***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 examine the risk of non-fatal idiopathic venous thromboembolism in current users of a combined oral contraceptive containing drospirenone  , relative to current users of preparations containing levonorgestrel .  Design Nested case-control study . Setting UK General Practice Research Data base . Participants Women aged 15 - 44 years without major risk factors for venous thromboembolism who started a new episode of use of an oral contraceptive containing 30 µg oestrogen in combination with either drospirenone or levonorgestrel between May 2002 and September 2009 . Cases were women with a first diagnosis of venous thromboembolism ; up to four controls , matched by age , duration of recorded information , and general practice , were r and omly selected for each case . Main outcome measures Odds ratios and 95 % confidence intervals estimated with conditional logistic regression ; age adjusted incidence rate ratio estimated with Poisson regression . Results 61 cases of idiopathic venous thromboembolism and 215 matched controls were identified . In the case-control analysis , current use of the drospirenone contraceptive was associated with a threefold higher risk of non-fatal idiopathic venous thromboembolism compared with levonorgestrel use ; the odds ratio adjusted for body mass index was 3.3 ( 95 % confidence interval 1.4 to 7.6 ) . Subanalyses suggested that referral , diagnostic , first time user , duration of use , and switching biases were unlikely explanations for this finding . The crude incidence rate was 23.0 ( 95 % confidence interval 13.4 to 36.9 ) per 100 000 woman years in current users of drospirenone and 9.1 ( 6.6 to 12.2 ) per 100 000 woman years in current users of levonorgestrel oral contraceptives . The age adjusted incidence rate ratio was 2.7 ( 1.5 to 4.7 ) . Conclusions These findings contribute to emerging evidence that the combined oral contraceptive containing drospirenone carries a higher risk of venous thromboembolism than do formulations containing levonorgestrel Abstract Objective : To test whether use of combined oral contraceptives containing third generation progestogens is associated with altered risk of venous thromboembolism .  Design : Matched case-control study . Setting : 10 centres in Germany and United Kingdom . Subjects : Cases were 471 women aged 16 - 44 who had a venous thromboembolism . Controls were 1772 women ( at least 3 controls per case ) unaffected by venous thromboembolism who were matched with corresponding case for age and for hospital or community setting . Main outcome measures : Odds ratios derived with stratified analyses and unconditional logistic regression to adjust for potential confounding variables . Results : Odds ratios ( 95 % confidence intervals ) for venous thromboembolism were : for any oral contraceptives versus no use , 4.0 ( 3.1 to 5.3 ) ; for second generation products ( low dose ethinyloestradiol , no gestodene or desogestrel ) versus no use , 3.2 ( 2.3 to 4.3 ) ; for third generation products ( low dose ethinyloestradiol , gestodene or desogestrel ) versus no use , 4.8 ( 3.4 to 6.7 ) ; for third generation products versus second generation products , 1.5 ( 1.1 to 2.1 ) ; for products containing gestodene versus second generation products , 1.5 ( 1.0 to 2.2 ) ; and for products containing desogestrel versus second generation products , 1.5 ( 1.1 to 2.2 ) . Probability of death due to venous thromboembolism for women using third generation products is about 20 per million users per year , for women using second generation products it is about 14 per million users per year , and for non-users it is five per million per year . Conclusions : Risk of venous thromboembolism was slightly increased in users of third generation oral contraceptives  compared with users of  second  generation products  . Key messages Key messages This case-control study examined risk of venous thromboembolism associated with different types of oral contraceptive Overall , there was a fourfold higher relative risk of thromboembolism associated with current use of any oral contraceptive versus no current use The risk of thromboembolism was 1.5 times higher for third generation contraceptives compared with second generation products Our data indicate the need for clinical prudence but allow doctors and women seeking contraception to exercise informed OBJECTIVES The study was conducted to compare risks of adverse cardiovascular and other events associated with the use of drospirenone (DRSP)-containing oral contraceptives ( OCs ) and other OCs .  METHODS AND MATERIAL S The European Active Surveillance study ( EURAS ) was a multinational , prospect i ve , noninterventional cohort study of new users of DRSP , levonorgestrel ( LNG ) and other progestin-containing OCs .  Semiannual follow-up was based on mailed question naires , with additional follow-up procedures when needed . RESULTS Overall , 58,674 women were followed for 142,475 women-years of observation . Loss to follow-up was 2.4 % . Serious adverse and fatal events were rare , and rate ratios were close to unity ( 1.0 ) . Cox regression analysis of cardiovascular outcomes yielded hazard ratios for DRSP-containing vs. LNG-containing and other OCs of 1.0 and 0.8 ( upper 95 % confidence limits , 1.8 and 1.3 ) for venous , and 0.3 and 0.3 ( upper 95 % confidence limits , 1.2 and 1.5 ) for arterial thromboembolism , respectively . CONCLUSIONS Risks of adverse cardiovascular and other serious events in users of a  DRSP-containing OC  are similar to those associated with the use of other OCs OBJECTIVES The " International Active Surveillance Study of Women Taking Oral Contraceptives " investigated the risks of short- and long-term use of an extended 24-day regimen of drospirenone and ethinylestradiol ( DRSP24d ) compared to established oral contraceptives ( OCs ) in a routine clinical setting . STUDY DESIGN Prospect i ve , controlled , noninterventional cohort study conducted in the United States and six European countries with three main cohorts : new users of DRSP24d , DRSP21d ( 21-day regimens of DRSP-containing OCs ) , and non-DRSP ( OCs without DRSP ) .  All self-reported clinical outcomes of interest ( OoI ) were vali date d via attending physicians and relevant source documents . Main OoI were serious clinical outcomes , in particular venous thromboembolism ( VTE ) . Comprehensive follow-up procedures were implemented . Statistical analyses were based on Cox regression models . Primary statistical variable was the VTE hazard ratio ( HR ) for DRSP24d vs. non-DRSP . RESULTS A total of 2285 study centers enrolled 85,109 women . Study participants were followed for 2 to 6 years , which generated 206,296 woman-years ( WY ) of observation . A low loss to follow-up of 3.3 % was achieved . DRSP24d , DRSP21d , non-DRSP and levonorgestrel-containing OCs ( LNG ) showed similar incidence rates of venous and arterial thromboembolism , fatal outcomes , cancer , severe depression and other serious adverse events . VTE incidence rates for DRSP24d , DRSP21d , non-DRSP and LNG were 7.2 , 9.4 , 9.6 and 9.8 VTE/10,000 WY , respectively . Adjusted HRs for DRSP24d vs. non-DRSP and DRSP24d vs. LNG were 0.8 [ 95 % confidence interval ( CI ) , 0.5 - 1.3 ] and 0.8 ( 95 % CI , 0.4 - 1.5 ) . CONCLUSION DRSP24d , DRSP21d , non-DRSP and LNG use was associated with similar risks of serious adverse events , and particularly VTE , during routine clinical use . IMPLICATION STATEMENT The 24-day regimen of drospirenone-containing combined OCs is associated with similar risks of venous and arterial thromboembolism , fatal outcomes , cancer , severe depression and other serious adverse events compared to 21-day regimens of drospirenone-containing combined OCs , OCs without drospirenone and LNGs 
    Output:
    
AUTHOR 'S CONCLUSIONS As a result of the method ological limitations of the individual studies , the VTE risk of drospirenone-containing COCs remains unknown .
The highest quality studies suggest there are no or slightly increased harmful effects , but their confidence limits do not rule out an almost doubling of the risk .
TWEETABLE ABSTRACT Systematic review of drospirenone : best studies show no or slightly increased VTE risk ( versus levonorgestrel )