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A novel approach for analyzing data on recurrent events with duration to estimate the combined cumulative rate of both variables over time.

ABSTRACT: Recurrent adverse events, once occur often continue for some duration of time in clinical trials; and the number of events along with their durations is clinically considered as a measure of severity of a disease under study. While there are methods available for analyzing recurrent events or durations or for analyzing both side by side, no effort has been made so far to combine them and present as a single measure. However, this single-valued combined measure may help clinicians assess the wholesome effect of recurrence of incident comprising events and durations. Non-parametric approach is adapted here to develop an estimator for estimating the combined rate of both, the recurrence of events as well as the event-continuation, that is the duration per event. The proposed estimator produces a single numerical value, the interpretation and meaningfulness of which are discussed through the analysis of a real-life clinical dataset. The algebraic expression of variance is derived, asymptotic normality of the estimator is noted, and demonstration is provided on how the estimator can be used in the setup of testing of statistical hypothesis. Further possible development of the estimator is also noted, to adjust for the dependence of event occurrences on the history of the process generating recurrent events through covariates and for the case of dependent censoring.

SUBMITTER: Bhattacharya S

PROVIDER: S-EPMC5898580 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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A novel approach for analyzing data on recurrent events with duration to estimate the combined cumulative rate of both variables over time.

Bhattacharya Sudipta S

Contemporary clinical trials communications 20180312

Recurrent adverse events, once occur often continue for some duration of time in clinical trials; and the number of events along with their durations is clinically considered as a measure of severity of a disease under study. While there are methods available for analyzing recurrent events or durations or for analyzing both side by side, no effort has been made so far to combine them and present as a single measure. However, this single-valued combined measure may help clinicians assess the whol ...[more]

PMID: 29696158

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Project description:Study questionHas cumulative live birth rate (CLBR) improved over time and which factors are associated with such an improvement?Summary answerDuring an 11-year period, 2007-2017, CLBR per oocyte aspiration increased significantly, from 27.0% to 36.3%, in parallel with an increase in blastocyst transfer and cryopreservation by vitrification.What is known alreadyWhile it has been shown that live birth rate (LBR) per embryo transfer (ET) is higher for fresh blastocyst than for fresh cleavage stage embryo transfer, CLBR per oocyte aspiration, including one fresh ET and all subsequent frozen embryo transfers (FET), does not seem to differ between the two culture strategies.Study design size durationA national register study including all oocyte aspirations performed in Sweden from 2007 to 2017 (n = 124 700 complete IVF treatment cycles) was carried out. Oocyte donation cycles were excluded.Participants/materials setting methodsData were retrieved from the Swedish National Registry of Assisted Reproduction (Q-IVF) on all oocyte aspirations during the study period where autologous oocytes were used. CLBR was defined as the proportion of deliveries with at least one live birth per oocyte aspiration, including all fresh and/or frozen embryo transfers within 1 year, until one delivery with a live birth or until all embryos were used, whichever occurred first. The delivery of a singleton, twin, or other multiples was registered as one delivery. Cryopreservation of cleavage stage embryos was performed by slow freezing and of blastocyst by vitrification.Main results and the role of chanceIn total, 124 700 oocyte aspirations were performed (in 61 313 women), with 65 304 aspirations in women <35 years and 59 396 in women ≥ 35 years, resulting in 38 403 deliveries with live born children. Overall, the CLBR per oocyte aspiration increased significantly during the study period, from 27.0% to 36.3% (odds ratio (OR) 1.039, 95% CI 1.035-1.043) and from 30.0% to 43.3% if at least one ET was performed (adjusted OR 1.055, 95% CI 1.050-1.059). The increase in CLBR was independent of maternal age, number of oocytes retrieved and number of previous IVF live births. The CLBR for women <35 and ≥35 years both increased significantly, following the same pattern. During the study period, a substantially increasing number of blastocyst transfers was performed, both in fresh and in FET cycles. Other important predicting factors for live birth, such as number of embryos transferred, could not explain the improvement. An increased single embryo transfer rate was observed with time.Limitations reasons for cautionThe retrospective design implicates that other confounders of importance for CLBR cannot be ruled out. In addition, some FET cycles might be performed later than 1 year post oocyte aspiration for the last year (2017) and are, thus, not included in this study. In addition, no data on 'dropouts', i.e. patients that do not continue their treatment despite having cryopreserved embryos, are available, or if this drop-out rate has changed over time.Wider implications of the findingsThe results suggest that blastocyst transfer, particularly when used in FET cycles and in combination with vitrification, is an important contributor to the improved live birth rates over time. This gives a possibility for a lower number of oocyte aspirations needed to achieve a live birth and a shortened time to live birth.Study funding/competing interestsThe study was financed by grants from the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (ALFGBG-70940) and by Hjalmar Svensson's research foundation. None of the authors declares any conflict of interest.

