In contrast, pure red cell aplasia is characterized by a reduction in red cells only. The diagnosis can only be confirmed with a bone marrow examination.Before this procedure is undertaken, a patient will generally have had other blood tests to find diagnostic clues, including a complete blood count, renal function and electrolytes, liver enzymes, thyroid function tests, vitamin B12 and folic acid levels. Tests that may aid in determining an etiology for aplastic anemia include:

History of iatrogenic exposure to cytotoxic chemotherapy: transient bone marrow suppression
Vitamin B12 and folate levels: vitamin deficiency
Liver tests: liver diseases
Viral studies: viral infections
Chest X-ray: infections
X-rays, computed tomography (CT) scans, or ultrasound imaging tests: enlarged lymph nodes (sign of lymphoma), kidneys, and bones in arms and hands (abnormal in Fanconi anemia)
Antibody test: immune competency
Blood tests for paroxysmal nocturnal hemoglobinuria
Bone marrow aspirate and biopsy: to rule out other causes of pancytopenia (i.e., neoplastic infiltration or significant myelofibrosis). Pathogenesis
For many years, the cause of acquired aplastic anemia was not clear. Now, autoimmune processes are considered to be responsible. The majority of cases are hypothesized to be the result of T-cell-mediated autoimmunity and destruction of the bone marrow, which leads to defective or nearly absent hematopoiesis. It is suggested that unidentified antigens cause a polyclonal expansion of dysregulated CD4+ T cells and overproduction of pro-inflammatory cytokines, such as interferon-γ and tumor necrosis factor-α. Ex vivo bone marrow models show an expansion of dysregulated CD8+ T cell populations.
Fibrates lower the risk of cardiovascular and coronary events, but there is no evidence to suggest that they reduce all-cause mortality.Anti-diabetic medication may reduce cardiovascular risk in people with Type 2 diabetes, although evidence is not conclusive. A meta-analysis in 2009 including 27,049 participants and 2,370 major vascular events showed a 15% relative risk reduction in cardiovascular disease with more-intensive glucose lowering over an average follow-up period of 4.4 years, but an increased risk of major hypoglycemia.Aspirin has been found to be of only modest benefit in those at low risk of heart disease, as the risk of serious bleeding is almost equal to the protection against cardiovascular problems. In those at very low risk, including those over the age of 70, it is not recommended. The United States Preventive Services Task Force recommends against use of aspirin for prevention in women less than 55 and men less than 45 years old; however, it is recommended for some older people.The use of vasoactive agents for people with pulmonary hypertension with left heart disease or hypoxemic lung diseases may cause harm and unnecessary expense.Antibiotics for secondary prevention of coronary heart disease
Antibiotics may help patients with coronary disease to reduce the risk of heart attacks and strokes. However, evidence in 2021 suggests that antibiotics for secondary prevention of coronary heart disease are harmful, with increased mortality and occurrence of stroke; the use of antibiotics is not supported for preventing secondary coronary heart disease.