Final answer:
The significant client response when evaluating treatment with erythropoietin (Epogen) is an elevation in hematocrit level, as EPO stimulates RBC production in the bone marrow which is reflected by increased hematocrit values in blood tests.
Step-by-step explanation:
The client response considered significant when evaluating the results of treatment with erythropoietin (Epogen) is C. Elevation in hematocrit level. Erythropoietin is a hormone that stimulates the production of red blood cells (RBCs) in the bone marrow. Hence, an increase in hematocrit, which is the proportion of blood volume that is occupied by RBCs, would be a direct indication that the EPO treatment is effective. EPO treatments are used medically to treat certain types of anemia, particularly those caused by cancer or renal failure, where increased RBC counts and oxygen levels are desirable to manage anemia.
While EPO can cause an elevation in RBC count, it should not typically cause an elevation in liver panel tests or a significant change in white blood cell (WBC) counts, which are not directly affected by erythropoietin therapy. Additionally, EPO is not used to treat Kaposi sarcoma or any related lesions, so a decrease in Kaposi sarcoma lesions would not be a relevant indicator of the effectiveness of EPO therapy.