The "unclear problem" category: an analysis of its patient and dispatch characteristics and its trend over time.

The UPC has different dispatch characteristics than the symptom-specific categories, with potential negative effects on the medical dispatch process. Moreover, the median age of individuals triaged with the UPC is higher than those triaged with symptom-specific categories. Nonetheless, the use of the UPC decreased throughout the study period after the medical dispatchers were alerted about the implications of its use.