Department of Medicine, Bayero University, PO Box 4445, Kano, Nigeria. kkaraye@yahoo.co.uk. Department of Medicine, Aminu Kano Teaching Hospital, Kano, Nigeria. kkaraye@yahoo.co.uk. Department of Public Health and Clinical Medicine, Umea University, Umeå, Sweden. kkaraye@yahoo.co.uk. Department of Medicine, Bayero University, PO Box 4445, Kano, Nigeria. Department of Medicine, Murtala Mohammed Specialist Hospital, Kano, Nigeria. Department of Medicine, Muhammad Abdullahi Wase Specialist Hospital, Kano, Nigeria. Department of Medicine, Aminu Kano Teaching Hospital, Kano, Nigeria. Department of Obstetrics and Gynaecology, Bayero University and Aminu Kano Teaching Hospital, Kano, Nigeria. Department of Chemical Pathology, Bayero University and Aminu Kano Teaching Hospital, Kano, Nigeria.