Abstract
The aim of this study is to investigate the concentration of ambulatory health care expenditure in a large Iranian outpatient population. This study used 2013-2016 individual-level claims data of Iranian Health Insurance Organization in East Azerbaijan province. All ambulatory care utilizers were included in the study. We determined characteristics and utilization pattern of high-cost patients as well as their predictors. A total of 1 128 149 patients were included. The top 10% of patients accounted for 62.56% of the total expenditure. This skewed expenditure pattern remained relatively stable over the study period. Female sex, older age, cancer, chronic obstructive pulmonary disease, cardiovascular disease, and diabetes increase the odds of being high cost.