***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: Objective To evaluate the effectiveness of register based , yearly chlamydia screening . Design Controlled trial with r and omised stepped wedge implementation in three blocks . Setting Three regions of the Netherl and s : Amsterdam , Rotterdam , and South Limburg . Participants 317 304 women and men aged 16 - 29 years listed on municipal registers at start of trial . Intervention From March 2008 to February 2011 , the Chlamydia Screening Implementation programme offered yearly chlamydia screening tests . Postal invitations asked people to use an internet site to request a kit for self collection of sample s , which would then be sent to regional laboratories for testing . Treatment and partner notification were done by the general practitioner or at a sexually transmitted infection clinic . Main outcome measures Primary outcomes were the percentage of chlamydia tests positive ( positivity ) , percentage of invitees returning a specimen ( uptake ) , and estimated chlamydia prevalence . Secondary outcomes were positivity according to sex , age , region , and sociodemographic factors ; adherence to screening invitations ; and incidence of self reported pelvic inflammatory disease . Results The participation rate was 16.1 % ( 43 358/269 273 ) after the first invitation , 10.8 % after the second , and 9.5 % after the third , compared with 13.0 % ( 6223/48 031 ) in the control block invited at the end of round two of the intervention . Chlamydia positivity in the intervention blocks at the first invitation was the same as in the control block ( 4.3 % ) and 0.2 % lower at the third invitation ( odds ratio 0.96 ( 95 % confidence interval 0.83 to 1.10 ) ) . No substantial decreases in positivity were seen after three screening rounds in any region or sociodemographic group . Among the people who participated three times ( 2.8 % of all invitees ) , positivity fell from 5.9 % to 2.9 % ( odds ratio 0.49 ( 0.47 to 0.50 ) ) . Conclusions There was no statistical evidence of an impact on chlamydia positivity rates or estimated population prevalence from the Chlamydia Screening Implementation programme after three years at the participation levels obtained . The current evidence does not support a national roll out of this register based chlamydia screening programme . Trial registration NTR 3071 ( Netherl and s Trial Register , www.trialregister.nl ) Objective To determine whether screening and treating women for chlamydial infection reduces the incidence of pelvic inflammatory disease over the subsequent 12 months . Design R and omised controlled trial . Setting Common rooms , lecture theatres , and student bars at universities and further education colleges in London . Participants 2529 sexually active female students , mean age 21 years ( range 16 - 27 ) . Intervention Participants completed a question naire and provided self taken vaginal swabs , with follow-up after one year . Sample s were r and omly allocated to immediate testing and treatment for chlamydial infection , or storage and analysis after a year ( deferred screening controls ) . Main outcome measure Incidence of clinical pelvic inflammatory disease over 12 months . Results Baseline prevalence of chlamydia was 5.4 % ( 68/1254 ) in screened women and 5.9 % ( 75/1265 ) in controls . 94 % ( 2377/2529 ) of women were followed up after 12 months . The incidence of pelvic inflammatory disease was 1.3 % ( 15/1191 ) in screened women compared with 1.9 % ( 23/1186 ) in controls ( relative risk 0.65 , 95 % confidence interval 0.34 to 1.22 ) . Seven of 74 control women ( 9.5 % , 95 % confidence interval 4.7 % to 18.3 % ) who tested positive for chlamydial infection at baseline developed pelvic inflammatory disease over 12 months compared with one of 63 ( 1.6 % ) screened women ( relative risk 0.17 , 0.03 to 1.01 ) . However , most episodes of pelvic inflammatory disease occurred in women who tested negative for chlamydia at baseline ( 79 % , 30/38 ) . 22 % ( 527/2377 ) of women reported being tested independently for chlamydia during the trial . Conclusion Although some evidence suggests that screening for chlamydia reduces rates of pelvic inflammatory disease , especially in women with chlamydial infection at baseline , the effectiveness of a single chlamydia test in preventing pelvic inflammatory disease over 12 months may have been overestimated . Trial registration Clinical Trials.gov NCT00115388 Background The advent of urine testing for Chlamydia trachomatis has raised the possibility of large-scale screening for this sexually transmitted infection , which is now the most common in the United Kingdom . The purpose of this study was to investigate the effect of an invitation to be screened for chlamydia and of receiving a negative result on levels of anxiety , depression and self-esteem . Methods 19,773 men and women aged 16 to 39 years , selected at r and om from 27 general practice s in two large city areas ( Bristol and Birmingham ) were invited by post to send home-collected urine sample s or vulvo-vaginal swabs for chlamydia testing . Question naires enquiring about anxiety , depression and self-esteem were sent to r and om sample s of those offered screening : one month before the dispatch of invitations ; when participants returned sample s ; and after receiving a negative result . Results Home screening was associated with an overall reduction in anxiety scores . An invitation to participate did not increase anxiety levels . Anxiety scores in men were lower after receiving the invitation than at baseline . Amongst women anxiety was reduced after receipt of negative test results . Neither depression nor self-esteem scores were affected by screening . Conclusion Postal screening for chlamydia does not appear to have a negative impact on overall psychological well-being and can lead to a decrease in anxiety levels among respondents . There is , however , a clear difference between men and women in when this reduction occurs Background DNA amplification assays are increasingly being used to facilitate the testing of asymptomatic individuals for urogenital Chlamydia trachomatis . The long-term clinical benefit in terms of avoided infertility and ectopic pregnancy is unknown . Methods In 1997 , 15 459 women and 14 980 men aged 21–23 years were living in Aarhus County , Denmark . A r and om sample of 4000 women and 5000 men was contacted by mail and offered the opportunity to be tested for C trachomatis by means of a sample obtained at home and mailed directly to the laboratory .  