Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 47 12 2018 12 01 1945 1952 Arash RASHIDIAN Dept. of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Ali AKBARI SARI Dept. of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Seyed Mostafa HOSEINI Dept. of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Moslem SOOFI Dept. of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Hoseyn AMERI Dept. of Health Management and Economics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran 2018 12 05 Background: Different definitions are nowadays adopted to estimate the threshold of exposure of households to catastrophic health expenditures and different thresholds are used in various studies. This study was conducted to compare these thresholds and select the most appropriate threshold for defining catastrophic health expenditure in Iran and Brazil. Methods: In this cross-sectional study, data were collected from 592 households from District 17 of Tehran, Iran, and 869 households from Porto Alegre, Brazil in 2013. Firstly, catastrophic health expenditures were calculated using two common proportions, i.e. out-of-pocket health payments, as a proportion of total cost and as a proportion of ability to pay. These proportions were analysed using the Receiver Operating Characteristic (ROC) curve and Kappa coefficient. Results: The appropriate cut off point for the thresholds of 5%, 10%, 15%, and 20% of the total expenditure was 0.52, 0.34, 0.28, and 0.46 in Iran, and 0.44, 0.36, 0.28, and 0.23 in Brazil, respectively. The appropriate cut off point for the thresholds of 20%, 25%, 30%, 35%, and 40% of ability to pay was 0.31, 0.28, 0.25, 0.34, and 0.40 in Iran and 0.36, 0.34, 0.30, 0.38, and 0.46 in Brazil, respectively. Conclusion: The appropriate cut off point for the proportion of out-of-pocket health payments to total expenditure and proportion of health expenditure to ability to pay was the threshold of 20% of total expenditure and 35% of ability to pay, respectively.   https://ijph.tums.ac.ir/index.php/ijph/article/view/15525 https://ijph.tums.ac.ir/index.php/ijph/article/download/15525/6238