Consider a nonstandard continuous-time bidimensional risk model with constant force of interest,in which the two classes of claims with subexponential distributions satisfy a general dependence structure and each pair...Consider a nonstandard continuous-time bidimensional risk model with constant force of interest,in which the two classes of claims with subexponential distributions satisfy a general dependence structure and each pair of the claim-inter-arrival times is arbitrarily dependent.Under some mild conditions,we achieve a locally uniform approximation of the finite-time ruin probability for all time horizon within a finite interval.If we further assume that each pair of the claim-inter-arrival times is negative quadrant dependent and the two classes of claims are consistently-varying-tailed,it shows that the above obtained approximation is also globally uniform for all time horizon within an infinite interval.展开更多
BACKGROUND Oesophageal cancer is a frequently observed and lethal malignancy worldwide.Surgical resection remains a realistic option for curative intent in the early stages of the disease.However,the decision to under...BACKGROUND Oesophageal cancer is a frequently observed and lethal malignancy worldwide.Surgical resection remains a realistic option for curative intent in the early stages of the disease.However,the decision to undertake oesophagectomy is significant as it exposes the patient to a substantial risk of morbidity and mortality.Therefore,appropriate patient selection,counselling and resource allocation is important.Many tools have been developed to aid surgeons in appropriate decision-making.AIM To examine all multivariate risk models that use preoperative and intraoperative information and establish which have the most clinical utility.METHODS A systematic review of the MEDLINE,EMBASE and Cochrane databases was conducted from 2000-2020.The search terms applied were((Oesophagectomy)AND(Risk OR predict OR model OR score)AND(Outcomes OR complications OR morbidity OR mortality OR length of stay OR anastomotic leak)).The applied inclusion criteria were articles assessing multivariate based tools using exclusively preoperatively available data to predict perioperative patient outcomes following oesophagectomy.The exclusion criteria were publications that described models requiring intra-operative or post-operative data and articles appraising only univariate predictors such as American Society of Anesthesiologists score,cardiopulmonary fitness or pre-operative sarcopenia.Articles that exclusively assessed distant outcomes such as long-term survival were excluded as were publications using cohorts mixed with other surgical procedures.The articles generated from each search were collated,processed and then reported in accordance with PRISMA guidelines.All risk models were appraised for clinical credibility,methodological quality,performance,validation,and clinical effectiveness.RESULTS The initial search of composite databases yielded 8715 articles which reduced to 5827 following the deduplication process.After title and abstract screening,197 potentially relevant texts were retrieved for detailed review.Twenty-seven published studies were ultimately included which examined twenty-one multivariate risk models utilising exclusively preoperative data.Most models examined were clinically credible and were constructed with sound methodological quality,but model performance was often insufficient to prognosticate patient outcomes.Three risk models were identified as being promising in predicting perioperative mortality,including the National Quality Improvement Project surgical risk calculator,revised STS score and the Takeuchi model.Two studies predicted perioperative major morbidity,including the predicting postoperative complications score and prognostic nutritional index-multivariate models.Many of these models require external validation and demonstration of clinical effectiveness.CONCLUSION Whilst there are several promising models in predicting perioperative oesophagectomy outcomes,more research is needed to confirm their validity and demonstrate improved clinical outcomes with the adoption of these models.展开更多
BACKGROUND Oesophageal cancer is the eighth most common malignancy worldwide and is associated with a poor prognosis.Oesophagectomy remains the best prospect for a cure if diagnosed in the early disease stages.However...BACKGROUND Oesophageal cancer is the eighth most common malignancy worldwide and is associated with a poor prognosis.Oesophagectomy remains the best prospect for a cure if diagnosed in the early disease stages.However,the procedure is associated with significant morbidity and mortality and is undertaken only after careful consideration.Appropriate patient selection,counselling and resource allocation is essential.Numerous risk models have been devised to guide surgeons in making these decisions.AIM To evaluate which multivariate risk models,using intraoperative information with or without preoperative information,best predict perioperative oesophagectomy outcomes.METHODS A systematic review of the MEDLINE,EMBASE and Cochrane databases was undertaken from 2000-2020.The search terms used were[(Oesophagectomy)AND(Model OR Predict OR Risk OR score)AND(Mortality OR morbidity OR complications OR outcomes OR anastomotic leak OR length