Project description:ObjectiveTo study the influence of endometriosis activity on the pregnancy outcomes of patients with recurrent implantation failure (RIF) in in-vitro fertilization/intra-cytoplasmic sperm injection (IVF/ICSI) cycles. The pregnancy outcomes were compared between RIF patients with endometriosis who received treatment at different occasions to explore the appropriate treatment plan for these patients and to optimize the pregnancy-support strategies.DesignAmbispective cohort study.MethodsA total of 330 patients with endometriosis were enrolled from 2008 to 2018 and included 1043 IVF/ICSI cycles. All patients were diagnosed with RIF after IVF/ICSI. Patients were assigned to three subtypes according to different control states of endometriosis, including the untreated, early-treatment, and late-treatment groups. The clinical pregnancy rate, live birth rate, and cumulative live birth rate of endometriosis patients with RIF were the main outcomes; additionally, the fertilization rate, available embryonic rate, and high-quality embryonic rate were also compared.ResultsThe early-treatment and late-treatment groups showed higher cumulative live birth rate than the untreated group (early-treated 43.6% vs. late-treated 46.3% vs. untreated 27.7%, P<0.001), though patients in the two treatment groups had higher rates of adenomyosis and ovarian surgery. The two treatment group showed a better laboratory result than the untreated and especially, the early-treatment group. The untreated group (46.24%) had a lower IVF fertilization rate than the treated group (early-treated [64.40%] and late-treated [60.27%] (P<0.001). In addition, the rates of available embryos and high-quality embryos in the early-treated group were much higher those that in the untreated group (90.30% vs. 85.20%, 76.50% vs. 64.47%). Kaplan-Meier curve showed that patients in the untreated group needed a mean of 23.126 months to achieve one live birth; whereas those in the treated group needed a comparatively shorter duration (early-treated: 18.479 ± 0.882 months and late-treated: 14.183 ± 1.102 months, respectively).ConclusionEndometriosis has a negative influence on IVF/ICSI outcome. The control of endometriosis activity can result in a higher cumulative live birth rate in patients. It is necessary for endometriosis patients to receive medical treatment to achieve a better prognosis especially for those with RIF.

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Project description:Background and purposeExpert consensus guidelines recommend low-density lipoprotein cholesterol as the primary serum lipid target for recurrent stroke risk reduction. However, mounting evidence suggests that other lipid parameters might be additional therapeutic targets or at least also predict cardiovascular risk. Little is known about the effects of nontraditional lipid variables on recurrent stroke risk.MethodsWe analyzed the Vitamin Intervention for Stroke Prevention study database comprising 3680 recent (<120 days) noncardioembolic stroke patients followed up for 2 years. Independent associations of baseline serum lipid variables with recurrent ischemic stroke (primary outcome) and the composite end point of ischemic stroke/coronary heart disease/vascular death (secondary outcomes) were assessed.ResultsOf all variables evaluated, only triglycerides/high-density lipoprotein cholesterol (HDL-C) ratio was consistently and independently related to both outcomes: compared with the lowest quintile, the highest triglycerides/HDL-C ratio quintile was associated with stroke (adjusted hazard ratio, 1.56; 95% confidence interval, 1.05-2.32) and stroke/coronary heart disease/vascular death (1.39; 1.05-1.83), including adjustment for lipid modifier use. Compared with the lowest quintile, the highest total cholesterol/HDL-C ratio quintile was associated with stroke/coronary heart disease/vascular death (1.45; 1.03-2.03). Low-density lipoprotein cholesterol/HDL-C ratio, non-HDL-C, elevated triglycerides alone, and low HDL-C alone were not independently linked to either outcome.ConclusionsOf various nontraditional lipid variables, elevated baseline triglycerides/HDL-C and total cholesterol/HDL-C ratios predict future vascular risk after a stroke, but only elevated triglycerides/HDL-C ratio is related to risk of recurrent stroke. Future studies should assess the role of triglycerides/HDL-C as a potential therapeutic target for global vascular risk reduction after stroke.

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A novel approach for analyzing data on recurrent events with duration to estimate the combined cumulative rate of both variables over time.

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A novel approach for analyzing data on recurrent events with duration to estimate the combined cumulative rate of both variables over time.

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