Summary: This study aimed to document and validate a new cost-effectiveness model of osteoporosis screening and treatment strategies. The state-transition microsimulation model demonstrates strong internal and external validity. It is an important tool for researchers and policy makers to test the cost-effectiveness of osteoporosis screening and treatment strategies.

Introduction: The objective of this study was to document and validate a new cost-effectiveness model of screening for and treatment of osteoporosis.

Methods: A state-transition microsimulation model using a lifetime horizon was constructed with seven Markov states (no history of fractures, hip fracture, vertebral fracture, wrist fracture, other fracture, postfracture state, and death) describing the most important clinical outcomes of osteoporotic fractures. Tracker variables were used to record patients' history, such as fracture events, duration of treatment, and time since last screening. The model was validated for Chinese postmenopausal women receiving screening and treatment versus no screening. Goodness-of-fit analyses were performed for internal and external validation. External validity was tested by comparing life expectancy, osteoporosis prevalence rate, and lifetime and 10-year fracture risks with published data not used in the model.

Results: The model represents major clinical facets of osteoporosis-related conditions. Age-specific hip, vertebral, and wrist fracture incidence rates were accurately reproduced (the regression line slope was 0.996, R ² = 0.99). The changes in costs, effectiveness, and cost-effectiveness were consistent with changes in both one-way and probabilistic sensitivity analysis. The model predicted life expectancy and 10-year any major osteoporotic fracture risk at the age of 65 of 19.01 years and 13.7 %, respectively. The lifetime hip, clinical vertebral, and wrist fracture risks at age 50 were 7.9, 29.8, and 18.7 % respectively, all consistent with reported data.

Conclusions: Our model demonstrated good internal and external validity, ensuring it can be confidently applied in economic evaluations of osteoporosis screening and treatment strategies.