of stay)].Articles were included if they assessed multivariate based tools incorporating preoperative and intraoperative variables to forecast patient outcomes after oesophagectomy.Articles were excluded if they only required preoperative or any post-operative data.Studies appraising univariate risk predictors such as preoperative sarcopenia,cardiopulmonary fitness and American Society of Anesthesiologists score were also excluded.The review was conducted following the preferred reporting items for systematic reviews and meta-analyses model.All captured risk models were appraised for clinical credibility,methodological quality,performance,validation and clinical effectiveness.RESULTS Twenty published studies were identified which examined eleven multivariate risk models.Eight of these combined preoperative and intraoperative data and the remaining three used only intraoperative values.Only two risk models were identified as promising in predicting mortality,namely the Portsmouth physiological and operative severity score for the enumeration of mortality and morbidity(POSSUM)and POSSUM scores.A further two studies,the intraoperative factors and Esophagectomy surgical Apgar score based nomograms,adequately forecasted major morbidity.The latter two models are yet to have external validation and none have been tested for clinical effectiveness.CONCLUSION Despite the presence of some promising models in forecasting perioperative oesophagectomy outcomes,there is more research required to externally validate these models and demonstrate clinical benefit with the adoption of these models guiding postoperative care and allocating resources.展开更多
BACKGROUND Colorectal cancer(CRC)is a significant global health issue,and lymph node metastasis(LNM)is a crucial prognostic factor.Accurate prediction of LNM is essential for developing individualized treatment strate...BACKGROUND Colorectal cancer(CRC)is a significant global health issue,and lymph node metastasis(LNM)is a crucial prognostic factor.Accurate prediction of LNM is essential for developing individualized treatment strategies for patients with CRC.However,the prediction of LNM is challenging and depends on various factors such as tumor histology,clinicopathological features,and molecular characteristics.The most reliable method to detect LNM is the histopathological examination of surgically resected specimens;however,this method is invasive,time-consuming,and subject to sampling errors and interobserver variability.AIM To analyze influencing factors and develop and validate a risk prediction model for LNM in CRC based on a large patient queue.METHODS This study retrospectively analyzed 300 patients who underwent CRC surgery at two Peking University Shenzhen hospitals between January and December 2021.A deep learning approach was used to extract features potentially associated with LNM from primary tumor histological images while a logistic regression model was employed to predict LNM in CRC using machine-learning-derived features and clinicopathological variables as predictors.RESULTS The prediction model constructed for LNM in CRC was based on a logistic regression framework that incorporated machine learning-extracted features and clinicopathological variables.The model achieved high accuracy(0.86),sensitivity(0.81),specificity(0.87),positive predictive value(0.66),negative predictive value(0.94),area under the curve for the receiver operating characteristic(0.91),and a low Brier score(0.10).The model showed good agreement between the observed and predicted probabilities of LNM across a range of risk thresholds,indicating good calibration and clinical utility.CONCLUSION The present study successfully developed and validated a potent and effective risk-prediction model for LNM in patients with CRC.This model utilizes machine-learning-derived features extracted from primary tumor histology and clinicopathological variables,demonstrating superior performance and clinical applicability compared to existing models.The study provides new insights into the potential of deep learning to extract valuable information from tumor histology,in turn,improving the prediction of LNM in CRC and facilitate risk stratification and decision-making in clinical practice.展开更多
Objective: To investigate the main risk factors of peripherally inserted central catheter(PICC) related upper extremity deep venous thrombosis and establish the risk predictive model of PICC-related upper extremity de...Objective: To investigate the main risk factors of peripherally inserted central catheter(PICC) related upper extremity deep venous thrombosis and establish the risk predictive model of PICC-related upper extremity deep venous thrombosis.Methods: Patients with PICC who were hospitalized between January 2014 and July 2015 were studied retrospectively; they were divided into a thrombosis group(n ? 52), with patients who had a venous thrombosis complication after PICC, and a no-thrombosis group(n ? 144), with patients without venous thrombosis. To compare between the two groups, significantly different variables were selected to perform multivariate logistic regression to establish the risk-predictive model.Results: The PICC catheter history, catheter tip position, and diameter of blood vessel were the key factors for thrombosis. The logistic regression predictive model was as follows: Y ? 3.338 t 2.040 PICC catheter history t1.964 catheter tip position 1.572 diameter of vessel. The area under the receiver operating characteristic curve for the model was 0.872, 95%CI(0.817e0.927). The cut-off point was 0.801,the sensitivity of the model was 0.832, and the specificity was 0.745.Conclusions: The PICC catheterization history, catheter tip position, the diameter of blood vessel were the key factors for thrombosis. The logistic regression risk model based on these factors is reliable for predicting PICC-related upper extremity deep venous thrombosis.展开更多
