Diagnostic tests are used to determine whether a disease or condition is present or absent in a patient, who will typically be suspected of having the disease or condition due to symptoms or clinical signs. Economic evaluations of diagnostic tests (e.g. cost-effectiveness analyses) can be used to determine whether a test produces sufficient benefit to justify its cost. Evidence on the benefits conferred by a test is often restricted to its accuracy, which means mathematical models are required to estimate the impact of a test on outcomes that matter to patients and health payers. It is important to realise the case for introducing a new test may not be restricted to its accuracy, but extend to factors such as time to diagnosis and acceptability for patients. These and other considerations may mean the common modelling approach, the decision tree, is inappropriate for underpinning an economic evaluation. There are no consensus guidelines on how economic evaluations of diagnostic tests should be conducted-this article attempts to explore the common challenges encountered in economic evaluations, suggests solutions to those challenges, and identifies some areas where further methodological work may be necessary.

Cost-effectiveness of biomarker- vs endoscopy-based treat-to-target monitoring in Crohn's disease (CD) is unknown.

A microsimulation model for CD was built to simulate biomarker (fecal calprotectin) vs endoscopy-based monitoring in a treat-to-target fashion. Published literature in combination with patient-level data from phase 3 clinical trials and population estimates for therapeutic drug monitoring were used to generate transition probabilities, costs, and utilities. Tracker variables were used to modify downstream probabilities and outcomes based on previous exposures, response patterns, and disease-related complications or surgery history. The primary outcome was cost-effectiveness over a 5-year horizon at a willingness-to-pay threshold of $100,000/quality-adjusted life-year. Probabilistic sensitivity analyses in addition to multiple 1-, 2-, and 3-way microsimulation sensitivity analyses were performed.

In the base-case model, the endoscopy-based monitoring strategy dominated the biomarker-based monitoring strategy over a 5-year horizon. Over shorter periods of observation, the biomarker-based monitoring strategy became progressively more cost-effective, with cost-effectiveness achieved for this strategy over a 1-year horizon. Therapeutic drug monitoring did not influence short-term cost-effectiveness of biomarker-based monitoring. Once in endoscopic remission, continued biomarker-based vs endoscopy-based monitoring was more cost-effective. A hybrid biomarker-endoscopy-based monitoring strategy dominated the endoscopy-based monitoring strategy over a 5-year horizon. The strongest determinants for cost-effectiveness were cost of colonoscopy and diagnostic performance of fecal calprotectin.

The most cost-effective approach for treat-to-target monitoring in CD is up-front biomarker-based monitoring followed by endoscopy-based monitoring if not in endoscopic remission by 1 year and then returning to biomarker-based monitoring once in endoscopic remission.

Although extended colectomy (EC) was recommended for HNPCC patients, previous studies did not show significantly improved overall survival. Immunohistochemical (IHC) stain of mismatch repair (MMR) gene protein expression is now a feasible and reliable test clinically. Therefore, we tried to investigate whether we could use MMR IHC stain to select operation types in HNPCC patients.

Between 1995 and 2013, 186 HNPCC patients were collected. Status of MMR protein expression, perioperative clinic-pathological variables and post-operative follow up status were analyzed by multivariate analyses.

Sixty-five percent (121 of 186) patients of these HNPCC patients demonstrated loss of at least one MMR protein. There were several significant differences existing between deficient MMR (dMMR) and proficient MMR (pMMR) subgroups in terms of clinic-pathological characteristics. With the average follow-up duration of 93.9 months, we observed significantly high risk of developing metachronous CRC between SC and EC subgroups (crude rate 8.5% vs. 0%, p = 0.035). However, no significant difference was observed among the presence of extra-colonic tumors (12.4% vs. 5.8%, p = 0.284). The positive and negative prediction rate of metachronous CRC in dMMR subgroup was 12.8 and 87.2% while 1.9 and 98.1% in the pMMR subgroup. Survival outcomes were significantly affected by MMR status and resection types by multivariate analysis. Significantly better OS in dMMR subgroup (HR = 0.479, 95% CI: 0.257-0.894, p = 0.021) comparing with pMMR subgroup was observed. However, significant improved DFS (HR = 0.367, 95% CI: 0.172-.0787, p = 0.010) but not significant for OS (HR = 0.510, 95% CI: 0.219-1.150, p = 0.103) for EC subgroup compared with SC subgroup. Differences existing among different subgroups by combing extent of resection and MMR status. In dMMR subgroup, SC, compared with EC, demonstrated significantly worse DFS by multivariate analyses (HR = 3.526, 95% CI: 1.346-9.236, p = 0.010) but not for OS (HR = 2.387, 95% CI: 0.788-7.229, p = 0.124), however, no significantly differences of OS and DFS in pMMR subgroup between SC and EC were found.

Significantly better overall survival and higher rate of metachronous CRC exist in dMMR subgroup of HNPCC patients comparing with pMMR subgroup. Extended colectomy significantly improved DFS and was thus recommended for dMMR subgroup but not pMMR subgroup of HNPCC patients.

