Diagnostic procedures
A diagnosis of myeloma is difficult to make on the basis of any single result or reported symptom and an accurate diagnosis can only be made after patients have undergone further tests or procedures. These include further laboratory tests and imaging alongside targeted or bone marrow biopsies which help to clarify the histological proof and extent of the disease.
View our Myeloma Diagnostic Tool and Guide for GPs for the tests and procedures used to diagnose myeloma.
The International Myeloma Working Group (IMWG) developed a set of criteria which must be met before a diagnosis of myeloma can be made. Fulfilling the criteria also helps to distinguish myeloma from other plasma cell disorders, such as monoclonal gammopathies of undetermined significance (MGUS), lymphomas or macroglobulinaemias.
Until 2014, a diagnosis of myeloma could only be made if there was evidence of end-organ damage (as defined by the ‘CRAB’ criteria above). But the inclusion of additional myeloma defining events (MDEs), when found in combination with clonal bone marrow plasma cells ≥10% or biopsy proven plasmacytoma, means a diagnosis can now be given, and treatment started, before these serious complications arise. The current UK working definition of active myeloma follows IMWG and is summarised in Table 1. It is often referred to as ‘SLiM-CRAB’.
Measurement of paraprotein remains an important part of the diagnostic workup although it is no longer a specific requirement in the IMWG guidelines. For patients who do not produce intact paraprotein i.e. if they have light-chain myeloma or certain types of non-secretory myeloma, it is important an additional urine or serum free light chain (SFLC) test is performed to ensure their diagnosis is not missed. Where available, sFLC assay is now the recommended test to investigate monoclonal light chains rather than urinary BenceJones protein.
It should be noted that there are still certain types of non-secretory myeloma that are undetectable by serum or urine measurements and, for these patients a diagnosis is predominantly based on the results of the bone marrow biopsy or in the case of a plasmacytoma, a targeted biopsy.