scholarly journals Meta-analysis of rare binary events in treatment groups with unequal variability

2017 ◽  
Vol 28 (1) ◽  
pp. 263-274 ◽  
Author(s):  
Lie Li ◽  
Xinlei Wang
Keyword(s):  
Random Effects ◽  
Mean Squared Error ◽  
Meta Analysis ◽  
Random Effects Model ◽  
Treatment Groups ◽  
Continuity Correction ◽  
Large Samples ◽  
Squared Error ◽  
The Mean ◽  
Simple Average

Meta-analysis has been widely used to synthesize information from related studies to achieve reliable findings. However, in studies of rare events, the event counts are often low or even zero, and so standard meta-analysis methods such as fixed-effect models with continuity correction may cause substantial bias in estimation. Recently, Bhaumik et al. developed a simple average estimator for the overall treatment effect based on a random effects model. They proved that the simple average method with the continuity correction factor 0.5 (SA_0.5) is the least biased for large samples and showed via simulation that it has superior performance when compared with other commonly used estimators. However, the random effects models used in previous work are restrictive because they all assume that the variability in the treatment group is equal to or always greater than that in the control group. Under a general framework that explicitly allows treatment groups with unequal variability but assumes no direction, we prove that SA_0.5 is still the least biased for large samples. Meanwhile, to account for a trade-off between the bias and variance in estimation, we consider the mean squared error to assess estimation efficiency and show that SA_0.5 fails to minimize the mean squared error. Under a new random effects model that accommodates groups with unequal variability, we thoroughly compare the performance of various methods for both large and small samples via simulation and draw conclusions about when to use which method in terms of bias, mean squared error, type I error, and confidence interval coverage. A data example of rosiglitazone meta-analysis is used to provide further comparison.

scholarly journals On estimating a constrained bivariate random effects model for meta-analysis of test accuracy studies

2022 ◽  
pp. 096228022110651
Author(s):  
Mohammed Baragilly ◽  
Brian Harvey Willis
Keyword(s):  
Sensitivity And Specificity ◽  
Random Effects ◽  
Coverage Probability ◽  
Mean Squared Error ◽  
Meta Analysis ◽  
Test Accuracy ◽  
Random Effects Model ◽  
Mahalanobis Distances ◽  
Constrained Model ◽  
True Values

Tailored meta-analysis uses setting-specific knowledge for the test positive rate and disease prevalence to constrain the possible values for a test's sensitivity and specificity. The constrained region is used to select those studies relevant to the setting for meta-analysis using an unconstrained bivariate random effects model (BRM). However, sometimes there may be no studies to aggregate, or the summary estimate may lie outside the plausible or “applicable” region. Potentially these shortcomings may be overcome by incorporating the constraints in the BRM to produce a constrained model. Using a penalised likelihood approach we developed an optimisation algorithm based on co-ordinate ascent and Newton-Raphson iteration to fit a constrained bivariate random effects model (CBRM) for meta-analysis. Using numerical examples based on simulation studies and real datasets we compared its performance with the BRM in terms of bias, mean squared error and coverage probability. We also determined the ‘closeness’ of the estimates to their true values using the Euclidian and Mahalanobis distances. The CBRM produced estimates which in the majority of cases had lower absolute mean bias and greater coverage probability than the BRM. The estimated sensitivities and specificity for the CBRM were, in general, closer to the true values than the BRM. For the two real datasets, the CBRM produced estimates which were in the applicable region in contrast to the BRM. When combining setting-specific data with test accuracy meta-analysis, a constrained model is more likely to yield a plausible estimate for the sensitivity and specificity in the practice setting than an unconstrained model.

scholarly journals Smartphone Interventions Effect in Pediatric Subjects on the Day of Surgery: A Meta-Analysis

2021 ◽  
Vol 8 ◽  
Author(s):  
Li Li ◽  
Jianping Ma ◽  
Dan Ma ◽  
Xiaokang Zhou
Keyword(s):  
Random Effects ◽  
Standard Care ◽  
Literature Search ◽  
Meta Analysis ◽  
Continuous Method ◽  
Mean Difference ◽  
Random Effects Model ◽  
Systematic Literature Search ◽  
Oral Midazolam ◽  
The Mean

Background: A meta-analysis was performed to evaluate the effect of smartphone interventions on the anxiety of the pediatric subjects at induction on the day of surgery compared to oral midazolam or standard care as control.Methods: A systematic literature search up to June 2021 was performed and nine studies selected 785 pediatric subjects on the day of surgery at the start of the study; 390 of them were using smartphone interventions, 192 were control, and 203 were using oral midazolam. They were reporting relationships between the effects of smartphone interventions on the anxiety of the pediatric subjects at induction on the day of surgery compared to oral midazolam or control. The mean difference (MD) with its 95% CIs was calculated to assess the effect of smartphone interventions on the anxiety of the pediatric subjects at induction on the day of surgery compared to oral midazolam or control using the continuous method with a fixed or a random-effects model.Results: Smartphone interventions in pediatric subjects were significantly related to lower anxiety at induction on the day of surgery (MD, −19.74; 95% CI, −29.87 to −9.61, p < 0.001) compared to control and significantly related to lower anxiety at induction on the day of surgery (MD, −7.81; 95% CI, −14.49 to −1.14, p = 0.02) compared to oral midazolam.Conclusion: Smartphone interventions in pediatric subjects on the day of surgery may have lower anxiety at induction compared to control and oral midazolam. Further studies are needed to confirm these findings.