Objectives: To identify independent risk factors for abdominal wound dehiscence and develop a risk model to recognize high risk patients. Methods: The samples studied were patients who underwent midline laparotomy in ...Objectives: To identify independent risk factors for abdominal wound dehiscence and develop a risk model to recognize high risk patients. Methods: The samples studied were patients who underwent midline laparotomy in the department of surgery, SMHS Hospital Srinagar from March 2009 to April 2015. For each case of abdominal wound dehiscence, three controls were selected from a group of patients who had undergone open abdominal surgery as close as possible in time. Preoperative, perioperative, and postoperative variables and in-hospital mortality were studied for all patients. Cases were compared with controls using the chi-square test or the Mann-Whitney U-test for categorical or continuous data, respectively. Subsequently, multivariate stepwise logistic regression with backwards elimination test used to identify main independent risk factors of abdominal wound dehiscence. The resulting regression coefficients for the major risk factors were used as weights for these variables to calculate a risk score for abdominal wound dehiscence. Results: 140 cases of abdominal wound dehiscence were reported and compared with 420 selected controls. All variables that were significant in univariate analyses were entered in a multivariate stepwise logistic regression to determine which variables were significant independent risk factors. Major independent risk factors were male gender, chronic pulmonary disease, corticosteroid use, smoking, obesity, anemia, jaundice, ascites, and sepsis, type of surgery, postoperative coughing, and wound infection. Based on these findings, a risk model was developed. Conclusions: The model can give an estimate of the risk of abdominal wound dehiscence for individual patients. High-risk patients may be planned preventive wound closing with reinforcements as mesh.展开更多
In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compo...In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compound poisson risk model ,we respectively get its survival probability in finite time period in case of exponential claim amounts.展开更多
This article considers a Markov-dependent risk model with a constant dividend barrier.A system of integro-differential equations with boundary conditions satisfied by the expected discounted penalty function,with give...This article considers a Markov-dependent risk model with a constant dividend barrier.A system of integro-differential equations with boundary conditions satisfied by the expected discounted penalty function,with given initial environment state,is derived and solved.Explicit formulas for the discounted penalty function are obtained when the initial surplus is zero or when all the claim amount distributions are from rational family.In two state model,numerical illustrations with exponential claim amounts are given.展开更多
In the present paper,we consider a kind of semi-Markov risk model(SMRM) with constant interest force and heavy-tailed claims,in which the claim rates and sizes are conditionally independent,both fluctuating according ...In the present paper,we consider a kind of semi-Markov risk model(SMRM) with constant interest force and heavy-tailed claims,in which the claim rates and sizes are conditionally independent,both fluctuating according to the state of the risk business.First,we derive a matrix integro-diferential equation satisfied by the survival probabilities.Second,we analyze the asymptotic behaviors of ruin probabilities in a two-state SMRM with special claim amounts.It is shown that the asymptotic behaviors of ruin probabilities depend only on the state 2 with heavy-tailed claim amounts,not on the state 1 with exponential claim sizes.展开更多
We consider a continuous time risk model based on a two state Markov process, in which after an exponentially distributed time, the claim frequency changes to a different level and can change back again in the same wa...We consider a continuous time risk model based on a two state Markov process, in which after an exponentially distributed time, the claim frequency changes to a different level and can change back again in the same way. We derive the Laplace transform for the first passage time to surplus zero from a given negative surplus and for the duration of negative surplus. Closed-form expressions are given in the case of exponential individual claim. Finally, numerical results are provided to show how to estimate the moments of duration of negative surplus.展开更多
