Exposure to Agent Orange increases the risk of CLL, and exposure to hepatitis C virus may increase the risk. There is no clear association between ionizing radiation exposure and the risk of developing CLL. Blood transfusions have been ruled out as a risk factor. Diagnosis
The diagnosis of CLL is based on the demonstration of an abnormal population of B lymphocytes in the blood, bone marrow, or tissues that display an unusual but characteristic pattern of molecules on the cell surface. CLL is usually first suspected by a diagnosis of lymphocytosis, an increase in a type of white blood cell, on a complete blood count test. This frequently is an incidental finding on a routine physician visit. Most often the lymphocyte count is greater than 5000 cells per microliter (µl) of blood but can be much higher. The presence of lymphocytosis in a person who is elderly should raise strong suspicion for CLL, and a confirmatory diagnostic test, in particular flow cytometry, should be performed unless clinically unnecessary. Molecular examination of peripheral blood and flow cytometry
The combination of the microscopic examination of the peripheral blood and analysis of the lymphocytes by flow cytometry to confirm clonality and marker molecule expression is needed to establish the diagnosis of CLL. Both are easily accomplished on a small amount of blood. A flow cytometer instrument can examine the expression of molecules on individual cells in fluids. This requires the use of specific antibodies to marker molecules, with fluorescent tags recognized by the instrument.
Myeloablative (bone marrow killing) forms of allogeneic stem cell transplantation, a high-risk treatment using blood cells from a healthy donor, may be curative, but treatment-related toxicity is significant. : 1458  An intermediate level, called reduced-intensity conditioning allogeneic stem cell transplantation, may be better tolerated by older or frail patients. Refractory CLL
"Refractory" CLL is a disease that no longer responds favorably to treatment within 6 months following the last cancer therapy. In this case, more aggressive targeted therapies, such as BCR or BCL2 pathway inhibitors, have been associated with increased survival. During pregnancy
Leukemia is rarely associated with pregnancy, affecting only about one in 10,000 pregnant women. Treatment for chronic lymphocytic leukemias can often be postponed until after the end of the pregnancy. If treatment is necessary, then giving chemotherapy during the second or third trimesters is less likely to result in pregnancy loss or birth defects than treatment during the first trimester. Prognosis
Prognosis can be affected by the type of genetic mutation that the person with CLL has. Some examples of genetic mutations and their prognoses are: mutations in the IGHV region are associated with a median overall survival (OS) of more than 20–25 years, while no mutations in this region is associated with a median OS of 8–10 years; deletion of chromosome 13q is associated with a median OS of 17 years; and trisomy of chromosome 12, as well as deletion of chromosome 11q, is associated with a median OS of 9–11 years.