Human immunodeficiency virus (HIV)-positive individuals on combination anti-retroviral therapy are ineligible Human immunodeficiency virus (HIV)-positive patients receiving combination anti-retroviral therapy are excluded from the study; appropriate studies will be undertaken in patients receiving combination anti-retroviral therapy when indicated; note: HIV testing is not required for entry into this protocol Human immunodeficiency virus (HIV)-positive patients receiving combination anti-retroviral therapy are excluded from the study; appropriate studies will be undertaken in patients receiving combination anti-retroviral therapy when indicated; Note: HIV testing is not required for entry into this protocol Patients who are positive for human immunodeficiency virus type (HIV-) and are receiving combination anti-retroviral therapy Patients with known human immunodeficiency virus (HIV) are excluded; appropriate studies may be undertaken in patients with HIV and those receiving combination anti-retroviral therapy in the future Human immunodeficiency virus (HIV)-positive patients receiving combination anti-retroviral therapy are excluded from the study; appropriate studies will be undertaken in patients receiving combination anti-retroviral therapy when indicated Human immunodeficiency virus (HIV)-positive patients receiving combination anti-retroviral therapy Known human immunodeficiency virus (HIV)-positive patients on combination anti-retroviral therapy are ineligible; appropriate studies will be undertaken in patients receiving combination anti-retroviral therapy when indicated