The remaining 11 459 women and 9980 men received usual care  and constituted the control population . All men and women were subsequently followed for 9 years by the use of Danish health registers . Data were collected on pelvic inflammatory disease ( PID ) , ectopic pregnancy ( EP ) , infertility diagnoses , in-vitro fertilisation ( IVF ) treatment and births in women , and on epididymitis in men . The intervention and control groups were compared using Cox regression analyses and the intention-to-screen principle . Results Among women , no differences were found between the intervention group and the control group : HR ( 95 % CI ) for PID 1.12 ( 0.70 to 1.79 ) ; EP 0.97 ( 0.63 to 1.51 ) ; infertility 0.87 ( 0.71 to 1.07 ) ; IVF treatment 0.88 ( 0.62 to 1.26 ) and births 1.02 ( 0.95 to 1.10 ) . In men , the HR for epididymitis was 1.25 ( 0.70 to 2.24 ) . Conclusions A population -based offer to be tested for urogenital C trachomatis infection by the use of non-invasive sample s and DNA amplification did not reduce the long-term risk of reproductive complications in women or of epididymitis in men . Trial registration number in www . clinical trials.gov NCT 00827970 Objective To compare vulvovaginal swabs with endocervical swabs as optimal diagnostic sample for detection of Chlamydia trachomatis infection . Design A diagnostic test study . Setting An urban sexual health centre . Participants 3973 women aged ≥16 years requesting testing for sexually transmitted infections . Interventions Participants took a vulvovaginal swab before routine examination , and clinicians took an endocervical swab during examination . Main outcome measure Diagnosis of chlamydia infection with sample s analysed using the Aptima Combo-2 assay ; positive results confirmed with the Aptima CT assay . Results Of the 3973 participants , 410 ( 10.3 % ) were infected with C trachomatis . Infected women were significantly younger ( 22 v 25 years , P<0.0001 ) and more likely to have symptoms suggestive of a bacterial sexually transmitted infection ( 53 % v 41 % , odds ratio 1.63 ( 95 % CI 1.30 to 2.04 ) ) , be a contact of someone with a sexually transmitted infection ( 25 % v 5 % , odds ratio 6.18 ( 4.61 to 8.30 ) ) , clinical ly diagnosed with cervicitis ( 17 % v 4 % , odds ratio 4.92 ( 3.50 to 6.91 ) ) , and have pelvic inflammatory disease ( 9 % v 3 % , odds ratio 2.85 ( 1.87 to 4.33 ) ) . When women co-infected with gonorrhoea were included in the analysis , there was an association with mixed ethnicity ( 10 % v 7 % , odds ratio 1.53 ( 1.07 to 2.17 ) ) ; but when those with gonorrhoea were removed , women of white ethnicity were significantly more likely to have chlamydia ( 85 % v 80 % , odds ratio 1.40 ( 1.03 to 1.91 ) ) . On analysis of complete paired results , vulvovaginal swabs were significantly more sensitive than endocervical swabs ( 97 % ( 95 % CI 95 % to 98 % ) v 88 % ( 85 % to 91 % ) , P<0.00001 ) ; corresponding specificities were 99.9 % and 100 % . In women with symptoms suggestive of a bacterial sexually transmitted infection , vulvovaginal swabs were significantly more sensitive than endocervical swabs ( 97 % ( 93 % to 98 % ) v 88 % ( 83 % to 92 % ) , P=0.0008 ) , as they were in women without symptoms ( 97 % ( 94 % to 99 % ) v 89 % ( 84 % to 93 % ) , P=0.002 ) . Conclusions Vulvovaginal swabs are significantly better than endocervical swabs at detecting chlamydia in women with and without symptoms suggestive of sexually transmitted infections . In those with symptoms , using endocervical sample s rather than vulvovaginal swabs would have missed 9 % of infections , or 1 in every 11 cases of chlamydia . Trial registration IS RCT N42867448 Objective To compare gonorrhoea detection by self taken vulvovaginal swabs ( tested with nucleic acid amplification tests ) with the culture of urethral and endocervical sample s taken by clinicians . Design Prospect i ve study of diagnostic accuracy . Setting 1 sexual health clinic in an urban setting ( Leeds Centre for Sexual Health , United Kingdom ) , between March 2009 and January 2010 . Participants Women aged 16 years or older , attending the clinic for sexually transmitted infection ( STI ) testing and consenting to perform a vulvovaginal swab themselves before routine examination . During examination , clinicians took urethral and endocervical sample s for culture and an endocervical swab for nucleic acid amplification testing . Interventions Urethra and endocervix sample s were analysed by gonococcal culture . Vulvovaginal swabs and endocervical swabs were analysed by the Aptima Combo 2 ( AC2 ) assay ; positive results from this assay were confirmed with a second nucleic acid amplification test . Main outcome measures Positive confirmation of gonorrhoea . Results Of 3859 women with complete data and test results , 96 ( 2.5 % ) were infected with gonorrhoea ( overall test sensitivities : culture 81 % , endocervical swabs with AC2 96 % , vulvovaginal swabs with AC2 99 % ) . The AC2 assays were more sensitive than culture ( P<0.001 ) , but the endocervical and vulvovaginal assays did not differ significantly ( P=0.375 ) . Specificity of all Aptima Combo 2 tests was 100 % . Of 1625 women who had symptoms suggestive of a bacterial STI , 56 ( 3.4 % ) had gonorrhoea ( culture 84 % , endocervical AC2 100 % , vulvovaginal AC2 100 % ) . The AC2 assays were more sensitive than culture ( P=0.004 ) , and the endocervical 
    Output:
    
Harms of screening included labeling , anxiety , false-positive and false-negative test results , and other consequences of testing .