***TASK***
the task is to simplify the input abstract of a biomedical literature

***INPUT***
the input is the abstract of a biomedical literature

***OUTPUT***
the output is the simplified abstract for the input abstract of a biomedical literature

***DOCUMENTATION***

***EXAMPLES***

Input: We included in this update 28 studies (4287 women) with sample sizes ranging from 20 to 372. Most studies had low risk of bias for randomisation, attrition, and selective reporting. Less than half of these studies had adequate allocation concealment, and most were unblinded. Using GRADE, we determined that the quality of evidence ranged from moderate to very low. We downgraded evidence for risk of bias, imprecision, and inconsistency. Overall comparison of second-generation versus first-generation (i.e. gold standard hysteroscopic ablative) techniques revealed no evidence of differences in amenorrhoea at 1 year and 2 to 5 years' follow-up (risk ratio (RR) 0.99, 95% confidence interval (CI) 0.78 to 1.27; 12 studies; 2145 women; I² = 77%; and RR 1.16, 95% CI 0.78 to 1.72; 672 women; 4 studies; I² = 80%; very low-quality evidence) and showed subjective improvement at 1 year follow-up based on a Pictorial Blood Assessment Chart (PBAC) (< 75 or acceptable improvement) (RR 1.03, 95% CI 0.98 to 1.09; 5 studies; 1282 women; I² = 0%; and RR 1.12, 95% CI 0.97 to 1.28; 236 women; 1 study; low-quality evidence). Study results showed no difference in patient satisfaction between second- and first-generation techniques at 1 year follow-up (RR 1.01, 95% CI 0.98 to 1.04; 11 studies; 1750 women; I² = 36%; low-quality evidence) nor at 2 to 5 years' follow-up (RR 1.02, 95% CI 0.93 to 1.13; 672 women; 4 studies; I² = 81%). Compared with first-generation techniques, second-generation endometrial ablation techniques were associated with shorter operating times (mean difference (MD) -13.52 minutes, 95% CI -16.90 to -10.13; 9 studies; 1822 women; low-quality evidence) and more often were performed under local rather than general anaesthesia (RR 2.8, 95% CI 1.8 to 4.4; 6 studies; 1434 women; low-quality evidence). We are uncertain whether perforation rates differed between second- and first-generation techniques (RR 0.32, 95% CI 0.10 to 1.01; 1885 women; 8 studies; I² = 0%). Trials reported little or no difference between second- and first-generation techniques in requirement for additional surgery (ablation or hysterectomy) at 1 year follow-up (RR 0.72, 95% CI 0.41 to 1.26; 6 studies: 935 women; low-quality evidence). At 5 years, results showed probably little or no difference between groups in the requirement for hysterectomy (RR 0.85, 95% CI 0.59 to 1.22; 4 studies; 758 women; moderate-quality evidence). Approaches to endometrial ablation have evolved from first-generation techniques to newer second- and third-generation approaches. Current evidence suggests that compared to first-generation techniques (endometrial laser ablation, transcervical resection of the endometrium, rollerball endometrial ablation), second-generation approaches (thermal balloon endometrial ablation, microwave endometrial ablation, hydrothermal ablation, bipolar radiofrequency endometrial ablation, endometrial cryotherapy) are of equivalent efficacy for heavy menstrual bleeding, with comparable rates of amenorrhoea and improvement on the PBAC. Second-generation techniques are associated with shorter operating times and are performed more often under local rather than general anaesthesia. It is uncertain whether perforation rates differed between second- and first-generation techniques. Evidence was insufficient to show which second-generation approaches were superior to others and to reveal the efficacy and safety of third-generation approaches versus first- and second-generation techniques.
Output:

This review identified 28 randomised controlled trials undertaken in 4287 women. Most of the women knew which treatment they were receiving, which may have influenced their judgements about menstrual blood loss and satisfaction. Other aspects of study quality varied among trials. Evidence is current to May 2018. Nineteen of the 28 trials acknowledged that they received funding, supplies of equipment, or technical assistance from the pharmaceutical industry and from equipment manufacturers. Moderate- to very low-quality evidence suggests that first- and second-generation approaches were equally effective in the treatment of HMB. Newer (second-generation) treatment approaches were safer in terms of rate of fluid overload, cervical lacerations, and haematometra, with similar rates of uterine perforation. The newer approaches (second-generation ablation) were quicker and were more likely to be done under local (rather than general) anaesthesia compared with first-generation approaches. Most women in both groups were satisfied with results of the procedure. Not enough evidence is available to show which second-generation approaches are superior to others, and information about third-generation approaches is not available for comparison. Evidence ranged from moderate to very low quality. Few studies were blinded, data were limited, and heterogeneity was substantial for some outcomes, leading to downgrading of the quality of evidence.