This study was supported by a research grant of Khon Kaen University (Project ID: 521903 and 534102). We are especially grateful to all volunteers for their cooperation and Dr. Suttiphan Kitcharoen from Faculty of Associated Medical Sciences, Khon Kaen University; Dr. Viraphong Lulitanond, Dr. Somchai Pinlaor, Dr. Watcharin Loilome and Miss Anonglak Manjai from Faculty of Medicine, Khon Kaen University; and Mr. Baramee Somnate and Mrs. Pimjai Saenjamla from Srinagarind Hospital, Khon Kaen University for their advice and help in the real-time PCR technique.