Fig. 2.

Item threshold map of the final model SF-HDQ domains in order of item difficulty. This figure illustrates the item threshold map for each final SF-HDQ domain in order of increasing difficulty from top to bottom, and with severity levels increasing from left to right (a–f). For example, in the physical domain 'trouble sleeping' is the item with least difficulty to 'feeling dizzy' which is the item with the most difficulty to score high levels of disability severity