What are the limitations of the slim crab criteria?

While the slim crab criteria is highly validated, it should not replace clinical judgment. OpiCalc provides the latest evidence-based limitations for the slim crab criteria to ensure safe bedside use and optimal diagnostic accuracy.

How does the slim crab criteria compare to other Hematology scores?

The slim crab criteria is a gold-standard diagnostic tool. OpiCalc provides side-by-side clinical guidance to help clinicians choose the most specific evidence-based tool for their patient's presentation.

Is the slim crab criteria free to use?

Yes. OpiCalc provides the slim crab criteria completely ad-free and optimized for mobile bedside use, ensuring you can calculate medical risk swiftly and without distraction.

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SLiM-CRAB Criteria

Myeloma Diagnosis: The presence of any ONE SLiM (biomarker) or CRAB (damage) feature in the context of clonal plasma cells defines "Active Myeloma" requiring therapy.

SLiM Biomarkers (Malignancy)

CRAB Criteria (End-Organ Damage)

Diagnostic Status (IMWG 2014)

Smoldering Myeloma / MGUS

Criteria for active disease are NOT met. If M-protein > 30 g/L or Marrow > 10%, classify as Smoldering Myeloma; else MGUS.

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Differentiating between Smoldering Myeloma (SMM) and Active Myeloma requiring treatment.

Evaluating patients with an M-protein or clonal marrow plasma cells.

Identifying patients with "biomarker-driven" active disease in the absence of end-organ damage.

Patient Population

Adult patients with a monoclonal gammopathy or suspected plasma cell dyscrasia.

Section 2

Formula & Logic

SLiM: "Biomarkers of Malignancy" (Any ONE = Treat)

S: Sixty percent — Bone marrow clonal plasma cells ≥ 60%.

Li: Light chains — Involved:uninvolved serum free light chain ratio ≥ 100 (involved FLC must be ≥ 100 mg/L).

M: MRI — > 1 focal lesion (at least 5mm each) on MRI.

CRAB: "End-Organ Damage" (Any ONE = Treat)

C: Calcium elevation (> 11 mg/dL or > 1 mg/dL above ULN).

R: Renal insufficiency (Creatinine > 2 mg/dL or CrCl < 40 mL/min).

A: Anemia (Hb < 10 g/dL or > 2 g/dL below LLN).

B: Bone lesions (1 or more osteolytic lesions on CT or PET-CT).

Section 3

Pearls/Pitfalls

The Paradigm Shift

Historically, CRAB features (end-organ damage) were required to start therapy. The 2014 IMWG update added the SLiM biomarkers because patients with these findings have an ~80% risk of developing CRAB features within 2 years. Treating early prevents irreversible organ damage.

Section 4

Evidence Appraisal

Primary Consensus

International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma.

Rajkumar SV et al. • Lancet Oncology. 2014;15(12):e538-48.

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Section 5

Literature

Consensus

Derived by the International Myeloma Working Group to modernize the 2003 criteria, reflecting improvements in imaging and biochemical assays.

Last Comprehensive Review: 2026

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SLiM-CRAB Criteria

Myeloma Diagnosis: The presence of any ONE SLiM (biomarker) or CRAB (damage) feature in the context of clonal plasma cells defines "Active Myeloma" requiring therapy.