[1] Aga Khan Univ, Nephrol Sect, Dept Med, Karachi, Pakistan
[2] Aga Khan Univ, Clin Epidemiol Unit, Dept Community Hlth Sci, Karachi, Pakistan
[3] Aga Khan Univ, Sect Ophthalmol, Dept Surg, Karachi, Pakistan
[4] Aga Khan Univ, Cardiol Sect, Dept Med, Karachi, Pakistan
[5] Pakistan Med Res Council, Islamabad, Pakistan
[6] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London SW7 2AZ, England
[7] Tufts Univ, New England Med Ctr, Div Nephrol, Dept Med,Sch Med, Boston, MA 02111 USA