title: [False hyperphosphoremia in multiple myeloma. Interference of monoclonal immunoglobulin G with the determination of blood phosphorus level].
abstract: A case of pseudohyperphosphataemia detected in a male patient with multiple IgG myeloma is reported. Phosphataemia, measured by a technique without previous deproteinization, reached 5.66 mM before any treatment and varied with treatment-induced changes in monoclonal immunoglobulin levels. Conversely, normal phosphataemia levels were found in blood samples taken before and after treatment when serum was deproteinized. This pseudohyperphosphataemia resulted from an increase in optic density due to interference between monoclonal immunoglobulin and the molybdic reagent used to determine phosphataemia. A retrospective investigation yielded three similar cases: two in patients with myeloma and one in a patient with non-myelomatous monoclonal dysglobulinaemia. A brief prospective study showed that this phenomenon was relatively frequent, as it was found in 2 out of 9 patients with monoclonal immunoglobulin (IgG in all 9 cases). These data indicate that the finding of marked hyperphosphataemia in subjects with monoclonal dysglobulinaemia should always prompt a control assay performed on deproteinized blood.
authors.affiliation: Service de Médecine Interne et Immunologie Clinique, CHU, Dijon.
authors.forename: B
authors.initials: B
authors.lastname: Lorcerie
authors.forename: J F
authors.initials: JF
authors.lastname: Besancenot
authors.forename: F
authors.initials: F
authors.lastname: Maillefert
authors.forename: M J
authors.initials: MJ
authors.lastname: Chantereau
authors.forename: O
authors.initials: O
authors.lastname: Olsson
authors.forename: B
authors.initials: B
authors.lastname: Chauffert
authors.forename: A
authors.initials: A
authors.lastname: Lalu-Fraisse
authors.forename: J
authors.initials: J
authors.lastname: Strauss
authors.forename: F
authors.initials: F
authors.lastname: Martin
mesh_terms: D004586:Electrophoresis; D005189:False Positive Reactions; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D009101:Multiple Myeloma / Q000097:blood*; D010758:Phosphorus / Q000097:blood*; D011446:Prospective Studies; D012189:Retrospective Studies
chemical_list: D007074:Immunoglobulin G; D010758:Phosphorus
vernacular_title: Fausse hyperphosphorémie au cours du myélome multiple. Interférence de l'immunoglobuline G monoclonale avec la détermination de la phosphorémie.