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Browsing by Author "Kong, Nan"
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Item Cost Effectiveness of Different Strategies for Detecting Cirrhosis in Patients With Non-alcoholic Fatty Liver Disease Based on United States Health Care System(Elsevier, 2020) Vilar-Gomez, Eduardo; Lou, Zhouyang; Kong, Nan; Vuppalanchi, Raj; Imperiale, Thomas F.; Chalasani, Naga; Medicine, School of MedicineBackground & Aims Several strategies are available for detecting cirrhosis in patients with non-alcoholic fatty liver disease (NAFLD), but their cost effectiveness is not clear. We developed a decision model to quantify the accuracy and costs of 9 single or combination strategies, including 3 noninvasive tests (fibrosis-4 [FIB-4], vibration controlled transient elastography [VCTE], and magnetic resonance elastography [MRE]) and liver biopsy, for detection of cirrhosis in patients with NAFLD. Methods Data on diagnostic accuracy, costs, adverse events, and cirrhosis outcomes over a 5-y period were obtained from publications. The diagnostic accuracy, per-patient cost per correct diagnosis of cirrhosis, and incremental cost-effectiveness ratios (ICER) were calculated for each strategy for base cirrhosis prevalence values of 0.27%, 2%, and 4%. Results The combination of the FIB-4 and VCTE identified patients with cirrhosis in NAFLD populations with a 0.27%, 2%, and 4% prevalence of cirrhosis with the lowest cost per person ($401, $690, and $1024, respectively) and highest diagnostic accuracy (89.3%, 88.5%, and 87.5% respectively). The combination of FIB-4 and MRE ranked second in cost per person ($491, $781, and $1114, respectively) and diagnostic accuracy (92.4%, 91.6%, 90.6%, respectively). Compared to the combination of FIB-4 and VCTE (least costly), the ICERs were lower for the combination of FIB-4 and MRE ($2864, $2918, and $2921) than the combination of FIB-4 and liver biopsy ($4454, $5156, and $5956) at the cirrhosis prevalence values tested. When goal was to avoid liver biopsy, FIB-4+VCTE and FIB-4+MRE had similar diagnostic accuracies, ranging from 87.5% to 89.3% and 90.6% to 92.4% for cirrhosis diagnosis, although FIB-4+MRE had a slightly higher cost. Conclusions In our cost effectiveness analysis based on United States health care system, we found that results from FIB-4, followed by either VCTE, MRE, or liver biopsy, detect cirrhosis in patients with NAFLD with a high level of accuracy and low cost. Compared to FIB-4 + VCTE which was the least costly strategy, FIB-4+MRE had lower ICER than FIB-4+LB.Item Optimizing strategies for population-based chlamydia infection screening among young women: an age-structured system dynamics approach(Springer (Biomed Central Ltd.), 2015) Teng, Yu; Kong, Nan; Tu, Wanzhu; Department of Biostatistics, School of Public HealthBACKGROUND: Chlamydia infection (CT) is one of the most commonly reported sexually transmitted diseases. It is often referred to as a "silent" disease with the majority of infected people having no symptoms. Without early detection, it can progress to serious reproductive and other health problems. Economical identification of asymptomatically infected is a key public health challenge. Increasing evidence suggests that CT infection risk varies over the range of adolescence. Hence, age-dependent screening strategies with more frequent testing for certain age groups of higher risk may be cost-saving in controlling the disease. METHODS: We study the optimization of age-dependent screening strategies for population-based chlamydia infection screening among young women. We develop an age-structured compartment model for CT natural progress, screening, and treatment. We apply parameter optimization on the resultant PDE-based system dynamical models with the objective of minimizing the total care spending, including screening and treatment costs during the program period and anticipated costs of treating the sequelae afterwards). For ease of practical implementation, we also search for the best screening initiation age for strategies with a constant screening frequency. RESULTS: The optimal age-dependent strategies identified outperform the current CDC recommendations both in terms of total care spending and disease prevalence at the termination of the program. For example, the age-dependent strategy that allows monthly screening rate changes can save about 5% of the total spending. Our results suggest early initiation of CT screening is likely beneficial to the cost saving and prevalence reduction. Finally, our results imply that the strategy design may not be sensitive to accurate quantification of the age-specific CT infection risk if screening initiation age and screening rate are the only decisions to make. CONCLUSIONS: Our research demonstrates the potential economic benefit of age-dependent screening strategy design for population-based screening programs. It also showcases the applicability of age-structured system dynamical modeling to infectious disease control with increasing evidence on the age differences in infection risk. The research can be further improved with consideration of the difference between first-time infection and reinfection, as well as population heterogeneity in sexual partnership.