On the effect of electronic patient portal on primary care utilization and appointment adherence Xiang Zhong1*, Muxuan Liang2, Reynerio Sanchez1, Menggang Yu3, Pamela R. Budd4, Julie L. Sprague4 and Marvin A. Dewar4 Abstract Background: The objective of this study was to investigate the impact of patient portal adoption on patients' primary.