Primary Outcome Measures:
- red blood cell mass [ Time Frame: 1 day ] [ Designated as safety issue: No ]
- plasma volume measurements [ Time Frame: 1 day ] [ Designated as safety issue: No ]
Patients will be enrolled from the "Anemia in the Elderly" study and thus will already have had a full hematologic evaluation for their anemia. They will have a complete blood count as part of this evaluation. After enrolling, they will have red blood cell mass and plasma volume measurements performed either at California Pacific Medical Center (CPMC) as per standard clinical practice or at Stanford Hospital and Clinics if this test becomes available at Stanford. We are in discussions with Dr. Michael Goris from Nuclear Medicine re: the possibility of having this test available here at Stanford. Tests will be scheduled as routine clinical tests at this institution (requiring approximately 2 weeks scheduling time). Red blood cell mass will be measured from the dilution of chromium-51 (51 Cr) labeled autologous fresh RBCs in the patient's blood volume. The plasma volume will be measured with labeled albumin.
On the same day as these tests, subjects will also give a blood sample (10 cc) for the following tests: complete blood count (CBC), spun hematocrit and serum erythropoietin level. They will also have their height and weight measured.