scholarly journals On the Simulation Study of Jackknife and Bootstrap MSE Estimators of a Domain Mean Predictor for Fay‑Herriot Model

2018 ◽  
Vol 5 (331) ◽  
pp. 169-183 ◽  
Author(s):  
Małgorzata Karolina Krzciuk
Keyword(s):  
Random Effects ◽  
Simulation Study ◽  
Mean Squared Error ◽  
Parametric Bootstrap ◽  
Jackknife Method ◽  
Squared Error ◽  
The Mean

 We consider the problem of the estimation of the mean squared error (MSE) of some domain mean predictor for Fay‑Herriot model. In the simulation study we analyze properties of eight MSE estimators including estimators based on the jackknife method (Jiang, Lahiri, Wan, 2002; Chen, Lahiri, 2002; 2003) and parametric bootstrap (Gonzalez‑Manteiga et al., 2008; Buthar, Lahiri, 2003). In the standard Fay‑Herriot model the independence of random effects is assumed, and the biases of the MSE estimators are small for large number of domains. The aim of the paper is the comparison of the properties of MSE estimators for different number of domains and the misspecification of the model due to the correlation of random effects in the simulation study. 

scholarly journals A meta-analysis of outcomes and complications of magnetic resonance–guided focused ultrasound in the treatment of essential tremor

2018 ◽  
Vol 44 (2) ◽  
pp. E4 ◽  
Author(s):  
Nasser Mohammed ◽  
Devi Patra ◽  
Anil Nanda
Keyword(s):  
Quality Of Life ◽  
Magnetic Resonance ◽  
Essential Tremor ◽  
Random Effects ◽  
Focused Ultrasound ◽  
Meta Analysis ◽  
Cochrane Library ◽  
Random Effects Model ◽  
The Mean

OBJECTIVEMagnetic resonance–guided focused ultrasound (MRgFUS) is a novel technique that uses high-intensity focused ultrasound to achieve target ablation. Like a lens focusing the sun’s rays, the ultrasound waves are focused to generate heat. This therapy combines the noninvasiveness of Gamma Knife thalamotomy and the real-time ablation of deep brain stimulation with acceptable complication rates. The aim of this study was to analyze the overall outcomes and complications of MRgFUS in the treatment of essential tremor (ET).METHODSA meta-analysis in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was made by searching PubMed, Cochrane library database, Web of Science, and Cumulative Index to Nursing and Allied Health Literature (CINAHL). Patients with the diagnosis of ET who were treated with MRgFUS were included in the study. The change in the Clinical Rating Scale for Tremor (CRST) score after treatment was analyzed. The improvement in disability was assessed with the Quality of Life in Essential Tremor Questionnaire (QUEST) score. The pooled data were analyzed by the DerSimonian-Laird random-effects model. Tests for bias and heterogeneity were performed.RESULTSNine studies with 160 patients who had ET were included in the meta-analysis. The ventral intermediate nucleus was the target in 8 of the studies. The cerebellothalamic tract was targeted in 1 study. There was 1 randomized controlled trial, 6 studies were retrospective, and 2 were prospective. The mean number of sonications given in various studies ranged from 11 ± 3.2 to 22.5 ± 7.5 (mean ± SD). The maximum delivered energy ranged from 10,320 ± 4537 to 14,497 ± 6695 Joules. The mean of peak temperature reached ranged from 53°C ± 2.3°C to 62.0°C ± 2.5°C. On meta-analysis with the random-effects model, the pooled percentage improvements in the CRST Total, CRST Part A, CRST Part C, and QUEST scores were 62.2%, 62.4%, 69.1%, and 46.5%, respectively. Dizziness was the most common in-procedure complication, occurring in 43.4%, followed by nausea and vomiting in 26.85% (pooled percentage). At 3 months, ataxia was the most common complication, occurring in 32.8%, followed by paresthesias in 25.1% of the patients. At 12 months posttreatment, the ataxia had significantly recovered and paresthesias became the most common persisting complication, at 15.3%.CONCLUSIONSThe MRgFUS therapy for ET significantly improves the CRST scores and improves the quality of life in patients with ET, with an acceptable complication rate. Therapy with MRgFUS is a promising frontier in functional neurosurgery.

scholarly journals Evaluation of SARS-CoV-2 clearance period in patients with COVID-19: a systematic review and meta-analysis

2020 ◽  
Author(s):  
Yasutaka Okita ◽  
Takayoshi Morita ◽  
Atsushi Kumanogoh
Keyword(s):  
Systematic Review ◽  
Random Effects ◽  
Selection Criteria ◽  
Web Of Science ◽  
Meta Analysis ◽  
Random Effects Model ◽  
Viral Shedding ◽  
The Mean