Different strategies toward implementing competing risks in discrete-event simulation (DES) models are available. This study aims to provide recommendations regarding modeling approaches that can be defined based on these strategies by performing a quantitative comparison of alternative modeling approaches.

Four modeling approaches were defined: 1) event-specific distribution (ESD), 2) event-specific probability and distribution (ESPD), 3) unimodal joint distribution and regression model (UDR), and 4) multimodal joint distribution and regression model (MDR). Each modeling approach was applied to uncensored individual patient data in a simulation study and a case study in colorectal cancer. Their performance was assessed in terms of relative event incidence difference, relative absolute event incidence difference, and relative entropy of time-to-event distributions. Differences in health economic outcomes were also illustrated for the case study.

In the simulation study, the ESPD and MDR approaches outperformed the ESD and UDR approaches, in terms of both event incidence differences and relative entropy. Disease pathway and data characteristics, such as the number of competing risks and overlap between competing time-to-event distributions, substantially affected the approaches' performance. Although no considerable differences in health economic outcomes were observed, the case study showed that the ESPD approach was most sensitive to low event rates, which negatively affected performance.

Based on overall performance, the recommended modeling approach for implementing competing risks in DES models is the MDR approach, which is defined according to the general strategy of selecting the time-to-event first and the corresponding event second. The ESPD approach is a less complex and equally performing alternative if sufficient observations are available for each competing event (i.e., the internal validity shows appropriate data representation).

Colorectal cancer (CRC) is one of the tumours with the highest incidence and mortality in the Spanish population. Nevertheless, the advances in prevention and treatment have contributed to an increased number of patients who survive for prolonged periods of time. In addition, despite recurrences, improved survival following metastasis resection is likewise on the rise. This underscores the importance of carrying out follow-up programmes even in low-risk patients for the early detection of recurrence. The main objective of this article is to provide a set of recommendations for optimising the follow-up of CRC survivors as well as for managing the sequelae that result from either pharmacological or surgical treatment.

Colorectal cancer (CRC) is a prevalent disease and represents a major cause of morbidity and mortality in the developed world. Intensive post-treatment surveillance is routinely recommended by major expert groups for early stage (II and III) CRC survivors because previous meta-analyses showed a modest, but significant survival benefit. This practice has been recently challenged based on data emerging from several large phase III randomized trials that demonstrated a lack of survival benefit from intensive surveillance strategies. In addition, findings from cost-effectiveness analyses of such an approach are inconsistent. Data on real-world practice, specifically adherence to these follow-up guidelines, are also limited. The debate is especially controversial in resected stage IV patients where there are currently no clear guidelines for follow-up. In an era of personalized medicine, there may be a shift towards a more risk-adapted approach to better define the optimal follow-up strategy. In this article, we review the evidence and highlight the role of surveillance in CRC survivors.

The objective was to explore the current advances and extent of DES (Discrete Event Simulation) applied to assisting with health decision making, as well as to categorize the wide spectrum of health-related topics where DES was applied.

A systematic review was conducted of the literature published over the last two decades. Original research articles were included and reviewed if they concentrated on the topic of DES technique applied to health care management with model frameworks explicitly demonstrated. No restriction regarding the settings of DES application was applied.

A total of 211 papers met the predefined inclusion criteria. The number of publications included increased significantly especially after 2010.101 papers (48%) stated explicitly disease areas targeted, the most frequently modeled of which are related to circulatory system, nervous system and Neoplasm. The DES applications were distributed unevenly into 4 major classes: health and care systems operation (HCSO) (65%), disease progression modeling (DPM) (28%), screening modeling (SM) (5%) and health behavior modeling (HBM) (2%). More than 68% of HCSO by DES were focused on specific problems in individual units. However, more attempts at modeling highly integrated health service systems as well as some new trends were identified.

DES technique has been an effective tool to approach a wide variety of health care issues. Among all DES applications in health care, health system operations research occupied the most considerable proportion and increased most significantly. Health Economic Evaluation (HEE) was the second most common topic for DES in health care, but with stable rather than increasing numbers of publications.

The gastroenterology literature emphasizes factors that increase colorectal cancer (CRC) incidence but presents little about management after initial CRC treatments. The purpose of this review is to describe the remarkably increasing numbers of CRC survivors in whom surveillance guidelines are often not followed and patient care is fragmented. The gastroenterologist can play an important role in this care to improve prognosis and overall health.

Existing surveillance recommendations by specialty societies for CRC survivors are fairly consistent but implementation occurs in less than half. The gastroenterologist can help to coordinate care to ensure appropriate surveillance and also can help to diagnose and treat chemotherapy and radiotherapy complications in survivors which can affect the quality of life long after the initial treatment. The gastroenterologist also can focus on host factors, including management of obesity, exercise programs, and the diet and can introduce potential chemopreventive agents such as nonsteroidal anti-inflammatory drugs when positive prospective studies are forthcoming. Interested gastroenterologists also have a role in participating in such prospective studies.

The gastroenterologist should enhance her/his role for coordinated management of CRC survivors to improve patient surveillance care, to treat posttherapy complications and encourage preventive measures to improve prognosis and quality of life.