Modeling developmental data using U-shaped threshold dose-response curves

This paper develops threshold models for developmental toxicity data. The distinguishing feature of these threshold models is their flexibility in modeling data below threshold with a U-shaped function if the data warrants. The method is applied to actual data from a developmental study which exhibits U-shaped behavior in early dose groups. Results from a simulation study demonstrate the flexibility of the threshold model to pick up on U-shaped trends in the data. In addition, the simulation study reveals important considerations in design of developmental studies.