Patient Portal Usability Gaps: A Heuristic Evaluation of Two Major EHR Systems

Background: Patient portals, as extensions of electronic health records (EHRs), play a critical role in providing patients with access to diagnoses, test results, and clinical communication. Despite their potential benefits, portals often inherit usability issues from EHRs, which can make information difficult to navigate or interpret, and errors can compromise patient safety and affect clinical decision-making. Objective: This study aims to evaluate usability shortcomings in patient portals by identifying heuristic violations in portal functions from two leading EHR vendors, Oracle Cerner, and Epic, and examine how these issues may limit patient understanding and engagement. Methods: Three human factors researchers independently conducted heuristic evaluations on 23 patient portal functions, focusing on ten key diagnostic-related areas (e.g., display of diagnoses, test results, etc.). Usability flaws were mapped to Nielsen–Schneiderman heuristics, assigned a four-level severity score, and reconciled through consensus review. Results: A total of eighty heuristic violations were identified, 76% from Oracle Cerner (n=61) and 24% from Epic (n=19). The most frequent violations involved system feedback, inconsistencies, and excess information. The portal functions with the highest number of violations were display of diagnoses, test results, messaging, and clinical notes. Most violations were minor (65%), followed by moderate (20%), with no critical issues observed. Discussion: Both portals displayed usability gaps, particularly in critical functions like diagnosis display and provider messaging, that may compromise patient understanding of diagnostic information and engagement in care. Although most issues were minor, cumulative effects in high-risk functions could compromise diagnostic safety. Addressing these gaps through human-centered design, standardized usability assessments, and collaboration among vendors, institutions, and policymakers is essential to improve patient understanding and reduce diagnostic error risk.