Tests for a Family of Survival Models Based on Extremes

2000 ◽  
pp. 307-321 ◽  
Author(s):  
Martin Crowder
Keyword(s):  
Survival Models

scholarly journals Radiomics and Dosiomics for Predicting Local Control after Carbon-Ion Radiotherapy in Skull-Base Chordoma

Cancers ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 339
Author(s):  
Giulia Buizza ◽  
Chiara Paganelli ◽  
Emma D’Ippolito ◽  
Giulia Fontana ◽  
Silvia Molinelli ◽  
...  
Keyword(s):  
Prognostic Factors ◽  
Skull Base ◽  
Local Control ◽  
Tumour Progression ◽  
Risk Groups ◽  
Carbon Ion Radiotherapy ◽  
Survival Models ◽  
Carbon Ion ◽  
Combined Models ◽  
Skull Base Chordoma

Skull-base chordoma (SBC) can be treated with carbon ion radiotherapy (CIRT) to improve local control (LC). The study aimed to explore the role of multi-parametric radiomic, dosiomic and clinical features as prognostic factors for LC in SBC patients undergoing CIRT. Before CIRT, 57 patients underwent MR and CT imaging, from which tumour contours and dose maps were obtained. MRI and CT-based radiomic, and dosiomic features were selected and fed to two survival models, singularly or by combining them with clinical factors. Adverse LC was given by in-field recurrence or tumour progression. The dataset was split in development and test sets and the models’ performance evaluated using the concordance index (C-index). Patients were then assigned a low- or high-risk score. Survival curves were estimated, and risk groups compared through log-rank tests (after Bonferroni correction α = 0.0083). The best performing models were built on features describing tumour shape and dosiomic heterogeneity (median/interquartile range validation C-index: 0.80/024 and 0.79/0.26), followed by combined (0.73/0.30 and 0.75/0.27) and CT-based models (0.77/0.24 and 0.64/0.28). Dosiomic and combined models could consistently stratify patients in two significantly different groups. Dosiomic and multi-parametric radiomic features showed to be promising prognostic factors for LC in SBC treated with CIRT.

Comparison of two recent ceramide-based coronary risk prediction scores: CERT and CERT-2

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
A Leiherer ◽  
A Muendlein ◽  
C.H Saely ◽  
R Laaksonen ◽  
M Laaperi ◽  
...  
Keyword(s):  
Cardiovascular Mortality ◽  
Coronary Event ◽  
Cardiovascular Death ◽  
Survival Models ◽  
Risk Category ◽  
Net Reclassification Improvement ◽  
Event Risk ◽  
Risk Predictor ◽  
Risk Categories

Abstract   The Coronary Event Risk Test (CERT) is a validated cardiovascular risk predictor that uses circulating ceramide concentrations to allocate patients into one of four risk categories. This test has recently been updated (CERT-2), now additionally including phosphatidylcholine concentrations. The purpose of this study was to investigate the power of CERT and CERT-2 to predict cardiovascular mortality in patients with cardiovascular disease (CVD). We investigated a cohort of 999 patients with established CVD. Overall, comparing survival curves (figure) for over 12 years of follow up and the predictive power of survival models using net reclassification improvement (NRI), CERT-2 was the best predictor of cardiovascular mortality, surpassing CERT (NRI=0.456; p=0.01) and also the 2019 ESC-SCORE (NRI=0.163; p=0.04). Patients in the highest risk category of CERT as compared to the lowest category had a HR of 3.63 [2.09–6.30] for cardiovascular death; for CERT-2 the corresponding HR was 6.02 [2.47–14.64]. Among patients with T2DM (n=322), the HR for cardiovascular death was 3.00 [1.44–6.23] using CERT and 7.06 [1.64–30.50] using CERT-2; the corresponding HRs among non-diabetic subjects were 2.99 [1.20–7.46] and 3.43 [1.03–11.43], respectively. We conclude that both, CERT and CERT-2 scores are powerful predictors of cardiovascular mortality in CVD patients, especially in those patients with T2D. Performance is even higher with CERT-2. Funding Acknowledgement Type of funding source: None

Nest cameras do not affect nest survival in a meadow-nesting shorebird

2020 ◽  
pp. 1-10
Author(s):  
VOLKER SALEWSKI ◽  
LUIS SCHMIDT
Keyword(s):  
Nest Survival ◽  
Bird Species ◽  
Conservation Strategies ◽  
Survival Models ◽  
Northern Germany ◽  
Term Study ◽  
Long Term Study ◽  
Limosa Limosa ◽  
Study Sites

