Which laboratory finding is required by the IMWG (International Myeloma Working Group) updated diagnostic criteria to define multiple myeloma as 'CRAB-independent' myeloma-defining event, allowing treatment initiation even in the absence of end-organ damage?

• A Bone marrow plasma cells ≥40%
• B Serum free light chain ratio >100
• C Serum free light chain ratio >200
• D Bone marrow plasma cells ≥60% ✓

Explanation

The 2014 IMWG update added three myeloma-defining events to the classic CRAB criteria: bone marrow plasma cells ≥60%, serum involved:uninvolved free light chain ratio ≥100, and >1 focal lesion on MRI. Among the options, bone marrow plasma cells ≥60% is correct. A free light chain ratio of ≥100 (not >200) is the threshold. These biomarkers identify patients at very high risk of progression to symptomatic myeloma, warranting early therapy.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.