[1] Lovisenberg Diaconal Hosp, Unger Vetlesen Inst, Dept Med, NO-0440 Oslo, Norway
[2] Populat Hlth & Res Inst, Trivandrum 695011, Kerala, India
[3] Thoothukudi Govt Med Coll, Thoothukudi 628002, Tamil Nadu, India
[4] Univ Oslo, Inst Basic Med Sci, Dept Biostat, Fac Med, NO-0318 Oslo, Norway
[5] Univ Oslo, Inst Hlth & Soc, Fac Med, NO-0318 Oslo, Norway
[6] Oslo Univ Hosp Ulleval, Inst Clin Med, Dept Gastroenterol & Hepatol, NO-0424 Oslo, Norway