If the reticulocyte count is low (it is normally elevated when hemoglobin and hematocrit are low), anemia may be caused by acquired or congenital bone marrow dysfunction, and the infant should be evaluated for causes of bone marrow suppression with Titers or polymerase chain reaction studies for congenital infection (rubella, syphilis, HIV, cytomegalovirus, adenovirus, parvovirus, human herpesvirus 6) Folate and vitamin B12 levels Iron and copper levels If these studies do not identify a cause of anemia, a bone marrow biopsy, genetic testing for congenital disorders of RBC production, or both may be necessary.