A clinical staging system based on a combination of laboratory findings that correlate with the myeloma cell mass has often been used. Patients are generally separated into those with low-cell mass (Stage I), high-cell mass (Stage III) and those whose cell mass is between Stages I and III (Stage II). A further classification divides patients according to whether they are "A" (kidney function test is normal or only slightly elevated, with a creatinine less than 2.0 mg/dL) or "B" (the serum creatinine is equal to or greater than 2.0 mg/dL). The plasma cell labeling index (measurement of the rate of growth of the myeloma cells) and the ,ß2-microglobulin (ß2-M) level are more helpful prognostic factors than the staging system.
