Clinical trial probability of success
The item-response approach consistently demonstrated higher PoS than the SoS approach for all trial durations (Figure 4, upper). For the item-response approach, the PoS was identical whether the tremor items were included or not. For the SoS approach, the PoS estimated based on all items was marginally higher than the one estimated without tremor items. To achieve a 60% PoS in a 2-year trial, the item-response method would require 280 patients per arm and the SoS analysis would require 570 patients per arm. As expected, longer trials produced higher PoS, regardless of the analytical approach.