Summary Identifying the fate of birds’ nests and the causes of breeding failure is often crucial for the development of conservation strategies for threatened species. However, collecting these data by repeatedly visiting nests might itself contribute to nest failure or bias. To solve this dilemma, automatic cameras have increasingly been used as a time-efficient means for nest monitoring. Here, we consider whether the use of cameras itself may influence hatching success of nests of the Black-tailed Godwit Limosa limosa at two long-term study sites in northern Germany. Annually between 2013 and 2019, cameras were used to monitor godwit nests. In 2014 and 2019, nests were randomly equipped with cameras or not, and nest survival checked independently of the cameras. Nest-survival models indicated that survival probabilities varied between years, sites and with time of the season, but were unaffected by the presence of cameras. Even though predation is the main cause of hatching failure in our study system, we conclude that predators did not learn to associate cameras with food either when the cameras were initially installed or after they had been used for several years. Cameras were thus an effective and non-deleterious tool to collect data for conservation in this case. As other bird species may react differently to cameras at their nests, and as other sets of predators may differ in their ability to associate cameras with food, the effect of cameras on breeding success should be carefully monitored when they are used in a new study system.

scholarly journals Social Influence and Uptake of Couples HIV Testing and Counselling in KwaZulu-Natal, South Africa

2021 ◽  
Author(s):  
Matthew J. Johnson ◽  
Lynae A. Darbes ◽  
Victoria Hosegood ◽  
Mallory O. Johnson ◽  
Katherine Fritz ◽  
...  
Keyword(s):  
Hiv Testing ◽  
Peer Support ◽  
Social Influences ◽  
Controlled Trial ◽  
Secondary Analysis ◽  
Sub Saharan Africa ◽  
Survival Models ◽  
Hiv Testing And Counselling ◽  
Randomised Controlled ◽  
Support Score

AbstractSocial influences may create a barrier to couples HIV testing and counselling (CHTC) uptake in sub-Saharan Africa. This secondary analysis of data collected in the ‘Uthando Lwethu’ randomised controlled trial used discrete-time survival models to evaluate the association between within-couple average ‘peer support’ score and uptake of CHTC by the end of nine months’ follow-up. Peer support was conceptualised by self-rated strength of agreement with two statements describing friendships outside of the primary partnership. Eighty-eight couples (26.9%) took up CHTC. Results tended towards a dichotomous trend in models adjusted only for trial arm, with uptake significantly less likely amongst couples in the higher of four peer support score categories (OR 0.34, 95% CI 0.18, 0.68 [7–10 points]; OR 0.53, 95% CI 0.28, 0.99 [≥ 11 points]). A similar trend remained in the final multivariable model, but was no longer significant (AOR 0.59, 95% CI 0.25, 1.42 [7–10 points]; AOR 0.88, 95% CI 0.36, 2.10 [≥ 11 points]). Accounting for social influences in the design of couples-focused interventions may increase their success.

Neighborhood Context and Juvenile Recidivism: A Spatial Analysis of Organizations and Reoffending Risk

2021 ◽  
pp. 001112872199933
Author(s):  
Kendra Thompson-Dyck
Keyword(s):  
Juvenile Offenders ◽  
Spatial Data ◽  
Neighborhood Disadvantage ◽  
Neighborhood Context ◽  
Survival Models ◽  
Juvenile Recidivism ◽  
Residential Proximity ◽  
Detention Centers ◽  
Point Level

Leveraging point-level spatial data from the Phoenix area, we consider the role of nearby organizations as contextual factors that amplify or reduce reoffending risk among juvenile offenders after court completion. Using survival models, we examine whether residential proximity to seven types of organizations impacts risk of recidivism, net of neighborhood disadvantage and offender characteristics. Aggregate neighborhood disadvantage was not associated with reoffending risk and organizational findings were mixed. Low-level offenders with more total organizations nearby had a higher risk of new property offenses, while the risk of drug and violent reoffending nearly doubled for diversion youth residing near police facilities or detention centers. Individual demographics and prior offense histories remained the strongest, most consistent predictors of juvenile recidivism.

scholarly journals Ewe Wastage in New Zealand Commercial Flocks: Extent, Timing, Association with Hogget Reproductive Outcomes and BCS

