ahmad danesh department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, p. o. box: 14155-6446, ir iran +98-2188987381, [email protected] saharnaz nedjat department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, p. o. box: 14155-6446, ir iran +98-2188987381, [email protected]; knowledge utilization research center, tehran university of medical sciences, ir iran fariba asghari medical ethics and history of medicine research center, tehran university of medical sciences, ir iran ali jafarian medical ethics and history of medicine research center, tehran university of medical sciences, ir iran; hepatobiliary and liver transplantation research center (imam khomeini hospital), school of medicine, tehran university of medical sciences, ir iran akbar fotouhi department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, p. o. box: 14155-6446, ir iran +98-2188987381, [email protected]; department of epidemiology and biostatistics, school of public health, tehran university of medical sciences, p. o. box: 14155-6446, ir iran +98-2188987381, [email protected]