The International Myeloma Working Group (IMWG) response criteria give haematologists a uniform language for how well a treatment is working in multiple myeloma. This calculator applies the 2016 criteria to your laboratory values and returns the matching response category.
How it works
The criteria are evaluated in a strict hierarchy. Progressive disease is checked first, then responses from most to least stringent:
PD ≥25% rise in serum or urine M-protein from nadir
sCR CR + normal free light-chain ratio + no clonal plasma cells
CR serum + urine immunofixation negative AND marrow plasma cells <5%
VGPR ≥90% serum reduction AND urine M-protein <100 mg/24h
PR ≥50% serum reduction AND (≥90% urine reduction OR urine <200 mg/24h)
MR 25–49% serum reduction (relapsed/refractory setting)
SD none of the above metThe percentage reduction is computed as (baseline − post) / baseline × 100
for both serum and urine fractions.
Example
For illustration: a patient with baseline serum M-protein of 4.0 g/dL falling to 0.3 g/dL is a 93% reduction; with urine M-protein dropping to 40 mg/24h this reaches VGPR. If serum and urine immunofixation then turn negative and marrow plasma cells fall below 5%, the response becomes CR. Note that this tool covers measurable M-protein disease only; light-chain-only and oligosecretory myeloma use serum free light-chain criteria that are not modelled here.
Why the response hierarchy matters clinically
Response depth has consistently predicted progression-free survival and overall survival in multiple myeloma trials. Patients achieving sCR or CR tend to have longer remissions than those achieving only PR, which motivates using deeper-response therapies and consolidation strategies in eligible patients. The hierarchy also anchors clinical trial endpoints: many modern myeloma trials use VGPR or better as a key secondary endpoint and stringent CR as a benchmark for evaluating novel agents.
Progressive disease: the priority check
PD is always evaluated first because it overrides all response criteria. A patient whose disease is progressing requires a change of therapy regardless of any apparent improvement in one marker. The 25% threshold applies relative to the lowest confirmed response value (nadir) during treatment, not the baseline, which prevents classifying normal fluctuation around the nadir as progressive disease.
The sCR distinction
Stringent complete response adds two confirmatory tests to the standard CR:
- A normal serum free light-chain ratio (kappa to lambda, or lambda to kappa depending on the clone) indicates that no excess immunoglobulin light chains are circulating.
- Absence of clonal plasma cells confirmed by immunohistochemistry or immunofluorescence on a bone marrow biopsy.
sCR is not just an academic distinction — in the context of transplant eligibility and MRD-driven treatment decisions, knowing whether a CR is stringent influences the clinical plan.
Limitations of this calculator
This tool applies the IMWG serum and urine M-protein framework for secretory myeloma. It does not model:
- Light-chain-only myeloma, which is assessed using the serum free light-chain ratio and the involved/uninvolved FLC difference.
- Non-secretory myeloma, where response is assessed by bone marrow biopsy alone.
- MRD status, which requires next-generation flow cytometry or sequencing on bone marrow and represents an emerging additional dimension beyond the standard IMWG categories.
- Plasmacytoma response, which is assessed separately by imaging.
For clinical decision-making, always apply the full IMWG 2016 criteria from the original publication and confirm values with the treating haematologist.