AIM To investigate the incidence and the determinants of cardiovascular morbidity in Greek renal transplant recipients(RTRs) expressed as major advance cardiac event(MACE) rate. METHODS Two hundred and forty-two adult...AIM To investigate the incidence and the determinants of cardiovascular morbidity in Greek renal transplant recipients(RTRs) expressed as major advance cardiac event(MACE) rate. METHODS Two hundred and forty-two adult patients with a functioning graft for at least three months and availabledata that were followed up on the August 31, 2015 at two transplant centers of Western Greece were included in this study. Baseline recipients' data elements included demographics, clinical characteristics, history of comorbid conditions and laboratory parameters. Follow-up data regarding MACE occurrence were collected retrospectively from the patients' records and MACE risk score was calculated for each patient. RESULTS The mean age was 53 years(63.6% males) and 47 patients(19.4%) had a pre-existing cardiovascular disease(CVD) before transplantation. The mean estimated glomerular filtration rate was 52 ± 17 mL /min per 1.73 m2. During follow-up 36 patients(14.9%) suffered a MACE with a median time to MACE 5 years(interquartile range: 2.2-10 years). Recipients with a MACE compared to recipients without a MACE had a significantly higher mean age(59 years vs 52 years, P < 0.001) and a higher prevalence of pre-existing CVD(44.4% vs 15%, P < 0.001). The 7-year predicted mean risk for MACE was 14.6% ± 12.5% overall. In RTRs who experienced a MACE, the predicted risk was 22.3% ± 17.1% and was significantly higher than in RTRs without an event 13.3% ± 11.1%(P = 0.003). The discrimination ability of the model in the Greek database of RTRs was good with an area under the receiver operating characteristics curve of 0.68(95%CI: 0.58-0.78).CONCLUSION In this Greek cohort of RTRs, MACE occurred in 14.9% of the patients, pre-existing CVD was the main risk factor, while MACE risk model was proved a dependable utility in predicting CVD post RT.展开更多
Let R(t)=u+ct-sum from(i=1) to (N(t)) Xi,t≥0 be the renewal risk model,with FX ( x )being the distribution function of the claim amount X. Let ψ (u ) be the ruin probability with initial surplus u. Under the conditi...Let R(t)=u+ct-sum from(i=1) to (N(t)) Xi,t≥0 be the renewal risk model,with FX ( x )being the distribution function of the claim amount X. Let ψ (u ) be the ruin probability with initial surplus u. Under the condition of FX (x) ∈ S *(γ ),γ≥ 0,by the geometric sum method,we derive the local asymptotic behavior for ψ (u ,u + z for every 0＜z＜∞. On one hand,the asymptotic behavior of ψ ( u) can be derived from the result obtained. On the other hand,the result of this paper can be applied to the insurance risk management of an insurance company.展开更多
In this paper, we consider a compound Poisson risk model with taxes paid according to a loss-carry-forward system and dividends paid under a threshold strategy. First, the closed-form expression of the probability fun...In this paper, we consider a compound Poisson risk model with taxes paid according to a loss-carry-forward system and dividends paid under a threshold strategy. First, the closed-form expression of the probability function for the total number of taxation periods over the lifetime of the surplus process is derived. Second, analytical expression of the expected accumulated discounted dividends paid between two consecutive taxation periods is provided. In addition, explicit expressions are also given for the exponential individual claims.展开更多
Consider a multidimensional renewal risk model, in which the claim sizes {X_k, k ≥1} form a sequence of independent and identically distributed random vectors with nonnegative components that are allowed to be depend...Consider a multidimensional renewal risk model, in which the claim sizes {X_k, k ≥1} form a sequence of independent and identically distributed random vectors with nonnegative components that are allowed to be dependent on each other. The univariate marginal distributions of these vectors have consistently varying tails and finite means. Suppose that the claim sizes and inter-arrival times correspondingly form a sequence of independent and identically distributed random pairs, with each pair obeying a dependence structure. A precise large deviation for the multidimensional renewal risk model is obtained.展开更多
This paper considers the one-and two-dimensional risk models with a non-stationary claim-number process.Under the assumption that the claim-number process satisfies the large deviations principle,the uniform asymptoti...This paper considers the one-and two-dimensional risk models with a non-stationary claim-number process.Under the assumption that the claim-number process satisfies the large deviations principle,the uniform asymptotics for the finite-time ruin probability of a one-dimensional risk model are obtained for the strongly subexponential claim sizes.Further,as an application of the result of onedimensional risk model,we derive the uniform asymptotics for a kind of finite-time ruin probability in a two dimensional risk model sharing a common claim-number process which satisfies the large deviations principle.展开更多
