Pseudohyperphosphatemia in a patient with incidentally identified progression of smoldering myeloma

Elizabeth R. Francis, Fengming Chen, Michal Kidacki, Ronald Miller, Mo'tasem Alkhasoneh, Giampaolo Talamo, Monica Straub, Kristin Klinefelter, Namratha Kodali, Yusheng Zhu

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Background: Pseudohyperphosphatemia is a rare laboratory finding in MM, especially in patients with smoldering myeloma (SMM) progressing to symptomatic multiple myeloma (MM). Laboratorians and clinicians should be aware of this phenomenon and take necessary actions to avoid misdiagnosis. Methods: Specimens from a monoclonal IgG kappa SMM patient with extremely high serum phosphorus concentrations measured by the Roche phosphomolybdate assay were re-evaluated using serial dilutions and the ORTHO VITROS assay free from monoclonal gammaglobulin interference. Serum free kappa/lambda chain ratio was also assessed. Results: Both serial dilutions and the ORTHO VITROS assay normalized serum phosphorus concentrations, suggesting the extremely high serum phosphorus concentrations measured by the Roche assay is due to interference from monoclonal gammaglobulin. Additionally, the patient's serum free kappa/lambda ratio was >100. Based on serum free kappa/lambda ratio, disease progression from SMM to MM was diagnosed. Conclusions: Prompt and appropriate laboratory investigations ensure correct diagnosis of pseudohyperphosphatemia and help clinicians properly manage patients. To our knowledge, this patient is the first reported case of pseudohyperphosphatemia in patients with progression from SMM to MM.

Original languageEnglish (US)
Pages (from-to)306-308
Number of pages3
JournalClinica Chimica Acta
Volume487
DOIs
StatePublished - Dec 2018

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Clinical Biochemistry
  • Biochemistry, medical

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