Research On Disease Screening Strategies Based On Delay-time Theory

Screening as one of the important method for disease prevention and health promotion is implemented periodically to identify a disease or risk of disease at an early stage in individuals who are presumed to be healthy.Many countries and organizations have released their screening guidelines for several diseases,but most of the disease screening strategies are still controversial.This highlight the significance of research on screening strategies.In general,screening strategy include three aspects:screening method,screening start and end time and screening period.In addition to these three aspects,selective screening includes the identification of high-risk population.In this paper,in view of the problems in the strategy modelling of mass screening and risk assessment of selective screening,the delay-time theory is extended from the prevention maintenance of industrial to disease screening of human.Specifically,take sexually transmitted diseases,cancer,hypertension and hepatitis C for example,studies on screening period,screening method and screening period,screening start time and screening period,risk factor assessment are conducted considering the characteristics of each disease.(1)A cost model of screening period is established based on the delay-time theory which considering the effect of imperfectness of the screening method and window period of the disease in the case of sexually transmitted diseases.The cost includes screening costs,the cost of treatment associated with delayed diagnosis and the costs of infecting others before detected.The validity of the model is verified in numerical researches.The impacts of the imperfect screening and window period are proved by the comparison of the optimization results of the models and sensitivity analysis of the probability of imperfect screening.(2)The cost models of the screening period are established based on the delay-time theory considering the differences in the cost and rates between two screening methods in the case of cancer.Three models are ordinary screening,comprehensive screening and the combination of ordinary screening and comprehensive screening,respectively.The total costs include the cost of ordinary screening,the cost of comprehensive screening,the cost of treatment associated with delayed diagnosis time before detection of the disease and the cost of life loss due to cancer.Numerical researches verify the validity of the model and show the advantage of the combination screening stratey on cost comparing with the other two strategies.(3)A two-stage screening detection rate model and a two-stage screening moribidity rate model are established based on the delay-time theory to optimize the screening start time and screening period in view of the correlation of the disease morbidity and age and the low awareness and control rate in the population in the case of hypertension.The screening period is divided into two phases in the model,where the first phase is a one-time screening and the second phase is a shorter periodical screening.Thus,the screening interval of the first phase is the start time of screening and the screening interval of the second phase is the screening period.Numerical studied show that the two-phase screening strategy has lower cost and higher rate than one-phase screening strategy.(4)Two-stage survival models of risk factors are proposed based on the delay-time theory and survival analysis considering the different effect of risk factors on every stage,correlation between the survival time of two stages,the delayed diagnosis and the non-random censoring in the case of Hepatitis C.The non-random censoring is included in the model by changing the hazard function and using bootstrap method and multiple imputation method to impute the non-random censored data.Simulation studies show that ignoring the correlation between two stages,delayed diagnosis and non-random censoring in the model can lead to non-negligible biases in the estimate of the risk factors,resulting in an incorrect recognition of high-risk population and wrong estimate of survival time.The above research enrich and expand the theory of delay time,which is extended from the field of equipment reliability to the field of population health,provides new scientific decision models and methods for the disease screening strategies and overcome the shortcomings of previous studies.This paper explores the modeling methods of disease screening strategies in many types of diseases.The optimization of screening strategies is helpful to realize the early diagnosis,early detection and early treatment of diseases,reduce the incidence of diseases,improve the survival rate of patients,reduce the social health burden and improve the health of the population.