In this paper,a new risk model is studied in which the rate of premium income is regarded as a random variable,the arrival of insurance policies is a Poisson process and the process of claim occurring is p-thinning pr...In this paper,a new risk model is studied in which the rate of premium income is regarded as a random variable,the arrival of insurance policies is a Poisson process and the process of claim occurring is p-thinning process.The integral representations of the survival probability are gotten.The explicit formula of the survival probability on the infinite interval is obtained in the special case-exponential distribution.The Lundberg inequality and the common formula of the ruin probability are gotten in terms of some techniques from martingale theory.展开更多
In this note we study the optimal dividend problem for a company whose surplus process, in the absence of dividend payments, evolves as a generalized compound Poisson model in which the counting process is a generaliz...In this note we study the optimal dividend problem for a company whose surplus process, in the absence of dividend payments, evolves as a generalized compound Poisson model in which the counting process is a generalized Poisson process. This model includes the classical risk model and the Pólya-Aeppli risk model as special cases. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. We show that under some conditions the optimal dividend strategy is formed by a barrier strategy. Moreover, two conjectures are proposed.展开更多
基金Supported by the Natural Science Foundation of China(12071487,11671404)the Natural Science Foundation of Anhui Province(2208085MA06)+1 种基金the Provincial Natural Science Research Project of Anhui Colleges(KJ2021A0049,KJ2021A0060)Hunan Provincial Innovation Foundation for Postgraduate(CX20200146)。
文摘Consider a nonstandard continuous-time bidimensional risk model with constant force of interest,in which the two classes of claims with subexponential distributions satisfy a general dependence structure and each pair of the claim-inter-arrival times is arbitrarily dependent.Under some mild conditions,we achieve a locally uniform approximation of the finite-time ruin probability for all time horizon within a finite interval.If we further assume that each pair of the claim-inter-arrival times is negative quadrant dependent and the two classes of claims are consistently-varying-tailed,it shows that the above obtained approximation is also globally uniform for all time horizon within an infinite interval.
文摘BACKGROUND Oesophageal cancer is a frequently observed and lethal malignancy worldwide.Surgical resection remains a realistic option for curative intent in the early stages of the disease.However,the decision to undertake oesophagectomy is significant as it exposes the patient to a substantial risk of morbidity and mortality.Therefore,appropriate patient selection,counselling and resource allocation is important.Many tools have been developed to aid surgeons in appropriate decision-making.AIM To examine all multivariate risk models that use preoperative and intraoperative information and establish which have the most clinical utility.METHODS A systematic review of the MEDLINE,EMBASE and Cochrane databases was conducted from 2000-2020.The search terms applied were((Oesophagectomy)AND(Risk OR predict OR model OR score)AND(Outcomes OR complications OR morbidity OR mortality OR length of stay OR anastomotic leak)).The applied inclusion criteria were articles assessing multivariate based tools using exclusively preoperatively available data to predict perioperative patient outcomes following oesophagectomy.The exclusion criteria were publications that described models requiring intra-operative or post-operative data and articles appraising only univariate predictors such as American Society of Anesthesiologists score,cardiopulmonary fitness or pre-operative sarcopenia.Articles that exclusively assessed distant outcomes such as long-term survival were excluded as were publications using cohorts mixed with other surgical procedures.The articles generated from each search were collated,processed and then reported in accordance with PRISMA guidelines.All risk models were appraised for clinical credibility,methodological quality,performance,validation,and clinical effectiveness.RESULTS The initial search of composite databases yielded 8715 articles which reduced to 5827 following the deduplication process.After title and abstract screening,197 potentially relevant texts were retrieved for detailed review.Twenty-seven published studies were ultimately included which examined twenty-one multivariate risk models utilising exclusively preoperative data.Most models examined were clinically credible and were constructed with sound methodological quality,but model performance was often insufficient to prognosticate patient outcomes.Three risk models were identified as being promising in predicting perioperative mortality,including the National Quality Improvement Project surgical risk calculator,revised STS score and the Takeuchi model.Two studies predicted perioperative major morbidity,including the predicting postoperative complications score and prognostic nutritional index-multivariate models.Many of these models require external validation and demonstration of clinical effectiveness.CONCLUSION Whilst there are several promising models in predicting perioperative oesophagectomy outcomes,more research is needed to confirm their validity and demonstrate improved clinical outcomes with the adoption of these models.
