1. Department of Medicine, School of Medicine, Aga Khan University, Karachi 74000, Pakistan
2. Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM 87106, USA
3. Department of Internal Medicine, University of New Mexico, Albuquerque, NM 87106, USA
4. Division of Pulmonology and Critical Care, Allegheny Health Network, Pittsburg, PA 15212, USA
5. Department of Family and Community Medicine, Texas Tech Health Sciences Center, Lubbock, TX 79409, USA
6. Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA