[1] SingHlth Polyclin Pasir Ris, Singapore 519457, Singapore
[2] SingHlth Polyclin Tampines, Singapore 529203, Singapore
[3] Changi Gen Hosp, Dept Gastroenterol, Singapore 529889, Singapore
[4] Clin Trials & Epidemiol Unit CTERU, Singapore 169039, Singapore