The presence of the antigen CD38 on B-CLL cells is a much discussed prognostic indicator in CLL. Whether it is a truly independent prognostic indicator or simply a reflection of IgV_H gene mutational status, CD38 clearly seems to have some relevance in predicting whether a patient's CLL is likely to have a favorable or unfavorable clinical course. CD38 is detected by flow cytometry, a diagnostic technique frequently used in confirming CLL.

Patients with less than 20 percent CD38+ B-CLL cells are likely to have a favorable clinical course requiring minimal or no therapy. Patients with equal to or greater than 20 percent CD38+ B-CLL cells are more likely to have an unfavorable clinical course requiring earlier and ongoing treatment. Significant differences in survival are also thought to exist between these two groups. CD38 expression remains stable over time in the majority of patients, but it is known to change in approximately 25 percent of cases. Its level of expression does not seem to be influenced by chemotherapy.

The connection between CD38 expression and IgV_H gene mutational status is not well understood. It appears that patients with less that 20 percent CD38+ B-CLL cells are likely to have mutated IgV_H genes while patients with greater than 20 percent+ B-CLL cells are more likely to have unmutated IgV_H genes. While this is often the case, there is approximately a 30 percent discordance between assays for CD38 and IgV_H mutational status (see also: What is the significance of IgV_H gene mutational status in CLL?)

Both CD38 and IgV_H gene mutation are thought to be useful prognostic indicators in B-CLL, but because of the relative ease of testing for CD38, it is a much more convenient test.

CD38 and IgV_H mutational status are just two of a number of prognostic indicators in CLL. Others include, circulating levels of beta-2-microglobulin and soluble CD23, lymphocyte doubling time, serum thymidine kinase levels, bone marrow histology, and chromosome abnormalities.