Animals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 779
Author(s):  
Kate J. Flay ◽  
Anne L. Ridler ◽  
Chris W. R. Compton ◽  
Paul R. Kenyon
Keyword(s):  
New Zealand ◽  
Key Management ◽  
Body Condition Score ◽  
Survival Models ◽  
Reproductive Outcomes ◽  
Increase Risk ◽  
Interval Censored ◽  
Mortality Incidence ◽  
Condition Score ◽  
On Farm

Ewe wastage is the combination of on-farm mortality and premature culling. Internationally, there is limited research on actual wastage incidence and causes in commercial sheep flocks. To the authors’ knowledge, this is the first study that reports both lifetime wastage and detailed annual wastage in a sample of commercial New Zealand flocks. This study utilized data collected from 13,142 ewes from four cohorts on three commercial New Zealand farms (Farm A 2010-born, Farm A 2011-born, Farm B, Farm C), during the period 2011–2017, as they aged from replacement hoggets to 6-year-old ewes (Farm A and Farm B) or 3-year-old ewes (Farm C). Data collection visits occurred at three or four key management times each year, namely pre-mating, pregnancy diagnosis, pre-lambing and weaning. At each visit, body condition score (BCS) was assessed and any ewes that were culled or had died on farm were recorded. As this was a lifetime study, each ewe was assigned an outcome and corresponding ‘exit age’. By the end of the study, all ewes that had exited their respective flocks, were classified as either prematurely culled, or dead/missing, or if still in the flock, as censored, and either the exact date or interval in which they exited the flock was recorded. Semi-parametric competing risk (premature culling vs. dead/missing), interval-censored survival models were developed to: 1. describe the association between hogget reproductive outcomes and risk of subsequent wastage, and 2. assess pre-mating BCS as a predictor of wastage in that production year. Of the 13,142 enrolled ewes, 50.4% exited their respective flocks due to premature culling and 40.0% due to on-farm dead/missing, giving a total of 90.4% that exited due to wastage. Annual mortality incidence ranged from 3.5 to 40.2%. As a hogget, wastage incidence ranged from 7.6 to 45.4%. Pregnancy or rearing a lamb as a hogget did not increase risk of subsequent wastage. In all years, pre-mating BCS was a predictor of ewe wastage, with odds of wastage lower with increasing BCS. Therefore, farmers should focus on improving pre-mating BCS to 3.5/5.0 by assessing ewe BCS at weaning, allowing poorer-BCS ewes to be managed to gain BCS before re-breeding.

scholarly journals A Repeated Time-to-Positive Symptoms Improvement among Malaysian Patients with Schizophrenia Spectrum Disorders Treated with Clozapine

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1121
Author(s):  
Orwa Albitar ◽  
Sabariah Noor Harun ◽  
Siti Nor Aizah Ahmad ◽  
Siti Maisharah Sheikh Ghadzi
Keyword(s):  
Visual Predictive Check ◽  
Clinical Importance ◽  
Antipsychotic Agent ◽  
Survival Models ◽  
Psychiatric Clinic ◽  
Positive Symptoms ◽  
Schizophrenia Spectrum Disorders ◽  
Mixed Effect ◽  
Essential Information ◽  
Schizophrenia Spectrum

Clozapine remains the drug of choice for resistant schizophrenia. However, its dose-response relationship is still controversial. The current investigation aimed to develop a repeated time-to-positive symptoms improvement following the onset of clozapine treatment in Malaysian schizophrenia spectrum disorder patients. Data from patients’ medical records in the Psychiatric Clinic, Penang General Hospital, were retrospectively analyzed. Several parametric survival models were evaluated using nonlinear mixed-effect modeling software (NONMEM 7.3.0). Kaplan–Meier-visual predictive check (KM-VPC) and sampling-importance resampling (SIR) methods were used to validate the final model. A total of 116 patients were included in the study, with a mean follow-up of 306 weeks. Weibull hazard function best fitted the data. The hazard of positive symptoms improvement decreased 4% for every one-year increase in age over the median of 41 years (adjusted hazard ratio (aHR), 0.96; 95% confidence intervals (95% CI), (0.93–0.98)). However, patients receiving a second atypical antipsychotic agent had four-folds higher hazard (aHR, 4.01; 95% CI, (1.97–7.17)). The hazard increased 2% (aHR, 1.02; 95% CI, (1.01–1.03)) for every 1 g increase in the clozapine six months cumulative dose over the median of 34 g. The developed model provides essential information on the hazard of positive symptoms improvement after the first clozapine dose administration, including modifiable predictors of high clinical importance.

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