Text and Data Mining valid from 2019-04-19
Received: 18 February 2019
Revised: 20 March 2019
Accepted: 8 April 2019
First Online: 19 April 2019
Compliance with ethical standards
: This study was approved by the Chiang Mai University Research Ethics Committee in compliance with the 1964 Declaration of Helsinki and its later amendment. All patients signed a written consent form at study entry.