- PAH- Human Immunodeficiency Virus (HIV): Patients will have a firm diagnosis with positive HIV testing (i.e. positive 4th generation immunoassay and positive confirmatory testing such as Western Blot or HIV-1/HIV-2 antibody differentiation immunoassay) and managed by an infectious disease/HIV specialist. These patients have hemodynamic criteria for PAH present, but the only association on workup is the presence of HIV.