach . Construct and Pretest Selection Forms After deciding on selection criteria , review ers can prepare customized forms that contain checklists of the selection criteria ( Figure 1 ) . Using these forms can simplify the selection process , increase reliability , and provide a record of the judgments made about each study . After drafting form prototypes , review ers pretest these forms for clarity , ease of application , and reliability . To pretest the forms , two or more independent review ers typically apply them to a r and om sample of studies identified by the literature search . Review ers compare their results to identify sources of ambiguity and then revise the forms accordingly . If the revisions are substantial , this process may need to be repeated before the forms can be used . Figure 1 . Example of a form that might be developed for the selection of studies for a systematic review evaluating the efficacy of -blockers for secondary prevention of variceal bleeding .  Write a Detailed Protocol Having a selection protocol as part of a larger protocol for the entire review helps review ers in two ways . First , it provides a document that explicitly states the review question and the selection criteria , making the process accountable . Review ers can later return to the protocol for guidance in resolving disagreements about article selection . Second , the selection protocol identifies what work will be done , by whom , in what manner , when , and for what reason ; thus , it provides a mode of communication within the review team . When review ers have a very large sample of studies from which to select , they can simplify this task by review ing all of the titles , then the abstract s , and then the full articles , excluding studies that do not meet one or more selection criteria at each step . In doing so , review ers should record ( on the selection forms ) the reasons for exclusion . After review ers have selected studies for the systematic review , they will move to the next task of critical appraisal . This procedure also requires careful planning . Appraising Studies for Systematic Review s Review ers appraise the studies selected for review with three objectives in mind : 1 ) to underst and the validity of the studies , 2 ) to uncover reasons for differences among study results other than chance , and 3 ) to provide readers with sufficient information with which to judge for themselves the applicability of the systematic review to their clinical practice . To achieve these goals , review ers use the strategies outlined in Table 2 and Table 3 to carefully reexamine many important features of the primary studies . Table 3 . Planning Study Appraisal Examine Important Clinical Features Although the selection criteria for a systematic review define the population , interventions , and outcomes of interest , the appraisal process involves a detailed assessment of the patients ( for example , high , medium , or low risk ) , the study interventions ( for example , frequency , degree , and duration ) , and the outcome measurements ( for example , definitions and degree of surveillance ) PURPOSE The purpose of this investigation was to assess the School-Based Adolescent Health Care Program , which provided comprehensive health-related services in 24 school-based health centers . METHODS The outcomes evaluation compared a cohort of students attending 19 participating schools and a national sample of urban youths , using logit models to control for observed differences between the two groups of youths . Outcome measures included self-reports concerning health center utilization , use of other health care providers , knowledge of key health facts , substance use , sexual activity , contraceptive use , pregnancies and births , and health status . RESULTS The health centers increased students ' access to health care and improved their health knowledge . However , the estimated impacts on health status and risky behaviors were inconsistent , and most were small and not statistically significant . CONCLUSIONS School-based health centers can increase students '  health knowledge and access to health-related services , but more intensive or different services are needed if they are to significantly reduce risk-taking behaviors Although millions of couples rely on male latex condoms to protect against unintended pregnancy and sexually transmitted infections , their use is limited in part by questions about their performance . Rates of condom breakage and slippage , two measures of performance , vary broadly across studies . This variation in part reflects study variability and limitations , including sample size , reliance on subjects ' memory , user population s , and products evaluated . In an effort to define condom performance in a group of monogamous couples typical of those using condoms for contraception , we conducted a clinical trial of a single br and of lubricated condoms ( Durex Ramses ) . A total of 4637 attempts to use the condom were evaluated . Six breaks occurred before intercourse ( non clinical breaks ) , and 10 condoms  broke during intercourse or were only noted to have broken upon withdrawal ( clinical breaks ) , result ing in a non clinical breakage rate of 0.13 % ( 95 % confidence interval , 0.05 - 0.28 % ) , clinical breakage rate of 0.28 % ( 0.15 - 0.48 % ) , and a total breakage rate of 0.41 % ( 0.25 - 0.64 % ) . The rate of complete slippage was 0.63 % ( 0.42 - 0.90 % ) , and total failure ( clinical breaks plus complete slips ) was 1.04 % ( 0.76 - 1.37 % ) . These rates are lower than those in other studies with the exception of one , a prospect i ve investigation in a population of female prostitutes . Results indicate that condoms can , in experienced , motivated population s , provide excellent performance and suggest that their efficacy at preventing pregnancy may equal that of the most reliable forms of contraception . Because this study involved a single condom br and , these results may not be generalizable to other br and Abstract Objective : To assess the effectiveness of a teacher led intervention to improve  teenagers ' knowledge about emergency contraception . Design : Cluster r and omised controlled trial . Setting : 24 mixed sex , state secondary schools in Avon , south west Engl and . Participants : 1974 boys and 1820 girls in year 10 ( 14 - 15 year olds ) . Intervention : Teachers gave a single lesson on emergency contraception to year 10 pupils . The teachers had previously received in-service training on giving the lesson . The pupils were actively involved during the lesson . Main outcome measures : Question naires distributed to pupils at baseline and six months after the intervention assessed their knowledge of the correct time limits for hormonal emergency contraception and for use of the intrauterine device as emergency contraception  , the proportion of pupils who were not virgins , the proportion who had used emergency contraception , and the pupils ' intention to use emergency contraception in the future . Results : The proportion of pupils knowing the correct time limits for both types of emergency contraception was significantly higher in the intervention group than in the control group at six months ' follow up ( hormonal contraception : proportion of boys 15.9 % higher ( 95 % confidence interval 6.5 % to 25.3 % ) , girls 20.4 % ( 10.4 % to 30.4 % ) ; intrauterine device used as  emergency contraception :  boys 4.2 % ( 0.7 % to 7.7 % ) , girls 10.7 % ( 0.4 % to 21.0 % ) . The number of pupils needed to be taught for one more pupil to know the correct time limits was six for boys and five for girls . The intervention and control groups did not differ in the proportion of pupils who were not virgins , in the proportion who had used emergency contraception , and in the proportion intending to use emergency contraception in the future . Conclusions : The intervention significantly improved the proportion of boys and girls knowing the correct time limits for both types of emergency contraception . The intervention did not change the pupils ' sexual activity or use of emergency contraception . What is already known on this topic Use of condoms as a sole method of contraception is increasing Emergency contraception — either hormonal or the intrauterine device used as emergency contraception — can be used when condoms or other methods fail or are not used Awareness of emergency contraception in school pupils is high , but knowledge of specific details , such as the time period within which it can be used , is poor What this study adds A single lesson on emergency contraception given by teachers who had previously been trained improves the proportion of pupils aware of the correct time limits for use of both types of emergency contraception Such a lesson does not increase sexual activity or use of emergency There has been an increasing interest in using expected 
    Output:
    
The systematic review showed that SBSHS are not associated with higher rates of sexual activity among young people , nor with an earlier age of first intercourse .
There was evidence to show positive effects in terms of reductions in births to teenage mothers , and in chlamydial infection rates among young men , although this evidence coming primarily from the USA .
Also evidence to suggest that broad-based , holistic service models , not restricted to sexual health , offer the strongest basis for protecting young people 's privacy and confidentiality , countering perceived stigmatisation , offering the most comprehensive range of products and services , and maximising service uptake .
Findings from the mapping study also indicate that broad-based services , which include medical practitioner input within a multiprofessional team , meet the stated preferences of staff and of young people most clearly .
Partnership-based developments of this kind also conform to the broad policy principles embodied in the Every Child Matters framework in the UK and allied policy initiatives .
Also , the distinction made in the question naire between ' general health ' and ' sexual health ' services did not prove robust .
There is no single , dominant service model in the UK .