A Mathematical Model for Timing Repeated Medical Tests

This paper presents a mathematical model that can be used to estimate the clinical and economic outcomes of monitoring patients with periodic examinations. The model can compare the consequences of monitoring for different disorders, with different tests, at different frequencies. The paper describes formulas that incorporate information about the incidence and natural history of disorders, the effectiveness of tests, the effectiveness of treatment, and the order and frequency of monitoring, to calculate the probability of detecting a disorder, the method and timing of detection, the earliness (e.g., stage) with which a disorder is detected, and the clinical and economic outcomes. The application of the model is described through a hypothetical example. The model has been used to analyze several cancer screening problems involving multiple disorders and multiple tests.