文摘BACKGROUND Oesophageal cancer is the eighth most common malignancy worldwide and is associated with a poor prognosis.Oesophagectomy remains the best prospect for a cure if diagnosed in the early disease stages.However,the procedure is associated with significant morbidity and mortality and is undertaken only after careful consideration.Appropriate patient selection,counselling and resource allocation is essential.Numerous risk models have been devised to guide surgeons in making these decisions.AIM To evaluate which multivariate risk models,using intraoperative information with or without preoperative information,best predict perioperative oesophagectomy outcomes.METHODS A systematic review of the MEDLINE,EMBASE and Cochrane databases was undertaken from 2000-2020.The search terms used were[(Oesophagectomy)AND(Model OR Predict OR Risk OR score)AND(Mortality OR morbidity OR complications OR outcomes OR anastomotic leak OR length of stay)].Articles were included if they assessed multivariate based tools incorporating preoperative and intraoperative variables to forecast patient outcomes after oesophagectomy.Articles were excluded if they only required preoperative or any post-operative data.Studies appraising univariate risk predictors such as preoperative sarcopenia,cardiopulmonary fitness and American Society of Anesthesiologists score were also excluded.The review was conducted following the preferred reporting items for systematic reviews and meta-analyses model.All captured risk models were appraised for clinical credibility,methodological quality,performance,validation and clinical effectiveness.RESULTS Twenty published studies were identified which examined eleven multivariate risk models.Eight of these combined preoperative and intraoperative data and the remaining three used only intraoperative values.Only two risk models were identified as promising in predicting mortality,namely the Portsmouth physiological and operative severity score for the enumeration of mortality and morbidity(POSSUM)and POSSUM scores.A further two studies,the intraoperative factors and Esophagectomy surgical Apgar score based nomograms,adequately forecasted major morbidity.The latter two models are yet to have external validation and none have been tested for clinical effectiveness.CONCLUSION Despite the presence of some promising models in forecasting perioperative oesophagectomy outcomes,there is more research required to externally validate these models and demonstrate clinical benefit with the adoption of these models guiding postoperative care and allocating resources.
文摘BACKGROUND Colorectal cancer(CRC)is a significant global health issue,and lymph node metastasis(LNM)is a crucial prognostic factor.Accurate prediction of LNM is essential for developing individualized treatment strategies for patients with CRC.However,the prediction of LNM is challenging and depends on various factors such as tumor histology,clinicopathological features,and molecular characteristics.The most reliable method to detect LNM is the histopathological examination of surgically resected specimens;however,this method is invasive,time-consuming,and subject to sampling errors and interobserver variability.AIM To analyze influencing factors and develop and validate a risk prediction model for LNM in CRC based on a large patient queue.METHODS This study retrospectively analyzed 300 patients who underwent CRC surgery at two Peking University Shenzhen hospitals between January and December 2021.A deep learning approach was used to extract features potentially associated with LNM from primary tumor histological images while a logistic regression model was employed to predict LNM in CRC using machine-learning-derived features and clinicopathological variables as predictors.RESULTS The prediction model constructed for LNM in CRC was based on a logistic regression framework that incorporated machine learning-extracted features and clinicopathological variables.The model achieved high accuracy(0.86),sensitivity(0.81),specificity(0.87),positive predictive value(0.66),negative predictive value(0.94),area under the curve for the receiver operating characteristic(0.91),and a low Brier score(0.10).The model showed good agreement between the observed and predicted probabilities of LNM across a range of risk thresholds,indicating good calibration and clinical utility.CONCLUSION The present study successfully developed and validated a potent and effective risk-prediction model for LNM in patients with CRC.This model utilizes machine-learning-derived features extracted from primary tumor histology and clinicopathological variables,demonstrating superior performance and clinical applicability compared to existing models.The study provides new insights into the potential of deep learning to extract valuable information from tumor histology,in turn,improving the prediction of LNM in CRC and facilitate risk stratification and decision-making in clinical practice.
文摘Objective: To investigate the main risk factors of peripherally inserted central catheter(PICC) related upper extremity deep venous thrombosis and establish the risk predictive model of PICC-related upper extremity deep venous thrombosis.Methods: Patients with PICC who were hospitalized between January 2014 and July 2015 were studied retrospectively; they were divided into a thrombosis group(n ? 52), with patients who had a venous thrombosis complication after PICC, and a no-thrombosis group(n ? 144), with patients without venous thrombosis. To compare between the two groups, significantly different variables were selected to perform multivariate logistic regression to establish the risk-predictive model.Results: The PICC catheter history, catheter tip position, and diameter of blood vessel were the key factors for thrombosis. The logistic regression predictive model was as follows: Y ? 3.338 t 2.040 PICC catheter history t1.964 catheter tip position 1.572 diameter of vessel. The area under the receiver operating characteristic curve for the model was 0.872, 95%CI(0.817e0.927). The cut-off point was 0.801,the sensitivity of the model was 0.832, and the specificity was 0.745.Conclusions: The PICC catheterization history, catheter tip position, the diameter of blood vessel were the key factors for thrombosis. The logistic regression risk model based on these factors is reliable for predicting PICC-related upper extremity deep venous thrombosis.