Abstract Background: There is insufficient consensus on the viral shedding period in each background of patients with coronavirus disease 2019 (COVID-19).Methods: We conducted a comprehensive systematic review and meta-analysis according to the PRISMA guidelines. PubMed and Web of Science were searched for original studies reporting the viral shedding period in patients with COVID-19. A random effects model was used to calculate the mean number of days from the onset. Subanalysis was performed focusing on age, sex, severity, locality, and treatment.Results Of 55 studies identified, 12 met the selection criteria. The viral shedding period tended to be longer in sputum (19.03 days) than in nasopharynx (14.58 days). The viral shedding period in nasopharynx tended to be longer in severe patients (23.65 days) than in nonsevere patients (12.67 days). It also tended to be longer in patients treated with steroid (21.24 days) than in patients treated without steroid (12.20 days). This period tended to be longer in Asia (16.07 days) than in Europe (12.57 days). Age, sex, and anti-viral drugs did not affect the viral shedding period.Conclusions Severity, steroid usage, and locality may affect the viral shedding period.

scholarly journals Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

2021 ◽  
Vol 178 (2) ◽  
pp. 313-339
Author(s):  
Michael L. Begnaud ◽  
Dale N. Anderson ◽  
Stephen C. Myers ◽  
Brian Young ◽  
James R. Hipp ◽  
...  
Keyword(s):  
Travel Time ◽  
Random Effects ◽  
Mean Squared Error ◽  
Random Effects Model ◽  
Location Error ◽  
Crust And Upper Mantle ◽  
Time Uncertainty ◽  
Uncertainty Estimates ◽  
Event Location ◽  
Travel Time Uncertainty

AbstractThe regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current distance-dependent uncertainty parameterization for RSTT using a random effects model to estimate slowness (inverse velocity) uncertainty as a mean squared error for each model parameter. The random effects model separates the error between observed slowness and model predicted slowness into bias and random components. The path-specific travel-time uncertainty is calculated by integrating these mean squared errors along a seismic-phase ray path. We demonstrate that event location error ellipses computed for a 90% coverage ellipse metric (used by the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (IDC)), and using the path-specific travel-time uncertainty approach, are more representative (median 82.5% ellipse percentage) of true location error than error ellipses computed using distance-dependent travel-time uncertainties (median 70.1%). We also demonstrate measurable improvement in location uncertainties using the RSTT method compared to the current station correction approach used at the IDC (median 74.3% coverage ellipse).

scholarly journals Gunshot Wounds to the Lumbosacral Spine: Systematic Review and Meta-Analysis

2021 ◽  
pp. 219256822110308
Author(s):  
Andrew Platt ◽  
Mostafa H. El Dafrawy ◽  
Michael J. Lee ◽  
Martin H. Herman ◽  
Edwin Ramos
Keyword(s):  
Systematic Review ◽  
Random Effects ◽  
Surgical Intervention ◽  
Meta Analysis ◽  
Gunshot Wounds ◽  
Operative Management ◽  
Operative Intervention ◽  
Lumbosacral Spine ◽  
Random Effects Model ◽  
Significant Difference

Study Design: Systematic review and meta-analysis. Objectives: Indications for surgical decompression of gunshot wounds to the lumbosacral spine are controversial and based on limited data. Methods: A systematic review of literature was conducted to identify studies that directly compare neurologic outcomes following operative and non-operative management of gunshot wounds to the lumbosacral spine. Studies were evaluated for degree of neurologic improvement, complications, and antibiotic usage. An odds ratio and 95% confidence interval were calculated for dichotomous outcomes which were then pooled by random-effects model meta-analysis. Results: Five studies were included that met inclusion criteria. The total rate of neurologic improvement was 72.3% following surgical intervention and 61.7% following non-operative intervention. A random-effects model meta-analysis was carried out which failed to show a statistically significant difference in the rate of neurologic improvement between surgical and non-operative intervention (OR 1.07; 95% CI 0.45, 2.53; P = 0.88). In civilian only studies, a random-effects model meta-analysis failed to show a statistically significant difference in the rate of neurologic improvement between surgical and non-operative intervention (OR 0.75; 95% CI 0.21, 2.72; P = 0.66). Meta-analysis further failed to show a statistically significant difference in the rate of neurologic improvement between patients with either complete (OR 4.13; 95% CI 0.55, 30.80; P = 0.17) or incomplete (OR 0.38; 95% CI 0.10, 1.52; P = 0.17) neurologic injuries who underwent surgical and non-operative intervention. There were no significant differences in the number of infections and other complications between patients who underwent surgical and non-operative intervention. Conclusions: There were no statistically significant differences in the rate of neurologic improvement between those who underwent surgical or non-operative intervention. Further research is necessary to determine if surgical intervention for gunshot wounds to the lumbosacral spine, including in the case of retained bullet within the spinal canal, is efficacious.

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