Presenting time-based risks of stroke and death for Patients facing carotid stenosis treatment options: Patients prefer pie charts over icon arrays.

Overview

OBJECTIVE: To user-test graphical display formats (icon arrays, pie, bar, and line charts) to identify preferred formats and metrics ('probability of death or stroke' or 'proportion of time lived without death or stroke') in order to display time-dependent risks of stroke or death for three carotid stenosis treatments: endarterectomy (surgery), stenting, and medical therapy. METHODS: Iterative cycles of semi-structured interviews with patients recruited from a Vascular Clinic. RESULTS: A total of 27 patients (mean age = 68; range: 50-85) were interviewed over four cycles. Patients strongly preferred the pie chart over icon arrays, and over bar or line graphs. The preference was based on patient recognition of the time-based increase in risk for stroke or death for treatment options. Patients preferred data presented as probabilities instead of the proportion of time lived. We did not assess patients' understanding. CONCLUSION: Patients preferred the pie chart formats and reported better realization that risks increase with time for each option and that tradeoffs exist when surgery has a higher short-term risk than medical therapy. PRACTICE IMPLICATIONS: There remains debate on how best to convey time-dependent risk information to patients, especially where low literacy and numeracy might exist.