文摘Objectives: To identify independent risk factors for abdominal wound dehiscence and develop a risk model to recognize high risk patients. Methods: The samples studied were patients who underwent midline laparotomy in the department of surgery, SMHS Hospital Srinagar from March 2009 to April 2015. For each case of abdominal wound dehiscence, three controls were selected from a group of patients who had undergone open abdominal surgery as close as possible in time. Preoperative, perioperative, and postoperative variables and in-hospital mortality were studied for all patients. Cases were compared with controls using the chi-square test or the Mann-Whitney U-test for categorical or continuous data, respectively. Subsequently, multivariate stepwise logistic regression with backwards elimination test used to identify main independent risk factors of abdominal wound dehiscence. The resulting regression coefficients for the major risk factors were used as weights for these variables to calculate a risk score for abdominal wound dehiscence. Results: 140 cases of abdominal wound dehiscence were reported and compared with 420 selected controls. All variables that were significant in univariate analyses were entered in a multivariate stepwise logistic regression to determine which variables were significant independent risk factors. Major independent risk factors were male gender, chronic pulmonary disease, corticosteroid use, smoking, obesity, anemia, jaundice, ascites, and sepsis, type of surgery, postoperative coughing, and wound infection. Based on these findings, a risk model was developed. Conclusions: The model can give an estimate of the risk of abdominal wound dehiscence for individual patients. High-risk patients may be planned preventive wound closing with reinforcements as mesh.
基金Supported by the Natural Science Foundation of China(10071019)
文摘In this paper we generalize the aggregated premium income process from a constant rate process to a poisson process for the classical compound Poinsson risk model,then for the generalized model and the classical compound poisson risk model ,we respectively get its survival probability in finite time period in case of exponential claim amounts.
基金supported in part by Hubei Normal University Post-graduate Foundation(2007D59 and 2007D60)the Science and Technology foundation of Hubei(D20092207)the National Natural Science Foundation of China(10671149)
文摘This article considers a Markov-dependent risk model with a constant dividend barrier.A system of integro-differential equations with boundary conditions satisfied by the expected discounted penalty function,with given initial environment state,is derived and solved.Explicit formulas for the discounted penalty function are obtained when the initial surplus is zero or when all the claim amount distributions are from rational family.In two state model,numerical illustrations with exponential claim amounts are given.
基金supported by the National Natural Science Foundation of China(11101451)Ph.D.Programs Foundation of Ministry of Education of China(20110191110033)
文摘In the present paper,we consider a kind of semi-Markov risk model(SMRM) with constant interest force and heavy-tailed claims,in which the claim rates and sizes are conditionally independent,both fluctuating according to the state of the risk business.First,we derive a matrix integro-diferential equation satisfied by the survival probabilities.Second,we analyze the asymptotic behaviors of ruin probabilities in a two-state SMRM with special claim amounts.It is shown that the asymptotic behaviors of ruin probabilities depend only on the state 2 with heavy-tailed claim amounts,not on the state 1 with exponential claim sizes.
基金Supported in part by the National Natural Science Foundation of China and the Ministry of Education of China
文摘We consider a continuous time risk model based on a two state Markov process, in which after an exponentially distributed time, the claim frequency changes to a different level and can change back again in the same way. We derive the Laplace transform for the first passage time to surplus zero from a given negative surplus and for the duration of negative surplus. Closed-form expressions are given in the case of exponential individual claim. Finally, numerical results are provided to show how to estimate the moments of duration of negative surplus.
文摘AIM To investigate the incidence and the determinants of cardiovascular morbidity in Greek renal transplant recipients(RTRs) expressed as major advance cardiac event(MACE) rate. METHODS Two hundred and forty-two adult patients with a functioning graft for at least three months and availabledata that were followed up on the August 31, 2015 at two transplant centers of Western Greece were included in this study. Baseline recipients' data elements included demographics, clinical characteristics, history of comorbid conditions and laboratory parameters. Follow-up data regarding MACE occurrence were collected retrospectively from the patients' records and MACE risk score was calculated for each patient. RESULTS The mean age was 53 years(63.6% males) and 47 patients(19.4%) had a pre-existing cardiovascular disease(CVD) before transplantation. The mean estimated glomerular filtration rate was 52 ± 17 mL /min per 1.73 m2. During follow-up 36 patients(14.9%) suffered a MACE with a median time to MACE 5 years(interquartile range: 2.2-10 years). Recipients with a MACE compared to recipients without a MACE had a significantly higher mean age(59 years vs 52 years, P < 0.001) and a higher prevalence of pre-existing CVD(44.4% vs 15%, P < 0.001). The 7-year predicted mean risk for MACE was 14.6% ± 12.5% overall. In RTRs who experienced a MACE, the predicted risk was 22.3% ± 17.1% and was significantly higher than in RTRs without an event 13.3% ± 11.1%(P = 0.003). The discrimination ability of the model in the Greek database of RTRs was good with an area under the receiver operating characteristics curve of 0.68(95%CI: 0.58-0.78).CONCLUSION In this Greek cohort of RTRs, MACE occurred in 14.9% of the patients, pre-existing CVD was the main risk factor, while MACE risk model was proved a dependable utility in predicting CVD post RT.
