Data Last Updated: Dec. 17, 2025

Serum Beta-2 Microglobulin Pretreatment Level

Description

Serum Beta-2 Microglobulin is a protein that is found on the surface of many cells and plentiful on the surface of white blood cells. Increased production or destruction of these cells causes Serum β2 (beta-2) Microglobulin level to increase. Elevated Serum β2 (beta-2) Microglobulin level is a prognostic factor for plasma cell myeloma. The Revised International Staging System (R-ISS or RISS) is now used to stage plasma cell myeloma (9732/3), using several different criteria. The stages are based on the absence or presence of the following related criteria. * 3931: Serum Beta-2 Microglobulin Pretreatment Level * 3930: Serum Albumin Pretreatment Level * 3857: High Risk Cytogenetics * 3869: LDH Level Required for Staging: The AJCC Staging System Plasma Cell Myeloma and Plasma Cell Disorders (9732/3 only) and EOD. * Note: R-ISS stage is not applicable for the descriptions of plasma multiple myeloma that are listed in the codes 1 and 9 in the SSDI Schema Discriminator 1: Plasma Cell Myeloma Terminology. If you have coded 1 or 9 for this Schema Discriminator, the four data items listed above are BLANK. The R-ISS stages are * Stage I: Serum Beta-2-microglobulin <3.5 mg/L and serum albumin > 3.5 g/dL and no high-risk cytogenetics and Normal LDH * Stage II: Not R-ISS I or III * Stage III: Serum Beta-2-microglobulin > 5.5 mg/L and high-risk cytogenetics and/or high LDH

Rationale

Serum Beta-2 Microglobulin Pretreatment Level is a prognostic factor required in AJCC 8th edition, Chapter 82 *Plasma Cell Myeloma and Plasma Cell Disorders*, for staging of plasma cell myeloma. It is a new data item for cases diagnosed 1/1/2018+.

Additional Info

**Source documents:** laboratory tests (blood only) **Other names include** B2M, Total Beta-2 microglobulin, B2-microglobulin, and B2M

Notes

**Note 1:** **Physician statement** * Physician statement of Serum Beta-2-Microglobulin Pretreatment Level can be used to code this data item when no other information is available (See Note 3) **Note 2:** **Pretreatment results only** * Record this data item based on a **blood test** performed at diagnosis (pre-treatment). Use the highest value available. * Do not use results from a urine test **Note 3:** **Component of R-ISS Stage** * Serum Beta-2 Microglobulin is part of the Revised International Staging (R-ISS). * Elevated serum microglobulin is defined as ≥ 5.5 mg/L * Use the cut points listed in the table below regardless of the lab’s reference range. * **Code 0** if physician states **RISS Stage 1** and there is no other information * **Code 2** if physician states **RISS Stage 3** and there is no other information

Coding Guidelines

**1) Code 5** if Schema Discriminator 1: Plasma Cell Myeloma Terminology is coded to 1 or 9 **2) Code 9** when there is no mention of the Serum beta-2-microglobulin
Code Description
0 β2-microglobulin < 3.5 mg/L
1 β2-microglobulin ≥ 3.5 mg/L < 5.5 mg/L
2 β2-microglobulin ≥ 5.5 mg/L
5 Schema Discriminator 1: Plasma Cell Myeloma Terminology coded to 1 or 9
7 Test ordered, results not in chart
9 Not documented in medical record
Serum Beta-2 Microglobulin Pretreatment Level not assessed or unknown if assessed