Interference of Therapeutic Monoclonal Antibodies With Routine Serum Protein Electrophoresis and Immunofixation in Patients With Myeloma: Frequency and Duration of Detection of Daratumumab and Elotuzumab

Am J Clin Pathol. 2018 Jul 3;150(2):121-129. doi: 10.1093/ajcp/aqy037.


Objectives: We investigated the frequency and pattern of detection of therapeutic monoclonal antibodies (t-mAbs) daratumumab and elotuzumab by routine serum protein electrophoresis (SPE) and immunofixation (IF) in treated patients with myeloma.

Methods: Detection of t-mAb was assessed in 22 patients by retrospective review of SPE/IF ordered prior to, during, and after 26 individual courses of therapy.

Results: t-mAb was distinguishable from M-protein in 16 of 26 courses, with daratumumab detected in nine of nine and elotuzumab in six of seven patients. t-mAb was detected on first follow-up SPE/IF in 12 patients, with earliest detection 7 days after therapy initiation and latest detection 70 days after therapy. t-mAb persisted throughout induction therapy in most patients, with loss of detection during maintenance daratumumab.

Conclusions: When distinguishable from M-protein, t-mAbs are detectable in 93% of treated patients as soon as 7 days after the initial dose and are consistently observed throughout induction therapy, warranting increased monitoring and careful interpretation of SPE/IF.

MeSH terms

  • Antibodies, Monoclonal / blood*
  • Antibodies, Monoclonal / therapeutic use
  • Antibodies, Monoclonal, Humanized / blood*
  • Antibodies, Monoclonal, Humanized / therapeutic use
  • Antineoplastic Agents, Immunological / blood
  • Antineoplastic Agents, Immunological / therapeutic use
  • Blood Protein Electrophoresis*
  • False Positive Reactions
  • Humans
  • Multiple Myeloma / drug therapy
  • Myeloma Proteins / analysis*


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents, Immunological
  • Myeloma Proteins
  • multiple myeloma M-proteins
  • elotuzumab
  • daratumumab