基金Supported by the National Natural Science Foundation of China (70273029)
文摘Let R(t)=u+ct-sum from(i=1) to (N(t)) Xi,t≥0 be the renewal risk model,with FX ( x )being the distribution function of the claim amount X. Let ψ (u ) be the ruin probability with initial surplus u. Under the condition of FX (x) ∈ S *(γ ),γ≥ 0,by the geometric sum method,we derive the local asymptotic behavior for ψ (u ,u + z for every 0＜z＜∞. On one hand,the asymptotic behavior of ψ ( u) can be derived from the result obtained. On the other hand,the result of this paper can be applied to the insurance risk management of an insurance company.
基金Supported in part by the National Natural Science Foundation of China, the Guangdong Natural Science Foundation (S2011010004511)the Fundamental Research Funds for the Central Universities of China (201120102020005)
文摘In this paper, we consider a compound Poisson risk model with taxes paid according to a loss-carry-forward system and dividends paid under a threshold strategy. First, the closed-form expression of the probability function for the total number of taxation periods over the lifetime of the surplus process is derived. Second, analytical expression of the expected accumulated discounted dividends paid between two consecutive taxation periods is provided. In addition, explicit expressions are also given for the exponential individual claims.
基金Supported by the National Natural Science Foundation of China(Nos.11571058&11301481)Humanities and Social Science Foundation of the Ministry of Education of China(No.17YJC910007)+1 种基金Zhejiang Provincial Natural Science Foundation of China(No.LY17A010004)Fundamental Research Funds for the Central Universities(No.DUT17LK31)
文摘Consider a multidimensional renewal risk model, in which the claim sizes {X_k, k ≥1} form a sequence of independent and identically distributed random vectors with nonnegative components that are allowed to be dependent on each other. The univariate marginal distributions of these vectors have consistently varying tails and finite means. Suppose that the claim sizes and inter-arrival times correspondingly form a sequence of independent and identically distributed random pairs, with each pair obeying a dependence structure. A precise large deviation for the multidimensional renewal risk model is obtained.
基金Supported by the 333 High Level Talent Training Project of Jiangsu Provincethe National Natural Science Foundation of China(71871046)Science and Technology Projects of Sichuan Province(2021YFQ0007)。
文摘This paper considers the one-and two-dimensional risk models with a non-stationary claim-number process.Under the assumption that the claim-number process satisfies the large deviations principle,the uniform asymptotics for the finite-time ruin probability of a one-dimensional risk model are obtained for the strongly subexponential claim sizes.Further,as an application of the result of onedimensional risk model,we derive the uniform asymptotics for a kind of finite-time ruin probability in a two dimensional risk model sharing a common claim-number process which satisfies the large deviations principle.
文摘In this paper,a new risk model is studied in which the rate of premium income is regarded as a random variable,the arrival of insurance policies is a Poisson process and the process of claim occurring is p-thinning process.The integral representations of the survival probability are gotten.The explicit formula of the survival probability on the infinite interval is obtained in the special case-exponential distribution.The Lundberg inequality and the common formula of the ruin probability are gotten in terms of some techniques from martingale theory.
文摘In this note we study the optimal dividend problem for a company whose surplus process, in the absence of dividend payments, evolves as a generalized compound Poisson model in which the counting process is a generalized Poisson process. This model includes the classical risk model and the Pólya-Aeppli risk model as special cases. The objective is to find a dividend policy so as to maximize the expected discounted value of dividends which are paid to the shareholders until the company is ruined. We show that under some conditions the optimal dividend strategy is formed by a barrier strategy. Moreover, two conjectures are proposed.
