User interactions with the PDQ cancer information system.

Searches by end users and intermediaries on the online PDQ (Physician Data Query) cancer information system were observed. With the National Library of Medicine (NLM) menu-based interface, end users (physicians) averaged fewer steps per question, while with the BRS command-drive interface, intermediaries appeared to be more efficient. Cancer Information Service (CIS) searchers, who have more PDQ experience than end users or intermediaries, made greater use of command stacking to anticipate menu selections. Retrieval was more complete in the NLM system, where both the menus and predefined print formats assisted the searchers.